text:
Behavioral and genetic mechanisms of social evolution: insights from incipiently and facultatively social bees
- 2.3k Downloads
- Citations
Facultatively social species exhibit behavioral plasticity in response to changes in ecological conditions and social environment, and thus provide a natural experiment to compare solitary and social behaviors in a single genome. Such species can therefore provide empirical insights into the evolution of eusociality. The small carpenter bees (genus Ceratina) and sweat bees (Halictidae) are of special interest because they exhibit rich behavioral plasticity. Species range from solitary to eusocial, and both groups benefit from detailed behavioral research and well-established phylogenies. As such, small carpenter and sweat bees are poised to further comparative sociogenomic studies which emphasize the necessity of a molecular phylogeny for understanding the evolution of molecular architecture underlying social phenotypes and organizational complexity. Here, we review behavioral, transcriptomic and genomic data in bees across the social spectrum, highlighting the importance of simple societies and facultatively social taxa to examine the genetic basis of cooperative traits and social evolution.
Keywordssocial evolution small carpenter bee sweat bee sociogenomics primitively social facultative early stage sociality phenotypic plasticity
1 Introduction
Phenotypic plasticity, an organism's ability to modify physiological or behavioral traits following environmental cues, has been comprehensively studied over the past four decades (West-Eberhard 1989; Nijhout 2003). In some cases, variation in the regulation of a conserved set of genes can lead to the expression of multiple, highly discrete phenotypes (Whitman and Agrawal 2009). Such polyphenisms are relatively common in the insects (Emlen and Nijhout 2000; Simpson et al. 2011) and are informative targets for addressing questions regarding the origins and elaboration of derived phenomena (e.g., caste determination, Evans and Wheeler 2001; Fjerdingstad and Crozier 2006) including the paradox of eusociality. Eusociality is considered the most complex form of social organization, and eusocial species are often ecologically dominant (Michener 1969; Wilson 1971). However, despite its biological prevalence and ecological success (ants alone represent as much as 25% of all terrestrial biomass, Schultz 2000), the emergence of eusociality remains a rare and highly derived event (Wilson and Hölldobler 2005; Nowak et al. 2010). Determining the molecular and environmental factors underlying the origins of eusocial behavior has consequently become a central focus in the field of social evolution (Michener 1974).
Social terminology—adapted from Rehan and Toth 2015
Social class
Cooperative brood care
Overlapping generations
Division of labor
Facultative sociality
Examples—with genomes
Megachile rotundata, Dufourea novaeangliae, Habropoda laboriosa (Kapheim et al. 2015)
Ceratina calcarata (Rehan et al. 2016)
Incipiently social
Ceratina australensis (Rehan et al. unpub. data)
Primitively eusocial
Lasioglossum albipes (Kocher et al. 2013); Bombus terrestris; Bombus impatiens (Sadd et al. 2015)
Advanced eusocial
Apis mellifera, Apis florea, Melipona quadrifasciata (Kapheim et al. 2015)
In solitary bees, reproductive females independently establish a nest and singly forage for their offspring, which require no care during their maturation (Michener 2007). Once provisioning is complete, females often either abandon their brood (e.g., Colletes and Osmia; Černá et al. 2013) or die before their offspring reach adulthood (Michener 2007). Though solitary species are not burdened by the increased risk of disease transmission associated with social living (Fu et al. 2015), they are extremely susceptible to parasitism and predation (Wcislo and Cane 1996). Increased parasitism and predation rates are thus considered primary ecological drivers towards social organization (Lin and Michener 1972; Wcislo et al. 2004; Rehan et al. 2011).
In a handful of seemingly solitary bees, the reproductive female will remain at her nest to guard and clean the developing brood (e.g., Ceratina japonica, Sakagami and Maeta 1984; Lasioglossum laticeps, Plateaux-Quénu 2008; and Ceratina calcarata, Rehan and Richards 2010a), and this extended parental care defines them as subsocial in their behavior (Michener 2007). Subsociality is the simplest form of social organization along the social spectrum (Rehan and Toth 2015) and is considered a necessary precondition for the evolution of more complex social groups (Wilson 1971; Michener 1974). Although subsocial bees are nest-loyal, and at least some are capable of nestmate recognition (Rehan and Richards 2013), they remain effectively casteless and independent as adults.
Like solitary and subsocial species, incipiently social bees remain totipotent throughout adulthood and are able to found nests of their own (Sakagami and Maeta 1989; Rehan et al. 2010b). They are distinguished from their subsocial cousins by their capacity to nest cooperatively under a simple division of labor to rear a single brood (West-Eberhard 1987). As they represent species at the origins of social organization, subsocial through incipiently social bees may be collectively referred to as early-stage social species (Table I; Rehan and Toth 2015).
On the other end of the social spectrum are bees representative of late stage sociality: the primitively eusocial species. In these groups, a reproductive female continues to lay eggs after initially founding her nest (either alone or with nestmate workers), and may do little else once the first generation of her offspring reach maturity (Wilson 1971; Michener 2007). Individuals of primitively eusocial species are typically monomorphic, though a division of labor based on age and body size is common (e.g., Halictus rubicundus, Soucy and Danforth 2002; Megalopta genalis, Smith et al. 2003; Halictus scabiosae, Brand and Chapuisat 2012). Worker-type offspring in primitively eusocial colonies may maintain a capacity for reproductive behavior, though ovary development is often inhibited (Michener 1974). These offspring are rarely limited to a single role, and may switch tasks over their lifetime. For instance, in both sweat bees and small carpenter bees, workers may rapidly develop into reproductives upon removal of a dominant reproductive nestmate (Eickwort 1986; Rehan et al. 2014b). The workers of advanced eusocial species, by contrast, develop into functionally sterile castes, often with distinct behaviors and morphologies (e.g., Apis and Melipona bees, Wilson 1971; Michener 1974, 2007). This distinct caste differentiation is considered a defining feature of advanced eusocial species, which are no longer capable of reverting to simpler forms of social organization (Wilson and Hölldobler 2005).
Intriguingly, early-stage social bees may demonstrate "facultative sociality," or a capacity to express more than one form of social organization (Figure 1; Smith et al. 2003; Rehan et al. 2011, 2014a, b). The crepuscular sweat bee (M. genalis), for instance, nests either solitarily or in small, primitively eusocial colonies (Smith et al. 2003; Wcislo et al. 2004; Kapheim et al. 2013; Jones et al. 2017). The subsocial small carpenter bee (C. calcarata), by comparison, is facultatively incipiently social and may rear a worker-like offspring to aid in brood care and feeding (Rehan and Richards 2010a, b; Rehan et al. 2014a). The behaviors characteristic of early-stage social bees are theorized to be necessarily antecedent to advanced eusociality, and thus provide a tractable opportunity to empirically test social evolutionary theory (e.g., Wilson 1971; Michener 1974; Seger 1983; Rehan and Toth 2015). Those which are also facultatively social, however, provide particularly informative insights, as the costs, benefits, and molecular mechanisms underlying multiple classes of social organization may be explored concurrently within a single species (West-Eberhard 2003; Rehan and Toth 2015). To make evolutionarily informed conclusions about the molecular origins of complex social behavior across the social spectrum, well-resolved phylogenetic histories and species delineations must first be established (Danforth et al. 2013). Fortunately, considerable efforts have been made to resolve the phylogenies of two socially diverse bee groups: the sweat bees (Halictidae) and carpenter bees (Xylocopinae).
Represented by solitary, facultatively social, and eusocial species, the wide behavioral diversity of the halictids has made them an informative system for studies of behavioral plasticity and social evolution (Schwarz et al. 2007; Kocher and Paxton 2014). Multiple revisions of halictid phylogeny (Danforth 2002; Brady et al. 2006; Gibbs et al. 2012) have come to posit two origins of eusociality within Halictidae: one in the tribe Augochlorini (Danforth and Eickwort 1997; Danforth et al. 2013) and another for the tribe Halictini (Figure 1; Halictus and Lasioglossum, Gibbs et al. 2012). This research has also provided evidence of multiple reversions from social to solitary behaviors in this group (Danforth et al. 2003).
The carpenter bees (subfamily Xylocopinae) collectively represent the entirety of the social spectrum across their four tribes: the solitary Manueliini, incipiently social Xylocopini, solitary to eusocial Ceratinini, and incipiently social to eusocial Allodapini (Figure 1). This rich diversity, combined with a well-resolved phylogeny (Rehan et al. 2010a, 2012; Rehan and Schwarz 2015) and phylogeography (Dew et al. 2016; Shell and Rehan 2016), makes the xylocopine bees an exceptional system for sociogenomic research (Rehan and Toth 2015). Further, as the Xylocopinae and Apinae are sister subfamilies (Cardinal and Danforth 2011), research involving carpenter bees may directly inform our understanding of the dynamics underlying advanced eusociality in corbiculate species (Figure 1; Rehan and Toth 2015; Toth and Rehan 2017). Phylogenetic work within the Xylocopinae has revealed a single origin of sociality followed by as many as four reversions to a solitary lifestyle (Schwarz et al. 2007; Rehan et al. 2012).
Well-resolved phylogenies among social lineages provide much-needed evolutionary frameworks by which to contextualize comparative molecular research (Rehan and Toth 2015; Romiguier et al. 2015; Branstetter et al. 2017; Peters et al. 2017). Such research has helped to reveal that species may evolve along a non-linear trajectory between simple and complex social organization: incipiently social lineages, for instance, frequently revert to solitary life (Wcislo and Danforth 1997; Rehan et al. 2012; Gibbs et al. 2012). Phylogenetic studies also indicate that the evolution of advanced eusociality is rare, and likely checked by prohibitive natural barriers (Rehan et al. 2012). Integrative research which builds off this phylogenetic foundation may now benefit from ongoing advances in genomic and transcriptomic sequencing methods. As such, studies which strive to integrate genomic, transcriptomic, and behavioral data are poised to gain meaningful insights into the molecular signatures of phenotypic plasticity.
In this review, we provide a detailed overview of sociogenomic research in bees of early stage and facultative sociality. The rich behavioral and ecological diversity of these species provides a powerful workspace in which to explore the molecular, developmental, and environmental drivers of social transition (West-Eberhard 1987; Rehan et al. 2014a; Patalano et al. 2015). Despite their informative value, however, there remains a paucity of research in these groups. We thus argue in support of additional sociogenomic research into bees of early-stage and facultative sociality, and highlight the socially diversified Ceratina small carpenter bees and halictid sweat bees as promising model systems for future studies.
2 Facultatively social bees
Facultative sociality is not a distinct social category (like subsociality or eusociality), but rather indicates a species' capacity for plasticity in its social organization. For example, conspecifics of some facultatively social sweat bees either establish a solitary nest, or found a primitively eusocial colony in which a helper generation assists in the rearing of a second brood of reproductive individuals (e.g., H. rubicundus, Soucy and Danforth 2002; M. genalis, Smith et al. 2003; Lasioglossum calceatum, Davison and Field 2016). Facultatively social nesting in some carpenter bees, by contrast, may involve incipiently social brood care by a cooperative pair of age-matched females (e.g., Ceratina australensis, Rehan et al. 2014b), or production of a single, worker-like offspring alongside future reproductives (e.g., C. calcarata, Rehan et al. 2014a; C. japonica, Sakagami and Maeta 1984). Where advanced eusocial Hymenoptera feature distinctive and often multifaceted reproductive and morphological caste systems, the behavioral phenotypes of facultatively social bees straddle species-specific ranges along the social spectrum. This behavioral diversity, both within and between facultatively social species, provides an exceptional opportunity to explore how phenotypic variation across modes of social organization is reflected at the molecular level (Kocher and Paxton 2014).
Facultatively social bees are particularly tractable models for comparative sociogenomic study be-cause variation in their social phenotype may be reliably elicited through experimental manipulation (Schwarz et al. 2007; Kocher and Paxton 2014; Rehan and Toth 2015). This can be seen, for example, in the induction of cooperative, multi-female nests in otherwise mainly subsocial species (e.g., C. japonica; Sakagami and Maeta 1984, 1987; Lasioglossum spp., Jeanson et al. 2005, 2008). Sakagami and Maeta (1995) elicited reproductive division of labor in the small carpenter bees, C. japonica (Sakagami and Maeta 1984) and C. okinawana (Sakagami and Maeta 1989), by constraining conspecific females to cohabitate. In these induced social nests, one female assumed queen-like behavior, laying eggs and defending the nest, while the second primarily foraged. In all cases of social nesting, the reproductive role was reliably adopted by the larger of the two females, in age-matched and even mother-daughter cooperative pairs (Sakagami and Maeta 1984, 1989, 1995). In similar fashion, Holbrook et al. (2009) observed that individuals of the normally solitary sweat bee (Lasioglossum NDA-1) assumed dedicated guarding or digging behaviors when forced to nest in pairs, though paired individuals secured deeper and better-guarded nests compared to their solitary counterparts. Holbrook et al. (2009) noted that such arrangements rarely occur in wild populations. Considerable phenotypic plasticity may thus be widespread in bees of early-stage sociality, even in those species which rarely demonstrate facultative sociality in the wild.
Environmental factors, including local climate, resource availability, predation, and parasite pressure, have long been theorized to comprise the primary ecological drivers of social evolution (Lin and Michener 1972; Evans 1977; Strassman and Queller 1989; Kocher et al. 2014). Accordingly, social complexity in facultatively social bees is often reliably predicted by ecological condition (Richards and Packer 1996; reviewed in Purcell 2011). For example, brood parasitism in the Australian small carpenter bee (C. australensis, Rehan et al. 2010b) appears to be a key selective pressure favoring social nesting (Rehan et al. 2011). The influence of environment on social organization has also been particularly well-documented in the sweat bees (Plateaux-Quénu et al. 2000; Schwarz et al. 2007; Davison and Field 2016). In H. rubicundus (Soucy and Danforth 2002), solitary or social reproduction appears to be largely dependent on geographic location: solitary H. rubicundus females produce a single brood in cooler regions (Eickwort et al. 1996), and social females produce two broods in warmer regions (Yanega 1989, 1993; Soucy 2002). Field et al. (2010) demonstrated this organizational lability by inducing the offspring of solitary or social populations to switch behavioral type via translocation between cool and warm locations. In other species of sweat bees, social phenotype has been reliably predicted specifically by altitude (L. calceatum, Sakagami and Munakata 1972) or even micro-habitat composition. For instance, in the sweat bee, L. balecium, social nests were consistently observed in warmer, sunnier sites, while solitary nests were typically found in adjacent, cooler, well-shaded locations (Hirata and Higashi 2008). In some cases, however, variation in social organization is neutrally or otherwise not predictably affected by environment (e.g., Lasioglossum apristum, Miyanaga et al. 1999; L. malachurum, Richards 2000; Wyman and Richards 2003), supporting the role of genetic architecture as primary in determining social phenotype (Soucy and Danforth 2002; Soro et al. 2010).
3 Behavioral and genetic mechanisms of social evolution
A suite of major theoretical frameworks has been put forward to explain the mechanisms by which complex social behavior may have evolved. Here, we provide an overview of some of these hypotheses which, though distinct in their viewpoints, are not mutually exclusive, and have been recently brought together in theoretical syntheses (Rehan and Toth 2015; Toth and Rehan 2017). A tendency to reuse a nesting substrate among kin groups is a well-supported precondition for the emergence of social behavior (Wild and Koykka 2014). As it may increase the opportunity for inclusive fitness benefits, reuse or inheritance of a "family" nest is expected to promote group nesting, even with some nestmate competition. Accordingly, nest reuse has been observed across facultatively social Ceratina (Sakagami and Maeta 1987; Rehan et al. 2009, 2014b, 2015) and in other basically social bees (e.g., H. rubicundus, Yanega 1990). By contrast, those species which are known to frequently disperse prior to the establishment of a new nest (e.g. C. calcarata and C. flavipes) are less likely to nest socially (Sakagami and Maeta 1987; Rehan and Richards 2010a, b). Along with nest reuse, multi-voltinism, the capacity to produce more than one brood during a reproductive season, has been suggested as antecedent to eusocial behavior (Seger 1983). The ability to produce multiple generations of offspring in a single breeding season establishes a scenario in which the offspring of mated, overwintering females have an opportunity to remain at the nest as helpers in the following reproductive season. This proposition has found demonstration in primitively eusocial bees (e.g., Halictus sexcinctus, Richards 2001) and is supported by research in bivoltine Ceratina (e.g., C. okinawana, Sakagami and Maeta 1995). The prolonged maternal care behavior often seen in multivoltine species has also been suggested as prerequisite to more complex social structuring (West-Eberhard 1987) and is likely readily reinforced through selection (Wade 2001).
It might be expected that the initial co-option of maternal care genes into relatively queen-like and worker-like phenotypes would be hindered, or outright prevented, by strict pleiotropic constraints on those genes (Gadagkar 1997). In consideration of this, Gadagkar (1997) proposed the concept of genetic release, in which a gene duplication event or significant variation in the timing of gene expression could free key genes from the effects of stabilizing selection. Variation in gene expression, in combination with the evolution of separate developmental programs, could then allow for the mutual decoupling of strictly reproductive activities (e.g., mating, egg laying) from brood care and nest maintenance tasks. Directional selection through inclusive fitness could then reinforce the expression of increasingly queen-like and worker-like behaviors and physiologies. The maternal heterochrony hypothesis builds on this concept by proposing that a shift in the timing of expression (heterochrony) of maternal care genes may account for the evolution of precocious, sib-social care behavior seen in advanced eusocial species (Linksvayer and Wade 2005). From this approach, the emergence of queen- and worker-type behaviors could result from a slight variation in the regulation of an otherwise conserved set of genes.
Rehan et al. (2014a) directly assessed the maternal heterochrony hypothesis through transcriptomic analysis of the subsocial small carpenter bee, C. calcarata. In C. calcarata, mothers may rear a worker-like daughter to aid in brood care and foraging, and thus enter an incipiently social stage (Rehan and Richards 2010b). Rehan et al. (2014a) compared brain gene expression of individuals from five focal stages in C. calcarata's reproductive season, and, as predicted by the maternal heterochrony hypothesis, gene expression patterns of worker-like daughters most closely mirrored those of post-reproductive mothers, and included upregulation of genes implicated in maternal care. Further support for the underlying role of molecular heterochrony in emergent brood care behavior has also been found through similar transcriptomic works in other Hymenoptera (e.g., Polistes metricus, Toth et al. 2007, 2010).
Complementary to both heterochrony and ground-plan hypotheses is the idea of the role of genetic "toolkits"—highly conserved genes which play a focal role in the developmental pathways of core physiological and behavioral traits across taxa (Toth and Robinson 2007). The genetic toolkit hypothesis suggests that modifications to these key genes, or the molecular pathways regulating their expression (i.e., transcription factors), could underlie the emergence of behaviors leading to social organization (Figure 2; True and Carroll 2002; Carroll 2005). Expanded by Bloch and Grozinger (2011), the functionality of socially co-opted toolkit genes or pathways could become sensitive to signals from the social environment, and thus become socially regulated. The genetic toolkit hypothesis has found support in widely conserved genetic signaling across both taxonomic and social lineages within bees (Woodard et al. 2011) and among social Hymenoptera more broadly (Toth et al. 2014; Berens et al. 2014; Woodard et al. 2014; Morandin et al. 2016). For instance, two species of primitively eusocial bumble bee, Bombus terrestris and B. impatiens, were found to share many genes and gene regulatory elements with both P. metricus and A. mellifera, including those involved in the regulation of social behaviors (Sadd et al. 2015). In a comparison of transcriptomes across hymenopteran lineages (i.e., bees, ants, and wasps), Berens et al. (2014) determined that, despite high variation in expressed genes, metabolic pathways and molecular functions were relatively well-conserved across distant social lineages. They thus suggested support for a "loose" genetic toolkit: even when relatively few genes are expressed in common, the expression of complex sociality appears to involve highly conserved transcription factor and molecular functional networks.
In contrast to the highly conserved nature of genetic toolkits, novel or taxonomically restricted genes (i.e., those unique to clades or lineages) have also gained support as likely to play a key role in the evolution of complex social behavior (Johnson and Tsutsui 2011; Sumner 2014). With the evolution of eusociality, it may be expected that group behavioral and physiological coordination would come to rely on specialized genes and gene expression networks (Johnson and Linksvayer 2010). Evidence of caste-specific expression in genes unique to bees (e.g., A. mellifera, Harpur et al. 2014) and other social Hymenoptera (e.g., Polistes wasps, Ferreira et al. 2013; Temnothorax ants, Feldmeyer et al. 2014) suggests positive selection on novel genes may underlie derived worker phenotypes (Kapheim et al. 2015). Accordingly, detection of lineage-specific variations in gene families, such as a bias towards gustatory chemoreceptors in Bombus (Sadd et al. 2015) or expansion in odorant receptor genes in the clonal raider ant (Ooceraea biroi; McKenzie et al. 2016), have helped to reveal how changes at the molecular level may dictate the evolutionary trajectory of social Hymenoptera. Despite many novel genes between eusocial lineages, a large body of research in toolkit genes indicates that complex gene expression networks and metabolic pathways remain highly conserved (Simola et al. 2013; Berens et al. 2014; Morandin et al. 2016). Therefore, in theory, (i) eusociality may evolve from a highly diverse suite of antecedent genetic profiles, but (ii) the composition of genes and functional regulatory networks underlying social phenotypes may be increasingly constrained as species approach advanced forms of social complexity. It remains unclear, however, whether the apparent acceleration in rates of positive selection detected among eusocial lineages may instead indicate relaxed selection operating on relatively reduced effective population sizes in these taxa (Harpur and Zayed 2013; Romiguier et al. 2014).
4 Sociogenomics: a comparative approach to social evolution
Broadly, sociogenomic research addresses the feedback circuit between genetics and environmental cues: (i) how molecular functions and expression affect behavior and social organization, and (ii) how social and environmental cues further modify signaling pathways, development, physiology, and behavior (Robinson 2002; Robinson et al. 2005). The publication of the A. mellifera genome represented a critical foundation for concerted sociogenomic research (The Honeybee Genome Sequencing Consortium 2006) and remains a valuable resource for comparative studies of behavioral plasticity and social evolution (Fischman et al. 2011; Dolezal and Toth 2014). As genes are generally conserved across genera, particularly within taxonomic clades, the expanding wealth of honey bee sociogenomic research can act as a guide for explorations into the molecular architecture of species considered antecedent to the eusocial form (Page and Amdam 2007; Fischman et al. 2011; Woodard et al. 2011).
The determination of the molecular signals underlying the origins of caste determination in advanced eusocial Hymenoptera represents a central endeavor in the field of sociogenomics (Toth et al. 2007; Toth and Robinson 2009), and has been astutely explored (Barchuk et al. 2007; reviewed in Berens et al. 2014). As with other complex traits of interest, caste determination can be traced to suites of genes whose functions are tied to key developmental (e.g., vitellogenin), hormonal (e.g., juvenile hormone), and metabolic pathways (e.g., insulin pathway genes; reviewed in Page and Amdam 2007; Corona et al. 2016). As the expression of these critical pathways remains highly sensitive to external cues (such as pheromone signaling, Grozinger et al. 2003; and nutritional intake, Ament et al. 2008), they can be considered as highly responsive to factors within the social environment. It has thus been theorized that gene pathways in eusocial taxa, which are involved in the ontogenetic determination of caste fate during the earliest stages of development, may have arisen through the co-opting of genes previously involved in core physiological processes (i.e., genetic toolkit hypothesis, see also Toth et al. 2007; Toth and Robinson 2009). We can use the power of comparative sociogenomic research across the social spectrum to trace the function of candidate genes across species of varying degrees of sociality (reviewed in Robinson et al. 2005; Smith et al. 2008).
5 Sociogenomics across the social spectrum
Continued advancements in the accuracy and accessibility of sequencing technologies havemade the acquisition and analysis of genomic and transcriptomic data an increasingly achievable undertaking, and have greatly expanded the molecular resources available for social bee lineages (Table I; Figure 1). Comparisons of differentially expressed genes (DEGs) within A. mellifera, for instance, have revealed clear distinctions in brain gene expression between scout, non-scout (Liang et al. 2012), and recruit worker behavioral variants (Southey et al. 2016). As genomic and transcriptomic resources are developed for species of early-stage and facultative sociality (e.g., Lasioglossum albipes; Kocher et al. 2013; C. calcarata; Rehan et al. 2014a, 2016), extended comparative studies within and between Hymenoptera of distinct social organizations and lineages will be made possible (reviewed in Berens et al. 2014; Kapheim 2016). In the genome of C. calcarata, for instance, key transcription factor and chemosensory gene groups were identified as significantly expanded (Rehan et al. 2016), directly in line with expectations from observed gene family expansions in A. mellifera (Kapheim et al. 2015).
Insights into the molecular signals of ontogenetic variation between social lineages have also been gained through DEG research in facultatively social bees. Analysis of transcriptomic data recently developed for M. genalis revealed that while both functional gene groups and associated expression levels varied greatly over the course of an offspring's development, there were consistent shifts in primary functional processes during each stage of maturation (Jones et al. 2015). As female M. genalis develop from egg to adult, expression patterns consistently shift from predominantly cellular development and differentiation, to establishment of neurological systems and specialized metabolic pathways at adulthood (Jones et al. 2015). These results contrast with similar DEG analyses of offspring caste determination in eusocial species, in which early nutritional signals lead to increasingly distinct developmental gene expression pathways towards adulthood as either a sterile worker or reproductive queen (as seen in A. mellifera, Barchuk et al. 2007; Polistes wasps, Hunt et al. 2010; and Formica ants, Morandin et al. 2015). More recently, however, research investigating differences in brain and abdominal gene expression among solitary and social M. genalis revealed stark differences between reproductive and non-reproductive roles. The abdominal gene expression patterns of workers that became replacement queens mirrored those of reproductive foundresses, while those of non-reproductive worker daughters stood apart. Differences in brain gene expression patterns among castes were not nearly as strong, however, suggesting that changes in reproductive functionality may precede changes in behavior (Jones et al. 2017). The caste-biased differences in abdominal gene expression detected in M. genalis were found to overlap with those of obligately eusocial taxa, suggesting there may be considerable conservation of the regulatory mechanisms underlying eusocial organization across evolutionary lineages. Further research comparing the transcriptomic profiles of offspring developmental stages and adult reproductive strategies (solitary vs. social) in other bees of early-stage sociality more broadly is a necessary next step.
Genomic and transcriptomic resources have also enabled the exploration of evolutionary developmental (evo-devo) theories as to how highly complex behavioral traits may emerge from a genetic functional architecture, which can be at once widely conserved (Rittschof et al. 2014) and pleiotropically constrained (Carroll 2008; Chen et al. 2013). Transcriptional regulatory networks (TRNs) are the highly complex and interconnected molecular signaling pathways (between transcription factors (TFs) and their target genes) underlying both gene expression and environmentally responsive regulation (Luscombe et al. 2004). TRN analysis in bees was pioneered by Chandrasekaran et al. (2011), who combined the brain transcriptomic profiles from 853 honey bees, representative of 48 distinct behavioral phenotypes, to assemble a brain TRN for A. mellifera. Their work indicated that brain gene expression would reliably predict behavioral phenotype, and that disparate behavioral phenotypes frequently rely on both shared and targeted TFs. A more recent population genomic study of the A. mellifera brain TRN revealed that regulatory and coding sequences throughout the TRN are under purifying selective pressure (Molodtsova et al. 2014). Proteins on the periphery of this regulatory network were most likely to be free of pleiotropic constraint and thus available for adaptive selection. Accordingly, this work provided additional support for the genetic toolkit theory within the evo-devo framework, highlighting the role of alterations to TFs regulating gene expression, rather than changes in the genes themselves, as likely critical in the emergence of complex social behaviors.
The importance of TF functionality in social evolution was further highlighted through comparative genomic studies at a phylogenetic scale. Kapheim et al. (2015) compared the genomic data of 10 bee species (representing three families and containing two independent origins of eusociality) to investigate conserved molecular dynamics across social lineages. In contrast to species of early-stage sociality, those of greater social complexity featured an increased frequency of transcription factor binding sites and putatively methylated genes. Additional evidence of accelerated evolution among eusocial taxa was also seen in similar studies (Woodard et al. 2011; Simola et al. 2013; Harpur and Zayed 2013; Harpur et al. 2014; Romiguier et al. 2014), and suggests that a capacity to regulate gene expression may become increasingly essential in the later stages of social organization. However, large sets of distinct and often lineage-specific genes were also detected in these studies (Woodard et al. 2011; Simola et al. 2013; Kapheim et al. 2015). Thus, despite considerable convergence in social organization and gene network functionality among eusocial taxa, there appears to be great variability in the possible evolutionary routes to complex social organization.
The increased achievability of sociogenomic methods opens doors to the integrative study of previously under-researched taxa. In the past 4 years, the A. mellifera genome has been joined by the draft genomes of two advanced eusocial (Apis florea and Melipona quadrifasciata; Kapheim et al. 2015) and two primitively eusocial bees (B. terrestris and B. impatiens, Sadd et al. 2015); three solitary (Megachile rotundata, Dufourea novaeangliae, and Habropoda laboriosa; Kapheim et al. 2015) and two facultatively social bees (L. albipes, Kocher et al. 2013; C. calcarata, Rehan et al. 2016); and one putatively facultatively social bee (Eufriesea mexicana, Kapheim et al. 2015; Table I, Figure 1). As genomic and transcriptomic data continue to be developed in additional social and solitary bees, we will continue to gain more comprehensive insights into how novel genes, genetic release from pleiotropic constraints, and convergent gene regulation underlie the foundational transitions in social form (Rehan and Toth 2015).
6 Epigenetics and phenotypic plasticity
Variation in gene expression via methylation is a well-appreciated mechanism of phenotypic plasticity across many taxa (Goldberg et al. 2007; Glastad et al. 2011). DNA methylation data from social Hymenoptera (Yan et al. 2015) indicate that a capacity for epigenetic response to ecological or social environment may play a role in the emergence of some complex traits (Weiner and Toth 2012; Kapheim et al. 2015). Studies investigating the epigenetics of phenotypic plasticity in A. mellifera (Lyko et al. 2010; Foret et al. 2012; Li-Byarlay et al. 2013) and bees of early-stage sociality (Kocher et al. 2013; Rehan et al. 2016) have detected conserved expansions in possible methylation sites (CpG densities), and have consequently proposed this expanded capacity for DNA methylation as putatively central in the evolution of social complexity (Glastad et al. 2011; Weiner and Toth 2012). Though CpG densities are indicators for the capacity of methylation (Weiner and Toth 2012; Bewick et al. 2017), only by examining an organism's total methyl-modified genome can one empirically explore changes in epigenetic architecture across behavioral states and taxa (e.g., bees, A. mellifera, Lyko et al. 2010; C. calcarata, Rehan et al. 2016; Polistes wasps, Patalano et al. 2015; Standage et al. 2016; and the clonal raider ant, Cerapachys biroi, Libbrecht et al. 2016; reviewed in Hunt et al. 2013). Nevertheless, studies exploring methylation activity in primitively eusocial Polistes wasps found little to no evidence of gene methylation in this group (P. canadensis, Patalano et al. 2015; P. dominula, Standage et al. 2016). Thus, though some form of epigenetic regulation of gene expression via DNA methylation appears widespread in many species, its exact function in the evolution of social organization remains irregular and unclear (Bewick et al. 2017). Despite a large body of literature regarding its implications in Hymenoptera, published methylome data in bees is currently limited to four species: A. mellifera (Lyko et al. 2010), C. calcarata (Rehan et al. 2016), L. albipes, and D. novaeangliae (Glastad et al. 2017). Additional resources for bees of early-stage and facultative sociality could help to further illuminate how methylation affects phenotype, and whether epigenetic modifications influence cooperative behavior at the origins of social organization (Weiner and Toth 2012).
7 The eco-evo-devo approach
As genomic and transcriptomic data provide unprecedented insights into the molecular drivers of phenotypic plasticity, the role of environmental factors in affecting gene expression pathways is becoming increasingly well appreciated (Gilbert 2012; Weiner and Toth 2012; Schlichting and Wund 2014). Social species are affected by signals from both their ecological habitat (e.g., temperature or predator pressure) and their social environment (Bloch and Grozinger 2011; Toth and Rehan 2017). Social environmental signals include pheromones (Conte and Hefetz 2008), maternal manipulation of provisions for developing larvae (Rehan and Richards 2010b; Lawson et al. 2016), or reproductive policing by nestmates (Olejarz et al. 2016), any of which may affect changes in an individual's development or behavior. By integrating measurements in the social and ecological environment with ontogenetic, phylogenetic, and genomic datasets, researchers now have the chance to capture an unprecedentedly holistic portrait of behavioral plasticity and social evolution (Toth and Rehan 2017). This revelation has formed the basis of the emerging "eco-evo-devo" approach, under which the flexible molecular architecture underlying an individual's developmental pathways is continuously influenced by environmental signal factors (reviewed in Abouheif et al. 2014; Gilbert et al. 2015; Toth and Rehan 2017).
Central to the eco-evo-devo framework is the concept of genetic assimilation, in which an initially plastic phenotypic response to local environmental pressure may gradually, through accommodating mutations and selective reinforcement, lead to canalization for discrete phenotypes (Waddington 1961). Evidence for genetic assimilation has been clearly demonstrated in the tobacco hornworm (Manduca sexta, Suzuki and Nijhout 2006), in which experimental alteration of environmental factors was shown to lead to novel phenotypic responses, which may then be readily reinforced at the genetic level through accommodating mutation. To date, comparative research in Apis (Woodard et al. 2011; Harpur et al. 2014) and among social bee lineages (Kapheim et al. 2015) has suggested that genetic assimilation may play a similar role in the evolution of insect sociality.
Recent sociogenomic research in M. genalis, however, offers the first empirical assessment of this idea in a facultatively eusocial species (Jones et al. 2017). Jones et al. (2017) found that genes with worker-biased expression in M. genalis overlapped with genes shown to be rapidly evolving in ten other bee species. Similarities in the patterns of evolutionary rate and caste-biased gene expression between M. genalis and advanced eusocial species (e.g., Apis) thus suggest that strong positive selection through genetic accommodation may have driven the elaboration of social phenotype (i.e., a worker caste) in the ancestors of modern eusocial taxa (Jones et al. 2017). The developmentally constrained caste systems of advanced eusocial bees may thus be the result of sustained environmental pressures operating on the flexible "substrate for selection" seen in bees of early and facultative sociality (Kapheim et al. 2015; Toth and Rehan 2017).
8 Conclusions
Phenotypic plasticity, particularly within the context of social evolution, is a multifaceted and highly dynamic phenomenon. Advanced eusocial species have provided a wealth of insight into the molecular mechanisms underlying highly elaborated insect societies; however, the complex nature of their sociality avails mainly inferential conclusions regarding the evolutionary origins of division of labor. Bees of early-stage sociality are most plausibly antecedent to the eusocial form and, in many cases, remain responsive to a wide range of social, biotic, and abiotic factors. As such, species of early-stage and facultative sociality represent particularly informative models towards a better understanding of the diverse origins and drivers of behavioral plasticity and social organization. Future comparative sociogenomic studies will benefit from the ongoing expansion of molecular resources for bees across the social spectrum, and through an integrative application of the emerging eco-evo-devo approach.
We thank two anonymous reviewers and members of the Rehan lab for constructive feedback on this manuscript. Funding from the University of New Hampshire, NSF-GRF no. 1450271, and NSF-IOS, Behavioral Systems Award no. IOS-1456296, supported this work.
WAS and SMR wrote the paper. All authors read and approved the final manuscript.
- Abouheif E., Favé M.J., Ibarrarán-Viniegra A.S., Lesoway M.P., Rafiqi A.M. (2014) Eco-evo-devo: the time has come. In: Landry, C.R., Aubin-Horth, N. (Eds.) Ecological Genomics: Ecology and the Evolution of Genes and Genomes. Springer, Netherlands. pp. 107–125Google Scholar
- Amdam G.V., Norberg K., Fondrk M.K., Page R.E. (2004) Reproductive ground plan may mediate colony-level selection effects on individual foraging behavior in honey bees. Proc. Natl. Acad. Sci. U.S.A. 101 (21), 11250–11255Google Scholar
- Amdam G.V., Csondes A., Fondrk M.K., Page R.E. (2006) Complex social behaviour derived from maternal reproductive traits. Nature 439 (7072), 76–78PubMedPubMedCentralGoogle Scholar
- Ament S.A., Corona M., Pollock H.S., Robinson G.E. (2008) Insulin signaling is involved in the regulation of worker division of labor in honey bee colonies. Proc. Natl. Acad. Sci. U.S.A 105 (11), 4226–4231PubMedPubMedCentralGoogle Scholar
- Barchuk A., Cristino A.S., Kucharski R., Costa L.F., Simões Z. L. P., Maleszka R. (2007) Molecular determinants of caste differentiation in the highly eusocial honeybee Apis mellifera. BMC Dev. Biol. 7 (70), 1–19Google Scholar
- Berens A.J., Hunt J.H., Toth A.L. (2014) Comparative transcriptomics of convergent evolution: different genes but conserved pathways underlie caste phenotypes across lineages of eusocial insects. Mol. Biol. Evol. 32 (3), 690–703PubMedGoogle Scholar
- Bewick A.J., Vogel K.J., Moore A.J., Schmitz R.J. (2017) The evolution of DNA methylation and its relationship to sociality in insects. Mol. Biol. Evol. In press Google Scholar
- Bloch G., Grozinger C.M. (2011) Social molecular pathways and the evolution of bee societies. Phil. Trans. R. Soc. B. 366, 2155–2170PubMedGoogle Scholar
- Boomsma J.J. (2009) Lifetime monogamy and the evolution of eusociality. Philos. T. Roy. Soc. B. 364, 3191–3207Google Scholar
- Brady S.G., Sipes S., Pearson A., Danforth B.N. (2006) Recent and simultaneous origins of eusociality in halictid bees. Proc. R. Soc. B. 273, 1643–1649PubMedGoogle Scholar
- Brand N., Chapuisat, M. (2012) Born to be bee, fed to be worker? The caste system of a primitively eusocial insect. Front. Zool. 9 (35), 1–9Google Scholar
- Branstetter M.G., Danforth B.N., Pitts J.P., Faircloth B.C., Ward P.S., Buffington M.L., Gates M.W., Kula R.R., Brady S.G. (2017) Phylogenomic insights into the evolution of stinging wasps and the origins of ants and bees. Curr. Biol. 27, 1019–1025PubMedGoogle Scholar
- Cardinal S., Danforth, B.N. (2011) The antiquity and evolutionary history of social behavior in bees. PLOS One 6 (6), e21086PubMedPubMedCentralGoogle Scholar
- Carroll S.B. (2005) Endless forms most beautiful. W. W. NortonGoogle Scholar
- Carroll S.B. (2008) Evo-devo and an expanding evolutionary synthesis: a genetic theory of morphological evolution. Cell 134, 25–36PubMedGoogle Scholar
- Černá K., Zemenová M., Macháčková L., Kolínová Z., Straka J. (2013) Neighborhood society: nesting dynamics, usurpations and social behaviour in solitary bees. PLOS One 8 (8), e73806PubMedPubMedCentralGoogle Scholar
- Chandrasekaran S., Ament S.A., Eddy J.A., Rodriguez-Zas S.L., Schatz B.R., Price N.D., Robinson G.E. (2011) Behavior-specific changes in transcriptional modules lead to distinct and predictable neurogenomic states. Proc. Natl. Acad. Sci. U.S.A. 108 (44), 18020–18025PubMedPubMedCentralGoogle Scholar
- Chen S., Krinsky B.H., Long M. (2013) New genes as drivers of phenotypic evolution. Nature Rev. Genet. 14, 645–660PubMedGoogle Scholar
- Conte, Y.L., Hefetz, A. (2008) Primer Pheromones in Social Hymenoptera. Annu. Rev. Entomol. 53 (1), 523–542PubMedGoogle Scholar
- Corona M., Libbrecht R., Wheeler D.E. (2016) Molecular mechanisms of phenotypic plasticity in social insects. Curr. Opin. Insect Sci. 13, 55–60PubMedGoogle Scholar
- Craik, F.I.M. & Lockhart, R.S. (1972). Levels of processing: A framework for memory research. J. Verbal Learn. Verbal Behav., 11(6), 671-684. doi: 10.1016/S0022-5371(72)80001-X Google Scholar
- Danforth B.N. (2002) Evolution of sociality in a primitively eusocial lineage of bees. PNAS. 99 (1), 286–290PubMedGoogle Scholar
- Danforth B.N., Eickwort G.C. (1997) The evolution of social behavior in the augochlorine sweat bees (Hymenoptera: Halictidae) based on a phylogenetic analysis of the genera. in: Choe J. C., Crespi B. J. (Eds.) The Evolution of Social Behavior in Insects and Arachnids. Cambridge University Press, Cambridge. pp. 270–292Google Scholar
- Danforth B.N., Conway L., Shuqing J. (2003) Phylogeny of eusocial Lasioglossum reveals multiple losses of eusociality within a primitively eusocial clade of bees (Hymenoptera: Halictidae). Syst. Biol. 52 (1), 23–36PubMedGoogle Scholar
- Danforth B.N., Cardinal S., Praz C., Almedia E.A.B., Michez D. (2013) The impact of molecular data on our understanding of bee phylogeny and evolution. Annu. Rev. Entomol. 58, 57–78PubMedGoogle Scholar
- Davison P.J., Field J. (2016) Social polymorphism in the sweat bee Lasioglossum (Evylaeus) calceatum. Insectes Soc. 63, 327–338PubMedPubMedCentralGoogle Scholar
- Dew R.M., Tierney S.M., Schwarz M.P. (2016) Social evolution and casteless societies: needs for new terminology and a new evolutionary focus. Insectes Soc. 63, 5–14Google Scholar
- Dolezal A.G., Toth A.L. (2014) Honey bee sociogenomics: a genome-scale perspective on bee social behavior and health. Apidologie 45, 375–395Google Scholar
- Eickwort G.C. (1986) First steps into eusociality: the sweat bee Dialictus lineatulus. Fla. Entomol. 69, 742–754Google Scholar
- Eickwort G.C., Eickwort J.M., Gordon J., Eickwort M.A. (1996) Solitary behavior in a high-altitude population of the social sweat bee Halictus rubicundus (Hymenoptera: Halictidae). Behav. Ecol. Sociobiol. 38 (4), 227–233Google Scholar
- Emlen D.J., Nijhout H.F. (2000) The development and evolution of exaggerated morphologies in insects. Annu. Rev. Entomol. 45, 661–708PubMedGoogle Scholar
- Evans H.E. (1977) Commentary: extrinsic versus intrinsic factors in the evolution of insect sociality. Bioscience 27 (9), 613–617Google Scholar
- Evans J.D., Wheeler D.E. (2001) Gene expression and the evolution of insect polyphenisms. Bio Essays 23, 62–68Google Scholar
- Feldmeyer B., Elsner D., Foitzik S (2014) Gene expression patterns associated with caste and reproductive status in ants: worker-specific genes are more derived than queen-specific ones. Mol. Ecol. 23, 151–161PubMedGoogle Scholar
- Ferreira P.G., Patalano S., Chauhan R., Ffrench-Constant R., Gabaldón T., Guigó R., Sumner S. (2013) Transcriptome analyses of primitively eusocial wasp reveal novel insights into the evolution of sociality and the origin of alternative phenotypes. Genome Biol. 14 (2), 1–14Google Scholar
- Field J., Paxton R.J., Soro A., Bridge C. (2010) Cryptic plasticity underlies a major evolutionary transition. Curr. Biol. 20 (22), 2028–2031PubMedGoogle Scholar
- Fischman B.J., Woodard S.H., Robinson G.E. (2011) Molecular evolutionary analyses of insect societies. Proc. Natl. Acad. Sci. U.S.A. 108 (Supplement 2), 10847–10854PubMedPubMedCentralGoogle Scholar
- Fjerdingstad E.J., Crozier R.H. (2006) The evolution of worker caste diversity in social insects. Am. Nat. 167 (3), 390–400PubMedGoogle Scholar
- Foret S., Kucharski R., Pellegrini M., Feng S., Jacobsen S.E., Robinson G.E., Maleszka R. (2012) DNA methylation dynamics, metabolic fluxes, gene splicing, in alternative phenotypes in honey bees. Proc. Natl. Acad. Sci. U.S.A. 109 (13), 4968–4973PubMedPubMedCentralGoogle Scholar
- Fu F., Kocher S.D., Nowak M.A. (2015) The risk-return trade-off between solitary and eusocial reproduction. Ecol. Lett. 18, 74–84PubMedGoogle Scholar
- Gadagkar R. (1997) The evolution of caste polymorphism in social insects: genetic release followed by diversifying evolution. J. Genet. 76 (3), 167–179Google Scholar
- Gibbs J., Brady S.G., Kanda K., Danforth B.N. (2012) Phylogeny of halictine bees supports a shared origin of eusociality for Halictus and Lasioglossum (Apoidea: Anthophila: Halictidae). Mol. Phylogenet. Evol. 65, 926–939PubMedGoogle Scholar
- Gilbert S.F. (2012) Ecological developmental biology: environmental signals for normal animal development. Evol. Dev. 14 (1), 20–28PubMedGoogle Scholar
- Gilbert S.F., Bosch T. C.G., Ledón-Rettig C. (2015) Eco-evo-devo: developmental symbiosis and developmental plasticity as evolutionary agents. Nature Rev. Genet. 16, 611–622PubMedGoogle Scholar
- Glastad K.M., Hunt B.G., Yi S.V., Goodisman M.A.D. (2011) DNA methylation in insects: on the brink of the epigenetic era. Insect Mol. Biol. 20 (5), 553–565PubMedGoogle Scholar
- Glastad, K.M., Arsenault, S.V., Vertacnik, K.L., Geib, S.M., Kay, S., Danforth, B.N., Rehan, S. M., Linnen, C.R., Kocher, S.D., Hunt, B.G. (2017) Variation in DNA methylation is not consistently reflected by sociality in Hymenoptera. Genome Biol. Evol. doi: 10.1093/gbe/evx128 PubMedPubMedCentralGoogle Scholar
- Goldberg A.D., Allis C.D., Bernstein E. (2007) Epigenetics: a landscape takes shape. Cell 128, 635–638PubMedGoogle Scholar
- Grozinger, C.M., Sharabash, N.M., Whitfield, C.W., Robinson, G.E. (2003) Pheromone-mediated gene expression in the honey bee brain. Proc. Natl. Acad. Sci. 100 (Supplement 2), 14519–14525Google Scholar
- Harpur B.A., Zayed A. (2013) Accelerated evolution of innate immunity proteins in social insects: adaptive evolution or relaxed constraint? Mol. Biol. Evol. 30 (7), 1665–1674PubMedGoogle Scholar
- Harpur B.A., Kent C.F., Molodtsova D., Lebon J.M.D., Alqarni A.S., Owayss A.A., Zayed A. (2014) Population genomics of the honey bee reveals strong signatures of positive selection on worker traits. Proc. Natl. Acad. Sci. U.S.A. 111 (7), 2614–2619PubMedPubMedCentralGoogle Scholar
- Hirata M., Higashi S. (2008) Degree-day accumulation controlling allopatric and sympatric variations in the sociality of sweat bees, Lasioglossum (Evylaeus) baleicum (Hymenoptera: Halictidae). Behav. Ecol. Sociobiol. 62, 1239–1247Google Scholar
- Holbrook C.T., Clark R.M., Jeanson R., Bertram S.M., Kukuk P.F., Fewell J.H. (2009) Emergence and consequences of division of labor in association of normally solitary sweat bees. Ethology 115, 301–310Google Scholar
- Honeybee Genome Sequencing Consortium (2006) Insights into social insects from the genome of the honeybee Apis mellifera. Nature 443, 931–949Google Scholar
- Hunt J.H., Wolschin F., Henshaw M.T., Newman T.C., Toth A.L., Amdam G.V. (2010) Differential gene expression and protein abundance evince otogenetic bias toward castes in a primitively eusocial wasp. PLoS One 5 (5), e10674PubMedPubMedCentralGoogle Scholar
- Hunt B.G., Glastad K.M., Yi S.V., Goodisman M.A.D. (2013) The function of intragenic DNA methylation: insights from insect epigenomes. Integr. Comp. Biol. 53 (2), 319–328PubMedGoogle Scholar
- Jeanson R., Kukuk P.F., Fewell J.H. (2005) Emergence of division of labour in halictine bees: contributions of social interactions and behavioural variance. Anim. Behav. 70, 1183–1193Google Scholar
- Jeanson R., Clark R., Holbrook C., Bertram S., Fewell J., Kukuk P. (2008) Division of labour and socially induced changes in response thresholds in associations of solitary halictine bees. Anim. Behav. 76 (3), 593–602Google Scholar
- Johnson B.R., Linksvayer T.A. (2010) Deconstructing the superorganism: social physiology, groundplans, and sociogenomics. Q. Rev. Biol. 85 (1), 57–79PubMedGoogle Scholar
- Johnson B.R., Tsutsui N.D. (2011) Taxonomically restricted genes are associated with the evolution of sociality in the honey bee. BMC Genomics. 12 (164), 1–10Google Scholar
- Jones B.M., Wcislo W.T., Robinson G.E. (2015) Developmental transcriptome for a facultatively eusocial bee, Megalopta genalis G3 Genses Genom. Genet. 5, 2127–2135Google Scholar
- Jones B.M., Kingwell C.J., Wcislo W.T., Robinson G,E. (2017) Caste-biased gene expression in a facultatively eusocial bee suggests a role for genetic accommodation in the evolution of eusociality. Proc. R. Soc. B. 284 (1846), 1–9PubMedGoogle Scholar
- Kapheim K.M. (2016) Genomic sources of phenotypic novelty in the evolution of eusociality in insects. Curr. Opin. Insect Sci. 13, 24–32PubMedGoogle Scholar
- Kapheim K.M., Smith A.R., Nonacs P., Wcislo W.T., Wayne R.K. (2013) Foundress polyphenism and the origins of eusociality in a facultatively eusocial sweat be, Megalopta genalis (Halictidae). Behav. Ecol. Sociobiol. 67, 331–340Google Scholar
- Kapheim K.M., Pan H., Li C., Salzber S.L., Puiu D., et al. (2015) Genomic signatures of evolutionary transitions from solitary to group living. Science. 348 (6239), 1139–1143PubMedPubMedCentralGoogle Scholar
- Kocher S.D., Paxton R. (2014) Comparative methods offer powerful insights into social evolution in bees. Apidologie 45, 289–305Google Scholar
- Kocher S.D., Li C., Yang W., Tan H., Yi S.V., et al. (2013) The draft genome of a socially polymorphic halictid bee, Lasioglossum albipes. Genome Biol. 14 (12), 1–14Google Scholar
- Kocher S.D, Pellisier L., Veller C., Purcell J., Nowak M.A. et al. (2014) Transitions in social complexity along elevational gradients reveal a combined impact on season length and development time on social evolution. Proc. R. Soc. B. 281, 1–8Google Scholar
- Lawson S.P., Ciaccio K.N., Rehan S.M. (2016) Maternal manipulation of pollen provisions affects worker production in a small carpenter bee. Behav. Ecol. Sociobiol. 70 (11), 1891–1900Google Scholar
- Liang Z.S., Nguyen T., Mattila H.R., Rodriguez-Zas S.L., Seeley T.D., Robinson G.E. (2012) Molecular determinants of scouting behavior in honey bees. Science 335, 1225–1228PubMedGoogle Scholar
- Libbrecht, R., Oxley, P.R., Keller, L., Kronauer, D.J.C. (2016) Robust DNA Methylation in the Clonal Raider Ant Brain. Curr. Biol. 26 (3), 391–395PubMedPubMedCentralGoogle Scholar
- Li-Byarlay H., Li Y., Stroud H., Feng S., Newman T.C. (2013) RNA interference knockdown of DNA methyl-transferase 3 affects gene alternative splicing in the honey bee. Proc. Natl. Acad. Sci. U.S.A. 110 (31), 12750–12755PubMedPubMedCentralGoogle Scholar
- Lin N., Michener C.D. (1972) Evolution of sociality in insects. Q. Rev. Biol. 47 (2), 131–159Google Scholar
- Linksvayer T.A., Wade M.J. (2005) The evolutionary origin and elaboration of sociality in the aculeate Hymenoptera: maternal effects, sib-social effects, and heterochrony. Q. Rev. Biol. 80 (3), 317–336PubMedGoogle Scholar
- Luscombe, N.M., Madan Babu, M., Yu, H., Snyder, M., Teichmann, S.A, Gerstein, M. (2004) Genomic analysis of regulatory network dynamics reveals large topological changes. Nature 431 (7006), 308–312PubMedGoogle Scholar
- Lyko F., Foret S., Kucharski R., Wolf S., Falckenhayn C., Maleszka R. (2010) The honey bee epigenomes: differential methylation of brain DNA in queens and workers. PLoS Biol. 8 (11), e1000506PubMedPubMedCentralGoogle Scholar
- McKenzie S.K., Fetter-Pruneda I., Ruta V., Kronauer D.J.C. (2016) Transcriptomics and neuroanatomy of the clonal raider ant implicate an expanded clade of odorant receptors in chemical communication. P. Natl. Aca. Sci. USA. DOI: 10.1073/pnas.1610800113 Google Scholar
- Michener C.D. (1969) Comparative social behavior of bees. Annu. Rev. Entomol. 14, 299–342Google Scholar
- Michener C.D. (1974) The social behaviour of the bees: a comparative study. Harvard University Press, Cambridge, MAGoogle Scholar
- Michener C.D. (2007) The bees of the world, 2nd edn. Baltimore, MD: John Hopkins University Press.Google Scholar
- Miyanaga R., Maeta Y., Sakagami S.F. (1999) Geographical variation of sociality and size-linked color patterns in Lasioglossum (Evylaeus) apristum (Vachal) in Japan (Hymenoptera, Halictidae). Insectes Soc. 46, 224–232Google Scholar
- Molodtsova D., Harpur B.A., Kent C.F., Seevananthan K., Zayed A. (2014) Pleiotropy constrains the evolution of protein but not regulatory sequences in a transcription regulatory network influencing complex social behaviors. Front. Genet. 5 (431), 1–7Google Scholar
- Morandin C., Dhaygude K., Paviala J., Trontti K., Wheat C., Helanterä H. (2015) Caste-biases in gene expression are specific to developmental stage in the ant Formica exsecta. J. Evol. Biol. 28, 1705–1718PubMedGoogle Scholar
- Morandin C., Tin M.M.Y., Abril S., Gómez C., Pontieri L., et al. (2016) Comparative transcriptomics reveals the conserved building blocks involved in parallel evolution of diverse phenotypic traits in ants. Genome Biol. 17 (43), 1–19Google Scholar
- Nijhout H.F. (2003) Development and evolution of adaptive polyphenisms. Evol. Dev. 5 (1), 9–18PubMedGoogle Scholar
- Nowak M.A., Tarnita C.E., Wilson E.O. (2010) The evolution of eusociality. Nature 466, 1057–1062PubMedPubMedCentralGoogle Scholar
- Olejarz J.W., Allen B., Veller C., Gadagkar R., Nowak M.A. (2016) Evolution of worker policing. J. Theor. Biol. 339, 103–116Google Scholar
- Page Jr. R.E., Amdam G.V. (2007) The making of social insect: development architectures of social design. Bio Essays 29 (4), 334–343Google Scholar
- Patalano S., Vlasova A., Wyatt C., Ewels P., Camara F., et al. (2015) Molecular signatures of plastic phenotypes in two eusocial insect species with simple societies. Proc. Natl. Acad. Sci. U.S.A. 112 (45), 13970–13975PubMedPubMedCentralGoogle Scholar
- Peters R.S., Krogmann L., Mayer C., Donath A., Gunkel S., et al. (2017) Evolutionary history of the Hymenoptera. Curr. Biol. 27, 1–6Google Scholar
- Plateaux-Quénu C. (2008) Subsociality in halictine bees. Insectes Soc. 55, 335–346Google Scholar
- Plateaux-Quénu C., Plateaux I., Packer L. (2000) Population-typical behaviours are retained when eusocial and non-eusocial forms of Evylaeus albipes (F.) (Hymenoptera, Halictidae) are reared simultaneously in the laboratory. Insectes Soc. 47, 263–270Google Scholar
- Purcell J. (2011) Geographic patterns in the distribution of social systems in terrestrial arthropods. Biol. Rev. 86, 475–491PubMedGoogle Scholar
- Rehan, S.M., Richards, M.H. (2010a) Nesting biology and subsociality in Ceratina calcarata (Hymenoptera: Apidae). Can. Entomol. 142 (1), 65–74Google Scholar
- Rehan S.M., Richards M.H. (2010b) The influence of maternal quality on brood sex allocation in the small carpenter bee, Ceratina calcarata. Ethology 116 (9), 876–887Google Scholar
- Rehan S.M., Richards M.H. (2013) Reproductive aggression and nestmate recognition in a subsocial bee. Anim. Behav. 85 (4), 733–741Google Scholar
- Rehan S.M., Schwarz M.P. (2015) A few steps forward and no steps back: long-distance dispersal patterns in small carpenter bees suggest major barriers to back-dispersal. J. Biogeogr. 42 (3), 485–494Google Scholar
- Rehan S.M., Toth A.L. (2015) Climbing the social ladder: the molecular evolution of sociality. Trends Ecol. Evol. 30 (7), 426–433PubMedGoogle Scholar
- Rehan S.M., Richards M.H., Schwarz M.P. (2009) Evidence of social nesting in Ceratina of Borneo. J. Kans. Entomol. Soc. 82, 194–209Google Scholar
- Rehan S.M., Chapman T.W., Craigie A., Richards M.H., Cooper S.J., Schwarz M.P. (2010a) Molecular phylogeny of the small carpenter bees (Hymenoptera: Apidae: Ceratinini) indicates early and rapid global dispersal. Mol. Phylogenet. Evol. 55, 1042–1054PubMedGoogle Scholar
- Rehan S.M., Richards M.H., Schwarz M.P. (2010b) Social polymorphism in the Australian small carpenter bee, Ceratina (Neoceratina) australensis. Insectes Soc. 57 (4), 403–412Google Scholar
- Rehan S.M., Schwarz M.P., Richards M.H. (2011) Fitness consequences of ecological constraints and implications for the evolution of sociality in an incipiently social bee. Biol. J. Linnean Soc. 103 (1), 57–67Google Scholar
- Rehan S.M., Leys R., Schwarz M.P. (2012) A mid-Cretaceous origin of sociality in Xylocopine bees with only two origins of true worker castes indicates severe barriers to eusociality. PLoS ONE 7 (4), e34690PubMedPubMedCentralGoogle Scholar
- Rehan S.M., Berens A.J., Toth A.L. (2014a) At the brink of eusociality: transcriptomic correlates of worker behaviour in a small carpenter bee. BMC Evol. Biol. 14 (260), 1–10Google Scholar
- Rehan, S.M., Richards, M.H., Adams, M., Schwarz, M.P. (2014b) The costs and benefits of sociality in a facultatively social bee. Anim. Behav. 97, 77–85Google Scholar
- Rehan S.M., Tierney S.M., Wcislo W.T. (2015) Evidence for social nesting in Neotropical creatinine bees. Insectes Soc. 62 (2), 465–469Google Scholar
- Rehan S.M., Glastad K.M., Lawson S.P., Hunt B.G. (2016) The genome and methylome of a subsocial small carpenter bee, Ceratina calcarata. Genome Biol. Evol. 8 (5), 1401–1410PubMedPubMedCentralGoogle Scholar
- Richards, M.H. (2000) Evidence for geographic variation in colony social organization in an obligately social sweat bee, Lasioglossum malachurum Kirby (Hymenoptera; Halictidae). Can. J. Zool. 78, 1259–1266Google Scholar
- Richards, M.H. (2001) Nesting biology and social organization of Halictus sexcinctus (Fabricius) in southern Greece. Can. J. Zool. 79 (12), 2210–2220Google Scholar
- Richards M.H., Packer L. (1996) The socioecology of body size variation in the primitively eusocial sweat bee, Halictus ligatus (Hymenoptera: Halictidae). Oikos 77 (1), 68–76Google Scholar
- Rittschof C.C., Bukhari S.A., Sloofman L.G., Troy J.M., Caetano-Anollés D. et al. (2014) Neuromolecular responses to social challenge: common mechanisms across mouse, stickleback fish, and honey bee. Proc. Natl. Acad. Sci. U.S.A. 111 (50), 17929–17934PubMedPubMedCentralGoogle Scholar
- Robinson G.E. (2002) Sociogenomics takes flight. Science 297 (5579), 204–205PubMedGoogle Scholar
- Robinson G.E., Grozinger C.M., Whitfield C.W. (2005) Sociogenomics: social life in molecular terms. Nat. Rev. Genet. 6 (4), 257–270PubMedGoogle Scholar
- Romiguier J., Lourenco J., Gayral P., Faivre N., Weinert L.A., et al. (2014) Population genomics of eusocial insects: the costs of a vertebrate-like effective population size. J. Evol. Biol 27, 593–603PubMedGoogle Scholar
- Romiguier J., Cameron S.A., Woodard S.H., Fischman B.J., Keller L., Praz C.J. (2015) Phylogenomics controlling for base compositional bias reveals a single origin of eusociality in corbiculate bees. Mol. Biol. Ecol. 33 (3), 670–678Google Scholar
- Sadd M., Barribeau S.M., Bloch G., de Graaf D.C., Dearden P., et al. (2015) The genomes of two key bumblebee species with primitive eusocial organization. Genome Biol. 16 (1), 1–31Google Scholar
- Sakagami S.F., Maeta Y. (1984) Multifemale nests and rudimentary castes in the normally solitary bee Ceratina japonica (Hymenoptera: Xylocopinae) J. Kans. Entomol. Soc. 57 (4), 639–656Google Scholar
- Sakagami S.F., Maeta Y. (1987) Sociality, induced and/or natural, in the basically solitary small carpenter bees (Ceratina). Anim. Soc. Theor. Fac. 1-16Google Scholar
- Sakagami S.F., Maeta Y. (1989) Compatibility and incompatibility of solitary life with eusociality in two normally solitary bees Ceratina japonica and Ceratina okinawana (Hymenoptera: Apoidea), with notes on the incipient phase of eusociality. Jpn. J. Ent. 57 (2), 417–439Google Scholar
- Sakagami S.F., Maeta Y. (1995) Task allocation in artificially induced colonies of a basically solitary bee Ceratina (Ceratinidia) okinawana, with a comparison of sociality between Ceratina and Xylocopa (Hymenoptera, Anthophoridae, Xylocopinae). Jpn. J. Ent. 63 (1), 115–150Google Scholar
- Sakagami, S.F., Munakata M. (1972) Distribution and bionomics of a transpalaearctic eusocial Halictine bee, Lasioglossum (Evylaeus) calceatum, in northern Japan, with reference to its solitary life cycle at high altitude. J. Fac. Sci. Hokkaido Univ. Ser. VI. Zool. 18 (3), 411–439Google Scholar
- Schlichting C.D., Wund M.A. (2014) Phenotypic plasticity and epigenetic marking: an assessment of evidence for genetic accommodation. Evolution 68 (3), 656–672PubMedGoogle Scholar
- Schultz T.R. (2000) In search of ant ancestors. Proc. Natl. Acad. Sci. U.S.A. 97 (26), 14028–14029PubMedPubMedCentralGoogle Scholar
- Schwarz, M.P., Richards, M.H., Danforth B.N. (2007) Changing paradigms in insect social evolution: insights from Halictine and Allodapine bees. Annu. Rev. Entomol. 52, 127–150PubMedGoogle Scholar
- Schwarz, M.P., Tierney, S.M., Rehan, S.M., Chenoweth, L.B., Cooper, S.J.B. (2011) The evolution of eusociality in allodapine bees: workers began by waiting. Biol. Lett. 7 (2), 277–280PubMedGoogle Scholar
- Seger J. (1983) Partial bivoltinism may cause alternating sex-ratio biases that favour eusociality. Nature 301, 59–62Google Scholar
- Shell W.A., Rehan S.M. (2016) Recent and rapid diversification of the small carpenter bees in eastern North America. Biol. J. Linnean Soc. 117, 633–645Google Scholar
- Simola D.F., Wissler L., Donahue G., Waterhouse R.M., Helmkampf M., et al. (2013) Social insect genomes exhibit dramatic evolution in gene composition and regulation while preserving regulatory features linked to sociality. Genome Res. 23, 1235–1247PubMedPubMedCentralGoogle Scholar
- Simpson S.J., Sword G.A., Lo N. (2011) Polyphenism in insects. Curr. Biol. 21, 738–749Google Scholar
- Smith A.R., Wcislo W.T., O'Donnell S. (2003) Assured fitness returns favor sociality in a mass-provisioning sweat bee, Megalopta genalis (Hymenoptera: Halictidae). Behav. Ecol. Sociobiol. 54, 14–21Google Scholar
- Smith C.R., Toth A.L., Suarez A.V., Robinson G.E. (2008) Genetic and genomic analyses of the division of labour in insect societies. Nature Rev. Genet. 9, 735–748PubMedGoogle Scholar
- Soro A., Field J., Bridge C., Cardinal S.C., Paxton R.J. (2010) Genetic differentiation across the social transition in a socially polymorphic sweat bee, Halictus rubicundus. Mol. Ecol. 19, 3351–3363PubMedGoogle Scholar
- Soucy S.L. (2002) Nesting biology and socially polymorphic behavior of the sweat bee Halictus rubicundus (Hymenoptera: Halictidae). Ann. Entomol. Soc. Am. 95 (1), 57–65Google Scholar
- Soucy S.L., Danforth B.N. (2002) Phylogeography of the socially polymorphic sweat bee Halictus rubicundus (Hymenoptera: Halictidae). Evolution 56 (2), 330–341PubMedGoogle Scholar
- Southey B.R., Zhu P., Carr-Markell M.K., Liang Z.S., Zayed A., et al. (2016) Characterization of genomic variants associated with scout and recruit behavioral castes in honey bees using whole-genome sequencing. PLoS One 11 (1), e0146430PubMedPubMedCentralGoogle Scholar
- Standage D.S., Berens A.J., Glastad K.M., Severin A.J. (2016) Genome, transcriptome and methylome sequencing of a primitively eusocial wasp reveal a greatly reduced DNA methylation system in a social insect. Mol. Ecol. 25, 1769–1784PubMedGoogle Scholar
- Strassman J.E., Queller D.C. (1989) Ecological determinants of social evolution, in: Breed, M. D., Page, R. E. (Eds.) The genetics of social evolution. Westview Press, Boulder Colorado pp. 81–101Google Scholar
- Sumner S. (2014) The importance of genomic novelty in social evolution. Mol. Ecol. 23, 26–28PubMedGoogle Scholar
- Suzuki Y., Nijhout H.F. (2006) Evolution of a polyphenism by genetic accommodation. Science 311, 650–652PubMedGoogle Scholar
- Toth A.L., Rehan S.M. (2017) Molecular evolution of insect sociality: an eco-evo-devo perspective. Annu. Rev. Entomol. 62, 419–442PubMedGoogle Scholar
- Toth A.L., Robinson G.E. (2007) Evo-devo and the evolution of social behavior. Trends Genet. 23 (7), 334–341PubMedGoogle Scholar
- Toth A.L., Robinson G.E. (2009) Evo-devo and the evolution of social behavior: brain gene expression analyses in social insects. Cold Spring Harb. Symp. Quant. Biol. 74, 419–426PubMedGoogle Scholar
- Toth A.L., Varala K., Newman T.C., Miguez F.E., Hutchison S.K., et al. (2007) Wasp gene expression supports an evolutionary link between maternal behavior and eusociality. Science 318 (5849), 441–444PubMedGoogle Scholar
- Toth, A.L., Varala, K., Henshaw, M.T., Rodriguez-Zas, S.L., Hudson, M.E., Robinson, G.E. (2010) Brain transcriptomic analysis in paper wasps identifies genes associated with behaviour across social insect lineages. Proc. R. Soc. B Biol. Sci. 277 (1691), 2139–2148Google Scholar
- Toth, A.L., Tooker, J.F., Radhakrishnan, S., Minard, R., Henshaw, M.T., Grozinger, C.M. (2014) Shared genes related to aggression, rather than chemical communication, are associated with reproductive dominance in paper wasps (Polistes metricus). BMC Genomics 15 (1), 75PubMedPubMedCentralGoogle Scholar
- True J.R., Carroll S.B. (2002) Gene co-option in physiological and morphological evolution. Annu. Rev. Cell. Dev. Biol. 18, 53–80PubMedGoogle Scholar
- Waddington C.H. (1961) Genetic assimilation. Adv. Genet. 10, 257–293PubMedGoogle Scholar
- Wade M.J. (2001) Maternal effect genes and the evolution of sociality in haplo-diploid organisms. Evolution 55 (3), 453–458PubMedGoogle Scholar
- Wcislo W.T., Cane J.H. (1996) Floral resource utilization by solitary bees (Hymenoptera: Apoidea) and exploitation of their stored foods by natural enemies. Annu. Rev. Entomol. 41, 257–286PubMedGoogle Scholar
- Wcislo W.T., Danforth B.N. (1997) Secondarily solitary: the evolutionary loss of social behavior. Trends Ecol. Evolut. 12 (12), 468–474Google Scholar
- Wcislo W.T., Arneson L., Roesch K., Gonzalez V., Smith A., Fernández H. (2004) The evolution of nocturnal behaviour in sweat bees, Megalopta genalis and M. ecuadoria (Hymenoptera: Halictidae): an escape from competitors and enemies? Biol. J. Linnean Soc. 83, 377–387Google Scholar
- Weiner S.A., Toth A.L. (2012) Epigenetics in social insects: a new direction for understanding the evolution of castes. Genet. Res. Int. 2012, 1–11Google Scholar
- West-Eberhard M.J. (1987) Flexible strategy and social evolution. Anim. Soc. Theor. Fac. 35-51Google Scholar
- West-Eberhard M.J. (1989) Phenotypic plasticity and the origins of diversity. Annu. Rev. Ecol. Syst. 20, 249–278Google Scholar
- West-Eberhard M.J. (1996) Wasp societies as microcosms for the study of development and evolution, in: Turillazzi, S. & West-Eberhard, M. J. (Eds.) Natural history and evolution of paper-wasps. Oxford University Press, Oxofrd, pp. 291–317Google Scholar
- West-Eberhard M.J. (2003) Developmental Plasticity and Evolution. Oxford University of Press, OxfordGoogle Scholar
- Whitman D.W., Agrawal A.A. (2009) What is phenotypic plasticity and why is it important? In: Whitman, D. W., Ananthakrishnan, T. N. (Eds.) Phenotypic plasticity of insects: mechanisms and consequences pp. 1–63Google Scholar
- Wild G., Koykka C. (2014) Inclusive-fitness logic of cooperative breeding with benefits of natal philopatry. Phil. Trans. R. Soc. B. 369, 1–9Google Scholar
- Wilson E.O. (1971) The Insect Societies. Belknap Press of Harvard University Press, Cambridge, MassachusettsGoogle Scholar
- Wilson E.O., Hölldobler B. (2005) Eusociality: origin and consequences. P. Natl. Aca. Sci. USA. 102, 13367–13371Google Scholar
- Woodard S.H., Fischman B.J., Venkat A., Hudson M.E., Varala K., et al. (2011) Genes involved in convergent evolution of sociality in bees. Proc. Natl. Acad. Sci. U.S.A. 108 (18), 7472–7477PubMedPubMedCentralGoogle Scholar
- Woodard S.H., Bloch G.M., Band M.R., Robinson G.E. (2014) Molecular heterochrony and the evolution of sociality in bumblebees (Bombus terrestris). Proc. R. Soc. B. 281, 1–8Google Scholar
- Wyman L.M., Richards M.H. (2003) Colony social organization of Lasioglossum malachurum Kirby (Hymenoptera, Halictidae) in southern Greece. Insectes Soc. 50, 201–211Google Scholar
- Yan H., Bonasio R., Simola D.F., Liebig J., Berger S.L., Reinberg D. (2015) DNA methylation in social insects: how epigenetics can control behavior and longevity. Annu. Rev. Entomol. 60, 435–452PubMedGoogle Scholar
- Yanega D. (1989) Caste determination and differential diapause within the first brood of Halictus rubicundus in New York (Hymenoptera: Halictidae). Behav. Ecol. Sociobiol. 24, 97–107Google Scholar
- Yanega D. (1990) Philopatry and nest founding in a primitively social bee, Halictus rubicundus. Behav. Ecol. Sociobiol. 27, 37–42Google Scholar
- Yanega D. (1993) Environmental influences on male production and social structure in Halictus rubicundus (Hymenoptera: Halictidae). Insectes Soc. 40, 169–180Google Scholar
Copyright information
Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.


text: Maverickk 0 Report post Posted June 3 Hey guys, I was recently browsing kijiji and saw a '98 VFR 800 with what appeared to be large black honda wing vinyl stickers, akin to those found on the RVT1000R/RC51. I've never seen these on any VFR before but I thought they looked amazing. Before I could ask him where he got them, the ad was taken down. It's possible that they were fairings, though they looked like the stock red VFR panels, besides the large black lines/wings. Anyone have any clue where one could purchase these? Edit: Actually managed to find an image of it! Quote Share this post Link to post Share on other sites

subset: commoncrawl


text:
The highly-rated Caio Collet will race for R-ace GP in 2019 and with the backing of the Renault Sport Academy. … [Read more...] about Formula Renault 2.0
Formula 2 0 renault
Hyundai i30 N v Renault Megane RS v Volkswagen Golf GTI comparison
Renault and Volkswagen engineers had the great minds to think alike in 1976. Each group took their respective manufacturer's humble three-door hatchback and beefed up it with go-faster components – creating a whole new breed of affordable performance car for enthusiasts. It's the Volkswagen Golf GTI, however, rather than the Renault 5 Alpine (or 5 Gordini, as … [Read more...] about Hyundai i30 N v Renault Megane RS v Volkswagen Golf GTI comparison
Renault Clio RS 16
Renault has taken the wraps off the Clio RS 16 at the Monaco Grand Prix. The concept car – which celebrates Renault Sport's 40th anniversary and return to Formula 1 – is quite a special thing, because it's powered by the company's most potent engine. This is of course the 275 hp and 360 Nm 2.0 litre power unit as seen on the Megane RS 275 Trophy-R, … [Read more...] about Renault Clio RS 16
Renault Megane R26.R: Spotted
A week ago we discovered that the Renault Sport Megane Trophy has improved on the bar set by the standard 280 model. It's slightly quicker and slightly sharper than its lower-powered sibling, and therefore worthy of both its badge and the premium charged for it. But is it as incisive as the previous generation Trophy? Even with four-wheel steer and all the latest party tricks? … [Read more...] about Renault Megane R26.R: Spotted
McLaren Refugee Vandoorne Finds New Home In Formula E
A solid third of the grid in Formula E is made up of former F1 drivers. And now they'll be joined by another in the likes of Stoffel Vandoorne. The 26-year-old Belgian pilot worked his way up the formula racing ladder over the course of this decade, winning the F4 Eurocup, Formula Renault 2.0 Eurocup, and the vital GP2 championship (now known as Formula 2) along the way. … [Read more...] about McLaren Refugee Vandoorne Finds New Home In Formula E


text:
All those measures keep the worst excesses of judges in check. Obviously, a three-branch government is not enough to address Taiwan's present situation.
I look forward to the day when the Control Yuan can make an exit from our national scene, but the necessary conditions for this have not been met.
For Taiwan's justice system to become truly independent, the system needs a rub-down. The "dinosaur judges" have to go. As long as vermin and cancerous cells remain in our judiciary system, there will be endless trouble regardless of what judicial reform scheme we try.
LT: You have previously mentioned that you would gather a group of legal consultants. Who would this group consist of?
Chen: I have invited a group of friends who are legal professionals to form such a group. They include lawyers, judges, grand justices and legal academics, among others. I plan to meet with them once every two weeks, to ask them about things that are on my mind.
There are three kinds of "dinosaur judges" in Taiwan. The first kind bends the law to punish pan-green camp politicians, the second protects pan-blue camp members and the third protects KMT assets. My duty is to deal with these three kinds of "dinosaurs."
I will bring up these questions with the group of consultants.
After I launch an investigation I will need to write an investigation report. These things need to be done thoroughly. I will be attentive and cautious in exercising my authority. I will seek the advice of the consultants even with regard to how I carry out the investigations.
LT: What type of internal reform is needed in the Control Yuan?
Chen: In a book that was published last month I wrote that the Control Yuan needs to be comprehensively reformed. This should include the establishment of a committee to investigate the facts of historical injustices and enact their redress, and to focus on high-level political justice cases and take the initiative in prioritizing their investigation.
At the same time, this should see the reorganization of the Presidential Office's Human Rights Consultative Committee. I suggest that instead of its members being appointed by the Control Yuan president, the rules be changed so that Control Yuan members can also make suggestions regarding the appointments.
Also, when public servants are accused of misconduct, their cases are sent to the Judicial Yuan's Public Functionary Disciplinary Sanction Commission, but the commission is largely made up of judges. Facing the [prevalence of] "dinosaur judges," it is hard to avoid a situation in which officials cover up for each other and administer lenient punishments.
In 1977, then-Control Yuan member Tao Pai-chuan (陶百川) proposed that the president, the Control Yuan and the Judicial Yuan each appoint three members of the commission. Only in this way can you avoid "people investigating their own people."
Furthermore, under current regulations, allegations of misconduct are brought up by two Control Yuan members. Cases are investigated by another nine members, and the two members that brought up the case are not permitted to be involved in investigations or voting on the case. This is strange and not very rational.
I have read the Additional Articles of the Constitution (憲法增修條文) carefully and they do not stipulate any such rules.


text:
Hyipocrates investments company managed to bring the investment field to a new level.Their service conducts all major investment HYIP projects daily analysis while selecting the most profitable and
Posts by tags Paying
DOGEX LTD up to 180% After 1 days
We make investments in the high potential of the blockchain and cryptocurrency technology field accessible to all. You can take a step towards a prosperous future right now, you just need to sign up for an account on our website and make a deposit.
Coinsmex Limited up to 800.00% after 3 days
With the advent of cryptocurrency many entrepreneurs have noticed that this is not only a convenient payment method but also great source of income in the area of online investment.
ELSA Game up to 5% per week
ELSA is an international new generation social-oriented project that is controlled by an Artificial Intelligence of the same name, i. e. me.
HourBull LTD up to 20% - 30% hourly for 20 hours
HourBull Wallstreet Master Help you to earn Up to 20% Hourly Profit, You can just Make test deposit as low as $5,You will see profit grow hourly also you can withdraw instantly,We are also provide 3%~10% Commission.
Future Destination Company upto 1.5% for 50 days
Future Destination Company was founded recently. It all started with a small enthusiast's group, striving to realize mining field as well as create something more global than just an amateur farm at home.
Bitcoin Bum - Simple work to make money
Friends, we are immensely glad to inform you about the launch of the largest project! Bitcoin Bum is not just a game! Here you will meet sparkling humor, new friends, opportunities for earnings and in general you can have a great time.
Arca Global - 1,7% daily for 30 days
Arca Global company is operated by a group of financial experts who are willing to help common investors get higher profit than banks without any experience or risks.
InstaFxCopy investment guide from A - Z
Copy transaction is considered as a form of Forex trading, Electronic money, CFD stocks, CFD commodities according to the outstanding trends in the 21st century.
WEL CAPITAL - Stable income long-term project
Wel Capital is a project established in the Caribbean with a collection of experts from Europe (England, France, Germany, ..) in the field of financial transactions.
Happy world - Invest $50 to receive $2500
Today, I introduce to you a project that can X10 accounts. This is one of the few existing projects with a clear corporate legal entity. With instant payment method; You will receive money immediately upon withdrawal.
Alpha Trade upto rofit for 200%
Alpha Trade is an international investment company that has been successfully trading in financial markets for years. Alpha Trade performs brokerage operations with stocks and debt instruments, support of capital raising transactions, direct investments and asset management.
Agrosoft LTD generates profits up to 4% daily
Agrosoft LTD is a finance company that invests capital in the agricultural sector. The company's experts have developed a unique energy boost block, increasing the energy properties and reducing the fuel consumption of agricultural equipment


text:
*screams for an hour*
Okay, calming down. So look, we went and meet with Jill Ann Nelson, Licensed Clinical Professional Counselor, and fellow Tuff Muffer, to talk about life and wellness and health and habits and how to make change and dear god she crushed my soul when she said EVERYTHING COMES DOWN TO FOOD. And then we went and met with personal trainer Soli Santos and she was like, your BMI ain't right, STOP EATING ALL THE BAD SHIT.
Look, I'm Midwestern Healthy. I eat pizza and drink light beer and love tacos and Coke and CHEESE, and my favorite vegetable is corn. I don't want to "eat to live." I want to eat for pleasure. Am I doomed?
ELIZABETH: It's over, Adrienne. I think we need to pack up our bags and move to Alaska where our chubbs will be used as a tool for survival in the cold. I don't think Jill meant to hurt our feelings, but damn, she cold.
Jill's not a nutritionist, but she's been in the personal training field for 15 years. She knows that to make big changes you have to consider your mindset and your food. I'm 100% sure that it doesn't take a professional to know that my diet today was terrible. I ate 1.5 slices of cold pizza for breakfast, a bag of cheddar popcorn for a "snack," ironically a vegan taco salad with a half order of fries was lunch, then my afternoon snack was a mini 100 grand bar and some watermelon. Damn! I feel the shame wave coming AND I haven't even had dinner yet.
ADRIENNE: I feel like I'm on a Fat Heauxs Last Supper Tour right now. Like I just want to eat all the things before Fat Heauxs takes them away. Yesterday before our fitness assessment I ate a Happy Meal in the car with my kid. SHAME BELL.
But, Elizabeth, I seem to know plenty of adults who are naturally able to make healthy choices, like they just want to or something? Like they just want to eat vegetables. That's not me. I'M AN AMERICAN. So why does it come to some people more easily than others? Why is it so hard to make meaningful change?
This is me: single mom of an eight-year-old child who will eat about three things: chicken nuggets, mac and cheese, pizza. Worker of full time job at desk. Side project hustler of all the things. Generally over committed. Not a big drinker. So this is how I feel: I took care of my kid, I went to work, I'm a goddamn HERO and I DESERVE to eat pizza and watch TV right now.
ELIZABETH: Telling Soli what I consumed yesterday made me curl up into a ball. There are a lot of reasons that we can't shift our ideas on food and the number one is I DON'T WANT TO DO IT! I look forward to french fries and nachos and french fries ON nachos. Jill made a good point that we have to make a million decisions a day, so we have to prioritize where we're going to do the most thinking and when it comes to eating, that's my last priority. I mean it's food and it can be ordered while I'm in my period stained underwear while binge watching Mindhunter. In our society, they've really cut out the "hunting" portion of getting food. Shit, I don't even need to walk to the 7-11 for that stuffed Doritos. JUST KIDDING! I don't eat that. I'm a hard boiled egg and string cheese from the refrigerated section gal myself.
Jill and Soli talked to us a lot about the mindset. The why we don't make good choices when it comes to eating and the reason we're supposed to eat FOOD. I will admit that on most days, I'm eating my emotions. Like even when I decide to try to live with a diet, I eat that celery slice thinking about how it won't make me fat anymore or that it's "healthy" and therefore I'm being "good." I don't know how to change that.
ADRIENNE: I just sighed a big sigh. Like a defeated sigh. I mean I like want to do it, but like I haven't figured out a way to want to do it forever. Like I've done the Whole 30. And then as soon as it's done I'm like PIZZA and a week later I'm back to my regular life.
That decision making thing is a real problem for me. I have a million projects and responsibilities and I don't want to focus my time or brain on making a kale salad. I want to scratch my indulge-itch and eat bagels and cream cheese and a coke.
Also, DIETS. Like there are so many and how do you know where to begin or what to do or how to make it sustainable?? Like maybe I should be a vegetarian. But then there's paleo. And what about intermittent fasting (which just sounds like calorie restriction to me, but ok). How the hell are we supposed to sift through all the info and pick something?
And can I just say that most of the skinny people I know literally just don't eat that much. They don't like follow some serious diet, they eat like one hard boiled egg in the morning, a yogurt for lunch, and like some salad for dinner and BAM SKINNY AF. They restrict.
ELIZABETH: Some people Live to Eat and some people Eat to Live and those people - the Eat to Live people - should be punched in the face because stop being so snide, Eat to Live people. Again, this is all about mindset. I am definitely a Live to Eat person. Today's breakfast consisted of 3 Vosges chocolates, two hard boiled eggs, a handful of gummi bears, and two coffees. I'm not a nutritionist, but I know that's not right.
I guess where this all leads us is where do we start? Do we begin a food journal? Do we pick a diet and kick off with that? What is the plan on Whole 30 on day 45? What have other folks done to get on the right food track? MORE IMPORTANTLY, how have they maintained that because, bitch, I am not food prepping on Sunday. Sundays are reserved for Game of Thrones and cheese curds.
ADRIENNE: Maybe we should interview some of those Eat to Live people?? Like let's find out what makes these people tick and see if we can ever be like them???
ELIZABETH: I just told you I hate them.
ADRIENNE: I know. But they probably know what's up. Let's find some and see why it's so goddamned easy for them to be like, YAY MOTHERFUCKING KALE SALAD NO DRESSING TAP WATER I FEEL AMAZING!
Are you an Eat to Live person? Do you want to talk to us about it? Reach out at firstname.lastname@example.com. Or are you a person who's tried a million diets and you know some shit? EMAIL US. Because we're fucking upset y'all.


text: In this video blog post i'm going to teach you how to create an online business that makes money while you sleep. When you learn how to structure a business properly you should be making money even when you're not working. And for more tips on how to make money online make sure you check […] Read More


text:
Blending oil paints is different from blending other mediums because the paints take so long to dry. Because you have more time to adjust your blend, you can make a more even gradient between two colors. Once you've got a hand on blending two colors, you can shade (darken) or tint (lighten) your drawings, too. You don't have to be Monet or Van Gogh to blend oil paints beautifully!
Method One of Three:
Blending Two Colors
1Apply the two colors you want on opposite sides of each other. Use two separate brushes or clean your brushes between use to keep the two sides unmixed. Leave a gap in the middle of the two colors so you can create a smooth blend.[1]
Expert AnswerQ
- Try blending on a practice sheet before you work on your painting.
- How much paint you lay down depends on what texture you want to give the artwork. For a thicker texture, add more paint.
When asked, "How do you blend oil pants?"
Kelly MedfordPlein Air PainterEXPERT ADVICE
Kelly Medford, a plein air artist, responded: "One way to blend colors is to put one color a brushstroke next to the other that is very close in value. Keep applying one stroke next to another with colors that are very close so that the edges between them are visually soft. You won't have an abrupt change, but gradual changes."
2Mix the colors on your palette. This will be a combination of the same colors you laid down beforehand. Make the mixture as even as possible. Add the same amount of each color, and use your paintbrush to combine the colors smoothly.[2]
3Apply the mixed color between the two colors. Fill the blank space in the middle of the two colors entirely with the mixed color. Do not begin blending the colors quite yet. Wash out your paintbrush with paint thinner first so you can create a clean blend.
4Move your paint brush back and forth between the colors. Pretend you are drawing a "Z." Make your paintbrush go in a zig-zag pattern between the two unblended colors and your mixed color. Then, brush up and down between the colors. Watch the color carefully as it blends into the mixture in the middle.[3]
5Finish your painting as it dries. Unlike acrylics, you have time to blend your colors evenly. Add fresh paint on top of your colors if the paint dries early. This will make the paint wet and able to blend again. When you're satisfied with your blending job, set the painting somewhere safe to dry completely.
- Oil paint generally takes between 3-7 days to cure completely.[4]
Method Two of Three:
Shading Your Art
1Apply the object's base color first as an undertone. Your first coat of paint should be light so you can add shade on top without adding the paint on too thickly. When you're satisfied with the object's base color, you are ready to start shading.
- If you're painting an apple, for example, apply red paint to your drawing as an undertone.
2Determine which direction the light is coming from. You will apply shade to the opposite side of the object facing the light source. The parts of your object closest to the light source will be brightest, while the parts furthest away will have the most shade. Pick a spot for your light source and paint accordingly.[5]
3Find your paint's complimentary color. Although you can use black to shade your painting, a darker shade of the object's complimentary color will provide a more natural shadowing. Consult a color wheel and mix a dark shade on your palette (to be applied on your object).[6]
- If your object is a red apple, for example, choose a dark shade of green.
4Add a dark shade of that color to your object based on the lighting. Paint on the darker color to the parts of your object further from the light source. Then, blend the shade into your object by moving between the dark and light color with your paintbrush (in a zig-zag pattern) until the edges between the two colors are soft.[7]
- To shade an apple, for example, add dark green paint on the parts of the apple furthest from the light source.
Method Three of Three:
Tinting Oil Paints
1Determine your light source. Your object will be tinted where the light source directly hits the object. Choose a position for your light source and plan to tint the object accordingly. Mark your light source down so you don't forget as you paint and tint the wrong areas.
- Combine tinting and shading on your object for a more realistic sense of depth.
2Apply your base color. Much like shading, apply the base color to everywhere except the area you plan to tint. For that part, leave an unpainted patch to fill in later. You might sketch the object in strong lines beforehand so you can avoid painting over the potentially tinted area.
- Sketch the object in pencil, charcoal, or ink before you paint.
- If you are painting a banana, for example, add a yellow base color.
3Mix your base color with white on your palette. The intensity of your light source will determine how much white you add to your color. If your source is brilliant, like the sun, add a larger amount of white. If your source is dim, like a light bulb, add less.[8]
- For example: mix yellow and white if you are painting a banana.
4Paint your mixed color in the center of the empty space. Then, begin blending the base color and mixed paint by moving your paintbrush back and forth in a zig-zag pattern. Wait until your paint is evenly blended, then find a safe place for your canvas to dry.[9]
- As an example, apply the white-yellow mix to the empty space on a banana painting.
Community Q&A
- Always begin with a sketch before you paint and blend.
- Begin with small blending portions, and work your way up to larger sections as you get a better grip on blending.
- Wear clothes that you won't mind staining while working with oil paints.
- Choose two colors close to each other when you begin blending to practice, then move onto more complimentary color mixes later on.
About This Article
To blend oil paint, start by using separate brushes to apply the 2 colors you want to combine to your palette, making sure to leave a gap between them. Then, use a clean brush to add the same amount of each color to a different spot on your palette, and mix them until you get a smooth, new color. Next, apply the new color to the gap between the 2 original colors, then clean your paintbrush with paint thinner. After that, move your brush in a zig-zag pattern across the 3 colors, then up and down to thoroughly blend your new color.
- ↑ https://www.youtube.com/watch?v=cZQenv3xU4A&feature=youtu.be&t=95
- ↑ https://www.youtube.com/watch?v=cZQenv3xU4A&feature=youtu.be&t=106
- ↑ http://guidetooilpainting.com/blends.html
- ↑ http://salvagedinspirations.com/paint-dry-and-paint-cure/
- ↑ http://guidetooilpainting.com/shadows.html
- ↑ https://www.youtube.com/watch?v=MbafYVQWGgY&feature=youtu.be&t=79
- ↑ https://www.artistsandillustrators.co.uk/how-to/Floral-Nature/1492/how-to-paint-yellow-shadows
- ↑ http://guidetooilpainting.com/colorForm.html
- ↑ http://painting.yoexpert.com/oil-painting-techniques/add-depth-to-your-oil-painting-6012.html
Reader Success Stories
SA"Very good guide, simple and easy to understand."
RA"Excellent! Very clear and concise. "
AB"A well-explained, simple guide."


text:
Today, I went to see Marcia Williams at the Bath Festival, talking about her wonderful book, 'Three Cheers for Women'. She wrote the book to redress the balance as her book about inventors was mostly about men.
She told us that one of her favourite characters in the book is Wangari Maathai and seemed delighted when a little girl in the audience was able to tell everyone all about this amazing peace activist. The audience then voted on which character we wanted to find out more about and Frida Kahlo won!
Marcia challenged the children in the audience to think about how to create a comic book, reminding them not to repeat what is said in the illustrations with the words or vice versa. Excellent advice! With the help of the audience, she created a comic strip about bee, a young girl in the audience whose dream is to be a pop star.
It was lovely to see how she puts the ideas together to create her iconic comic book style.
When asked which character she would like to meet, Marcia found it hard to choose, but Jane Austen was certainly one of them and Frida Kahlo another 'because she's terrific!'
Another question was which of her books is her favourite. Her answer was 'Archie's War' and the follow up, 'My Secret War Dairy'. The photographs are of Marcia's relations, taken from family albums. She found she had to write the second book as her uncle whose photo became Archie, died on the first day of action he saw in the second world war, having grown up during the first. Marcia had to find out what happened to her Archie as he grew through the same experience.
It was such a lovely session, combining the joy of storytelling in pictures and words, which did much to inspire the next generation of children's author/ illustrators.
You can read our review of 'Three Cheers for Women' here.