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Sixty-seven species newly recorded for the flora of Angola: recent findings from vegetation surveys and herbarium collections

Angola is a tropical country with many biogeographical units and, therefore, has a high floristic diversity. Although an increasing number of floristic studies has been carried out in Angola in recent years, the country is still considered to be underinvestigated as many species being collected were previously unknown there. Several scientific groups working in different parts of Angola contributed to this paper their data from biodiversity assessments. With this we can add 67 species newly recorded for Angola, including two new generic records and five alien species, to the almost 7,300 vascular plant taxa known so far for Angola. Most of the new records for Angola are also present in different neighbouring countries, but they are little known, and their IUCN threat status has not been assessed yet. However, ongoing fieldwork and exploration are needed to complete the floristic knowledge of the understudied country.


Introduction
Angola is a tropical country encompassing 15 terrestrial ecoregions that range from coastal deserts, through miombo woodland-grassland mosaics to dense Congolian rainforests (Burgess et al. 2004). Figueiredo et al. (2009) presented 6,735 indigenous plant species for Angola, with a rate of endemism of 14.8%. An extensive review of floristic research in Angola since the 17 th century was given by Goyder and Gonçalves (2019) and Figueiredo and Smith (2021), building on earlier summaries by Mendonça (1962) and Figueiredo and Smith (2008).
Although recent collections and descriptions of new species are adding more and more information (e.g. Hind and Goyder 2014;Darbyshire and Goyder 2019), knowledge on floristic diversity in Angola is still far from complete. The "Angolan Protected Area Expansion Strategy -APAES" (Huntley 2010) highlighted 11 areas of particular biological significance. According to Goyder and Gonçalves (2019), much recent botanical study has focused on these areas.
The floristic findings presented here were contributed by several scientific groups working in different parts of Angola (Fig. 1). The northern provinces are characterized by elements of both the Guineo-Congolian and the Zambezian Regions and form a Regional Transition Zone of high complexity (White 1983). Recent botanical studies in this region have focused on new records or species of vascular plants (Cheek et al. 2015;Abrahamczyk et al. 2016;Lautenschläger et al. 2020b, Smith and, ferns and lycophytes (Mezonda et al. 2020), and mosses (Müller 2015;Müller et al. 2018Müller et al. , 2019, or on the documentation of traditional knowledge regarding plant uses (Göhre et al. 2016;Lautenschläger et al. 2018Lautenschläger et al. , 2020a. Darbyshire et al. (2014) updated the checklist of the flowering plants, gymnosperms, and pteridophytes of Lunda-Norte Province provided by Cavaco in 1959. The Bié Plateau in Central Angola is characterized by an undulating, small-scale mosaic of wetlands, grasslands, and miombo woodlands. The upper catchment areas of some of the largest rivers in Angola are located there (Huntley 2019). This plateau is a diversity hotspot for geoxyles (Zigelski et al. 2019), and the heterogeneous landscape is rich in woody species in general (Monteiro 1970;Revermann et al. 2017a). East of the Bié Plateau lies the upper Zambezi basin, in which wide plains covered by savannahs and swamp forests get inundated annually (Huntley 2019). The seasonal inundations lead us to expect highly adapted plant species, but except for a general overview of the Cameia region of eastern Moxico Province (Zigelski et al. 2018), no comprehensive floristic work has been published so far.
The middle and lower Cubango (Okavango) river traverses the south-eastern corner of Angola and is fringed by open woodland and gallery forests. Some recent botanical work in this sparsely populated area has been done with regard to the impact of land use patterns (Wallenfang et al. 2015;Revermann et al. 2017b), while the botanical diversity of the Cuito headwaters was reviewed by Goyder et al. (2018). Further expeditions have taken place in the very arid south-western corner of Angola, where the northern part of the Namib Desert and Kaokoveld Center of Endemism is located. Several species, and even a genus new to science were described from this area recently (e.g. Van Jaarsveld and Van Wyk 2005; Swanepoel 2019; Tripp and Darbyshire 2020;Swanepoel et al. 2021). Even in well-studied, easily accessible areas like the escarpment viewpoint Tundavala near Lubango, botanical discoveries are ongoing (Hind and Goyder 2014), which stresses the need for further floristic assessments.

Study Area
Angola is a tropical country in southern central Africa with a size of 1.25 million km². Due to its location between the Congolian rainforests to the north, the miombo woodland region to the east, the Namib and Kalahari (semi-) deserts to the south, and the Atlantic Ocean to the west, Angola takes part in numerous African ecoregions. Collections from some of those ecoregions are presented in this article. Our collections from northern Angola have been made in rainforest fragments, wet savannahs, and limestone formations. In eastern Angola, collections stem from flooded savannahs and miombo woodlands, which are part of the Cameia National Park. In southern Angola, collections have been made in Baikiaea-Burkea woodlands (partly within the Bicuar National Park), in Afromontane grasslands, and in the coastal Namib desert (partly within Iona National Park). Lastly, collections in central Angola come from miombo woodland-grassland mosaics, and integrated wetlands. National parks are legally protected, but often only poorly so. Outside of national parks is mostly community land, which is not protected.

Methods
Unless otherwise stated, the new records are based on herbarium specimens that have been collected during scientific expeditions since 2000. Floristic research in Uíge Province has been conducted since 2012 in cooperation between the Universidade Kimpa Vita and the Technische Universität Dresden. The specimens are stored at the Herbarium Dresdense (DR). Duplicates will be transferred to Uíge as soon as suitable conditions including a herbarium are established. The biodiversity assessments in central, southern, and eastern Angola (Bié, Cuando-Cubango, Huíla, and Moxico Provinces) were conducted under the framework of The Future Okavango (TFO) (2011)(2012)(2013)(2014)(2015)(2016) and South African Science Service Centre for Climate Change and Adapted Land Management (SASSCAL) (2011-2020), while assessments in  Barbosa (1970). The numbers 2-6 combined with the letters A-H mark the locations of important habitats that are shown in Figure 2, and of the species depicted in Figures 3-6, respectively. Map made with QGIS v. 3.10.14.
south-western Angola (Namibe Province) are linked to BIOTA Southern Africa (2000. All Angolan specimens collected in the context of BIOTA, TFO, and SASSCAL are deposited at the Herbarium Hamburgense (HBG) in Hamburg. If sufficient material was available, a duplicate was made, which is stored at the herbarium LUBA in Lubango, Angola.
Additionally, herbarium specimens from LUBA were studied for new records: findings from the Namibe province in south-western Angola mostly trace back to work in the context of Skeleton Coast-Iona Transfrontier Conservation Area (SCIONA 2018), and to specimens deposited in the herbarium LUBA collected in 2009 by Ernst van Jaarsveld. Further collections stored at LUBA from David Goyder, Nigel Barker, Ralph Clark, and Nicola Bergh on the escarpment near Humpata, close to Lubango, Huíla province, also contributed two new records. We also studied six new records from the Hess collection, collected in 1951-1952 and being stored at the United Herbaria (Z+ZT) of the University of Zurich and ETH Zurich.
We used the Plants of the World Online database PoWO (2021) as source for accepted species names, taxon authorities, plant family affiliation and distributions, except for Pteridophyta where Hassler (2021) was used. The distribution of taxa presented in this study is characterized by four categories: localized -a taxon is endemic to one contingent ecoregion or country, e.g. a Katanga (D.R. Congo) endemic; regional -a taxon occurs within one contingent biome, e.g. in miombo woodlands; widely -a taxon occurs widely within Africa, distribution can be patchy, e.g. when occurring in disturbed places; beyond Africa -a taxon occurs also beyond Africa. The conservation status of each taxon was retrieved from the IUCN Red List database (2022). The indicated habitats are the habitats in Angola where the given samples were found.
All records were also cross-checked against the evidence in GBIF (2022, last cross-check in June 2022). Some species would be new records for Angola, as they are not listed in the checklist (Figueiredo and Smith 2008). They were not included in this study; however, if they are already documented in GBIF for Angola, or in publications newer than the checklist (e.g., Pavetta gardeniifolia Hochst. ex A.Rich var. gardeniifolia, Sher bournia hapalophylla subsp. wernhamiana (N.Hallé) Sonké & L.Pauwels).

Results
The present study documents records for 67 species newly reported for the flora of Angola, including two new generic records (Remusatia Schott and Cyclocarpa Afzel. ex Urb.). Of these, 62 are native species (1 Pteridophyta, 23 monocotyledons, and 38 dicotyledons) and five are neophytes (5 dicotyledons).
The records belong to 32 plant families, with mostly single to few records per family except for some larger families such as Commelinaceae, Cyperaceae, and Lamiaceae. 92.5% of the recorded species also occur in neighbouring countries. Five species show disjunct distribution patterns. Sixteen species have narrow and localized distributions (sub-ecoregion), and 25 have more regional patterns (supra-ecoregion). The remaining species show either wide often patchy intra-African distributions (18), or wide distributions also beyond Africa (8). An overview of the 67 species with information about their distribution patterns and IUCN conservation status is presented in Table 1. In the following text, the species are sorted by groups and families and alphabetically within the families.

Identification.
A medium-sized to large species of As plenium with fronds to ca. 50 cm long, with the genusspecific linear sori following the straight flabellate veins on the underside of the pinnae. This species is recognized by the dark brown petiole and rhachis and the particular shape of the pinnae, which are fan-shaped to rhomboid with a long-excurrent tip and serrate margins. The blade is not tapering at the tip but ends in an apical segment similar to the lateral pinnae. A regular epiphyte but also often found growing on rocks in full sun. Being a widespread species in Africa, its presence in Angola is not surprising. Distribution and habitat. Burundi, D.R. Congo, Kenya, Malawi, Mozambique, Rwanda, São Tomé and Príncipe, Sierra Leone, Sudan (MacLeay 1953), Tanzania, Uganda, Zambia (Hassler 2021). Rainforest. References. Schelpe (1977); Roux (2009 Identification. Chlorophytum sparsiflorum is a variable species with mostly unbranched inflorescences longer than the leaves, that carry about 2-5 flowers per node, with the pedicels jointed at or below the middle. Our specimen has about 5.0-6.5 cm broad leaves arranged in a rosette. It differs from similar species such as C. lan cifolium Welw. ex Baker and C. brachystachyum Baker, for example, in having a distinct petiole shorter than the leaf blade, a minutely scabrid inflorescence axis, and lax racemes. Distribution and habitat. Tropical Africa. Rainforest. References. Hepper (1968a); Meerts (2015). Figure  Reference. Kimpouni (1994).

Family Orchidaceae
Habenaria humilior Rchb.f. Figure 3F Examined material. Identification. Dicliptera carvalhoi Lindau encompasses 4 subspecies. This specimen is allied to subsp. laxi flora but differs in habit and may be a distinct taxon/ subspecies. The subspecies laxiflora shows at least some pedunculated umbels, with the primary peduncle up to 9(-16) mm long and not compounded into a verticillate synflorescence. Furthermore, the capsules are 5.5-6.5 mm long with seeds smooth or tuberculate (then the tubercles less dense and shorter than in subsp. erinacea).
The cymule bracts are 6.5-10.0 mm long. Hitherto, D. carvalhoi was only listed for Angola as doubtful . Distribution and habitat. Eastern miombo region. Montane grasslands and shrublands. References. Darbyshire (2008); Darbyshire et al. (2015). Identification. This species was previously considered to be endemic to Gabon where it grows as a rheophyte (Heine 1966;Sosef et al. 2006). The Angolan specimen is a good match for the type material, for example in the narrow lanceolate leaves and lax, long-pedunculate inflorescences. However, this species is closely allied to H. triflora (Forssk.) Roem. and Schult., which is one of the four species of Hypoestes previously recorded in Angola (Darbyshire 2015), and it may ultimately prove to be an extreme variant of that widespread species. Distribution and habitat. Gabon. Amongst rocks along streams and rivers. References. Heine (1966); Sosef et al. (2006); Darbyshire (2015).

Family Amaranthaceae
Calicorema capitata (Moq.) Hook.f. Figure 4A Examined material. Identification. This is a poorly known taxon of which only the original description and type material are available. The diagnostic leaves are markedly discoloured, with a pale golden-brown underside that is densely tomentose, whereas the upper side is dark brown-green and glabrous. Reference. Gonçalves (1987b Reference. Taylor (1932). Figure 3C Examined material. Reference. Hubner et al. (1963). Identification. Very few described species of Rotheca flower without leaves. Rotheca wildii is easily distinguished from other species by the bark being purplishgrey when young, becoming pale to dark greyish-brown and corky and longitudinally wrinkled when dry, with whitish prominent lenticels and concave cordate-elliptic to semicircular leaf scars surrounded by raised corky margins. Rotheca wildii is widespread, but this occurrence in Angola is disjunct being over 1500 km from the nearest other collections which are in Mazabuka and Chiwefwe Districts of in southern and central Zambia respectively and Nunga river area in north-western Botswana. Elsewhere, it is found on sandy soils around granite outcrops and on dry rocky hillsides in dry wooded grassland at 150-1500 m. Although the distribution is wide, the habitat is naturally fragmented and long-distance dispersal is the most likely cause of the disjunct pattern. Distribution and habitat. Botswana, Malawi, Mozambique, South Africa (Limpopo), Zambia, Zimbabwe. On limestone rock, 800 m.

Family Rhamnaceae
Helinus mystacinus (Aiton) E.Mey. ex Steud. Figure 5D Examined material.  Hutchinson et al. (1958b); Friis (1991). Identification. Also known as Urera flaminigiana Lambinon, but this genus was recently revised by one of the co-authors (see Wells et al. 2021) and is yet not changed in PoWO. With a distinctively dense covering of hairs on leaves, which are often tinted silver or reddish-golden. Inflorescences are compact corymbs, generally with a pronounced initial fork in the peduncle. Female flowers are subtended by a dense ring of stinging hairs, and the perianth is almost entirely fused, covering the entire ovary. Distribution and habitat. West tropical Africa, from eastern Nigeria to D.R. Congo. Rainforest. References. Sosef et al. (2018); Wells et al. (2021). Identification. Also known as Urera repens Wedd., but this genus was recently revised by one of the co-authors (see Wells et al. 2021) and is yet not changed in PoWO. The slender stems and trailing habit distinguish this species from the majority of Scepocarpus species, which are generally shrubby lianas growing to many metres in height. Also distinctive are the suborbicular to broadly cordate leaves and the compact corymbs. are broadly triangular at the base. Distribution and habitat. Tropical America. Often cultivated and escaped. Reference. Hutchinson and Dalziel (1954).

Discussion
This study provides records of 67 plant species that were not previously known from Angola. This is a remarkable number, which highlights the need for further surveys of old collections stored in herbaria, and for new plant collections from more remote areas.
In comparison, recent studies reporting new records in tropical regions list fewer species, e.g. 11 new records in Singapore (Lim et al. 2018), 23 from Shan state in Myanmar (Kang et al. 2018), or 55 from Santa Catarina, Brazil (Funez et al. 2017). Those studies focus on a single region, whereas our study combines the work of several groups working in Angola, thus providing more new floristic knowledge at once. This work adds to recent reports of new records (Lautenschläger et al. 2020b) and species (e.g. Swanepoel et al. 2021) in Angola, and we expect more to come if survey efforts will be increased, and/or more alien species are introduced (Rejmánek et al. 2017).
With their occurrence now confirmed in Angola, five species show a disjunct distribution pattern, with several hundreds to thousands of kilometres to the nearest known population, e.g. Senecio venosus and Cyperus longispicula. Several explanations are possible for such patterns, e.g. populations in between exist but have not been found yet; populations in between existed under past climatic conditions but are now extinct (Ehrich et al. 2007;Kuhn et al. 2016); long distance dispersal of seeds (Popp et al. 2011;Villaverde et al. 2015) or human transport and introduction (Hulme 2009).
For instance, Senecio venosus is found in humid Afromontane regions in western Angola, and far away South Africa/Eswatini. But from there, it ranges throughout the wetter eastern part of Southern Africa as far as southern Zambia, making the distance superable. The remaining gap might be conquerable via aerial seed dispersal, of which particularly Asteraceae species are capable of, because of their pappi (Muñoz et al. 2004).
Similarly, Rotheca wildii is known from elevated rocky sites in southern East Africa, and the population nearest to the Angolan one is in Zambia, 1500 km away. Since Rotheca does not have wind dispersed seeds, this distribution pattern is more likely caused by animal dispersal (Popp et al. 2011), or by a broader corridor of Afromontane habitats in this area during the Pleistocene (Allen et al. 2021).
Several findings from eastern Angola (Moxíco) represent logical range extension from similar and contingent habitats in western Zambia and southern D.R. Congo, being part of the Flora zambesiaca area. Eriocau lon glandulosum for instance was originally collected in wetlands directly at the Angola/D.R. Congo boarder, but on the Congolian side; we collected it approximately 180 km away from this place in similar habitats on the Angolan side. Such patterns are not surprising as Angola, and particularly Eastern Angola, are floristically still little explored (Goyder and Gonçalves 2019).
Within our study, we identified two species hitherto thought to be endemic to D.R. Congo as new records for Angola (Commelina robynsii and Vernonia luala baensis), thereby expanding their geographic range. Both are poorly sampled and little-known species. Therefore, we provide additional information about their habitat and distribution. Commelina robynsii, Vernonia luala baensis, and Dolichos subcapitatus var. angustifolius are known from the Upper Katanga (copperbelt) area, where metal-rich soils promote a unique flora (Malaisse et al. 2016). In Angola, they occur in comparable woodland-grassland mosaics on shallow bedrock (Bié Plateau), where the soils have a lower metal content and are rather dominated by iron/aluminium than by copper/cobalt (Gröngröft 2013). More than 900 km including the Zambezi graben separate these populations, but this Katanga-Bié distribution pattern has been reported before, for example for the Asteraceae Schistostephium crataegifolium (DC.) Fenzl ex Harv. .
Many of the new records from Uíge presented here have a Guineo-Congolian background. This is because the mountain ranges in Uíge are covered by evergreen tropical forest and represent an exclave of the Guineo-Congolian Floristic Region (Lautenschläger et al. 2020b). Probably, the exclave is a remnant of a broader expanse of montane habitats in the Pleistocene, when a corridor of evergreen tropical forests likely spanned from Cameroon over Angola to East Africa (Allen et al. 2021). The finding of a high number of new records in Uíge province in the recent past reflects increasing research effort, but also improved accessibility into the steep mountain ranges by logging companies (Lautenschläger pers. obs.). However, increasing uncontrolled deforestation, agroforestry and bushmeat hunting (Teutloff et al. 2021) follows this improved access.
Four of the five newly documented alien species originate from the Neotropics. The only neophytic species of Asian and northern Australian origin, Brucea javanica, was already documented for the provinces of Kinshasa and Équateur in the adjacent D.R. Congo (GBIF 2022).
It was found in savannah at the edge of a village and may well have been introduced to Angola from the D.R. Congo recently by local people because of its medicinal properties (Chen et al. 2013).
All of the five alien species new to Angola are already known from tropical Africa. Lantana horrida subsp. tili ifolia was up to now only found in Zambia and Burundi. Amaranthus tortuosus was already found in West Africa (Benin, Cote d'Ivoire, Senegal, and Burkina Faso) as well as in East Africa (Tanzania and Rwanda). It may have escaped from cultivation as a green vegetable for human nutrition or as a medicinal herb (CABI 2021). According to the CABI website, several African countries list A. tortuosus as invasive. Still, neither this species nor the remaining ones are listed as invasive by the IUCN Global Invasive Species Database (ISSG 2015).
Unless Angola's number of naturalised aliens compared to Zimbabwe and South Africa is still rather modest (Rejmánek et al. 2016;Spear et al. 2013;Smith and Figueiredo 2017;Figueiredo and Smith 2022), constant monitoring in the future is needed as higher rates are to be expected due to decreasing isolation of the country.
Only 10 of the 67 listed taxa are assessed for the IUCN Red List (2022) ( Table 2). Two of these are categorized as Vulnerable with unknown population status (Hypoestes potamophila and Pterygota bequaertii). The finding of additional populations and areas of occurrence in Angola will therefore improve their conservation status. This kind of information is urgently needed for reliable updated assessments. Seven taxa are listed as least concern, the remaining 58 taxa are stable, or their population trend is unknown. Thus, the conservation status of 85% of the species presented here is not assessed yet, which sadly is representative of many other tropical regions globally, where status of plant species is Data Deficient (Brummitt et al. 2008). For instance, 15 of the taxa presented here that where not assessed for the IUCN Red List show localized distributions (Table  1). This could be threatening for the taxa when their area of occurrence is experiencing habitat loss and/or climate change (Brooks et al. 2002).
Angola is undergoing rapid land use change and intensification since the end of the civil war, often in an uncontrolled way resulting in habitat degradation and loss. It has one of the highest rates of tree cover loss in Africa due to poorly controlled and increasing extraction of natural resources (Hansen et al. 2013;Catarino et al. 2020). Chiteculo et al. (2018) states that clearance for timber and charcoal production heavily affects the miombo region. In the northern area of the country, agricultural activities and sand mining are additional threats. The seasonally flooded savannahs in the Moxíco province have been targeted for large-scale rice plantations, even within the Cameia National Park (Chiambo et al. 2019;Finckh and Meller pers. obs.). On top of that, southern Angola is expected to get warmer and drier in the near future due to climate change (Barros et al. 2014).
With most of the Angolan flora not assessed by the IUCN Red List, it is difficult to predict which effect this habitat loss will have on single species (Brooks et al. 2002). However, established and highly specialized species seldom benefit from habitat loss, and it is much more likely that generalist or invasive species will be at an advantage (Marvier et al. 2004). With ongoing fieldwork and exploration in Angola additional new records are very likely to be documented. However, time is of the essence as several habitats are at high risk of irreversible change, degradation or destruction from different human activities and climate change. collectors. The University Kimpa Vita was an essential base for our fieldwork in northern Angola and provided logistical support. We are also grateful to the Botanical Garden of the TU Dresden for cultivating plants until essential characters for identification had developed. The fieldwork in Angola was supported by the program "Strategic Partnerships" of the TU Dresden. The published results were obtained in collaboration with the Instituto Nacio-