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Checklist of the vascular alien flora of Catalonia (northeastern Iberian Peninsula, Spain)

This is an inventory of the vascular alien flora of Catalonia (northeastern Iberian Peninsula, Spain) updated to 2018, representing 1068 alien taxa in total. 554 (52.0%) out of them are casual and 514 (48.0%) are established. 87 taxa (8.1% of the total number and 16.8 % of those established) show an invasive behaviour. The geographic zone with more alien plants is the most anthropogenic maritime area. However, the differences among regions decrease when the degree of naturalization of taxa increases and the number of invaders is very similar in all sectors. Only 26.2% of the taxa are more or less abundant, while the rest are rare or they have vanished. The alien flora is represented by 115 families, 87 out of them include naturalised species. The most diverse genera are Opuntia (20 taxa), Amaranthus (18 taxa) and Solanum (15 taxa). Most of the alien plants have been introduced since the beginning of the twentieth century (70.7%), with a strong increase since 1970 (50.3% of the total number). Almost two thirds of alien taxa have their origin in Euro-Mediterranean area and America, while 24.6% come from other geographical areas. The taxa originated in cultivation represent 9.5%, whereas spontaneous hybrids only 1.2%. From the temporal point of view, the rate of Euro-Mediterranean taxa shows a progressive reduction parallel to an increase of those of other origins, which have reached 73.2% of introductions during the last 50 years. The most important way of introduction is gardening (58.0%), followed by agriculture and commerce, while forestry is marginal. Invasive taxa mainly come from gardening and trade, but the proportion of the latter that become invasive is higher (6.1% and 15.6%, respectively). Most of the established aliens are annual and perennial forbs, while other biological types are less represented. Annual and perennial forbs are also dominant among the invasive alien species, although there is a noticeable increase of trees and climbers.


Introduction
Biological invasions are a global phenomenon and comparison of geographically distant regions and their introduced biota is a crucially important methodological approach for elucidation of the determinants of invasiveness and invasibility (Pyšek et al., 2004). Our understanding of the general patterns of plant invasions substantially improved by means of comparative studies, such as checklists of exotic floras. Catalonia (northeastern Iberian Peninsula, Spain), has a native flora of 3745 taxa (species and lower taxonomic levels, incl. hybrids) (authors, unpublished data).
In the Mediterranean region, Catalonia has the singularity of having experienced an important industrialization since the nineteenth century, a factor that favoured intense trade by sea and land and, later, a strong urbanization of some parts of the territory. These changes have favoured conditions for the penetration of non-native flora. Another singularity in the Mediterranean area -also shared with some regions in southern France-is the beginning of botanical studies in the 17 th century and its continuity since the 19 th century, which has provided a good floristic knowledge over the last 150 years. As a result of these studies, three regional flora compilations have been published (Costa, 1877;Cadevall & Font Quer, 1913-1937Bolòs & Vigo, 1984-2001. The flora of Catalonia has also been recently covered by Flora iberica project (Castroviejo, 1986(Castroviejo, -2018, which is not yet concluded. All these floristic works also included data on allochthonous plants, although without any particular attention. Casasayas (1989), in the first and so far only synthetic work on alien plants in Catalonia, listed 461 taxa. Catalonia is also a part of the territory considered in the synthesis of the Spanish alien flora (Sanz et al., 2004), with a number of 845 species (Canary Islands excluded). The interest for allochthonous species has notably increased in the last decade, period in which the knowledge about escaped ornamental species has been noticeably improved. In the last years, the regional administration also promoted a database of exotic species in Catalonia that includes about 700 vascular plant taxa, dated on 14 th June 2019 (http://exocatdb. creaf.cat/base_dades/).
In this paper, the checklist of alien plant taxa in Catalonia is updated by incorporating new data accumulated in the lasts decades, reassessing the status of taxa resulting from improved knowledge. Moreover, the trends in the alien flora of Catalonia are analysed and compared to those of other areas in Europe.

The study area
Catalonia is a territory with an area of 32,108 km 2 (data from https://www.idescat.cat/) located in the northeastern Iberian Peninsula, Spain (Figure 1), between the Pyrenees Range and the Mediterranean Sea. The resident population is about 7.5 million inhabitants and the most important city is Barcelona. As for the whole of the Mediterranean area, the human influence on the landscape and vegetation is intense and ancient, with a high agricultural land-use for at least 3000 years.
Three major sectors with different natural and anthropic conditions are recognized: a) Littoral area: northeast-southwest strip between the Mediterranean Sea and the Catalan Coastal Range, with a width of 30-50 km and an area of about 14000 km 2 . The altitudes are generally less than 500 m asl, but they can reach more than 1500 m asl in some mountain areas. The climate and the vegetation are of Mediterranean type, from subarid to humid. The annual rainfall average is 400-600 mm in the southern half and 600-800 mm in the north, and exceeds 1000 mm in some mountains. This is the most populated sector in the studied area, in which the main cities are concentrated, and has a very high population density, c. 2,000 hab./km 2 in the central part (metropolitan area of Barcelona) and generally 100-200 hab./km 2 in the rest, although in the extreme south it falls to 50 hab/km 2 . A very large part of the surface is urbanized, but there are still important agricultural extensions and the mountains are mostly covered by woods and bushland. Most of the strict coastal strip was built between 1960 and 2000, for residential and tourist use, and has become an extensive suburban area. b) Inland area: Low and medium altitude lands (100-700 m asl, rarely up to 1000 m asl) located to the west of the Catalan Coastal Range. It is an area of about 10000 km 2 that is part of the large river Ebro Depression. The climate is Mediterranean, from subarid to subhumid, with a continental trend and an average rainfall from 350 mm (west) to 700 mm (east). The vegetation is of Mediterranean or sub-Mediterranean type, but historically it dramatically changed as a result of the heavy agricultural use of the territory that, at the moment, still occupies the greater part of the area. The average density of the population is about 70 hab./km 2 , higher in the eastern sectors (100-150 hab./km 2 ). Urban areas occupy a small percentage of the area. c) Pyrenees: Catalan part of the Pyrenean Range, to the north of the territory and with an area of about 8000 km 2 . It is a mountain area with an altitude generally higher than 1000 m asl and up to a maximum of 3140 m asl. The climate is of Mediterranean mountain type, with the exception of the NW extreme where it is Atlantic. Rainfall is generally 800-1200 mm (but only 600-700 in some inland valleys). Natural and semi-natural vegetation occupies most of the area and is generally extra-Mediterranean (sub-Mediterranean, Eurosiberian or Alpine). Historically, the valleys were very populated, but much of the population left in the second half of the 20 th century and nowadays the densities are low (5-30 hab./km 2 ), but there is a high residential houses and tourist movements.

Data source and taxonomic backbone
The data were obtained between 2013 and 2018, as a result of the process of elaboration of the Checklist of the flora of Catalonia (authors, unpublished data). The basis for the checklist is all published literature on plants from the studied area, which are mostly included in databases (especially the Banc de Dades de Biodiversitat de Catalunya: http://biodiver.bio. ub.es/biocat). In addition, herbarium material was revised and field research undertaken. The Euro+Med PlantBase serves as a taxonomic standard and backbone (with some exceptions) for this study. The taxonomic circumscription of the families follows PPG I (2016) for lycophytes and ferns, Christenhusz et al. (2011) for gymnosperms and APG IV (2016) for angiosperms.

Relative abundance
The current frequency of each taxon in Catalonia was assessed according to the following five categories (ranked by increasing order of abundance): Vanished (V): taxa not recorded for >50 years. Rare (R): <5 known localities. Scattered (S): few localities (typically <20) and locally scarce.
Locally abundant (L): few known localities but locally abundant.
Common (C): widespread and often locally abundant.

Definitions and degree of naturalization
We consider as alien plants those which arrival to Catalonia has been man-mediated, proven or inferred, in any historical time, or which have arrived to our area without the help of people from a nearby area in which they are alien. We do not consider as alien plants those that apparently arrived by natural long-distance dispersal (especially bird-dispersed aquatic plants). The alien taxa have been differentiated into three groups, depending on the degree of implantation in the studied area: Casual: Taxa that do not form self-sustaining populations. Generally they are represented by a few individuals that are observed in a short period of time, but in some cases they can also establish temporary populations that do not have midterm continuity.
Naturalised: Taxa that form populations apparently self-sustaining at mid-term, without direct intervention by people, or despite human intervention, in any of these two cases: 1) These populations are limited to anthropogenic habitats; 2) Populations are established in (semi)natural habitats, but much localized and they do not show a significant expansion. This category includes the taxa that usually occur in cultivated fields, some of which have been present for centuries (archeophytes). The naturalised populations are generally selfsustaining by sexual reproduction, but in some cases their persistence and expansion is only by vegetative multiplication.
Invasive: Taxa that have become naturalised and, in a second phase, have shown a clear expansive tendency in (semi)natural habitats of the territory, where they compete with the native flora. The attribution of this category in a functional-ecological sense does not imply that these plants are invasive species in the sense of IUCN (2000).
The categories of naturalised and invasive taxa form the group of established alien plants which can also be qualified as naturalised in a broad sense. They are already integrated into the flora of the territory or have a high probability of integration at mid-term.
Attribution to the categories produced some uncertainties which were resolved as followed: a) A specific taxon can have a different behaviour in several parts of the territory (e.g. invasive in one area but only casual in others); in this case, the highest observed category is assigned to the whole of the territory. b) For some species it is unclear if they are relics of cultivation or garden escapes; in such cases, they have been included if they show long-term persistence (typically >20 years) after garden abandonment. c) As elsewhere in the Mediterranean basin, it is often uncertain whether or not species that are present for centuries and currently basically linked to crops, are part of the native flora; the criterion adopted has been to consider as alien those that are only exceptionally observed outside of crops or other anthropogenic habitats; these plants basically correspond to what has traditionally been called archaeophytes, which may have been underestimated by the adopted criteria. Some examples of this problematic situation correspond to plants that usually occur in anthropic habitats but that often can also appear in natural or semi-natural habitats (Bunias erucago, Descurainia sophia, Diplotaxis erucoides, etc.).

Residence time
A period of introduction (well known or inferred) has been assigned to each species: Before 1500 AD. Period previous to large intercontinental trade, in which short distance trips predominated and plant imports came basically from Europe, the Mediterranean region and the Near East.
Between 1500 and 1900 AD. Period during which intercontinental trade became frequent and increased plant imports from oversea countries. The economy was still mostly based on agriculture, but in the 18th and 19th centuries an industrialization process began and there was a significant population increase.
Between 1900 and 1970 AD. A period of deep transformation of the territory, characterized by a strong industrialization, a very high population increase due to various migratory waves, its gradual concentration in urban areas near Mediterranean sea and the abandonment of the mountain areas.
After 1970 AD. Period in which some previous tendencies have been exacerbated, especially: a) Coastal urbanization, which became a nearly continuous urbansuburban landscape. b) A very high increase in the frequency of long-distance trade and intercontinental voyages.
Considering that the botanical knowledge of the territory is only accessible for the last 100-150 years, information on introduction time is almost nihil for the species arrived before 1900. Between 1900 and 1970 the floristic information much increased, but the attention for alien species was still limited, particularly for the casual taxa and the garden escapes. After 1970 the interest for allochthonous flora increased and data became more precise.

Geographic origin
Taxa have been classified according to their geographic origin (native range). One (or more) of these geographic origins are assigned to each alien taxa: Mediterranean (ME): Lowlands and mountains of the Mediterranean Basin (S Europe, N Africa, SW Asia).
Eastern and Southern Asia (AS): Temperate, subtropical and tropical areas, from Japan to India.
Tropical Africa (AF): African continent without Mediterranean and Cape regions.
South Africa (CA): Mainly plants of the Cape floristic region, but also from other regions of the Republic of South Africa. This group has been separated from the previous (AF) due to its singularity and because it is especially well represented in the studied area.
Australasia ( Spontaneous hybrids (Hyb): Hybrids or hybridogenous species that spontaneously originated in Europe with at least one alien parental species.

Introduction pathways
Four main introduction pathways are distinguished. The form of introduction is not more concise because in many cases knowledge is limited, especially for plants arrived before 1970.
Agriculture (A): Plants associated with the crops, introduced voluntarily to cultivate them or involuntarily as weeds.
Gardening (G): Garden plants. This category also includes some unusual orchard crops and some species used for "environmental restoration" in public works and aquarium species. Forestry (F): Trees planted in forested areas, with the aim of timber production or for other purposes.
Trade (T): Taxa that involuntarily arrived due to the transport of seeds mixed with goods.

Intentionality of introduction
A distinction is made between deliberate (D) or accidental (A) introductions. The taxa deliberately introduced are those that have been transported to Catalonia or the neighbouring areas voluntarily by man, usually for their use as crops, ornamental plants or other aims. The taxa accidentally introduced are those that have arrived involuntarily, generally by transport of seeds mixed with goods.

Life history
Only for the established alien species, we have assigned the plant growth form according to ten categories: annual grasses (AG), annual forbs (AF), perennial grasses (PG), perennial forbs (PF), bulbous monocots (BU), aquatic plants (AQ), climbers (CL), succulent plants (SU), shrubs (SH) and trees (TR). These categories follow those used in the synthesis of Pyšek et al. (2017), with the addition of the bulbous and the succulent.

Diversity of the alien flora, frequency of the taxa and degree of naturalization
The known alien flora of Catalonia is constituted of 1068 taxa at the species and subspecies levels, including those of hybrid origin (Appendix 1 and Table S1 in Supplementary Material). This represents more than twice that of the first synthesis of the Catalan alien flora (Casasayas, 1989). It also increases by 50 % the number of alien plants officially recognized by the Catalan administration which includes about 700 vascular plant taxa, dated on 14th June 2019 (http://exocatdb.creaf. cat/ base_dades/). We excluded from the list uncertain autochthonous taxa, which could be either alien (archaeophytes) or native plants.
In the European context, the number of taxa in Catalonia is situated in the upper range of the alien flora recorded in medium or large administrative territories (Lambdon et al., 2008), but it is far from the 1,969 taxa from Belgium (Verloove, 2006) with an extent similar to that of Catalonia.
Compared to other regions of the Mediterranean basin with a medium extent, the number of aliens detected is clearly higher than in Valencia in the Iberian Peninsula (663 taxa: Sanz et al., 2011), the island of Sardinia (541: Podda et al., 2012) or, in the Italian Peninsula, Lombardy (619: Banfi & Galasso, 2010), Veneto (539: Masin & Scortegagna, 2012) or Tuscany (597: Arrigoni & Viegi, 2011). It also far exceeds the data for Portugal as a whole, with an area three times larger but only 772 alien taxa (Domingues de Almeida, 2018). This result points to a high regional concentration of alien plants, although data from the different territories can not be fully compared. High diversity is probably linked with the ecological heterogeneity of the territory, to its intense anthropization and, also, to the relatively good knowledge of the local flora since the nineteenth century. Surprisingly, the number of alien taxa is much higher than that of Eastern Mediterranean countries: 387 in Greece (Bazos, 2017) or 340 in Turkey (Uludağ et al., 2017). This contrast between the two ends of the Mediterranean basin would be explained mainly by three factors: i) many alien taxa of Mediterranean origin found in the western Mediterranean region are native to the eastern Mediterranean, ii) the urbanization intensity of the territory is earlier and higher in the west than in the east, iii) a weaker and more recent floristic prospection in the eastern Mediterranean region.
The relative frequency of most taxa is low or very low. Half of them are rare (536 taxa), that is, they have been observed in less than five sites. Another 197 taxa have been classified as scarce because they have been detected in a higher number of sites but always in low number of individuals. It is assumed that the 55 taxa that are considered vanished were also rare or scarce in the past. The locally abundant species, restricted to few places, are 110 and, finally, 170 are considered common because they have a wide regional distribution and a large number of individuals. Overall, taxa that have achieved a major implantation in the territory (common + locally abundant) are 26.2 % and those that show little colonization success (rare + scarce + vanished) 73.8 %.
Regarding the degree of naturalization, about half of the known taxa (554) are casual aliens, 427 are considered naturalised and 87 invasive. The established aliens (naturalised + invasive) are 513, 48.0 % of the recorded taxa. This percentage is lower than that for the whole of Europe (65% according to data from Lambdon et al., 2008), but very similar to the 49.5% recently obtained in Italy (Galasso et al., 2018). The ratio of established aliens that have become invasive in Catalonia is 16.8 %, lower than in the Italian results (27.9%).
Established alien plants represent 12.0% of the whole currently known flora of Catalonia, which includes 4,259 taxa (at the species and subspecies levels, hybrids included) without taking into account casual alien taxa. This percentage is close to the average of 10% indicated by Pyšek et al. (2017) for temperate and Mediterranean zonobiomes in the continental areas of the Old World, although there are important differences between regions.
Regarding the geographical distribution pattern, the alien taxa are clearly more abundant in the littoral area (933 taxa) than in the inland area (439) and the Pyrenees (407) (Figure 2). This distribution is not surprising because the maritime fringe is the most anthropogenic area and with a more intense trade, factors that favour the arrival of new alien species and their establishment in anthropised environments. But this important difference between regions in the total number of alien taxa decreases if only established aliens are considered and it is very weak if the numbers of invasive species are compared ( Figure  2). These data suggest that casual aliens take advantage of the opportunities offered by the most disturbed areas, but that natural and semi-natural habitats show a similar resistance to alien colonization throughout the territory.

Residence time
The introduction time of the alien plants is estimated to be earlier than 1500 AD for 106 taxa. 207 taxa were introduced during the period 1500-1900, 218 taxa in the period 1900-1970 and 537 after 1970. A clear increase of introductions is observed after 1900, and especially in the last 50 years, with a temporary pattern similar to that for the whole of Europe (Pyšek et al., 2009). Taxa introduced after 1900 represented 70.7 % and that introduced after 1970 represent 50.3 %. This increase is probably genuine, but its extent is not well known, because the data prior to 1900 are deficient and the introductions could be underestimated, especially for casual aliens.
The percentage of taxa introduced in ancient times (archaeophytes) is 9.9 %. This rate is almost the same to that obtained for Italy, 9.8 % (Galasso et al., 2018). If we consider that there are 30 doubtful archaeophytes not incorporated into the list of alien plants, their percentage could rise to 12.7 %.

Geographic origin
The geographical origin of the alien flora is diverse ( Figure 5). One third comes from geographically nearby areas, located in the Mediterranean basin (19.7% of taxa) and other regions in Western Palearctic (12.4%). Another third is of American origin (17.5% in South America, 15.1% in North America). The plants from Asia and South Africa (10.8 and 7.5%) also have an outstanding participation, while those from tropical Africa, Australasia and Pantropicals do not reach 5%. The group of taxa artificially generated as crops or garden plants in different areas and times (9.5%) is also well represented. The taxa with spontaneous hybrid origin are negligible (1.2%).  The relative importance of each origin changes when the degree of naturalization is considered ( Figure 5). If only established taxa are considered, species from the Western Palearctic, South Africa and America increase their percentage, while those from Mediterranean and Asian origin decrease. The percentage reduction is even more marked for cultivated plants and spontaneous hybrids. In the transition between established to invasive there are further important changes. More than half (59.0%) of the invasive species are of American origin, and the most successful are those from North America. Their relative representation doubles (from 15.1% of the established to 36.0% of the invasives). The percentage of Asian plants also increases among invasive aliens, while for taxa with other origins it decreases.
Taxa of anthropogenic origin show very little capacity to become invasive, as they pass from 9.5% of the total to only 1.1% of the invasive aliens. Conversely, natural hybrids increase their representation (from 1.2% to 4.6%) thanks to the invasive behaviour of three Oenothera taxa and Symphytum uplandicum.
As it is predictable, temporal changes in the origin of the introduced plants are observed (Table 1, Figure  6). Until 1500 AD the allochthonous plants came from nearby geographical regions or were domesticated taxa. In the period 1500-1900, as a result of intercontinental trade, alien flora diversified with species coming from all continents, apparently with the exception of Australasian plants. This tendency intensifies between 1900 and 1970, a period in which Australasian species are already detected, and the total number of plants of distant geographical areas (outside Western Palearctic) reaches more than half of the aliens (62.0%). In the most recent period, after 1970, the rate of new species arrivals becomes higher and those of distant origin has increased to 73.2%. In all the periods after 1500, the species of distant regions come basically from America and Asia. The only exception are the South African plants, that reach a percentage of 12.9% in the post-1970 period, which must be attributed to the rise of the xerogardening in the urbanized areas of the Mediterranean coastline. The taxa from tropical Africa, Australasia or the pantropics always remained unimportant representations of less than 5%. The relative importance of the arrival of Mediterranean and Western Palearctic taxa has gradually decreased, being reduced to less than 20% in recent times. Anthropogenic taxa also decreased their representation after 1500, but then they maintained percentages of 6-9 %, which can be explained by the new introductions of agricultural species and garden cultivars.

Means of introduction
By far, the most common way of introduction has been gardening ( Figure 7), with 620 taxa or 58.0%, a percentage very close to that obtained in Valencia, also in the Iberian Mediterranean area, by Sanz et al. (2011). Garden introductions have become even more common in recent times, as it is the origin of 68.5% of taxa detected after 1970. This was a predictable result, because gardening has already been pointed out as the most important introduction way in Europe (Lambdon et al., 2008) and also at global scale (Bell et al., 2003). Other means of introduction have been agriculture (229 taxa), closely followed by trade (198 taxa). Agriculture was the main way by which the majority of plants (85%) arrived before 1500 AD. However, this way was progressively reduced and represents only 6.8% of introductions in the post-1970. Forestry has a marginal role as an introduction way, with just 21 taxa.
If we consider the intentionality of the introductions, 767 taxa (71.9%) have arrived deliberately and 299 (28.1%) accidentally (spontaneous hybrids in situ originated are excluded). The rates are very similar to those obtained for the whole of Europe (Lambdon et al., 2008). Usually, plants associated with gardening and forestry have been deliberately introduced and the species that arrived by trade accidentally, while those associated with agriculture are found in both categories.
Differences are observed in the degree of naturalization achieved by taxa introduced through different ways ( Figure 7). The relative importance of the plants introduced by gardening decreases in the established aliens and more among invasives, while in those arrived by trade the tendency is all the opposite. The relative frequency of those related to agriculture somewhat increases among the established plants, but decreases among invasives.
Around 40-60% of the taxa introduced by agriculture, gardening and trade establish viable mid-term populations (54.6%, 43.1 and 59.1 %, respectively), while the proportion is lower among forestry species (19.0%). Regarding invasive capacity, the trade plants are more successful (15.6% of the total number are invasive) than those of agriculture and gardening (7.0 and 6.1%), while those of forestry show an intermediate success (9.5%).

Life history of the established alien plants
The growth type has been taken into account only for established (naturalised + invasive) alien taxa. Figure  8 shows the percentage of each category among the total number of established aliens and among invasives.  For established alien taxa, the most common forms are the annual and perennial forbs, which together reach nearly half of the total number (45.0%). These two groups (and in the same order: annual-perennial) are also the most frequent on a global scale in continental regions . All other categories represent less than 10% of non-native taxa, and in the case of aquatic and bulbous plants they do not reach 5%. The frequency of succulent plants is outstanding because it is unusual in Europe, but has also been observed in the adjacent region of Valencia (Sanz et al., 2011) and is due to the important modern use of these plants in gardens of the Mediterranean coast.
Some changes in the percentages of diverse growth types are observed among invasive plants. Two categories (climbers and trees) clearly increase their relative frequency, so these growth forms seem to have more invasive capacity, probably because they are more competitive in the regional semi-natural habitats. On the contrary, the annual grasses, bulbous monocots, shrubs and succulents show a decrease. The low invasive fitness of bulbous and succulents is probably related to their weak dispersal capacity, since in the local context, it is very frequent that they only spread vegetatively. In the case of annual grasses and shrubs, the cause could be the heavy competition of native taxa, as these growth types are very common in the Mediterranean habitats.
Appendix 1. Checklist of the Catalonian vascular alien flora. Data are presented in the table with the following information fields: taxon (arranged alphabetically, incl. hybrid taxa), which are also organized alphabetically; family; degree of naturalisation (Nat. D.; C: casual; N: naturalised; I: invasive); geographic origin (Origin; ME: Mediterranean; WP: Western Paleartic; AS: Eastern and Southern Asia; TRO: Tropical and Subtropical regions; AU: Australasia; AF: Tropical Africa; CA: South Africa; NA: North America; SA: South America; Cult: Cultivated; Hyb: Spontaneous hybrids); abundance (Abun.; R: rare; S: scattered; L: locally abundant; C: common; V: vanished) and regional distribution (Pyr: Pyrenees; In: inland; Lit: littoral; +: presence confirmed; ?: uncertain presence). See also Table S1 in Supplementary material for information on residence time, introduction pathway and intentionality of introduction.
Scientific name Family Nat. D. Origin Abun.

Regional Distribution
. Acer negundo L.
Sapindaceae Amaryllidaceae Poaceae  Table S1. Checklist of the Catalonian vascular alien flora. Data are presented in the table with the following information fields: taxon (arranged alphabetically, incl. hybrid taxa, which are also organized alphabetically); family; residence time (