DOI: 10.5061/dryad.2z34tmpq5
title: Diaspore traits specialized to animal adhesion and sea current dispersal are positively associated with the naturalization of European plants across the World

description: Understanding what drives non-native species naturalization (the
 establishment of a self-sustainable population outside its native range)
 is a central question in invasion science. Plants’ capacity for long
 distance dispersal (LDD) is likely to influence the spread and
 naturalization of non-native species differently according to their
 introduction pathways. These pathways include intentional introductions
 (for economic use, e.g. for agriculture), unintentional introductions
 (e.g. seed contaminants), plant dispersal via human infrastructures (e.g.
 roads), and plant spread from an adjacent region where the species was
 previously introduced. Herein, we tested the relationship between sets of
 LDD traits (syndromes) of 10,308 European plant species and their global
 naturalization incidence (i.e. whether a species has become naturalized or
 not) and extent (i.e. the number of regions where a species has become
 naturalized) using the most comprehensive database of naturalized plants
 worldwide (GloNAF). Diaspore traits allowed the identification of four
 traditional LDD syndromes, namely those with specializations for dispersal
 by: wind (anemochorous), animal ingestion (endozoochorous), attached to
 animals (epizoochorous), and sea currents (thalassochorous). These
 evolutionary specializations have been historically interpreted by
 biologists even though actual dispersal is not always related to diaspore
 syndromes. We found that while epizoochorous and thalassochorous traits
 are positively associated with global plant naturalization incidence,
 anemochorous and endozoochorous traits show a negative relationship.
 Species´ residence time outside their native range, their economic use and
 presence of epizoochorous traits (such as hooks, hairs and adhesive
 substances) are positively associated with global naturalization extent.
 Furthermore, we found that plants’ economic use reduces the influence of
 LDD syndromes on the naturalization incidence of intentionally introduced
 plants. While the success of non-native plants is influenced by a broad
 array of species- and context-specific factors, LDD syndromes play an
 important role in this context depending on the economic use of plants.
description: We used information on LDD syndromes from a comprehensive
 database of European Spermatophytes (Heleno & Vargas, 2015), which
 includes 10,308 species from 137 families native to Europe. Here, each
 species was assigned LDD syndromes based on diaspore (typically seeds and
 fruits) morphology, including five classes (Table 1). Diaspores with wings
 or pappus (plumose hairs), which facilitate dispersal by wind, were
 considered anemochorous. Diaspores with fleshy and nutritive tissues,
 which favor animal ingestion, were considered endozoochorous. Diaspores
 with hooks or sticky substances, which promote the external adhesion to
 animals, were considered epizoochorous. Diaspores with corky tissues or
 air chambers, which favor floatability and protection in saltwater, were
 considered thalassochorous. Finally, diaspores with no specialized
 dispersal structures for LDD were considered unspecialized (Heleno
 & Vargas, 2015). Since some plants show heterocarpy (production of
 different kinds of diaspores) and others show diaspore traits that
 facilitate LDD through more than one dispersal vector, we included both
 species with one and species with multiple LDD syndromes, following Heleno
 and Vargas (2015). In this way, we acknowledge the fact that some plants
 might take advantage of more than one LDD strategy. However, for
 comparison purposes we built a second LDD syndrome database where we
 considered only plants with a single LDD syndrome, discarding all plants
 with multiple LDD syndromes. Dispersal syndromes that favor short distance
 (local) dispersal, such as myrmecochory and autochory, were assigned to
 the unspecialized category because they are not relevant for LDD (Heleno
 & Vargas, 2015). We obtained distributional
 data of naturalized vascular plants from the GloNAF database v. 1.2, which
 includes information of 13,939 taxa and 1,029 regions, based on 210 data
 sources (van Kleunen et al., 2019). A region is defined here as the
 smallest geographic area for which a list of non-native plants is
 available (mostly countries, or distinct sub-national regions such as
 federal states or islands), including 648 mainland regions and 381 island
 regions. Species names in the GloNAF database have been standardized
 according to The Plant List (www.theplantlist.org). For merging the
 database on LDD syndromes with the GloNAF database, we also standardized
 species names to The Plant List by using the “TPL” function from the
 “taxonstand” package (Cayuela et al., 2012). We used two complementary
 proxies for naturalization success: naturalization incidence and
 naturalization extent (Razanajatovo et al., 2016). Naturalization
 incidence is a binary response variable (yes or no) that considers if a
 species has been recorded as naturalized outside its native range. For a
 given LDD syndrome the naturalization incidence is an indicator of the
 likelihood that a species with a particular LDD syndrome has naturalized
 outside its native range. From the 10,308 species in the LDD syndrome
 database, 2416 (23.44 %) were recorded as naturalized in at least one
 region according to the GloNAF database. For these 2416 species we
 estimated the naturalization extent: the number of GloNAF regions where
 each species is reported to be naturalized. This metric is an indicator of
 the capability to spread across large regions for a species with a
 particular LDD syndrome. A recent study (van Kleunen et
 al., 2020) has shown that economic use of plants increases their global
 naturalization success, likely because economic use of plants increases
 propagule pressure, particularly for intentional introductions (e.g. for
 horticulture). We propose that species with economic use and species
 without economic use are mostly under the influence of different
 introduction pathways (as defined by Hulme et al. (2008) and CBD (2014))
 (Figure 1). Species with economic use are mostly introduced intentionally,
 and then either intentionally released in nature (e.g. for erosion control
 or landscaping) or escape cultivation (mainly through seed dispersal)
 (Hulme et al., 2008; Harrower et al., 2018). Species without any economic
 use can be introduced accidentally by human vectors such as a contaminant
 of a commodity (e.g. as seed contaminant) or attached to (or within) a
 transport vector (e.g. in ships ballast water) (Hulme et al., 2008;
 Harrower et al., 2018). Alternatively, these species without economic use
 can disperse using human infrastructure that connects previously
 unconnected regions, or can colonize a region through unassisted dispersal
 from adjacent regions, where they were previously introduced (Hulme et
 al., 2008; Harrower et al., 2018). To test for the effect of the economic
 use of plants on naturalization incidence and extent, we used the dataset
 by van Kleunen et al. (2020) and assigned the 10,308 species from our LDD
 syndrome database, with which we estimated naturalization incidence and
 extent using GloNAF, into two groups – i.e. plants with and without
 economic use. We acknowledge that this is not a perfect proxy for
 introduction effort: some variation of introduction effort will not be
 explained by the economic use of plants. Further, the economic use of
 plants does not account for their accidental introductions by humans. In
 this regard, variations in propagule pressure (not explained by economic
 use) among species (Pyšek et al., 2015), for which we don’t have further
 data, may also influence naturalization patterns. To
 account for species’ residence time outside their native range, a key
 driver that favors plant naturalization (Pyšek et al., 2015; Fristoe et
 al. 2021), we used data on the date of first record for each species. We
 expected that plant species with earlier first record date would show
 higher naturalization extent because they had more residence time outside
 their native range. To estimate species´ minimum residence time outside
 their native range we used a global database of first record dates for
 non-native species compiled by Seebens et al. (2017) and updated by
 Seebens et al. (2018). This database includes first record dates for
 11,450 non-native vascular plants around the world. To test for the effect
 of the first record date on naturalization extent, we used the dataset by
 Seebens et al. (2017, 2018) and assigned the 2416 species from our LDD
 syndrome database, with which we estimated naturalization extent using
 GloNAF, their earliest first record date outside their native range. In
 other words, for each naturalized species we used its earliest record date
 anywhere in the world to account for its residence time outside its native
 range. We acknowledge that this approach has its limitations. First, data
 on first record are only available for a subset of regions around the
 world. Second, there may be a time lag between the introduction of a new
 species and its first record. Third, data on first record is only
 available for a subset of naturalized species around the world. Out of the
 2416 naturalized species in our LDD syndrome database we obtained data on
 their first record for 1986 species (83.23 %), so we restricted our
 dataset for analyses of naturalization extent to these 1986
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description: The files included are simple spreadsheets and no specific
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