DOI: 10.5061/dryad.gqnk98sm5
title: Traits data of naturalized and non-naturalized alien species of four Indonesian Botanic Gardens

description: The establishment of new botanic gardens in tropical regions highlights a
 need for weed risk assessment tools suitable for tropical ecosystems. The
 relevance of plant traits for invasion into tropical rainforests has not
 been well studied.  Working in and around four botanic gardens in
 Indonesia where 590 alien species have been planted, we estimated the
 effect of four plant traits, plus time since species introduction, on: a)
 the naturalization probability and b) abundance (density) of
 naturalized species in adjacent native tropical rainforests; and
 c) the distance that naturalized alien plants have
 spread from the botanic gardens.   We found that
 specific leaf area (SLA) strongly differentiated 23 naturalized from 78
 non-naturalized alien species (randomly selected from
 577 non-naturalized species) in our study. These trends may
 indicate that exotics with high SLA benefit from at least two factors when
 establishing in tropical forests: high growth rates and occupation of
 forest gaps. We also found that height was unrelated to
 naturalization probability, but naturalized aliens were having high SLA
 and were short.  Exotic species that
 were present in the gardens for over 30 years and those
 with small seeds also had higher probabilities of becoming
 naturalized, indicating that garden plants can invade the understorey of
 closed canopy tropical rainforests, especially when invading species are
 shade-tolerant and have sufficient time to establish. On average, exotic
 species that were not animal dispersed spread 78 m further into the
 forests than animal-dispersed species. We did not detect relationships
 between the measured traits and estimated density
 of naturalized exotics in the adjacent forests. Synthesis: Traits
 were able to differentiate exotic species from botanic gardens that
 naturalized in native forest from those that did not; this is promising
 for developing trait-based risk assessment in the tropics. To limit the
 risk of invasion and spread into adjacent native forests, we
 suggest tropical botanic gardens avoid planting exotic species
 with fast carbon capture strategies and those that are shade tolerant.
description: Trait data collection involved a combination of measurements in
 the field and extracting data from the following repositories: Global
 Biodiversity Information Facility (gbif.org), Hawaiian Ecosystem at Risk
 (hear.org), efloras.org, and Biodiversity Heritage Library
 (biodiversitylibrary.org) (plant description only, did not include
 herbarium collections). We measured SLA for every
 individual of the naturalized alien species we detected (a total of 23
 species and 913 individuals) and for non-naturalized aliens (195
 individuals with the average and minimum number of individuals per species
 being 6 and 2 respectively). SLA values at the individual level were
 averaged (without prior transformation) and then we calculated the mean
 value within each species to obtain mean SLA values at the species
 level. For SLA data of non-naturalized aliens, we sampled shaded leaves
 instead of fully sun-exposed as suggested by Pérez-Harguindeguy et al.
 (2013) to avoid bias toward environmental differences between shaded
 forests and open areas of botanic gardens. Plant height
 (m) was measured following the method suggested by Pérez-Harguindeguy et
 al. (2013). Not all height data were obtained from direct measurement
 during surveys due to measurement difficulties in the field. Direct
 measurements were conducted for 40% of the species (i.e. 40/102 species).
 All of the 40 directly measured species were mature individuals, and were
 exist in relatively common environmental conditions. For the remaining 62
 species, we collected median height data from botanical descriptions (e.g.
 http://www.efloras.org/ and http://hear.org), and then calibrated these
 data using data we collected in the field for the other 40 species.  We
 did this calibration using the following process: First, we plotted the
 average of heights from direct measurement (39 species) against the median
 height value from the databases of the same 39 species  (Figure S9). Then,
 we fitted a model to describe the relationship between these two sources
 of information (direct measured height data and database height data). We
 chose the model with best fit based on r2 values (Table S10). Then, we
 ‘calibrated’ the height of the remaining 62 alien species based on the
 fitted model, using the median height data from databases as the predictor
 variable. The scatter plot between the model prediction and the real data
 presented in Figure S11. We did not measure seed mass
 directly because of limited fruit availability in the study
 sites during the survey period. Secondary seed mass data (mg) for
 naturalized and non-naturalized aliens were obtained from the Kew Seed
 Information Database (&lt;http://data.kew.org/sid/&gt;). When we
 did not find seed mass data for a species in the databases (i.e.
 33/102 species), we used the average data of the corresponding genus (29
 species) or family (4 species) from the same database, using a minimum of
 30 other species. We included dispersal method, origin
 and growth-form as categorical variables. We categorized dispersal method
 as whether the plants are dispersed by animals or not. We focused on
 animal dispersal because animals are suggested as important vectors for
 tropical invasion (Swarbrick, 1993; Dawson et al., 2011). The origin of
 aliens denotes whether the species is native to a tropical or non-tropical
 region. We classified species into tropical vs non-tropical categories
 because we expected that tropical plant species would be more likely to
 naturalize in tropical forests than non-tropical species because of
 habitat suitability (i.e. the study region is tropical). Finally, we
 classified growth-form of alien plants into herbs, shrubs, and trees (we
 excluded other growth forms, including ferns and vines, due to very low
 detection rates). Data on dispersal method, origin, and growth-form
 were collected from databases, including
 &lt;http://data.kew.org/sid/&gt;, &lt;http://www.ars-grin.gov/&gt;, &lt;http://www.gbif.org&gt;, &lt;http://www.pfaf.org/&gt;, and &lt;http://www.hear.org/pier/&gt;.  Information on minimum residence time, i.e. the number of years elapsed since the species was first known to be present in the botanic gardens to the date of the survey was obtained from botanic gardens’ catalogue collections (Cibodas: 1930, 1963, 1977, and 1988; Bali: 1989, 1999, and 2006) and planting date official records (Kuningan and Baturraden). We used minimum residence time in our analyses to account for the potential lag time between the introduction and establishment of an alien species.
description: We used ImageJ in this study to measure leaf area from leaf photo
 data.