DOI: 10.5061/dryad.jm63xsj81
title: Traits data of exotic species in four tropical botanic gardens and adjacent natural forests

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 600 exotic species have
 been planted, we estimated the effect of four plant traits and time since
 species were introduced on: a) naturalization probability of
 exotic species; b) the abundance (density) of
 naturalized species in adjacent native tropical rainforests; and
 c) the distance that naturalized exotics have spread from the
 botanic gardens.   We found that specific leaf area
 (SLA) strongly differentiated 23 naturalized from 78
 non-naturalized exotic 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. 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 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 that
 naturalized from botanic gardens from those that did
 not; this is promising for developing trait-based risk
 assessment in the tropics. We suggest tropical botanic gardens
 avoid planting exotic species with fast carbon capture strategies and
 those that are shade tolerant, to limit the risk of invasion and
 spread into adjacent native forests.
description: The dataset consists of
 specific leaf area (SLA), height, seed mass, dispersal method, and
 residence time. We measured traits for every individual of the naturalized
 exotic species we detected (a total of 23 species and 913 individuals) and
 for non-naturalized exotics (195 individuals with the average and minimum
 number of individuals per species being 6 and 2 respectively).
 For SLA data of
 non-naturalized exotics, 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. For the remaining 60%, data were
 obtained from the ‘calibrated’ median height data available in
 botanical descriptions (e.g. http://www.efloras.org/ and http://hear.org).
 We transformed this information into height estimates as follows. First,
 we plotted measured heights against the corresponding median available in
 databases. Then, we fitted a model to describe the relationship between
 these two sources of information. We chose the best fitted model based on
 the largest r<sup>2</sup> value. Then, we ‘calibrated’ the height of the remaining 60% of exotic species based on the fitted model, using the median height secondary data from databases as the predictor variable. We did not measure seed mass directly because of limited fruit availability in the study sites during the survey period. Secondary seed mass data for naturalized and non-naturalized exotics were obtained from the Kew Seed Database (&lt;http://data.kew.org/sid/&gt;) and defined as 1000 dry seed mass (mg). When we did not find seed mass data for a species in the database, 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 categorized dispersal method as whether the plants are dispersed by animals or not. We classified growth-form of exotic 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;, 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 lag time between the introduction and establishment of an exotic species.