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Data from: Different functional characteristics can explain different dimensions of plant invasion success

Citation

Liao, Huixuan et al. (2020), Data from: Different functional characteristics can explain different dimensions of plant invasion success, Dryad, Dataset, https://doi.org/10.5061/dryad.tmpg4f4xd

Abstract

The success of invasive plant species can be evaluated using different dimensions, such as, range size, abundance, and impact. These different dimensions do not always covary but are rarely separated, suggesting an urgency to disentangle the functional mechanisms behind them.

A dataset of leaf traits and four dimensions of invasion success (i.e., range size, local abundance, impact on native plant abundance, and impact on native plant diversity) were compiled for 395 non-native plant species in the US and Europe. Associations among dimensions of invasion success and between leaf traits and dimensions were analyzed with general linear models (LMs) and supplemented by phylogenetic generalized least square (PGLS) models, which control for the phylogenetic relatedness across species.

The pair-wise associations between most pairs of invasion dimensions were weak or neutral. The only exception was the association between impact on native plant abundance and impact on native plant diversity, which was strongly positive. Traits of species that have large range sizes were associated with a high metabolic rate; whereas, traits of species that were abundant or had a strong impact at the local scale were associated with low metabolic rate. In addition, traits of species with a large range size or having strong impacts on native plant abundance were associated with acquisitive strategies; whereas, traits of species with a high local abundance or strong impacts on native plant diversity were associated with conservative strategies.

Synthesis: Different dimensions of invasion success were associated with different functional traits. Invasion success at the regional scale was related to traits that promote rapid colonization; whereas, invasion success at the local scale was related to traits that are potentially less preferred by herbivores. Some locally successful invaders even possessed traits that facilitate a high-stress tolerance and conservative strategy, which were similar to locally abundant native species. Therefore, an ambiguous definition of “invasion success” in mechanism-related studies may produce inconsistent or even controversial conclusions, highlighting the importance of separately studying different dimensions of invasion success.

Methods

Four dimensions of invasion success were calculated: two occupancy and abundance dimensions (range size and local abundance) and two impact dimensions (impact on native plant abundance and impact on native plant diversity). The range size of each non-native species was quantified as the relative occurrence frequency of the focal species which was based on the number of equal-sized grid cells occupied by each species in its non-native range, and was projected from the geographic records in the Global Biodiversity Information Facility (GBIF) (https://www.gbif.org/). The local abundance of each non-native species was calculated as the median percent cover of the focal species across all sites that it occurred. The impact of each non-native species on native plant abundance (or diversity) was quantified as the cover (or diversity) loss of native species due to a 1% increase in the cover of the focal species [i.e., the opposite of the estimated coefficient of the log-linear regression between the cover of the focal non-native species and the total cover (or Shannon-Wiener index) of the native plants at those sites containing the focal species]. After removing the coefficients of the models with insignificant R2 values, we obtained a total of 63 and 83 available estimates for each species’ impact on the abundance and diversity of native plants, respectively.

As to leaf trait data, we downloaded the values of 8 frequently measured leaf traits [leaf carbon content (LCC), leaf nitrogen content (LNC), leaf carbon/nitrogen ratio (C:N), leaf dry weight (LDW), leaf fresh weight (LFW), leaf dry matter content per dry weight (LDMC), leaf area (LA), and specific leaf area (SLA)] from the TRY trait database (https://www.try-db.org/) (request ID 5836). For the 96 species that were exclusively non-native to the US, we extracted their trait values as measured in North America and obtained data for 51 species with at least one available trait value. Similarly, for the 28 species that were exclusively non-native to Europe, we extracted their trait values as measured in Europe and obtained available data for 19 species. For the 512 species that were non-native to both ranges, we extracted their trait values from both ranges and calculated the averaged value across the two ranges. If the value of a trait was only available for one range, we used that available value to represent the trait value across ranges.