Invaders among locals: Alien species decrease phylogenetic and functional diversity while increasing dissimilarity among native community members

Abstract

1. Plant invasions can drastically change the structure of native communities, but it is not fully understood whether alien species occupy phylogenetic and functional space within the range occupied by natives, or provide a novel set of evolutionary origins and traits to the invaded communities.2. Here, we evaluated this open question with data on a large number of plant communities from different terrestrial habitats. We used ~27,000 vegetation plots from 26 terrestrial habitats in the Czech Republic and compared phylogenetic and functional diversity (PD and FD, respectively) and community trait means in invaded and non-invaded plots. We tested for differences (1) between invaded vs. non-invaded plots, (2) among natives in invaded vs. non-invaded plots, and (3) in invaded plots only, with and without aliens. To minimize habitat filtering effects on PD and FD, we ran these tests within the habitat-specific species pools of the 26 vegetation types.3. In general, PD, FD and trait mean values changed with invasion, with changes being rather consistent across the habitats considered. Invaded plots were less phylogenetically, but more functionally diverse than non-invaded plots. The greater FD in invaded plots, compared to non-invaded ones, was due to greater dissimilarity between natives. In fact, native species in invaded plots showed higher PD and FD than native species in non-invaded plots, while alien species reduced PD and FD in invaded plots. Changes in the trait means with invasion were due to differences in native species in invaded and non-invaded plots, rather than to an effect of alien species. Within most habitats, the trait means and variance of all aliens were similar to those of all natives, while in some habitats, the variability in traits was greater between aliens that belonged to phylogenetically closer clades. Synthesis.Our results suggest that alien species more often occupy a phylogenetic and functional space within the range formed by the native species in a community. They do so either by filling empty gaps or by excluding natives from the | 2231Journal of Ecology LOIOLA et AL.

Reconciling Darwin’s naturalization and pre‐adaptation hypotheses: An inference from phylogenetic fields of exotic plants in Japan

“…In addition, at the vegetation‐plot level, the exotic species with clustered phylogenetic fields tended to be phylogenetically closely related to their recipient native species (Figure ). This pattern is in line with previous findings in the Czech Republic, where exotic plant species more often occupied an existing phylogenetic space created by native species at the local community level (Loiola et al, ) and species pool level (Lososová et al, ). These findings indicated that exotic plant species that were closely related to native species were sorted into local assemblages that suggested the predominance of habitat filtering, even at a local scale, through phylogenetically conserved ecological niches (Chytrý et al, ).…”

Linking Darwin’s naturalisation hypothesis and Elton’s diversity–invasibility hypothesis in experimental grassland communities

“…Observational studies frequently reported a positive association between the diversity of native communities and the likelihood of being invaded (e.g. Loiola et al, 2018;Stohlgren, Barnett, & Kartesz, 2003). However, with a few exceptions (Robinson & Dickerson, 1984), studies with experimentally constructed communities that tested for Elton's diversity-invasibility hypothesis often found evidence that diversity is a barrier to species invasions (e.g.…”

Similarities between invaders and native species: Moving past Darwin's naturalization conundrum

“…By contrast, the ability to overcome biotic filters is best represented by similarity to the species present within the local community (Figure b). Such an approach can increase our understanding of the role of phylogenetic relatedness in invasion by identifying scale‐dependent relationships (e.g., within multiple community types in the Czech Republic; Lososová et al., ; Loiola et al., ); however, examples of closely and distantly related invaders being successful are common at both local and regional spatial scales according to a recent review (Cadotte et al., ). This suggests that phylogenetic relationships, on their own, may be unable to predict how invaders respond to either environmental or biotic filters.…”