Phylogenetic and functional structure of climbing plant assemblages in woody patches advancing over Campos grassland

Abstract

Analysing taxonomic, phylogenetic and functional species distribution across a metacommunity allows understanding of how landscape dynamics may influence forest expansion over grassland. In this context, climbing plants are particularly interesting vegetation components, since they actively prospect the best sunlight position, altering forest structure. We investigated if forest structure differentiation along a patch size/isolation gradient would determine the distribution of phylogenetic clades, dispersal and/or establishment-related traits in climbing plant assemblages. We hypothesized that taxonomic, phylogenetic and functional species diversities would show a nested pattern along the gradient of increasing vegetation complexity. Furthermore, less mobile diaspores, as well as climbing mechanisms independent of support limitations, and deeper phylogenetic clades characterized by shade-tolerant species would be associated with more developed and less isolated patches.

Location Subtropical grassland surrounded by Araucaria forest, southern Brazil.

Method We recorded the composition and abundance of climbing plant species along a gradient of forest patches increasing in size and isolation from the surrounding continuous forest. We performed an analysis of principal coordinates of phylogenetic structure (PCPS) to investigate the distribution of phylogenetic clades across sites, tested its relationship with patch area and isolation using linear models, and for the correlation to species dispersal traits and climbing mechanisms. We employed the treeNODF (Nestedness based on Overlap and Decreasing Fill) method to estimate if there was a phylogenetic, compositional and/or functional nested pattern of the metacommunity structure during forest expansion over grassland.

Results We found that species composition distribution was explained by patch size and isolation, but not by phylogeny. Dispersal traits were more structured along the gradient compared to climbing mechanisms. We also found a nested pattern of combined species and phylogenetic/functional diversities, where smaller patches are subsets of larger patches and of continuous forest sites.

Conclusion Patch area, isolation and dispersal traits play significant roles in the distribution of climbing plants during the process of forest advance over grassland, independently of phylogenetic relatedness among species. The nested pattern indicated that continuous forest and larger patches provide all the diaspores that colonize the smaller patches in this process, making them important targets for conservation.