Phylogenetic structure of understorey annual and perennial plant species reveals opposing responses to aridity in a Mediterranean biodiversity hotspot

• Published in: The Science of the total environment Vol. 761; p. 144018
• Main Authors: Massante, Jhonny Capichoni, Köbel, Melanie, Pinho, Pedro, Gerhold, Pille, Branquinho, Cristina, Nunes, Alice
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 20.03.2021
• Subjects: Biodiversity; Climate Change; Holm-oak; Mediterranean basin; Montado; Phylogenetic relatedness; Phylogenetic turnover; Phylogeny; Plants; Seasons; Understorey vegetation; Mediterranean basin; Understorey vegetation; Montado; Holm-oak; Phylogenetic relatedness; Phylogenetic turnover
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2020.144018

Aridity is a critical driver of the diversity and composition of plant communities. However, how aridity influences the phylogenetic structure of functional groups (i.e. annual and perennial species) is far less understood than its effects on species richness. As perennials have to endure stressful conditions during the summer drought, as opposed to annuals that avoid it, they may be subjected to stronger environmental filtering. In contrast, annuals may be more susceptible to interannual climatic variability. Here we studied the phylogenetic structure of the annual and perennial components of understorey plant communities, along a regional aridity gradient in Mediterranean drylands. Specifically, we asked: (1) How do species richness (S) and phylogenetic structure (PS) of annuals and perennials in plant communities respond to aridity? (2) What is the contribution of other climatic and topo-edaphic variables in predicting S and PS for both components? (3) How does the taxonomic and phylogenetic turnover of annuals and perennials vary with spatial and environmental distances? We assessed annuals' and perennials' species richness, the phylogenetic structure at deep and shallow phylogenetic levels, and taxonomic and phylogenetic turnover along spatial and environmental distances. We found no relationship between annuals' richness and aridity, whereas perennials' richness showed a unimodal pattern. The phylogenetic structure of annuals and perennials showed contrasting responses to aridity and negatively correlated with topo-edaphic variables. We found phylogenetic clustering at intermediate-to-higher aridity levels for annuals, and at lower aridity levels for perennials. Both taxonomic and phylogenetic turnover in annuals and perennials correlated with the environmental distance rather than with spatial distance between communities, suggesting adaptation to local factors. Overall, our results show a decoupling in the response of the phylogenetic structure of annual and perennial components of plant communities to aridity in Mediterranean drylands. Our findings have significant implications for land management strategies under climate change. [Display omitted] •Aridity is a critical driver of changes in ecological communities.•We studied its effects on the richness and phylogenetic structure of annual and perennial species.•Annual richness was not related to aridity, whereas perennial's showed a unimodal pattern.•Annuals showed phylogenetic clustering at medium-to-higher aridity; perennials at lower.•Our results suggest a decoupling of annuals and perennials and have significant implications for restoration strategies.