Phylogenetic and spatial analyses suggest minimum temperature as an environmental filter for turtle communities

Abstract

AbstractAimThis study aims to evaluate phylogenetic structure of turtle communities and their potential correlates on a global scale. More specifically, we tested whether cold temperatures and low precipitation could act as potential environmental filters of turtle communities and whether the dispersal limitation caused by altitudinal range could generate phylogenetic clustered patterns in these communities.LocationGlobal.TaxonTurtles.MethodsWe used phylogenetic and distributional data of 257 species of turtles on a grid of 100 km × 100 km to generate measures of phylogenetic structure (mean nearest taxon distance and the mean pairwise distance, and their standardized effect sizes—SES) of turtle communities using three different species pools. We evaluated the relationship between SESs with climatic and altitudinal data in order to evaluate our hypotheses. Finally, we inspected whether there was phylogenetic signal in the climatic variables classified as potential filters, as it is a basic assumption for using phylogenetic structure metrics to infer assembly rules.ResultsPhylogenetic clustering was generally stronger than phylogenetic overdispersion in turtle communities. There was a positive relationship between minimum temperature and the phylogenetic structure metrics, while minimum precipitation and altitudinal range were negatively related to these metrics. We found a strong phylogenetic signal in the minimum temperature, while precipitation had a weak signal.Main conclusionsThe positive correlation between phylogenetic community structure metrics and minimum temperature and the phylogenetic signal present in this climatic variable are in accordance with our initial hypothesis regarding minimum temperature acting as an environmental filter for turtles. However, we did not find evidence to support minimum precipitation as a filter. Altitudinal range followed the expected patterns, suggesting that it increases dispersal limitation and allows a concentration of closely related species.