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

Abstract

Aim:This study aims to evaluate phylogenetic structure of turtle communities andtheir potential correlates on a global scale. More specifically, we tested whethercold temperatures and low precipitation could act as potential environmental filtersof turtle communities and whether the dispersal limitation caused by altitudinalrange could generate phylogenetic clustered patterns in these communities.Location:Global.Taxon:Turtles.Methods:We used phylogenetic and distributional data of 257 species of turtles ona grid of 100 km×100 km to generate measures of phylogenetic structure (meannearest taxon distance and the mean pairwise distance, and their standardizedeffect sizes—SES) of turtle communities using three different species pools. Weevaluated the relationship between SESs with climatic and altitudinal data in orderto evaluate our hypotheses. Finally, we inspected whether there was phylogeneticsignal in the climatic variables classified as potential filters, as it is a basic assump-tion for using phylogenetic structure metrics to infer assembly rules.Results:Phylogenetic clustering was generally stronger than phylogenetic overdis-persion in turtle communities. There was a positive relationship between minimumtemperature and the phylogenetic structure metrics, while minimum precipitationand altitudinal range were negatively related to these metrics. We found a strongphylogenetic signal in the minimum temperature, while precipitation had a weaksignal.Main conclusions:The positive correlation between phylogenetic community struc-ture metrics and minimum temperature and the phylogenetic signal present in thisclimatic variable are in accordance with our initial hypothesis regarding minimumtemperature acting as an environmental filter for turtles. However, we did not findevidence to support minimum precipitation as a filter. Altitudinal range followed theexpected patterns, suggesting that it increases dispersal limitation and allows a con-centration of closely related species.