Global patterns of functional trait variation along aridity gradients in bats

Ricardo Rocha,Luca Santini,Danilo Russo,Ara Monadjem,Shai Meiri,Irene Conenna,Mar Cabeza

doi:10.1111/geb.13278

Abstract

AbstractAimOur understanding of the biological strategies employed by species to cope with challenges posed by aridity is still limited. Despite being sensitive to water loss, bats successfully inhabit a wide range of arid lands. We here investigated how functional traits of bat assemblages vary along the global aridity gradient to identify traits that favour their persistence in arid environments.LocationGlobal.Time periodContemporary.Major taxa studiedBats.MethodsWe mapped the assemblage‐level averages of four key bat traits describing wing morphology, echolocation and body size, based on a grid of 100‐km resolution and a pool of 915 bat species, and modelled them against aridity values. To support our results, we conducted analyses also at the species level to control for phylogenetic autocorrelation.ResultsAt the assemblage level, we detected a rise in values of aspect ratio, wing loading and forearm length, and a decrease in echolocation frequency with increasing aridity. These patterns were consistent with trends detected at the species level for all traits.Main conclusionsOur findings show that trait variation in bats is associated with the aridity gradient and suggest that greater mobility and larger body size are advantageous features in arid environments. Greater mobility favours bats’ ability to track patchy and temporary resources, while the reduced surface‐to‐volume ratio associated with a larger body size is likely to reduce water stress by limiting cutaneous evaporation. These findings highlight the importance of extending attention from species‐specific adaptations to broad scale and multispecies variation in traits when investigating the ability of species to withstand arid conditions.

Highlights

Arid and semi-arid regions cover c. one third of the planet's land surface, encompassing key habitats for a wide array of species (Safriel et al, 2005)
Main conclusions: Our findings show that trait variation in bats is associated with the aridity gradient and suggest that greater mobility and larger body size are advantageous features in arid environments
We examined how a bat assemblage's measures of wing morphology, echolocation frequency and body size vary along the aridity gradient

Summary

Introduction

Arid and semi-arid regions cover c. one third of the planet's land surface, encompassing key habitats for a wide array of species (Safriel et al, 2005). Vertebrates may reduce water stress in several manners, e.g. via increased skin resistance to cutaneous evaporative water loss, burrowing habits and high mobility to access scattered resources (Fuller et al, 2014; Oliveira & Scheffers, 2019; Rymer et al, 2016; Williams & Tieleman, 2005) These adaptations have been mostly studied in species inhabiting deserts, and we still have a poor understanding of which traits favour the presence of species with increasing aridity across broad geographical extents. Describing variation of species traits along aridity gradients can, provide insights on which features contribute to the ability of species to withstand arid conditions (Rymer et al, 2016)

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