Biogeographic position and body size jointly set lower thermal limits of wandering spiders.

Jérémy Monsimet,Hervé Colinet,Olivier Devineau,Denis Lafage,Julien Pétillon

doi:10.1002/ece3.7286

Abstract

Most species encounter large variations in abiotic conditions along their distribution range. The physiological responses of most terrestrial ectotherms (such as insects and spiders) to clinal gradients of climate, and in particular gradients of temperature, can be the product of both phenotypic plasticity and local adaptation. This study aimed to determine how the biogeographic position of populations and the body size of individuals set the limits of cold (freezing) resistance of Dolomedes fimbriatus. We compared D. fimbriatus to its sister species Dolomedes plantarius under harsher climatic conditions in their distribution range. Using an ad hoc design, we sampled individuals from four populations of Dolomedes fimbriatus originating from contrasting climatic areas (temperate and continental climate) and one population of the sister species D. plantarius from continental climate, and compared their supercooling ability as an indicator of cold resistance. Results for D. fimbriatus indicated that spiders from northern (continental) populations had higher cold resistance than spiders from southern (temperate) populations. Larger spiders had a lower supercooling ability in northern populations. The red‐listed and rarest D. plantarius was slightly less cold tolerant than the more common D. fimbriatus, and this might be of importance in a context of climate change that could imply colder overwintering habitats in the north due to reduced snow cover protection. The lowest cold resistance might put D. plantarius at risk of extinction in the future, and this should be considered in conservation plan.

Highlights

The ability of a species to cope with variations in abiotic conditions influences its distribution range (Gaston 2003)
Our study showed that the supercooling point (SCP) of northern fishing spiders from a continental climate was lower than the SCP of southern Dolomedes from a temperate climate
Was positively related to body size for both species, but this relationship differed between the two climates for D. fimbriatus

Summary

Introduction

The ability of a species to cope with variations in abiotic conditions influences its distribution range (Gaston 2003). Freeze intolerant arthropods, which include freeze-avoidant, chill tolerant, chill-susceptible and opportunistic-survival classes, can exhibit deep supercooling ability, ranging from -15 to. Many different measures are used to illustrate the thermal performance of populations (Sinclair et al 2015) It could be depicted by a thermal performance curve representing how a temperature gradient influences arthropod activity (Sinclair et al 2012, 2015). As the estimation of thermal performances is influenced by many factors such as phenotypic plasticity (Schulte et al 2011) or evolutionary adaptation (Jensen et al.2019), measuring an anchor point like the SCP is useful to assess the cold tolerance class of species. Many ectotherms classified as chill-susceptible or opportunistic-survival, die at temperatures well above SCP, the latter being less resistant than the former (Overgaard and MacMillan 2017, Bale 2002)

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