Modeling Sexual Differences of Body Size Variation in Ground Beetles in Geographical Gradients: A Case Study of Pterostichus melanarius (Illiger, 1798) (Coleoptera, Carabidae).

Sergey Luzyanin,Nadezhda Ukhova,Sargylana Nogovitsyna,Igor Solodovnikov,Viktor Brygadyrenko,Rifgat Shagidullin,Raisa Sukhodolskaya,Viktor Alexanov,Anatoly Saveliev,Anatoliy Anciferov,Iraida Vorobyova,Teodora Teofilova

doi:10.3390/life12010112

Abstract

The aim of this study was to test the steepness of body size variation in males and females in the widespread ground beetle Pterostichus melanarius in geographical gradients. Beetles were sampled in 15 regions of Europe and Asia, and sampling territories differed 17° in latitude and 121° in longitude. We measured six linear traits in every captured beetle and formed a data set that included 2154 individuals. Body size variation in all traits in general was sawtooth, both in latitude and in longitude gradients. Regression analysis showed slight trends: in the latitude gradient, elytra parameters increased, pronotum length did not change but the width increased, and head parameters decreased. In the longitude gradient, the changes were as follows: elytra length increased, but its width did not change; pronotum length did not change, but its width increased; the head parameters decreased. Thus, we observed the elytra length increase and the head parameters decrease northwards and eastwards. We compared female and male regression curves (trait size on latitude/longitude): p-levels were significant only in four cases out of 12. Thus, we conclude that, in general, there is no evidence for the steepness in trait variation in males compared with females.

Highlights

A fundamental problem for biologists is to discover the processes driving intra- and interspecific variation in phenotypic traits [1]
It was common for both gradients that males were smaller than females
Our study identified an interesting pattern in lifehistory strategies, with sawtooth body size variation, which was expressed in males and females

Summary

Introduction

A fundamental problem for biologists is to discover the processes driving intra- and interspecific variation in phenotypic traits [1]. Body size is an essential trait to study, because size variation directly affects fitness, physiology, and most life-history traits [2,3]. It is one of the key life-history traits in ectotherms [4,5], because it is considered a proxy for fecundity, body condition, and survival [6,7,8]. Species with wide distributional ranges show clines in body size These may be the result of “ecogeographical rules” that discuss spatial patterns of phenotypic variation in terms of environmental variation [11,12]

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Results