Impact of climatic factors on sexual size dimorphism in ground beetle Pterostichus melanarius (Illiger, 1798) (Coleoptera, Carabidae)

Abstract

Intra-specific body size variation in ground beetles is studied insufficiently, especially in response to climatic factors. Even less studied is the sexual dimorphism (hereinafter referred to as the SSD), its geographic variation patterns and response to climatic factors. We sampled ground beetles Pterostichus melanarius in 15 regions of Northern Eurasia along latitude and longitude gradients (in 17 degrees and 121 degrees, respectively), including differing habitats (open and forested) in the spectrum of anthropogenic impact (cities, suburbs, arable lands and natural). 7677 specimens were measured by six morphometric traits – elytra, pronotum, head length and width, distance between eyes. Our software applied made it possible both to catch the smallest changes in the size of traits in females and males, and to determine their direction. Temperature related factors mostly reduced beetles traits values, but precipitation related factors – enlarged them. Elytra and pronotum parameters were the traits which response differently in males and females to climatic factors, these traits showed more pronounced SSD. Head parameters showed SSD in response to those factors too. That response had the similar direction and was expressed more, either in females or males. The latter processes implemented to a greater extent in relation to the temperature including bioclimatic factors.