Sexual Dimorphism in Physiological Reactions to Biotope Type (the Case Study in Ground Beetles)

*Eugeniy Khomitskiy, Tamara Avtaeva, Shapaat Kushalieva, Alexandr Zamotajlov, Rifgat Shagidullin and Raisa Sukhodolskaya*

## **Abstract**

Sexual size dimorphism (SSD) (the difference between males and females in size) is considered to be the physiological reaction to environmental conditions. We estimated body size variation and SSD in two populations of ground beetle *Carabus exaratus*. Beetles were sampled in Krasnodar Province (Russia) in the forb-cereal meadow and beech-hornbeam forest. We processed morphometric measurements in 521 specimen for six linear traits. Beetles from the meadow were slightly larger than from the forest. SSD was pronounced in a half of traits being the highest by elytra length. On a whole, SSD did not differ in the populations studied.

**Keywords:** sexual size dimorphism, ground beetles, body size variation, physiological reaction, stress

## **1. Introduction**

A lot of studies deal with the relationships between the sizes of different parts or entire bodies of organisms. They investigate how such body size variation affects different morphologies and important functions, that is, physical strength, metabolic rates, and transport of resources [1]. Such size patterns can be studied both within individuals and species and across species of plant or animal. Male and female insects often differ morphometrically, by size [2]. Females are usually larger than males, while males demonstrate lower phenotypic plasticity [3, 4]. Phenotypic plasticity is induced by ecological and environmental variables.

The aim of our study was to top up the knowledge in sexual size dimorphism (SSD) in insects, specifically in ground beetles. The former studies showed SSD variability in these beetles depending on environmental conditions. We chose Caucasian species 0 *Carabus exaratus* Quencel, which was not sufficiently investigated. So we hypothesized that: (i) SSD in it is female-biased; (ii) the beetles from different

biotopes will differ in body size; and (iii) SSD by different traits will vary and will be the highest by elytra width.
