**3. Results and discussion**

SSD in ground beetles is female-biased [8]. It is common for the vast number of species in invertebrates. The value of SSD is not constant because phenotypic plasticity of body size can vary substantially between the sexes and can cause intraspecific variation [9]. The most interesting opinion on SSD was expressed in Evolutionary Theory of Sex [10]: Males are the vanguard of evolution. They are more variable than females and become very variable in unusual conditions. Purely mathematically, this leads to the reduction of differences between males and females. So in severe environment SSD values increase. On the contrary, in stable environment, without any destabilizing effects, SSD will decrease. Some studies in ground beetles confirmed that suggestion. In mountain populations of ground beetles *Carabus odoratus* Schill. and *Pterostichus montanus* Motsch. SSD highly correlated with population number [11]. It is well known that these conditions lead to resources lack, stress etc. And exactly in those severe conditions SSD in those populations was high. In relation to *C. exaratus*, the highest values in SSD were recorded in severe conditions of high mountains [10]. In our study, the situation was somewhat another. We recorded SSD not by all traits investigated (**Figures 1** and **2**): In elytra length SSD was pronounced in both biotopes, but it was not recorded in elytra width, and was male-biased by pronotum length in the meadow population, and was not recorded in pronotum width and head parameters in the forest population of *C. exaratus*.

Those facts evidenced that environmental conditions were quite stable in area studied. Probably estimated biotopes differed slightly in food resource procuring. Beetles were slightly larger in the meadow, and larva nutrition is considered the main factor that impacts imagoes size. Ground beetles are largely predators feeding on soil micro- and macrofauna representatives—microbes, Formicidae, Silphidae larvae, small species of Staphylinidae, Coccinellidae, Dermestidae, larvae of Lepidoptera, Hemiptera, Thomisidae, Opiliones, and Lumbricidae [12, 13]. Sometimes, carabids consume their "relatives," for example, *Pterostichus melanarius* Ill. fed readily on *Stomis pumicatus* (Panzer, 1795), *Harpalus amplicollis* Mentries, 1848, *Panagaeus bipustulatus* (Fabricius, 1775) [14]. Distribution of ground beetles preys is spatially very diverse. This fact can explain biotope impact on beetle size variation. In arable lands of Europe, the size in ground beetle *Poecilus cupreus* L. in rye differed greatly from the crops. The authors correlated with that fact to the peculiarities of rye cultivation: strong root system and shallow seed embedding. Besides, beetle body

**Figure 1.** *Elytra length variation in* C. exaratus*.*

**Figure 2.** *Traits value variation in* C. exaratus.

size and their shape differed in the crops with heavy above-ground parts (carrot, pea, vetch, and oat) and rarefied ones (lawn, meadows) [15]. In *Carabus granulatus* L. beetles were larger in the meadows, but significantly smaller in oak and elm forests if compared with birch ones [16]. Such the differences are based on the different litter decomposition in cited biotopes, where carabid preys dwell [17].

In our case, the beetles in the forest and at the meadow did not differ in size significantly (except their elytra width). This, to our mind, means that the place in area should be taken into account too when exploring body size variation in different populations of ground beetles [18, 19]. For several species of carabids, the distinct curves of size variation were shown in latitude gradient [19] and often males and female response to latitude gradient differed [20, 21]. The plots we explored were situated in nearby locations, so they did not differ significantly in weather conditions and climate in a whole. The latter also affects ground beetle size variation [22, 23].

Besides real size variation the variation of shape should be studied. Our investigated species—*C. exaratus*—showed distinct shape variation in altitude gradient with elongated specimen in low mountains [24].

As for sexual size dimorphism the samples we studied followed the established rule that SSD in carabids is female-biased [25] females being larger than males. On a whole when considering all traits we did not find significant differences in SSD value in the meadow and forest populations (**Figure 3**).

In any way our findings contribute greatly into our knowledge in SSD variation in both carabids and insects. Intra-specific level of investigation allows us to frame mechanisms of body size variation in different habitats and in different sexes. The latter highlight ways of SSD evolution. And it is sufficiently important as SSD is considered to be the indicator of environmental quality.

As mentioned in Material and Methods we are presenting here the fragment of our large study. In previous papers, we put forward the hypothesis that body size variation in ground beetles is genera-specific in latitude gradient: In Carabus beetles, the curve

*Sexual Dimorphism in Physiological Reactions to Biotope Type (the Case Study in Ground Beetles) DOI: http://dx.doi.org/10.5772/intechopen.113819*

#### **Figure 3.**

*Sexual size dimorphism (as the mean by all traits investigated) in* C. exaratus.

monotonically falls northwards but in Pterostichus ones it is saw-tooth. The latter can be explained by life-cycle changes. As for studied *C. exaratus*, we have the only one region else to be compared with Krasnodar Province—Chechen Republic [10]. The following step of our studies will include comparative analysis of this species samples from different regions and replenishment of our dataset with new data.
