Morphological variability among populations of Harpalus rufipes (Coleoptera, Carabidae): What is more important - the mean values or statistical peculiarities of distribution in the population?

The paper analyzes the variability of 19 characteristics (14 linear measurements, 4 angular characteristics and density of elytra downiness), as well as 8 morphometric indices for 391 imagoes of Harpalus rufipes (De Geer, 1774) collected in 9 forest, field and steppe ecosystems under various degrees of anthropogenic pressure in four administrative districts of Dnipropetrovsk region, Ukraine. The presence of significant (P < 0.001) negative asymmetry in females and absence thereof (P > 0.05) in males is typical for body length, head length, elytra length, distance between eyes, head width, prothorax width between the front angle and the back angle, elytra width between humeral angles, and maximum elytra width. For all these characteristics, the excess in males is not significant (P > 0.05), while in females in most cases it is significantly positive (P < 0.05), which is evidence that there is a large number of females with a greater length of the body and greater width of the head, prothorax and elytra. The absence of significant asymmetry (P > 0.05) in males and females proves the absence of directional selection in the populations of H. rufipes on the density of elytra downiness and value of the prothorax back angle. A significant negative asymmetry was recorded both in males and females for the maximum width of prothorax (P < 0.001) and body height (P < 0.05), i.e. unidirectional increase in these characteristics takes place in specimens of both sexes. As distinct from the linear measurements, for all 8 considered proportions of the body in specimens of both sexes the excess is significantly positive (P < 0.001), suggesting higher constancy of bodily proportions in H. rufipes than of absolute size. For most of the linear characteristics, a significant (P < 0.001) sexual dimorphism is recorded. No marked differences between the 9 populations studied within the groups of specimens of the same sex are recorded. In the areas where the annual burning of crop residues and litter is observed, differences between males and females in length are two times higher than the differences between males and females for the ecosystems with no such burning. In the driest areas, maximum elytra width - prothorax width ratio is observed in females. The vertex angle of elytra significantly differs in the populations of the various administrative districts. The average density of elytra downiness in males is 13.3% lower than in females. The results of PCA (principal component analysis) have shown that most of the linear characteristics were connected with the sex of the beetle, while variations in the angular characteristics and degree of elytra downiness bore no relationship to the sex of the H. rufipes specimens. The results of our research suggest that the mean values of morphometric characteristics in environmental studies may have less diagnostic value than the type of their distribution in the population.