Morphometric variability of ground beetles Bembidion minimum (Coleoptera, Carabidae): who should change more, males or females?

Abstract

Morphological variability can be used as an indicator of the state of invertebrate populations. Microevolutionary processes can show up in the morphological differentiation of populations. This includes differences between morphometric characters in the two sexes. The variability of 12 populations of Bembidion minimum (Coleoptera, Carabidae) was assessed by 24 morphometric characteristics and indices in this article. Bembidion minimum is a halophile that lives in ecosystems of Protected Areas in Ukraine (Black Sea Biosphere Reserve, Dniprovsko-Orilskyi Nature Reserve, Ornithological Sanctuary «Bulakhovsky Liman», Regional Landscape Park «Dniprovi Porogy», Samara Forest). The coefficients of variation for males, females, and combined populations of males and females were estimated in the article. The studied populations inhabited different soil and plant conditions and were under the influence of anthropogenic factors of varying intensity. The redundancy analysis shows three clusters. In the first cluster, morphometric characteristics and indices in both males and females were linked to environmental variables (herb layer, salt, composition of soil). The second cluster had morphometric characteristics and indices in both males and females with a link to environmental variables (pH, litter, recreational load, cattle grazing). The third cluster formed morphometric characteristics and indices in both males and females that are not affected by any environmental variables. The coefficient of variation for most of the linear morphometric characteristics of B. minimum (width of head, length of prothorax, width of prothorax, length of elytra and distance between setae on the elytra) for males was significantly lower than for the combined sample of males and females. The variability of width of elytra and length of body was significantly higher for females than for males. The degree of variability of males, females and their combined sample did not significantly differ for nonlinear morphometric characteristics, as well as for the six morphometric indices (body proportions) studied by us. In general, in the 12 studied populations of B. minimum, the coefficient of variation for most of the studied measurements was insignificantly lower in males (CV = 5.59%) than in females (6.10%) or in the combined sample of males and females (6.75%). The lowest variability in populations of B. minimum was found for morphometric indices: CV = 3.89% for males, CV = 3.76% for females, and CV = 3.86% for the combined population (males + females). The absence of differences in the mean values of the coefficient of variation between males, females and the combined sample of males and females for each individual population suggests that both males and females make a relatively equal contribution to the polymorphism of B. minimum populations. An assessment of the morphological variability of invertebrates, and especially the variation of coefficients of linear parameters and morphometric indices, can be used to indicate the state of ecosystems in Protected Areas in Ukraine and other countries.