Morphological variability of Bembidion minimum (Coleoptera, Carabidae) populations under the influence of natural and anthropogenic factors

Abstract

Morphological variability is the result of interaction between genetic diversity of the population and environmental selection. Despite the large number of studies of morphological variability of ground beetles, there is very little research dedicated to influence of environmental factors on it. This article discusses the influence of natural and anthropogenic factors on the variability of Bembidion minimum (Fabricius, 1792). B. minimum is a West Palearctic species which is distributed in North Africa, Europe, Western Asia. It is a macropterous species that lives in humid biotopes along the shores of seas, rivers and standing water bodies. 410 specimens were collected from 12 ecosystems differing by plant cover, degree of litter development, mechanical composition of the soil, mineralization and acidity of soil solution, type and intensity of anthropogenic impact. 13 linear characteristics, one angular characteristic, density of elytra puncturing and contrast of spots on the beetles’ elytra were measured. Additionally 6 morphometric indices were calculated. More than a third of the variability of imagoes in the studied populations was found to be determined by the general body size. Sexual dimorphism was observed on all linear parameters and most morphometric indices. Females do not differ from males in the back angles of the prothorax. Natural and anthropogenic factors to a greater or lesser degree were shown to affect the morphological variability of B. minimum: soil acidity and mineralization have the greatest impact. The soil acidity causes significant variability of most linear parameters; mineralization – body length, head length, prothorax length and width, elytra width. Plant cover and mechanical composition of the soil have a slight impact on imago morphology. The type and structure of vegetation significantly affect head width, prothorax length and width, and the mechanical composition of the soil – body length and head length. Degree of litter development does not cause significant changes in the linear dimensions of beetles. With thickening of the litter the posterior spots on the elytra become brighter, they have sharper contours, and density of elytra puncturing also changes. The mean value of the back angles is affected by the herb layer of meadow vegetation, soil mineralization and acidity. The variability of morphometric indexes under the influence of natural factors was found to be lower than variability of linear characteristics. The recreational load and cattle grazing cause similar changes in linear measurements and morphometric indexes of B. minimum. With escalation of these factors, the body length, length and width of elytra of both females and males decrease. Assessing the natural morphological variability of populations in ecosystems whose environmental factors are within extreme and sub-extreme values for a given population is a promising direction of research in modern ecology.