Population structure of Formica aquilonia (Hymenoptera, Formicidae) at the boundary of boreal and subboreal landscapes in the Volga River region

Abstract

The data on the population structure of Formica aquilonia in the Middle Volga Area based on the variation of pilosity and coloration of workers are presented. Two population groups were distinguished by the pilosity characters: the northern group included the southern taiga population and the one located at the southern boundary of this subzone; the southern group comprised the populations of the mixed and broad-leaved forests. The pilosity characters reveal the F. aquilonia population structure at the regional level. They can be related to the ways of postglacial colonization of the territory and to the formation of the forest belt in the Quaternary. Phenotypic changes with respect to all the characters studied were revealed in the worker population of the anthill complex of F. aquilonia during 4 years of observation. They appear to have been caused by stochastic intrapopulation processes. The phenotypic homogeneity of the worker population was greater in the sites with higher settlement capacity (the sum of the areas of anthill dome bases related to the area of the settlement). Changes in the frequencies of the morphological characteristics were observed in the zones with low settlement capacity; the location of such zones has remained unchanged for some years. The stability of the spatial structure of the settlements appears to be associated with the distribution of forest biotopes suitable for dwelling of ants. The phenotypic heterogeneity of the complex has increased during the four-year period indicating the beginning of its fragmentation.