Patterns of genetic differentiation and gene flow in Central Italian populations of Dinocras cephalotes (Curtis, 1827) (Insecta, Plecoptera)

Abstract

Dispersal is a crucial phenomenon which has a strong influence on the ecology and evolution of species, determining the extent of gene flow among conspecific populations. In this paper, we present data on the degree of genetic structuring in 11 populations of the stonefly Dinocras cephalotes, focusing our attention on three Central Italian rivers: Aniene, Nera and Velino. We studied the genetic variation at 28 enzymatic loci by means of starch gel electrophoresis: 19 loci were polymorphic in one population at least. The degree of genetic structuring and levels of gene flow were estimated by F-statistics using WEIR & COCKERHAM'S estimators. Relatively high levels of genetic differentiation were revealed, considerably higher than those obtained in other studies of stonefly species. Neighbour-joining analysis provided a geographic scheme of relationships of the study populations, grouping them according to the river of origin. This analysis was supported by bootstrap values. We were not able to detect an unequivocal relationship between gene flow and geographic distances between sites within each river; this led us to hypothesise that equilibrium has not been reached between genetic drift and gene flow.