The use of genetic markers for the diagnosis of sibling species in the genus Isotomurus (Insecta, Collembola)

Two independent genetic markers (allozymes and mitochondrial DNA sequences) were used to demonstrate that Isotomurus palustris palustris and Isotomurus palustris maculatus (Collem- bola, Isotomidae), interpreted either as varieties or subspecies by the various authors, are, actually, well differentiated species. Specimens were collected sympatrically in five different sampling sites in Italy and southern France, and, in all of them, the two forms were fixed for alternative alleles at some enzyme loci. The absence of hybrids demonstrates that the two species, discriminated morphologically by body pigmentation, do not cross. The rate of sequence divergen- ce of the mitochondrial COII gene confirms a significant degree of differentiation