Genetic differentiation of six sympatric species of Isotomurus (Collembola, Isotomidae); is there any difference in their microhabitat preference?

Genetic markers (allozymes and DNA sequences) were used to evaluate the taxonomic importance of small features of the pigmentation patternsamong individuals of the genus Isotomurus. Such markers allowed the detection of six genetically well differentiated species, all coexisting in the same locality. The presence of loci fixed for alternative alleles ruled out the possibility of hybrid formation and confirmed that the taxa deserve the rank of species. In spite of the difficulty, at least in some cases, of recognizing the species on a morphological basis, they were all genetically well differentiated. Genetic markers werealso used to infer phylogenetic relationships. Reconstructions based on different data sets and different methods were not always concordant, but the close affinity of Isotomurus palustris, I. ghibellinus and I. indipendente can reasonably be accepted. No apparent ecological difference was detected among the six species, however they showed substantial microgeographic segregation, with each species exhibiting preference for certain microhabitats. In the absence of a clear analysis of ecological differentiation, partial microhabitat preference is taken as a proof of such a differentiation. Microhabitat preference could be the cause and/or the effect of the speciation process. A synthetic description of three new species (Isotomurus ghibellinus n. sp., I. italicus n. sp. and I. indipendente n. sp.), and of I. unifasciatus (erected to the rank of species) is given.