Assessing species boundaries and evolutionary relationships in a group of south-western European species of Isotomurus (Collembola, Isotomidae) using allozyme data

Abstract

In this study allozyme data were used to examine evolutionary relationships in the cosmopolitan collembolan genus Isotomurus. Fifty-six south-western European populations from 13 species were compared, with the aim of delimiting species boundaries and testing the robustness of the most frequently used morphological characters for species identification. Observed allozyme variability suggests that genetic differentiation is more pronounced than the amount of morphological variability among and within species. Convergence in models of pigmentation pattern may lead to erroneous taxonomic identification when this is the only feature used for species diagnosis. In this respect, this study confirms that diagnosis is greatly improved when assisted by biochemical or molecular analyses. Allozyme data have also been used to reconstruct evolutionary hypotheses for relationships at the species and population level. The monophyly of Isotomurus maculatus, I. unifasciatus, I. fucicolus, I. nebulosus and I. pseudopalustris was confirmed on molecular grounds. Conversely, the monophyly of I. ghibellinus and I. palustris was rejected, suggesting the presence of cryptic species.