New insights in the Porcellionides pruinosus complex (Isopoda, Oniscidea):: Biological, behavioural, and morphological approaches

The terrestrial isopod, Porcellionides pruinosus (Brandt, 1833) is commonly viewed as one of the most widespread species of woodlice, mainly because of its synanthropic nature. Recent investigations have, however, suggested that some populations, although morphologically closely similar, may consist in fact of separate species. In this study, six populations from distant localities were examined in a taxonomic perspective. Laboratory crossings first confirmed the reproductive isolation between two groups of populations. Behavioural tests then revealed a pre-zygotic reproductive isolating mechanism in the absence of sexual recognition between males and females from the two groups. These results, together with previously found molecular data, gave congruent evidence for the existence of two well-defined species. Yet, morphological investigations failed to detect any meristic characters that would allow a strict discrimination between P. pruinosus and the other species. From the literature, it was impossible to assign the herein recognized sibling species to any previously described taxa. This study gives new insights in the P. pruinosus complex but also highlights the difficulties to identify and name species in the absence of revised and updated diagnoses of the genus Porcellionides.