Morphology and phylogeny of the subterranean genera Alpioniscus and Utopioniscus from Sardinia, Italy (Crustacea, Oniscidea, Trichoniscidae)

At present the genus Alpioniscus Racovitza, 1908 includes two species in Sardinia: A. fragilis (Budde-Lund, 1909), distributed in many caves in the central- and south-eastern part of the island, and A. thanit Taiti & Argano, 2009, collected in endogean habitat and in a cave in the central-eastern part. According to the present taxonomic definition, both species are included in the subgenus Illyrionethes Verhoeff, 1927, which also includes several species from the Balkan area and a species from Spain. The genus Utopioniscus is presently known with one aquatic species (U. kuehni Schmalfuss, 2005) from two anchialine caves off the eastern coast of central Sardinia. For its morphology and aquatic life the species was considered to be the most primitive representative of the family Trichoniscidae. Recent investigations in many Sardinian caves revealed the presence of U. kuehni also in freshwater lakes in the Bue Marino Cave, and of a new aquatic species in Su Palu Cave, which shows intermediate morphological characters between Alpioniscus spp. and Utopioniscus kuehni. Moreover, different cave populations of A. fragilis showed some morphological differences (e.g. granulated vs. smooth dorsum) which might prove to be more than one species. Several populations from Sardinia belonging to Alpioniscus, the population of U. kuehni from Bue Marino Cave and the aquatic population from Su Palu Cave have been analysed morphologically. A molecular analysis was performed using mtDNA sequences (COI) to reconstruct their molecular phylogeny. In the molecular analysis also Alpioniscus (Alpioniscus) feneriensis (Parona, 1880) from two caves in Piedmont (north-western Italy) and A. (Illyrionethes) strasseri (Verhoeff, 1927) from a cave near Trieste have been included. Results show that: 1) both the aquatic species from Su Palu and the aquatic Utopioniscus kuehni are included in the same clade with Alpioniscus spp., suggesting that the latter species is not the most primitive Trichoniscidae but rather a species within Alpioniscus secondarily returned and morphologically adapted to an aquatic way of life; 2) high levels of genetic divergence among the Sardinian populations of Alpioniscus from caves and endogean habitats were found, suggesting the occurrence of more species than just A. fragilis and A. thanit. Combined analysis of mitochondrial and nuclear genes will shed more light on the phylogeny of this group.