Molecular phylogeny and taxonomy of troglobiotic Alpioniscus (Illyrionethes) species from the Dinaric Karst (Isopoda: Trichoniscidae)

Species richness of terrestrial isopods is high in caves of the Dinaric Karst, which hosts ~10% of the world's nominal oniscidean troglobionts. The most widespread taxon is the southern European genus Alpioniscus, which consists of two subgenera: Alpioniscus s.s. and Illyrionethes. Before this study, 14 nominal troglobiotic Illyrionethes taxa were recorded from the Dinaric Karst. Our molecular analyses using two mitochnodrial DNA (16S rRNA and COI) fragments and a nuclear gene (H3) fragment on all known Dinaric taxa identified three distinct lineages: strasseri-, heroldi- and magnus-lineage. Our results confirmed the validity of most nominal species. The exceptions are Alpioniscus balthasari, which consists of two different species including Alpioniscus iapodicus, and Alpioniscus heroldi, which is paraphyletic with respect to Alpioniscus bosniensis. The strasseri-lineage was highly supported by all phylogenetic methods used; therefore, we performed a detailed morphological analysis to distinguish and characterize the species of this group. New morphological characters, such as body part ratios, are proposed for future species identification. In addition, we redescribe three known species (Alpioniscus strasseri, Alpioniscus christiani and Alpioniscus balthasari) and describe two new ones (Alpioniscus hirci sp. nov. and Alpioniscus velebiticus sp. nov.). As a result, 15 nominal species of Illyrionethes are currently known from the Dinaric Karst.