Species boundaries and phylogeography of the "Euscorpius carpathicus complex" (Scorpiones: Euscorpiidae) in Italy

Euscorpius tergestinus (C.L. Koch, 1837), Euscorpius concinnus (C.L. Koch, 1837) and Euscorpius sicanus (C.L. Koch, 1837), three presumed closely related species belonging to the “carpathicus group”, occur in the Italian peninsula with a largely parapatric distribution and some zones of range overlap. These areas of sympatry represent interesting opportunities to investigate species boundaries in natural populations. Here we report on a study exploring genetic variation in sympatric populations of the three species from central Tuscany. Additional collecting sites, from different localities across Italy, were also included in the analysis in order to explore the phylogeographic structure of the group. Species boundaries and evolutionary relationships were examined by sequence comparison of mitochondrial 16S rRNA and nuclear ITS-1 rRNA gene fragments. DNA sequence data show no evidence of genetic introgression between different evolutionary lineages from the area of range overlap, suggesting the absence of either past or ongoing inter-specific gene flow. It is therefore probable that reproductive barriers exist, preventing gene pools from amalgamating. Furthermore, our results support the recent morphological distinction of E. tergestinus, as traditionally classified, into two different species: E. tergestinus and E. concinnus. Both mitochondrial and nuclear sequence data clearly indicate that the two taxa represent well-supported and deeply divergent lineages. Euscorpius sicanus seems to represent a monophyletic taxon, but the high genetic variability observed within this taxon calls for future investigation. The present distribution patterns across the Italian peninsula were mainly interpreted as the consequence of climatic oscillations.