Inferring the demographic history of the Adriatic Flexopecten complex

Phylogenetic analysis of DNA sequences can be a useful tool in taxonomical studies, which has important implications in terms of species traceability. The aim of our study is to solve the controversy regarding the taxonomical status of the Flexopecten group, which includes two putative sister species (F. glaber and F. proteus) that co-occur in the Adriatic Sea and are clearly distinguishable on the basis of morphometric characters. Our molecular analysis using three mitochondrial genes (COI, 12S rRNA and 16S rRNA) and one nuclear gene (Histone H3) suggest that F. glaber and F. proteus are the same species, as evidenced by both putative species appearing mixed in all genetic trees with no clustering according to species. Using a Bayesian approach, we inferred the demographic history of the Flexopecten group, which suggests that first F. glaber occurred in the Mediterranean, then F. glaber colonized the Adriatic sometime in the last 18,000 years, and finally the F. proteus morph appeared only recently in the Adriatic Sea. We propose F. proteus to be synonymized with F. glaber, which should have priority and be used in the future.