Escape from the Ponto-Caspian: evolution and biogeography of an endemic goby species flock (Benthophilinae: Gobiidae: Teleostei).

Endemic Ponto-Caspian gobies include a flock of 24 "neogobiin" species (containing the nominal genera and subgenera Apollonia, Babka, Neogobius, Mesogobius, Ponticola, and Proterorhinus; Teleostei: Gobiidae), of which a large proportion (5 species; 21%) recently escaped to invade other freshwater Eurasian systems and the North American Great Lakes. We provide its first comprehensive phylogenetic and biogeographic analysis based on 4709 bp sequences from two mitochondrial and two nuclear genes with maximum parsimony, likelihood, and Bayesian approaches. We additionally compare its relationships with the tadpole gobies (Benthophilus and Caspiosoma), which comprise a related endemic Ponto-Caspian gobiid group; along with a variety of postulated relatives and outgroups. Results of all phylogenetic approaches are highly congruent and provide very strong support for recognizing the subfamily Benthophilinae; which encompasses both the "neogobiins" and tadpole gobies, and genetically diverges from other Gobiidae subfamilies-including (non-monophyletic) Gobiinae and Gobinellinae. Benthophilinae contains three tribes: Neogobiini (Neogobius, which is synonymized here with Apollonia; containing the type species N. fluviatilis, along with N. melanostomus and N. caspius), Ponticolini (containing the genera Mesogobius, Proterorhinus, Babka, and Ponticola-elevating the latter two from subgenera and removing them from the formerly paraphyletic Neogobius), and Benthophilini (tadpole gobies). Within Ponticolini, Proterorhinus and Mesogobius comprise the sister clade of the Ponticola and Babka clade. Further work is needed to clarify the interrelationships of the tadpole gobies. Invasiveness is widespread in freshwater and euryhaline taxa of Neogobius, Proterorhinus, Babka, and Ponticola; but not in marine species, Mesogobius, or tadpole gobies.