Neogene and present-day zoogeography of killifishes ( Aphanius and Aphanolebias) in the Mediterranean and Paratethys areas

Abstract

It has been suggested that the Recent zoogeography and diversification of the killifish Aphanius is a result of the palaeogeographic reorganisation of the Mediterranean area during the Neogene. However, little is known about the fossil distribution of killifishes in the Mediterranean, and literature data are scattered. This paper summarizes the data on the stratigraphic range and palaeoecology of the Aphanius and Aphanolebias species from three time intervals in the Miocene of southwestern Europe, the Paratethys, and the Aegean based on previously described otoliths and articulated skeletons, and newly collected otoliths from Spain. Moreover, the mollusc palaeocommunities that co-occur with the otoliths from Spain are considered. Our data indicate that species-diversity and zoogeography of fossil killifishes is closely linked to those palaeogeographic and climate conditions that affect the abundance of brackish and swamp habitats. The appearance of fossil Aphanolebias or Aphanius in continental deposits of Early and Middle Miocene age can be considered indicative of a warm palaeoclimate with seasonal or interannual aridity. The relatively wide geographic distribution of the Late Miocene Aphanius crassicaudus is strikingly different from the zoogeographic pattern exhibited by the Early and Middle Miocene Aphanius species, and probably resulted from (i) increased numbers of brackish and swamp habitats due to the Messinian event, and (ii) the closure of the deep seaway between the former island of Italy and the mainland to the north. We hypothesize that the wide geographic distribution of the present-day A. fasciatus in the Mediterranean Sea, as well as the limited zoogeography of A. iberus and A. baeticus along the Spanish coast, is a result of zoogeographic history of their ancestors in the Late Miocene. Moreover, the present-day ability of Aphanius to survive under extreme conditions probably represents a vestige of the broad ecological tolerance of the Miocene Aphanius species.