Effects of current and historic habitat fragmentation on the genetic structure of the sand goby Pomatoschistus minutus (Osteichthys, Gobiidae) EMILIE BOISSIN*†, THIERRY BERNARD HOAREAU‡ and PATRICK BERREBI§ Laboratoire Ecosystèmes Lagunaires, UMR 5119, Université Montpellier 2, cc093, place E. Bataillon, 34095 Montpellier, Cedex 05, France Received 1 April 2010; accepted for publication 3 August 2010 Habitat fragmentation is a major force that will influence the evolution of a species and its distribution range. Pomatoschistus minutus, the sand goby, has a North Atlantic–Mediterranean distribution and shows various level of habitat fragmentation along its geographic repartition. The use of mitochondrial sequences of the cytochrome b (cyt b) gene and two co-dominant sets of nuclear markers (introns and microsatellites) allowed us to describe the relationships between P. minutus populations belonging to several different geographical regions of Europe and to assess the structure of populations inhabiting the Golfe du Lion, along the French Mediter- ranean coast. The present study confirms that the taxon located in the Adriatic Sea (Venice) should be con- sidered as a distinct species, separated approximately 1.75 Mya. The comparison of P. minutus between the Atlantic and western Mediterranean coasts using polymorphic co-dominant markers revealed that they belong to two demographically independent units, and thus could be considered as well as distinct species, more recently separated (0.3 Mya). The Pleistocene glaciations seem therefore to have played an important role in the diversification of this complex. Finally, at a regional scale in the Golfe du Lion, P. minutus appears to form a single huge homogeneous population. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 102, 175–198. ADDITIONAL KEYWORDS: glacial refugium – historical demography – Mediterranean Sea – population expansion. INTRODUCTION The geographic distribution of marine species is shaped over time by complex interactions between abiotic processes (e.g. past geological events or current oceanographic features) and intrinsic biological ability or requirements (e.g. dispersal abilities or ecological niche). In light of these interactions, habitat fragmen- tation is a major force that will influence the evolution of a species and its distribution range. This fragmen- tation can be: (1) historic and not visible in the current range of a species, but residual as a signature in some regions of the genome, or (2) contemporaneous and easily visible using co-dominant markers such as mic- rosatellites. Using appropriate markers such as mito- chondrial ones or slowly evolving nuclear ones, some studies have identified several historical events that have split apart the populations of the Atlantic and Mediterranean biogeographic provinces for several species. For example, lowering of the Mediterranean Sea level during the Messinian Salinity Crisis (MSC: 5.6 Mya), precluded any gene flow between the two *Corresponding author. E-mail: eboissin@gmail.com †Current address: Forestry and Agricultural Biotechnology Institute, Department of Genetics, University of Pretoria, Pretoria 0002, Pretoria, RSA. ‡Current address: Molecular Ecology and Evolution Programme, Department of Genetics, University of Pretoria, Pretoria 0002, Pretoria, RSA. §Current address: Institut des Sciences de l’Evolution, UMR UM2/CNRS/IRD 5554, Université Montpellier 2, cc065, place E. Bataillon, 34095 Montpellier cedex 05, France. Biological Journal of the Linnean Society, 2011, 102, 175–198. With 5 figures © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 102, 175–198 175 Downloaded from https://academic.oup.com/biolinnean/article/102/1/175/2450616 by guest on 08 December 2022