title: Evolutionary melting pots: a biodiversity hotspot shaped by ring diversifications around the Black Sea in the Eastern tree frog (Hyla orientalis).
abstract: Hotspots of intraspecific genetic diversity, which are of primary importance for the conservation of species, have been associated with glacial refugia, that is areas where species survived the Quaternary climatic oscillations. However, the proximate mechanisms generating these hotspots remain an open issue. Hotspots may reflect the long-term persistence of large refugial populations; alternatively, they may result from allopatric differentiation between small and isolated populations, that later admixed. Here, we test these two scenarios in a widely distributed species of tree frog, Hyla orientalis, which inhabits Asia Minor and southeastern Europe. We apply a fine-scale phylogeographic survey, combining fast-evolving mitochondrial and nuclear markers, with a dense sampling throughout the range, as well as ecological niche modelling, to understand what shaped the genetic variation of this species. We documented an important diversity centre around the Black Sea, composed of multiple allopatric and/or parapatric diversifications, likely driven by a combination of Pleistocene climatic fluctuations and complex regional topography. Remarkably, this diversification forms a ring around the Black Sea, from the Caucasus through Anatolia and eastern Europe, with terminal forms coming into contact and partially admixing in Crimea. Our results support the view that glacial refugia generate rather than host genetic diversity and can also function as evolutionary melting pots of biodiversity. Moreover, we report a new case of ring diversification, triggered by a large, yet cohesive dispersal barrier, a very rare situation in nature. Finally, we emphasize the Black Sea region as an important centre of intraspecific diversity in the Palearctic with implications for conservation.
authors.affiliation: Department of Ecology & Evolution, University of Lausanne, Biophore Building, Lausanne, 1015, Switzerland.
authors.forename: Christophe
authors.initials: C
authors.lastname: Dufresnes
authors.affiliation: Institute of Cytology, Russian Academy of Sciences, Tikhoretsky pr. 4, St. Petersburg, 194064, Russia.
authors.forename: Spartak N
authors.initials: SN
authors.lastname: Litvinchuk
authors.affiliation: Department of Ecology & Evolution, University of Lausanne, Biophore Building, Lausanne, 1015, Switzerland.
authors.forename: Julien
authors.initials: J
authors.lastname: Leuenberger
authors.affiliation: Department of Ecology & Evolution, University of Lausanne, Biophore Building, Lausanne, 1015, Switzerland.
authors.forename: Karim
authors.initials: K
authors.lastname: Ghali
authors.affiliation: The Museum of Nature, V. N. Karazin Kharkiv National University, Trinkler st. 8, Kharkiv, 61058, Ukraine.
authors.forename: Oleksandr
authors.initials: O
authors.lastname: Zinenko
authors.affiliation: Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Müggelseedamm 301, Berlin, D-12587, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Stöck
authors.affiliation: Department of Ecology & Evolution, University of Lausanne, Biophore Building, Lausanne, 1015, Switzerland.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Perrin
mesh_terms: D000818:Animals; D001001:Anura / Q000235:genetics*; D001208:Asia; D044822:Biodiversity; D059038:Black Sea; D005061:Europe, Eastern; D014644:Genetic Variation; D005828:Genetics, Population; D058974:Phylogeography; D000068236:Refugium
keywords: Quaternary glaciations; amphibian; conservation; hotspot; intraspecific diversity; isolation by distance; phylogeography; refugia within refugia; ring species