Data from: Evolutionary melting pots: a biodiversity hotspot shaped by ring diversifications around the Black Sea in the Eastern tree frog (Hyla orientalis)

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.