Tracking climate change in the spatial distribution pattern and the phylogeographic structure of Hyrcanian wood frog,Rana pseudodalmatina(Anura: Ranidae)

Abstract

Climate change has essential effects on patterns of population persistence, connectivity, and divergence. We used mtDNA sequences and species distribution modeling to assess the impact of climatic changes in the past (Last Glacial Maximum [LGM: 21 Kya] and Mid-Holocene [6 Kya]), recent (1970–2000), and future (2070) on the phylogeography and spatial distribution of populations of the Hyrcanian wood frog, Rana pseudodalmatina, in northern Iran. Based on two mitochondrial genes (cytochrome b and 16S ribosomal RNA), we found evidence for two regional patterns that diverged in the Pleistocene (1.6 Mya) and are distributed in the eastern and western sections of the current species range. Biogeographic analyses support the hypothesis that both vicariance (an increase in the Caspian Sea water levels) and dispersal events have been involved in shaping the species' genetic structure. Reconstruction of the ancestral distribution of R. pseudodalmatina suggests the species' range contracted in two independent eastern and western glacial refugia during the LGM, expanding from the Mid-Holocene to the present to occupy Hyrcanian forests continuously. According to future climate projections, the species' range shows a tendency to shift to higher altitudes. Landscape connectivity analyses support higher population continuity in the central part of the current range, with isolated populations in the easternmost and westernmost extremes. Our integrative study of R. pseudodalmatina provides support for the “refugia-within-refugia” scenario in the Hyrcanian forests.