Relict groups of spiny frogs indicate Late Paleogene-Early Neogene trans-Tibet dispersal of thermophile faunal elements.

Background: The Himalaya-Tibet orogen (HTO) presents an outstanding geologically active formation that contributed to, and fostered, modern Asian biodiversity. However, our concepts of the historical biogeography of its biota are far from conclusive, as are uplift scenarios for the different parts of the HTO. Here, we revisited our previously published data set of the tribe Paini extending it with sequence data from the most western Himalayan spiny frogs and and using them as an indirect indicator for the potential paleoecological development of Tibet.

Methods: We obtained sequence data of two mitochondrial loci (16S rRNA, COI) and one nuclear marker (Rag1) from samples from Kashmir Himalaya as well as sequence data from the Hindu Kush available from GenBank to complement our previous data set. A Maximum likelihood and dated Bayesian gene tree were generated based on the concatenated data set. To resolve the inconsistent placement of , we performed different topology tests.

Results: Consistent with previous results, the Southeast Asian genus is sister to all other spiny frogs. The results further reveal a basal placement of relative to and with an estimated age of 26 Mya. Based on the topology tests, the phylogenetic position of as a sister clade to seems to be most likely, resulting in a paraphyletic genus and a separation from the latter clade around 20 Mya, although a basal position of to the genus cannot be entirely excluded. Both, the placements of and support the presence of basal Paini lineages in the far northwestern part of the HTO, which is diametrically opposite end of the HTO with respect to the ancestral area of spiny frogs in Southeast Asia. These striking distributional patterns can be most parsimoniously explained by trans-Tibet dispersal during the late Oligocene (subtropical ) respectively early Miocene (warm temperate ). Within spiny frogs, only members of the monophyletic + clade are adapted to the colder temperate climates, indicating that high-altitude environments did not dominate in the HTO before 15 Mya. Our results are consistent with fossil records suggesting that large parts of Tibet were characterized by subtropical to warm temperate climates at least until the early Miocene. They contradict prevalent geological models of a highly uplifted late Paleogene proto-Plateau.