True frogs of the genus Rana are widely used as model organisms in studies of development, genetics, physiology, ecology, behavior, and evolution. Comparative studies among the more than 100 species of Rana rely on an understanding of the evolutionary history and patterns of diversification of the group. We estimate a well-resolved, time-calibrated phylogeny from sequences of six nuclear and three mitochondrial loci sampled from most species of Rana, and use that phylogeny to clarify the group's diversification and global biogeography. Our analyses consistently support an "Out of Asia" pattern with two independent dispersals of Rana from East Asia to North America via Beringian land bridges. The more species-rich lineage of New World Rana appears to have experienced a rapid radiation following its colonization of the New World, especially with its expansion into montane and tropical areas of Mexico, Central America, and South America. In contrast, Old World Rana exhibit different trajectories of diversification; diversification in the Old World began very slowly and later underwent a distinct increase in speciation rate around 29-18 Ma. Net diversification is associated with environmental changes and especially intensive tectonic movements along the Asian margin from the Oligocene to early Miocene. Our phylogeny further suggests that previous classifications were misled by morphological homoplasy and plesiomorphic color patterns, as well as a reliance primarily on mitochondrial genes. We provide a phylogenetic taxonomy based on analyses of multiple nuclear and mitochondrial gene loci. [Amphibians; biogeography; diversification rate; Holarctic; transcontinental dispersal.
Biogeographic studies are important for understanding the natural history of faunas. To comprehend the geographical patterns of genetic variation in anurans in Taiwan, we investigated the genetic structure of Sylvirana latouchii (Anura, Ranidae) from 31 populations by using mitochondrial DNA (mtDNA) cytochrome b sequences. A neighbor-joining tree of 38 haplotypes revealed three major divergences in Taiwanese S. latouchii: the northern, western, and eastern-and-southern clades. Each clade was restricted to a single geographical district and showed obvious differentiation. The patterns of geographical divergence in this species reflect common historical events experienced by other native animals distributed in Taiwan. The order of divergence times between clades was inferred using a molecular clock test. The population relationship of S. latouchii between Taiwan and mainland China is discussed. Further study employing more populations of S. latouchii from mainland China is necessary to clarify the original geographical patterns and migratory history of this species.
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