Systematics and the Unexpected High Mitochondrial Genetic Divergence of Nelsonia goldmani (Rodentia: Cricetidae) from Mexican Highlands

Nelsonia is a Mexican endemic genus of woodrat and includes only two uncommon species: N. neotomodon and N. goldmani . This genus is of great phylogenetic interest, but has been ignored in most taxonomic studies and revisions due to the scarcity of its representatives in museum collections. The phylogenetic position of this genus is poorly known, and its interspecific and intraspecific relationships are unclear. The aim of this study was to infer the phylogenetic position of Nelsonia within the Cricetidae family, to determine whether the two species are monophyletic groups, and to assess the intraspecific genetic variation of N. goldmani . We amplified two mitochondrial markers: cytochrome b and cytochrome oxidase subunit 1 from specimens collected recently and museum samples from the type locality in 1903 to 1981 sampling half the known individuals reported to date. Sequences were analyzed by Bayesian and maximum likelihood to generate a phylogenetic hypothesis. Divergence time was performed to infer the biogeographic history. The genus Nelsonia was monophyletic and sister group of the current Xenomys , Hodomys , and Neotoma diverging in the middle-late Miocene. Nelsonia goldmani was also monophyletic, diverged from N. neotomodon during the late Miocene, and was formed by four highly divergent lineages. Further evidence may support a rank of full species for each of the four clades. Our results along with fossil data suggest that likely the genus Nelsonia diverged from Repomys or Protorepomys in the region of Californian-Rocky Mountains of the United States of America, and posteriorly invaded the Western Sierra Madre and Transmexican Volcanic Belt in Mexico.