Review of the Philippine genera Chrotomys and Celaenomys (Murinae) and description of a new species

The murine genera Celaenomys and Chrotomys comprise a group of semifossorial, vermivorous rodents endemic to the Philippines. Analysis of variation within this group supports the recognition of 4 named species occurring on the large islands of Luzon and Mindoro, as well as our description of a 5th species from Sibuyan, a small island in the central Philippines that has remained isolated from the other islands by deep water channels. Examination of cytochrome-b gene sequence data from 4 of the 5 taxa indicates that Celaenomys silaceus may be basal and sister to the other taxa but morphological and chromosomal data do not support the recognition of Celaenomys as a separate genus. Analysis of the sequence data indicates a relatively early separation of the Sibuyan species and a later split between 2 species of Chrotomys on Luzon. Diversification of Chrotomys appears to have involved speciation associated with both habitat vicariance on Luzon and overwater dispersal to neighboring islands. Most of the members of this clade are restricted to mid- or high-elevation forests, have limited geographic ranges within the archipelago, and some may be imperiled due to loss of natural habitat.