A phylogenetic analysis of Neotoma varia (Rodentia: Cricetidae), a rediscovered, endemic, and threatened rodent from Datil Island, Sonora, Mexico

Abstract

The systematics of the rediscovered and threatened rodent, Neotoma varia, from Datil Island in the Gulf of California, was assessed using sequences from the mitochondrial cytochrome b gene (Cyt b) regarding specimens of N. albigula from Tiburon Island and populations on the mainland off Datil Island. Neotoma varia was originally described as a species and subsequently considered a subspecies, relegated to subspecific status based on morphologic characters and few specimens; no genetic analyses have been published. Bayesian inference, maximum-parsimony, maximumlikelihood, and distance optimality criteria based on 828-bp of the Cyt b gene from individuals representing 11 populations, converged on essentially identical tree topologies, consistent with the inclusion of N. varia within N. albigula. The population of Datil Island is related to specimens from Tiburon Island and the adjacent mainland populations showing low levels of genetic differentiation with other subspecies of N. albigula (0.2–1.4%). Previous morphologic analyses indicated inconstancy in characters regarding the holotype; however, N. varia is morphologically different in the oclusal view of the upper molars. Under these conditions, we consider N. varia as a subspecies of N. albigula. N. a. varia has a very specific habitat and is present only on a very small part of the island; in spite of low divergence regarding other N. albigula subspecies, N. a. varia possesses a genetic identity and needs to be considered as a critically endangered population.