Phylogeographic variation in two Central American pocket gophers (Orthogeomys)

Abstract

Restriction-site data for mitochondrial DNA were used to test the isolation-by-distance model of genetic variation in two species of Central American pocket gophers, Orthogeomys cherriei and O. underwoodi. Maximum- likelihood and parsimony analyses yielded trees with topologies concordant with predictions based on physiography. Relationships within O. cherriei reveal probable effects of a partial geographic barrier in the form of the CordiLlera de Tilaran in northcentral Costa Rica. The phylogenetic tree for O. underwoodi branches in a ladder-like fashion from south to north suggesting the absence of obstructions to gene flow. Results of Mantel tests indicated that variation of mtDNA within O. cherriei is not consistent with a hypothesis of isolation-by-distance, whereas variation within O. underwoodi shows a statistically significant association with geographic distance. Estimates of intraspecific sequence divergence indicate that the present distributions of these two species resulted from climatic shifts in the Pleistocene.