Molecular systematics of the genus Sigmodon: results from mitochondrial and nuclear gene sequences.

Phylogenetic relationships within the genus Sigmodon Say and Ord, 1825 were examined using sequence data from multiple gene regions, including exon 1 of the nuclear-encoded interphotoreceptor retinoid binding protein, intron 7 of the nuclear beta-fibrinogen gene, and the mitochondrial cytochrome b gene from 27 individuals representing 11 species of Sigmodon. Nuclear genes were analyzed independently, combined with each other, and combined with the mitochondrial data. Topologies were constructed using parsimony and Bayesian methods, with nodal support provided by bootstrap and posterior probability values. All analyses recovered four independent clades (I-IV), each representing unique species groups: hispidus, fulviventer, peruanus, and alstoni. The analyses from the combined data also provided support for relationships previously proposed within those species groups.