Cytosystematic Evidence against Monophyly of the Peromyscus boylii Species Group (Rodentia: Cricetidae)

Although the Peromyscus boylii species group (Rodentia: Cricetidae) traditionally has been considered monophyletic, recent morphologic analyses indicate that the member taxa comprise two phenotypic groups (Carleton, 1977). The magnitude of phenetic differences between these groups suggests that the boylii group consists of two distinct lineages. However, investigators advocating a dual-lineage hypothesis have restricted ingroup analyses to boylii-group members and have assumed a priori that the group was monophyletic. Because non-monophyletic alternatives are possible, a more inclusive approach using non-boylii group members is needed. A cladistic analysis of the boylii species group was performed by use of chromosomal-banding data from 31 species of Peromyscus, including eight species (comprising 12 taxa) belonging to the boylii group. Based on these data, the most parsimonious reconstruction of the phylogenetic affinities within the subgenus does not support monophyly of the boylii group, and does not corroborate the dual-lineage hypothesis. The boylii group is fragmented into several clades and, like the truei group, appears to be polyphyletic.