Evolutionary history of the most speciose mammals: Molecular phylogeny of muroid rodents

Phylogenetic relationships between 32 species of rodents representing 14 su bfamilies of Muridae and four subfamilies of Dipodidae were studied using s equences of the nuclear protein-coding genes Lecithin Cholesterol Acyl Tran sferase (LCAT) and von Willebrand Factor (vWF). An examination of some evol utionary properties of each data matrix indicates that the two genes are ra ther complementary, with lower rates of nonsynonymous substitutions for LCA T. Both markers exhibit a wide range of GC3 percentages (55%-89%), with sev eral taxa above 70% GC3 for vWF, which indicates that those exonic regions might belong to the richest class of isochores. The primary sequence data a pparently harbor few saturations, except for transitions on third codon pos itions for vWF, as indicated by comparisons of observed and expected pairwi se values of substitutions. Phylogenetic trees based on 1,962 nucleotidic s ites from the two genes indicate that the 14 Muridae subfamilies are organi zed into five major lineages. An early isolation leads to the clade uniting the fossorial Spalacinae and semifossorial Rhizomyinae with a strong robus tness. The second lineage includes a series of African taxa representing ne somyines, dendromurines, cricetomyines, and the sole living member of mystr omyines. The third one comprises only the mouselike hamster Calomyscus. The fourth clade represents the cricetines, myospalacines, sigmodontines, and arvicolines, whereas the fifth one comprises four "traditional" subfamilies (Gerbillinae, Murinae, Otomyinae, and Acomyinae). Within these groups, we confirm the monophyly of almost all studied subfamilies, namely, Spalacinae , Rhizomyinae, Nesomyinae, Cricetomyinae, Arvicolinae, Sigmodontinae, Crice tinae, Gerbillinae, Acomyinae, and Murinae. Finally, we present evidence th at the sister group of Acomyinae is Gerbillinae, and we confirm a nested po sition of Myospalacinae within Cricetinae and Otomyinae within Murinae. Fro m a biogeographical point of view, the five main lineages spread and radiat ed from Asia with different degrees of success: the first three groups are now represented by a limited number of species and genera localized in some regions, whereas the last two groups radiated in a large variety of specie s and genera dispersed all over the world.