Maximum Likelihood and Bayesian Analyses of Mitochondrial and Nuclear Genes

Author manuscript, published in "Molecular Phylogenetics and Evolution 28, 2 (2003) 261-75" Delsuc et al. Molecular systematics of armadillos 2 ABSTRACT The thirty living species of armadillos, anteaters and sloths (Mammalia: Xenarthra) represent one of the three major clades of placentals. Armadillos (Cingulata: Dasypodidae) are the earliest and most speciose xenarthran lineage with twenty-one described species. The question of their tricky phylogeny was here studied by adding two mitochondrial genes (NADH dehydrogenase subunit 1 [ND1] and 12S ribosomal RNA [12S rRNA]) to the three protein-coding nuclear genes (α2B Adrenergic receptor [ADRA2B], Breast Cancer Susceptibility exon 11 [BRCA1], and von Willebrand Factor exon 28 [VWF]) yielding a total of 6,869 aligned nucleotide sites for thirteen xenarthran species. The two mitochondrial genes were characterized by marked excesses of transitions over transversions—with a strong bias toward CT transitions for the 12S rRNA—and exhibited two-to five-fold faster evolutionary rates than the fastest nuclear gene (ADRA2B). Maximum likelihood and Bayesian phylogenetic analyses supported the monophyly of Dasypodinae, Tolypeutinae and Euphractinae, with the latter two armadillo subfamilies strongly clustering together. Conflicting branching points between individual genes involved relationships within the subfamilies Tolypeutinae and Euphractinae. Owing to a greater number of informative sites, the overall concatenation favored the mitochondrial topology with the classical grouping of Cabassous and Priodontes within Tolypeutinae, and a close relationship between Euphractus and Chaetophractus within Euphractinae. However, low statistical support values associated with almost equal distributions of apomorphies among alternatives suggested that two parallel events of rapid speciation occurred within these two armadillo subfamilies. Mitochondrial and nuclear markers – Maximum Likelihood and Bayesian phylogenetics.