Resolution of the laurasiatherian phylogeny: evidence from genomic data

Abstract

Despite great progress over the past decade, some portions of the mammalian tree of life remain unresolved. In particular, relationships among the different orders included within the supraordinal group Laurasiatheria have been proven difficult to determine, and have received poor support in the vast majority of phylogenomic studies of mammalian systematics. We estimated interordinal relationships within Laurasiatheria using sequence data from 3733 protein-coding genes. Our study included data from from 11 placental mammals, corresponding to five of the six orders of Laurasiatheria, plus five outgroup species. Ingroup and outgroup species were chosen to maximize the number single-copy ortholog genes for which sequence data was available for all species in our study. Phylogenetic analyses of the concatenated dataset using maximum likelihood and Bayesian methods resulted on an identical and well supported topology in all alignment strategies compared. Our analyses provide high support for the sister relationship between Chiroptera and Cetartiodactyla and also provide support for placing Perissodactyla as sister to Carnivora. We obtained maximal estimates of bootstrap support (100%) and posterior probability (1.00) for all nodes within Laurasiatheria. Our study provides a further demonstration of the utility of very large and conserved genomic dataset to clarify our understanding of the evolutionary relationships among mammals.