Parallel adaptive radiations in two major clades of placental mammals

Higher level relationships among placental mammals, as well as the historic al biogeography and morphological diversification of this group, remain unc lear(1-3). Here we analyse independent molecular data sets, having aligned lengths of DNA of 5,708 and 2,947 base pairs, respectively, for all orders of placental mammals. Phylogenetic analyses resolve placental orders into f our groups: Xenarthra, Afrotheria, Laurasiatheria, and Euarchonta plus Glir es. The first three groups are consistently monophyletic with different met hods of analysis. Euarchonta plus Glires is monophyletic or paraphyletic de pending on the phylogenetic method. A unique nine-base-pair deletion in exo n 11 of the BRCA1 gene provides additional support for the monophyly of Afr otheria, which includes proboscideans, sirenians, hyracoids, tubulidentates , macroscelideans, chrysochlorids and tenrecids. Laurasiatheria contains ce tartiodactyls, perissodactyls, carnivores, pangolins, bats and eulipotyphla n insectivores. Parallel adaptive radiations have occurred within Laurasiat heria and Afrotheria. In each group, there are aquatic, ungulate and insect ivore-like forms.