Parallel adaptive radiations in two major clades of placental mammals

Abstract

Higher level relationships among placental mammals, as well as the historical biogeography and morphological diversification of this group, remain unclear. 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 four groups: Xenarthra, Afrotheria, Laurasiatheria, and Euarchonta plus Glires. The first three groups are consistently monophyletic with different methods of analysis. Euarchonta plus Glires is monophyletic or paraphyletic depending on the phylogenetic method. A unique nine-base-pair deletion in exon 11 of the BRCA1 gene provides additional support for the monophyly of Afrotheria, which includes proboscideans, sirenians, hyracoids, tubulidentates, macroscelideans, chrysochlorids and tenrecids. Laurasiatheria contains cetartiodactyls, perissodactyls, carnivores, pangolins, bats and eulipotyphlan insectivores. Parallel adaptive radiations have occurred within Laurasiatheria and Afrotheria. In each group, there are aquatic, ungulate and insectivore-like forms.

Early Tertiary mammals from North Africa reinforce the molecular Afrotheria clade

“…Molecular phylogenies argue for an unusual case of endemism in Africa of Afrotheria from the Cretaceous to the Miocene (approx. 105-20 Myr ago; Madsen et al 2001;Springer et al 2003), while our results suggest the existence of dispersal events between Africa, Euramerica and Asia. According to the fossil record (figure 5), such events might have occurred around the Palaeocene/Eocene (P/E) boundary during which numerous intercontinental mammalian dispersals occurred (Bowen et .…”

“…For Afrotheria, there is a broad molecular consensus for its monophyly deriving from various nuclear and mitochondrial genes as well as from rare genomic changes that constitute probable synapomorphies ( Madsen et al 2001). In contrast, morphological data have until now failed to provide strong support for Afrotheria (Shoshani & McKenna 1998;Archibald 2003;Robinson & Seiffert 2004;Zack et al 2005).…”

Cross-species chromosome painting in the golden mole and elephant-shrew: support for the mammalian clades Afrotheria and Afroinsectiphillia but not Afroinsectivora

“…The molecular studies of Madsen et al (2001), Murphy et al (2001a,b), Scally et al (2001), Waddell et al (2001), Delsuc et al (2002) and Waddell & Shelley (2003), among others, provide evidence for the placement of the root of the evolutionary tree between the Afrotheria and the remaining clades. However, they could not statistically exclude Xenarthra, or Xenarthra plus Afrotheria (Atlantogenata; Waddell et al 1999b) as sister to all other placentals.…”

“…Madsen et al 2001;Murphy et al 2001a,b;Scally et al 2001;Waddell et al 2001) have generated relatively well-resolved phylogenies which suggest that extant placental (eutherian) mammals can be divided into four major supraordinal clades. One of these is the Afrotheria (Stanhope et al 1998a), a clade of probable African origin that includes elephantshrews (Macroscelidea), golden moles (Chrysochloridae) and tenrecs (Tenrecidae) that are grouped with aardvarks (Tubulidentata), hyraxes (Hyracoidea), elephants (Proboscidea) and the dugongs and manatees (Sirenia).…”

Evolutionary transformations of fetal membrane characters in Eutheria with special reference to Afrotheria

“…Of particular note is the view that all extant eutherian species belong to one of four superordinal clades (Madsen et al, 2001;Murphy et al, 2001a,b;Waddell et al, 2001;Springer et al, 2005a,b). These ideas about mammalian evolution have provoked fruitful debate and stimulated research to test them by using morphological data (Asher, 2001;Symonds, 2005).…”