Abstract
Understanding the early evolution of placental mammals is one of the most challenging issues in mammalian phylogeny. Here, we addressed this question by using the sequence data of the ENCODE consortium, which include 1% of mammalian genomes in 18 species belonging to all main mammalian lineages. Phylogenetic reconstructions based on an unprecedented amount of coding sequences taken from 218 genes resulted in a highly supported tree placing the root of Placentalia between Afrotheria and Exafroplacentalia (Afrotheria hypothesis). This topology was validated by the phylogenetic analysis of a new class of genomic phylogenetic markers, the conserved noncoding sequences. Applying the tests of alternative topologies on the coding sequence dataset resulted in the rejection of the Atlantogenata hypothesis (Xenarthra grouping with Afrotheria), while this test rejected the second alternative scenario, the Epitheria hypothesis (Xenarthra at the base), when using the noncoding sequence dataset. Thus, the two datasets support the Afrotheria hypothesis; however, none can reject both of the remaining topological alternatives.
Highlights
The relationships among mammalian lineages have recently been revised using multiple gene phylogenetic analyses leading to the recognition of four main placental clades: Euarchontoglires, Laurasiatheria, Xenarthra, and Afrotheria
The three possible scenarios for the position of the root of placental mammals are: (1) Afrotheria at the base of Placentalia (Xenarthra grouping with Boreoeutheria in the Exafroplacentalia); this hypothesis emerged from molecular phylogenetic studies [2,7]
Recent molecular phylogenetic studies have shown that living placental mammals belong to one of the three subgroups: Boreoeutheria, Afrotheria, or Xenarthra, but the relations between these are still unknown
Summary
The relationships among mammalian lineages have recently been revised using multiple gene phylogenetic analyses leading to the recognition of four main placental clades: Euarchontoglires, Laurasiatheria, Xenarthra, and Afrotheria. The remaining placental lineage is called Afrotheria due to the African origin of its stem members and includes elephants, Sirenia, Hyracoidea, Tubulidentata, Macroscelida, Tenrecidae, and Chrysochloridae [2]. It is still unclear, how Afrotheria, Xenarthra, and Boreoeutheria are interrelated, though most molecular studies favor Afrotheria as the basal placental lineage (e.g., [2,5,6]). The three possible scenarios for the position of the root of placental mammals are: (1) Afrotheria at the base of Placentalia (Xenarthra grouping with Boreoeutheria in the Exafroplacentalia); this hypothesis emerged from molecular phylogenetic studies [2,7].
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
