Oolon Colluphid
01 Apr 2009, 11:49 AM
PNAS vol. 106 no. 13 pp. 5235-5240 (31 March 2009 )
Retroposon analysis and recent geological data suggest near-simultaneous divergence of the three superorders of mammals
Nishihara, Maruyama and Okada
As a consequence of recent developments in molecular phylogenomics, all extant [currently alive] orders of placental mammals have been grouped into 3 lineages: Afrotheria [noted for their puffball hair], Xenarthra, and Boreotheria, which originated in Africa, South America, and Laurasia, respectively.
Despite this advancement, the order of divergence of these 3 lineages remains unresolved. Here, we performed extensive retroposon analysis with mammalian genomic data.
Surprisingly, we identified a similar number of informative retroposon loci that support each of 3 possible phylogenetic hypotheses: the basal position [diverged first] for Afrotheria (22 loci), Xenarthra (25 loci), and Boreotheria (21 loci).
This result indicates that the divergence of the placental common ancestor into the 3 lineages occurred nearly simultaneously.
Thus, we examined whether these molecular data could be integrated into the geological context by incorporating recent geological data. We obtained firm evidence that complete separation of Gondwana into Africa and South America occurred 120 ± 10 Ma. Accordingly, the previous reported time frame (division of Pangea into Gondwana and Laurasia at 148–138 Ma and division of Gondwana at 105 Ma) cannot be used to validate mammalian divergence order. Instead, we use our retroposon results and the recent geological data to propose that near-simultaneous divisions of continents leading to isolated Africa, South America, and Laurasia caused nearly concomitant divergence of the ancient placental ancestor into 3 lineages, Afrotheria, Xenarthra, and Boreotheria, ≈120 Ma.
Open Access article (http://www.pnas.org/content/106/13/5235.full) (whole thing for free)
Retroposon analysis and recent geological data suggest near-simultaneous divergence of the three superorders of mammals
Nishihara, Maruyama and Okada
As a consequence of recent developments in molecular phylogenomics, all extant [currently alive] orders of placental mammals have been grouped into 3 lineages: Afrotheria [noted for their puffball hair], Xenarthra, and Boreotheria, which originated in Africa, South America, and Laurasia, respectively.
Despite this advancement, the order of divergence of these 3 lineages remains unresolved. Here, we performed extensive retroposon analysis with mammalian genomic data.
Surprisingly, we identified a similar number of informative retroposon loci that support each of 3 possible phylogenetic hypotheses: the basal position [diverged first] for Afrotheria (22 loci), Xenarthra (25 loci), and Boreotheria (21 loci).
This result indicates that the divergence of the placental common ancestor into the 3 lineages occurred nearly simultaneously.
Thus, we examined whether these molecular data could be integrated into the geological context by incorporating recent geological data. We obtained firm evidence that complete separation of Gondwana into Africa and South America occurred 120 ± 10 Ma. Accordingly, the previous reported time frame (division of Pangea into Gondwana and Laurasia at 148–138 Ma and division of Gondwana at 105 Ma) cannot be used to validate mammalian divergence order. Instead, we use our retroposon results and the recent geological data to propose that near-simultaneous divisions of continents leading to isolated Africa, South America, and Laurasia caused nearly concomitant divergence of the ancient placental ancestor into 3 lineages, Afrotheria, Xenarthra, and Boreotheria, ≈120 Ma.
Open Access article (http://www.pnas.org/content/106/13/5235.full) (whole thing for free)