Molecular estimation of eulipotyphlan divergence times and the evolution of "Insectivora"

Insectivores are one of the key groups in understanding mammalian origins. For years, systematics of "Lipotyphia" taxa remained extremely unstable and challenged. Today, with the application of molecular techniques, "Lipotyphla" appears to be a paraphyletic assemblage that encompasses hedgehogs, shrews, and moles (i.e., Eulipotyphla-a member of Laurasiatheria), and golden moles and tenrecs (i.e... Afrosoricida-a member of Afrotheria). Based on nuclear genes and on this well-established phylogenetic framework. we estimated Bayesian relaxed molecular clock divergence times among major lineages of "Lipotyphla." Crown placental mammals are shown to diversify 102 +/- 6 million years ago (Mya; mean one standard-deviation), followed by Boreoeutheria (94 +/- 6 Mya),. Laurasiatheria (85 +/- 5 Mya), and Eulipotyphla (73 +/- 5), with moles separating from hedgehogs + shrews just at the K/T boundary (65 +/- 5 Mya). During the Early and Middle Eocene, all extant eulipotyphlan subfamilies originated: Uropsilinae (52 +/- 5 Mya), and Desmaninae, Talpinae, Erinaceinae, Hylomyinae, Soricinae, and Crocidurinae (3842 +/- 5 Mya). Afrosoricida separated from Macroscelidae 69 +/- 5 Mya, golden moles from tenrecs 63 +/- 5 Mya, and the diversification within tenrecs Occurred 43 +/- 5 Mya. Divergence times are shown to be in reasonably good agreement with the fossil record of eulipotyphlans, but not with the one of afrosoricid "insectivores." Eulipotyphlans diversification might have been sculpted by variations in paleoclimates of the cenozoic era. (C) 2003 Elsevier Science (USA). All rights reserved.