Molecular Evidence for the Major Clades of Placental Mammals

Authors: Scally M.¹; Madsen O.²; Douady C.J.¹; de Jong W.W.³; Stanhope M.J.⁴; Springer M.S.⁵

Source: Journal of Mammalian Evolution, Volume 8, Number 4, December 2001 , pp. 239-277(39)

Publisher: Springer

Purchase options

The full text electronic article is available for purchase. You will be able to download the full text electronic article after payment.

$47.00 plus tax Refund Policy

More like this?

In this: publication
By this: publisher
In this Subject: Zoology
By this author: Scally M. ; Madsen O. ; Douady C.J. ; de Jong W.W. ; Stanhope M.J. ; Springer M.S.

Content Key:

- Free

- New

- Open Access

- Subscribed

- Free Trial

Abstract:

Higher-level relationships among placental mammals, as well as the historical biogeography of this group against the backdrop of continental fragmentation and reassembly, remain poorly understood. Here, we analyze two independent molecular data sets that represent all placental orders. The first data set includes six genes (A2AB, IRBP, vWF, 12S rRNA, tRNA valine, 16S rRNA; total = 5.71 kb) for 26 placental taxa and two marsupials; the second data set includes 2.95 kb of exon 11 of the BRCA1 gene for 51 placental taxa and four marsupials. We also analyzed a concatenation of these data sets (8.66 kb) for 26 placentals and one marsupial. Unrooted and rooted analyses were performed with parsimony, distance methods, maximum likelihood, and a Bayesian approach. Unrooted analyses provide convincing support for a fundamental separation of placental orders into groups with southern and northern hemispheric origins according to the current fossil record. On rooted trees, one or both of these groups are monophyletic depending on the position of the root. Maximum likelihood and Bayesian analyses with the BRCA1 and combined 8.66 kb data sets provide strong support for the monophyly of the northern hemisphere group (Boreoeutheria). Boreoeutheria is divided into Laurasiatheria (Carnivora + Cetartiodactyla + Chiroptera + Eulipotyphla + Perissodactyla + Pholidota) and Euarchonta (Dermoptera + Primates + Scandentia) + Glires (Lagomorpha + Rodentia). The southern hemisphere group is either monophyletic or paraphyletic, depending on the method of analysis used. Within this group, Afrotheria (Proboscidea + Sirenia + Hyracoidea + Tubulidentata + Macroscelidea + Afrosoricida) is monophyletic. A unique nine base-pair deletion in exon 11 of the BRCA1 gene also supports Afrotheria monophyly. Given molecular dates that suggest that the southern hemisphere group and Boreoeutheria diverged in the Early Cretaceous, a single trans-hemispheric dispersal event may have been of fundamental importance in the early history of crown-group Eutheria. Parallel adaptive radiations have subsequently occurred in the four major groups: Laurasiatheria, Euarchonta + Glires, Afrotheria, and Xenarthra.

Keywords: Biogeography; BRCA1; Eutheria; placentals; systematics

Language: English

Document Type: Regular paper

Affiliations: 1: Department of Biology, University of California, Riverside, California 92521, USA. Queen's University of Belfast, Biology and Biochemistry, 97 Lisburn Road, Belfast, BT9 7BL, United Kingdom 2: Department of Biochemistry, University of Nijmegen, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands 3: Department of Biochemistry, University of Nijmegen, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands. Institute for Systematics and Population Biology, P.O. Box 94766, 1090 GT Amsterdam, The Netherlands 4: Queen's University of Belfast, Biology and Biochemistry, 97 Lisburn Road, Belfast, BT9 7BL, United Kingdom. Bioinformatics, GlaxoSmithKline, Collegeville, Pennsylvania 19426, USA. Michael.J.Stanhope@gsk.com 5: Department of Biology, University of California, Riverside, California 92521, USA. Graduate Group in Genetics, University of California, Riverside, California 92521, USA. mark.springer@ucr.edu