Making sense of mammals

Abstract

The higher level relationships of eutherian mammals have long been a phylogenetic puzzle, the main reason being a temporal inconsistency: although most of the major lineages (‘orders’) of placental mammals originated well before the Cretaceous–Tertiary (K) boundary, they only diversified in a massive adaptive radiation after this event. Therefore, much of the early evolutionary history is difficult for morphological studies to address and often only the adaptive radiation is reflected as unresolved relationships at the base of the tree. Molecular studies hold more promise at seeing past the K–T boundary, but this promise has been largely unfulfilled owing to limited data. Comparatively few, distantly related eutherian species have been sampled for only a few molecular markers, a scenario for which accurate phylogenetic estimation is known to be difficult. Now, three research groups 1 Madsen O. et al. Parallel adaptive radiations in two major clades of placental mammals. Nature. 2001; 409: 610-614 Crossref PubMed Scopus (552) Google Scholar , 2 Murphy W.J. et al. Molecular phylogenetics and the origins of placental mammals. Nature. 2001; 409: 614-618 Crossref PubMed Scopus (1112) Google Scholar , 3 Liu F-G.R. et al. Molecular and morphological supertrees for eutherian (placental) mammals. Science. 2001; 291: 1786-1789 Crossref PubMed Scopus (198) Google Scholar using two different approaches have attempted to address these limitations to present the first comprehensive mammalian trees. The results show a surprising degree of concordance.