Ancestry of the Australian termitivorous numbat

The Australian numbat, Myrmecobius fasciatus, is the only marsupial that feeds almost exclusively on termites and that has a life following the diurnally restricted and dynamic geographical distribution of termites. The millions of years of this adaptation led to unique morphological and anatomical features, especially basicranial and dental characteristics, that make it difficult to identify a clear phylogenetic affiliation to other marsupials. From DNA sequence analyses, the family Myrmecobiidae is placed within the dasyuromorph marsupials, but the exact position varies from study to study, and support values are mostly rather modest. Here, we report the recovery and analysis of approximately 110,000 quasifossilized traces of mobile element insertions into the genome of a dasyurid marsupial (Tasmanian devil), 25 of which are phylogenetically informative for early dasyuromorphial evolution. Fourteen of these ancient retroposon insertions are shared by the 16 Dasyuromorphia species analyzed, including the numbat, but are absent in the outgroups. An additional 11 other insertions are present in all Dasyuridae but are absent in the numbat. These findings place numbats as the sister group to all living Dasyuridae and show that the investigated Dasyuromorphia, including the Myrmecobiidae, constitutes a monophyletic group that is separated from Peramelemorphia, Notoryctemorphia, and other marsupials.