Résumé
Armadillos, anteaters, and sloths (Order Xenarthra) comprise 1 of the 4
major clades of placental mammals. Isolated in South America from the
other continental landmasses, xenarthrans diverged over a period of about
65 Myr, leaving more than 200 extinct genera and only 31 living species.
The presence of both ancestral and highly derived anatomical features has
made morphoanatomical analyses of the xenarthran evolutionary history
difficult, and previous molecular analyses failed to resolve the
relationships within armadillo subfamilies. We investigated the
presence/absence patterns of retroposons from ∼7,400 genomic loci,
identifying 35 phylogenetically informative elements and an additional 39
informative rare genomic changes (RGCs). DAS-short interspersed elements
(SINEs), previously described only in the Dasypus novemcinctus genome,
were found in all living armadillo genera, including the previously
unsampled Chlamyphorus, but were noticeably absent in sloths. The
presence/absence patterns of the phylogenetically informative retroposed
elements and other RGCs were then compared with data from the DNA
sequences of the more than 12-kb flanking regions of these retroposons.
Together, these data provide the first fully resolved genus tree of
xenarthrans. Interestingly, multiple evidence supports the grouping of
Chaetophractus and Zaedyus as a sister group to Euphractus within
Euphractinae, an association that was not previously demonstrated. Also,
flanking sequence analyses favor a close phylogenetic relationship between
Cabassous and Tolypeutes within Tolypeutinae. Finally, the phylogenetic
position of the subfamily Chlamyphorinae is resolved by the noncoding
sequence data set as the sister group of Tolypeutinae. The data provide a
stable phylogenetic framework for further evolutionary investigations of
xenarthrans and important information for defining conservation priorities
to save the diversity of one of the most curious groups of mammals.