Genome sequencing of Macrotrachela quadricornifera

Several hypotheses have been advanced to explain why, despite its substantial costs, sexual reproduction is nearly universal in eukaryotes and why its loss generally leads to early extinction. Posing an apparent challenge to all such hypotheses are a few groups that arose millions of years ago and are thought to be entirely asexual. Of these, the most extensively studied are the rotifers of Class Bdelloidea, common freshwater invertebrates of worldwide distribution. Here we present genomic evidence showing that a bdelloid species, Macrotrachella quadricornifera, is facultatively sexual, removing a challenge to hypotheses for the evolutionary benefit of sex and supporting the view that sexual reproduction is essential for long-term evolutionary success in eukaryotes.