ABSTRACT
Many 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 exception to all such hypotheses are a few groups thought to be entirely asexual that arose millions of years ago. 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 making it likely that sexual reproduction is essential for long-term evolutionary success in all eukaryotes.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
Data Availability The sequencing reads (Illumina and Nanopore) and assemblies generated in this study are available from NCBI BioProject XXXXX (accession pending).
Difference matrices, phylograms, alignments (tic plots), and raw data are available at https://github.com/tsackton/rotifer-outcrossing
