Evidence for the evolution of bdelloid rotifers without sexual reproduction or genetic exchange

The Class Bdelloidea of the Phylum Rotifera is the largest metazoan taxon i n which males, hermaphrodites, and meiosis are unknown. We conducted a mole cular genetic test: of this indication that bdelloid rotifers may have evol ved without sexual reproduction or genetic exchange. The test is based on t he expectation that after millions of years without these processes, genome s will no Longer contain pairs of closely similar haplotypes and instead wi ll contain highly divergent descendants of formerly allelic nucleotide sequ ences. We find that genomes of individual bdelloid rotifers, representing f our different species, appear to Lack pairs of closely similar sequences an d contain representatives of two ancient Lineages that began to diverge bef ore the bdelloid radiation many millions of years ago when sexual reproduct ion and genetic exchange may have ceased.