Who Needs Sex?

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Science  19 Nov 2010:
Vol. 330, Issue 6007, pp. 1022-1023
DOI: 10.1126/science.330.6007.1022-d

Despite the advantages conferred by mixing one's genes through sexual reproduction, many organisms, including plants, fungi, and animals, reproduce asexually. Asexual species are generally assumed to be evolutionary dead ends, however, because of the lack of genetic recombination and accumulation of mutations. As such, they are expected to reach extinction rapidly, which may explain their relative rarity. Stöck et al. examined the evolutionary history of the asexual Amazon Molly, a fish thought to have arisen through hybridization of two parental species. Crosses of their putative ancestors failed to recapitulate the asexual phenotype. A survey of nuclear and mitochondrial loci within the asexual lineages showed considerable genetic variation and suggested a monophyletic origin, which indicates that the Amazon Molly originated from a single, or very small number, of founders. These results suggest that asexual fish species may be rare not because of the deleterious effects of asexuality but rather because the genomic conditions under which they can arise are rare.

Mol. Ecol. 10.1111/j.1365-294X.2010.04869.x (2010).

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