Wednesday, March 21, 2007

Sex not necessary for evolving new species

A new study over at PLoS Biology shows that sex is not a necessary mechanism for the evolution of a new species.

Independently Evolving Species in Asexual Bdelloid Rotifers

Asexuals are an important test case for theories of why species exist. If asexual clades displayed the same pattern of discrete variation as sexual clades, this would challenge the traditional view that sex is necessary for diversification into species. However, critical evidence has been lacking: all putative examples have involved organisms with recent or ongoing histories of recombination and have relied on visual interpretation of patterns of genetic and phenotypic variation rather than on formal tests of alternative evolutionary scenarios. Here we show that a classic asexual clade, the bdelloid rotifers, has diversified into distinct evolutionary species. Intensive sampling of the genus Rotaria reveals the presence of well-separated genetic clusters indicative of independent evolution. Moreover, combined genetic and morphological analyses reveal divergent selection in feeding morphology, indicative of niche divergence. Some of the morphologically coherent groups experiencing divergent selection contain several genetic clusters, in common with findings of cryptic species in sexual organisms. Our results show that the main causes of speciation in sexual organisms, population isolation and divergent selection, have the same qualitative effects in an asexual clade. The study also demonstrates how combined molecular and morphological analyses can shed new light on the evolutionary nature of species.

This is interesting. This shows that one of the assumptions of evolutionary biology isn't quite true. While sex probably speed up the process, asexual species can evolve as well.
It doesn't in any way invalidate the theory of evolution, but the exact mechanisms need to be re-evaluated. Science in action!

PLoS Biology has a synopsis of the study for those of us not as well versed in biology: Who Needs Sex (or Males) Anyway?. I highly recommend reading it.



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