All-female species goes 100 million years without a shag

No, not Anne Widdecombe

By Lester Haines • Get more from this author

Posted in Biology, 22nd March 2007 15:32 GMT

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A microscopic animal has shown its ability to evolve without reproduction, thereby refuting "the idea that sex is necessary for diversification into evolutionary species', the Times reports.

That's according to an international team of researchers, including experts from Imperial College London, the University of Cambridge, and the Royal Botanic Gardens, Kew, who studied exclusively-female bdelloid rotifers and discovered that although they'd not had sex for 100 million years, they had "diversified under pressure of natural selection".

Specifically, two sister specimens were identified living in close proximity on a water louse's body - one around the host's legs, the other near the chest. Genetic analysis and the shape of the animals' jaws showed they were different species, but, as Tim Barraclough of Imperial College explained, they "almost certainly arrived on the louse as one species and later evolved to take better advantage of the environment".

While "asexual" species don't usually last long in evolutionary terms (they can evolve through mutations "into another species, but only into one species and at the cost of its original form", the Times clarifies), the bdelloid rotifers have rather cleverly diversified into various species. This ability "may explain why they have survived so long" - so long, in fact, that one example was trapped in amber 40 million years ago, while DNA analysis points to their having survived 100 million years without a shag.

Barraclough summed it up with: "These really are amazing creatures, whose very existence calls into question scientific understanding."

The team's research is published in PLoS Biology. ®

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