While almost all multicellular organisms reproduce sexually, this form of reproduction is much less efficient than asexual reproduction (or mitosis) whereby females effectively make clones of themselves. Although asexual organisms often enjoy short-term success against their sexual ancestors, they are rarely found as higher-order taxa, implying that they cannot survive in evolutionary time.
While many hypotheses have addressed this problem, the paradox raises one of the most perplexing questions in biology: If asexual reproduction is more efficient than sexual reproduction, why does sexual reproduction predominate so thoroughly? New research from MBL evolutionary biologists may help scientists come closer to an answer.
In a paper to be published in next week's Proceedings of the National Academy of Sciences (PNAS), MBL scientists Jessica Mark Welch and her colleagues David Mark Welch and Matthew Meselson provide the strongest evidence to date that a higher-ranking taxon has evolved without sexual reproduction.
The researchers studied the bdelloid rotifer, a microscopic animal found throughout the world in almost all aquatic habitats. Bdelloids appear to have given up sex 50 million years ago, yet the organism has evolved into 370 described species. While the researchers previously demonstrated that bdelloid genomes contain two or more divergent gene copies, an observation consistent with long-term asexual reproduction, a significant shortcoming of their approach was the inability to detect nearly identical gene pairs, as might
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Contact: Gina Hebert
ghebert@mbl.edu
508-289-7725
Marine Biological Laboratory
20-Jan-2004