Date:5/2/2011

oducing forefathers. In sexual populations, two individuals need to get together to reproduce, but in asexual populations every individual can reproduce on its own, giving asexuals twice the reproductive potential. Theoretically, the asexual advantage should enable the hybrids to outcompete sexual dace living in the same pond. But in reality that doesn't happen. Sexual and asexual dace are known to live side-by-side. So why doesn't the hybrid dace take over? According to a study by researchers from the University of British Columbia, it's because the hybrids aren't as healthy. Using swimming speed as a proxy for overall health, the researchers found that hybrids performed worse than at least one of the parent species in a series of speed tests. The results suggest that at minimum, the hybrid has no physiological performance advantage over the sexual species, and is probably at something of a disadvantage. The lower physiological performance may counteract the hybrids' reproductive advantage, preventing them from taking over. The results offer one possible explanation for why sexual reproduction has stayed dominant in vertebrates.

Jonathan A. Mee, Colin J. Brauner, and Eric B. Taylor, "Repeat Swimming Performance and Its Implications for Inferring the Relative Fitness of Asexual Hybrid Dace (Pisces: Phoxinus) and Their Sexually Reproducing Parental Species."

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Small sea birds hold heat rather than cranking up the furnace

A new study offers some clues about how small aquatic birds survive in extremely cold climates. Staying warm is hard work for aquatic birds. Heat loss is around twenty times greater in water than in air, so aquatic birds have to increase their resting metabolism to generate heat on the water. Heat loss is an even greater issue for small birds, so it was assumed that small birds would have to increase their metabolism in water even more than large birds do. But according to a study by researchers at t
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Contact: Kevin Stacey kstacey@press.uchicago.edu 773-834-0386 University of Chicago Press Journals Source:Eurekalert

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