10) Selective survival in wild guppies
Natural selection favours traits that increase fitness. Over time, such selection might be expected to exhaust genetic variation by driving advantageous genetic variants to fixation at the expense of less advantageous or deleterious variants. In fact, natural populations often show large amounts of genetic variation. So how is it maintained?
An example is the genetic polymorphism seen in the colour patterns of male guppies (Poecilia reticulata). As reported in 2006, Kimberly Hughes from the University of Illinois at Urbana-Champaign and her colleagues manipulated the frequencies of males with different colour patterns in three wild guppy populations in Trinidad. They showed that rare variants have much higher survival rates than more common ones. In essence, variants are favoured when rare, and selected against when common. Such ‘frequency-dependent’ survival, in which selection favours rare types, has been implicated in the maintenance of molecular, morphological and health-related polymorphisms in humans and other mammals.
Reference
Olendorf, R. et al. Nature 441, 633–636 (2006).
Additional resource
Foerster, K. et al. Nature 447, 1107–1110 (2007).
Author websites
Kimberly Hughes: http://www.bio.fsu.edu/faculty-hughes.php
Anne Houde: http://www.lakeforest.edu/academics/faculty/houde
David Reznick: http://www.biology.ucr.edu/people/faculty/Reznick.html
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