There's a downside to being attractive - at least if you are a guppy, Robert Brooks of James Cook University, Queensland, Australia, suggests this week [Nature, Vol. 406, Issue 6791, July 6, 2000]. The guppy (Poecilia reticulata) is a fish in which the ornamentation that females like so much is linked to the Y chromosome. Brooks finds that survival in these animals is negatively correlated with both attractiveness and ornamentation owing to the high mortality of male offspring in attractive families.
It is often assumed that female mating preferences result from a genetic association between male attractiveness and offspring fitness. But in the guppy, it seems that genes enhancing sexual attractiveness may actually be associated with "costs or heavy mutational loads", says Brooks. One possible explanation is that the presence of many colour pattern genes near the non-recombining section of the Y chromosome helps the accumulation of deleterious genes by genetic hitch-hiking.
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