Peacocks’ tails and fireflies’ bums: Resolving the lek paradox

This week’s post is a guest contribution by Tom Houslay, a doctoral student at the University of Stirling in Scotland who studies sexual selection. Tom blogs about insects, sex, and evolution at his personal website, which would be totally NSFW if you were a sage grouse. If you have an idea for a post, and you’d like to contribute to Nothing in Biology Makes Sense, e-mail Jeremy to inquire.

Firefly

Male fireflies emit species-specific patterns of light flashes as they fly – these patterns are answered by receptive females, enabling the males to find them. Image courtesy Rick Lieder

Whenever I read the Dobzhansky quote from which this blog takes its name, it puts me in mind of another famous phrase:

“The sight of a feather in a peacock’s tail, whenever I gaze at it, makes me sick!”

Such were the words of Charles Darwin in correspondence with botanist Asa Gray in 1860, a year after the publication of On the Origin of Species. Taken at face value, it is easy to see why Darwin felt such discomfort when gazing upon a peacock’s feathers—if animals adapt to their environment, surely a cumbersome train of colourful feathers would be counterproductive? Not only should it attract the attention of predators, but it would surely impede any attempts to evade them.

ResearchBlogging.orgWhile peacocks are the posterboys for such traits, they are far from the only offenders. Time and again in the animal kingdom, we see exaggerated ornaments, vibrant colours, and fantastic acoustic and visual displays. Frogs and crickets advertise their whereabouts with loud calls, fireflies flash patterns with bioluminescence; greater sage grouse strut brazenly in open pastures. While they undoubtedly brighten up the world around us, these behaviours and morphologies can seem not only unnecessary, but downright detrimental to the survival of an individual. How, then, can their existence be resolved with our knowledge of evolution? Furthermore, why are these characters generally seen only in the males of a species?

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