Anyone familiar with animal behavior and evolution can tell you that animals do some pretty strange things to attract mates. According to sexual selection, the physical features, songs, or behaviors most attractive to females will become exaggerated in the males due to generations of selection for that trait. These traits or behaviors can range from typical (like the bright flashy plumage of a peacock) to weird (like the elaborate nest decorating done by male bowerbirds). But as always, they serve a distinct purpose: To advertise their superior size, strength, health, and overall ability to survive and provide relative to their competitors. However, a recent discovery of a bizarre sexually selected trait in Japanese dancing flies (family Empididae) is stumping scientists. In studying male dancing flies on Mt. Fuji, researchers discovered that many individuals have a modified fore tarsus on just one leg. This protrusion causes one leg to be oversized, and causes the fly to be asymmetrical. This in turn detracts the fly’s ability to fly efficiently. According to the authors of this study, such a massive polymorphic asymmetry occurring with so high an incidence in a population has never been discovered previously. The researchers in this study found so many cases of the asymmetrical male protrusions, that they ruled it out as a random freak of nature. Instead they hypothesize that the protrusion is a secondary sexual character meant to attract females. But why just the one? And is it worth the cost of flying well? The authors suggest that perhaps the male needs one leg to sit securely in one spot and wave his modified leg to attract females. Or, the oversized tarsus could contain a silk-secreting gland that can be used to catch and advertise a prey item to potential mates. But on the other hand, many males within the population had the protrusion on both legs, and others had none at all. More research must be done before any conclusions can be made, but what do you think? What would be the benefit of having one oversized leg and flying poorly, versus having two and flying ok, versus having none and flying well? And shouldn’t the females be attracted to males who can fly away quickly and avoid predators? I’m stumped.
-Jane de Verges
Fall 2010, Group A
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Perhaps the males with only one protrusion seem less appetizing and possibly sickly to preditors and thus have a better chance of survival so females are more frequently mating with them. Or maybe they just have great personalities!
ReplyDeleteEveryone knows that female flies love dancing its a given.
ReplyDeleteIt seems strange to me that a trait that decreases survival ability would also increase the ability of a male to find a mate. Usually a female would want to mate with the male whose chances of survival are best, right? Although I guess other displays used to attract mates might also decrease survival ability. Colorful displays in birds help them attract mates, but also decrease their ability to camoflauge.
ReplyDeleteSo in conclusion... I'm also confused!
-Lauren Lynch