October 22, 2013
Confused Insects Accidentally Mate With Same-Sex Partners
April Flowers for redOrbit.com - Your Universe Online
Many species of spiders and insects engage in homosexual behavior such as courting, mounting and trying to mate with same sex partners. In this curious situation, it is unclear what role evolution has played. Homosexual behavior, like heterosexual behavior, takes time and energy. Such behavior might also be dangerous, and it lacks the possible benefit of producing offspring.
A new study, led by Dr. Inon Scharf of Tel Aviv University's Department of Zoology and Dr. Oliver Martin of ETH Zurich, found that such homosexual behavior in bugs is more than likely accidental in most cases. The findings, published in Behavioral Ecology and Sociobiology, suggest that in the rush of mating, bugs do not take much time to ascertain their mates' gender, which could lead to same-sex mating.
"Insects and spiders mate quick and dirty," Dr. Scharf said in a recent statement. "The cost of taking the time to identify the gender of mates or the cost of hesitation appears to be greater than the cost of making some mistakes."
Homosexual behavior in birds and mammals has been shown to have evolutionary benefits, as it provides "practice" for young adults and maintains alliances within groups. Recent studies have tried to find explanations for similar behavior in insects. These studies have suggested that such behavior could be preparation for heterosexual courtship, to dispose of old sperm, to discourage predators, and to distract competitors.
The current study reviewed research on some 110 species of male insects and spiders, finding that the evidence presented did not strongly support such adaptive theories. The literature did not show a clear benefit from homosexual behavior in insects. The analysis, however, did show considerable costs for such behavior, including expending sperm, wasting time that could go toward other activities, and boosting the risk of injury, disease, and predation. This behavior is at least as dangerous as heterosexual mating. A previous study by the same team found that all of these factors shorten the lives of heterosexually active males by an average of 25 percent, and they expect homosexual behavior to have a similar cost.
In some species, however, up to 85 percent of males engage in homosexual behavior. This is not because bugs directly benefit from the behavior, according to the scientists, but because they mistake other males for females. Nearly 80 percent of the homosexual behavior observed seemed to be the result of misidentification or belated identification of gender. Males who have just mated carry the scent of the female, sending confusing signals to other males. In other instances, the males and females look so similar that other males cannot tell the difference until after they have mounted them.
According to the study, insects and spiders probably have not evolved to be more discriminating in their mating choices. This is because the cost of rejecting an opportunity to mate with a female is greater than that of mistakenly mating with a male. The fact that many species that exhibit homosexual behavior also mate with related species or inanimate objects - like beer bottles - supports the confusion explanation. It also indicates a general tendency toward misidentification. The researchers say sexual enthusiasm in bugs might also be related to other evolutionarily beneficial traits.
"Homosexual behavior may be genomically linked to being more active, a better forager, or a better competitor," says Dr. Schart. "So even though misidentifying mates isn't a desirable trait, it's part of a package of traits that leaves the insect better adapted overall."
The team plans to continue their research by studying the conditions that make homosexual behavior more or less likely in bugs, and investigating male resistance to homosexual mating.