New research suggests that while homosexuality is prevalent among many species, insects and arachnids might only engage in same-sex mating behavior by mistake.
By now it is fairly well established that homosexuality isn’t just prevalent among humans, with evidence of life long courtships documented among many mammalian and bird species.
The evolutionary advantages of homosexuality might not at first seem apparent, but there are a number of theories why homosexuality might be good for a species. One such theory is that homosexuality can help strengthen the bonds between groups of animals, allowing for greater unity and social order. In species like bottlenose dolphins, bonobo and other apes, as well as bird species like mallards and penguins, that seems perfectly reasonable.
Yet, for species that have little to no care or even time for social bonding — namely insects like the dragonfly, fruitfly and various spider species — why is there a wealth of observational data showing that they, too, engage in same-sex sexual behavior?
New research from scientists in Tel Aviv suggest it’s probably because insects and spiders, in their rush to pass on their genes as quickly as possible, simply don’t take the time to differentiate or can’t easily deduce the sex of their partner.
The study, by Inon Scharf and team from Tel Aviv University, and Oliver Martin and team from ETH Zurich, and published this week in Behavioral Ecology and Sociobiology, reviewed research that covered 110 species of male insects and spiders.
While researchers found only weak evidence to support what are known as so called adaptive theories, in general they could find no clear benefit to homosexual behavior among insects or spiders. What’s more, mating in general is incredibly risky for insects and spiders as it dramatically increases the threat of injury and predation. Homosexual pairings have the added danger of taking time and wasting energy. So why engage in same-sex behavior?
The drive to pass on genes is overwhelming for many if not all species and, the researchers believe, the insects and spiders may simply be driven to throw caution to the wind and attempt to engage in sexual activity whenever they can: in effect, they have to be in the genetic race in order to win it and so a few misfires with same-sex bugs isn’t nearly as costly to the genetic lineage as being to0 discriminating and risking not passing on their genes at all.
“Insects and spiders mate quick and dirty,” Dr. Scharf is quoted as saying. “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.”
As to why the confusion happens so often for some insect species is a question that will need further research. A couple of simple explanations may be that in many cases, the male and females of a particular species look so much alike that identifying their sex in a high pressure encounter will be difficult for an amorous male.
Another explanation could be that the males on the receiving end of such same-sex attention may be carrying around the scent of females they have successfully mated with, sending out confusing signals to other male insects and spiders. It’s not all bad news for those insects and spiders that appear less than discriminating, though.
The researchers theorize that while mistaken homosexual bonding carries little genetic benefit of itself, it may be part of a wider package of traits, for example a brazen attitude, or a more competitive attitude, that add up to the insect probably being more likely to be successful in passing on its genes than those that dither about the sex of their prospective partner.
“Homosexual behavior may be genomically linked to being more active, a better forager, or a better competitor,” Dr. Schart details. “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 researchers want to investigate their theory further, with studies lined up to explore the specific conditions that might make homosexual behavior more or less likely. They also want to look at what might prompt greater and lesser resistance among males of the species to homosexual mating.
While the current research is by no means conclusive, the prospect of further insight into this interesting aspect of animal behavior is certainly tantalizing.
Photo credit: Thinkstock.
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