Scientists might have explained promiscuous behaviour
- 23 September 2011 Last updated at 00:14 GMT
Scientists might have explained promiscuous behaviourFlour beetles are a major pest in grain stores worldwide
Scientists have shown that inbreeding leads to female promiscuity.
The team, who report their findings in the journal Science, witnessed this change in mating behaviour when they bred female flour beetles with their close relatives.
The researchers suspect that promiscuous females are avoiding the ill affects of inbreeding by exposing themselves to a larger pool of sperm.
The results help explain why females mate multiply despite incurring costs.
For females, sex can be traumatic. In some insects, insemination involves wounding females and infecting them with dangerous microbes.
In many other species mating reduces females' lifespans.
Given that a single mating is generally enough to fertilise all the eggs in most species, females have little incentive to mate again. And yet, in many species females mate multiple times with different males.
The new results help evolutionary biologists explain this perplexing phenomenon.Driving extinction
By driving a population of flour beetles, Tribolium castaneum, to the brink of extinction, and then allowing their numbers to recover from a few individuals, the researchers at the University of East Anglia created highly inbred populations.
The researchers found that females in these inbred populations were more eager to mate than those females that had not been forced through a bottleneck.
Attempting to explain why unbridled mating was on the increase, the researchers went on to show that inbred females left twice as many descendents as those that mated with just one male.Highly magnified Tribolium sperm fight it out within the female reproductive tract
"It is quite easy to imagine how promiscuity could spread through the population if [promiscuous females] leave more descendents," explained evolutionary biologist Matthew Gage from the University of East Anglia who led the study.
When a population is inbred, the risk of mating with a genetically similar male is heightened, and so hedging your bets and mating with more suitors is a sensible strategy, he explained.
Dr Gage suspects that promiscuous females collect a large pool of sperm and select sperm that are more genetically dissimilar to them to fertilise their eggs. Mating with more males gives females a larger pool of sperm to pick between.
However, Dr Gage warned that he and his colleagues may not have witnessed "the evolution" of a new mating behaviour.
Rather than changing genetically, he explained, the females might simply have been adjusting their behaviour to their new environmental conditions.
Dr Gage and his team are now looking into this.