Biologists have long known that sexual selection is a force that can mould the evolution of a species. Occasionally adaptations developed by males and females are at conflict with one another.
Credit: MIT
LONDON: Male flies are not the most romantic lovers in the animal world: they struggle to prolong sex, while female flies would prefer they didn't, says a new study.
They do so to prevent competing males from mating with the same female, says the study in the journal BMC Evolutionary Biology.
“The study clearly shows that the males and the females have conflicting desires over the length of copulation in Drosophila montana,” says Anneli Hoikkala study co-author and evolutionary geneticist from the University of Jyvaskyla in Finland.
Sexual conflict
Biologists have long known that sexual selection is a force that can mould the evolution of a species. Occasionally adaptations developed by males and females are at conflict with one another.
Males are likely to have adaptations to ensure their paternity. Females, on the other hand, are likely to have adaptations that minimise costs incurred during mating and allow them to seek out the mates with the best genes.
To document a case where these goals come into conflict researchers including Hoikkala and Dominique Mazzi, at the Swiss Federal Institute of Technology in Zurich, observed Drosophila montana flies copulating.
They found that after a period of harmonious intercourse, the females vigorously kick with their hind legs and flick their wings to dislodge the males, who struggle to stay on top and continue with the copulation.
Adaptive battlefield
“Copulation is by no means a harmonious cooperative enterprise in this species, but rather a battlefield fueling the evolution of male adaptations that harm females, and, in turn, the evolution of female adaptations meant to alleviate the imposed harm,” said Mazzi.
The researchers found that prolonged copulation didn’t improve the chances of insemination nor increase the number of offspring that males had, but it did reduce the chance of other competitors inseminating the female.
Males were more likely to attempt longer copulation in the presence of potential competitors with whom the female could mate immediately afterwards.
