Sexual selection, a mechanism of evolution that can drive the appearance of bright feathers and elaborate horns, is often assumed to operate largely among males. But a fresh analysis of the data suggests it is more widespread among females than many researchers expected.
It was Charles Darwin who originally suggested that sexual selection is at work in animals. He emphasised that males often compete against other males for females to mate with 鈥� which he argued could help explain why, for instance, some male birds have developed brightly coloured plumage even though this makes them a more obvious target for predators.
More recently, biologists have begun to realise that sexual selection operates widely among females too 鈥� although at the Centre for Functional and Evolutionary Ecology in France and his colleagues say it is still assumed to be a rare peculiarity.
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Now, Janicke and his colleagues have collected evidence of female-orientated sexual selection in 72 species across the animal kingdom from scientific literature published between 2015 to 2020. They say the analysis suggests that competition for mates occurs frequently in females and should be considered the norm rather than a rarity.
The researchers used statistical analysis to measure the strength of sexual selection in females across those 72 species. They found that females, just as is widely assumed for males, typically benefit from having more than one mating partner.
鈥淲e believe that our view of how we see sex differences in general, and also sexual selection in particular, is still very biased towards males,鈥� says Janicke.
The analysis shows evidence of female sexual selection in a broad range of animals. 鈥淲e have [sexual selection] in nearly all vertebrate groups, like fish, amphibians, birds and reptiles, but then also invertebrates, like snails and flatworms,鈥� says Janicke.
For example, in some fish, like various species of pike, it is the female that is the more colourful, with more stripes to attract potential mates. And in some tropical wading birds, such as it is females that fight each other for the attention of the highest quality male.
鈥淪exual selection is a process that may affect any sex,鈥� says at Uppsala University in Sweden. This evidence should help to bring 鈥渁n openness to what traits, behaviours and selection we can expect in female and male animals鈥�, she says.
The researchers hope to highlight the bias in scientific literature and invite scientists to investigate these behaviours in females more.
Reference: bioRxiv,
