Pelvicachromis taeniatus is a dwarf cichlid from West Africa that is occasionally kept as an aquarium fish In this species, females seek to impress potential mates as well by fanning out their large, violet pelvic fin.

 

The results, published this month in BMC Evolutionary Biology, also suggest male choice can drive females to evolve exaggerated traits, a finding that disputes the traditional belief that sexual selection is a one-way road, allowing only females to affect male appearance.

 

Scientists have widely studied the effect of female choice on male traits, such as the peacock’s extravagant tail or the stag beetle’s massive horns, but until relatively recently neglected the effect of male choice on female appearance.

 

Typically, females of a species will invest a great deal of energy into eggs or young, and males will invest nearly none, causing females to be highly selective with their mates and males to take whatever they can get. However, in biparental species, where both males and females invest equally in their young, “males will become very choosy as well,” said Sebastian Baldauf, a postdoctoral student at the University of Bonn in Germany and first author on the paper. ■