Speaker
Description
Exceptions to the rule constitute powerful examples to test commonly accepted ideas.
Within classical Darwinian sex roles, females are choosy, whereas males compete and try to mate with as many females as possible. This translates into higher variation in reproductive success and a stronger correlation between reproductive and mating success (Bateman gradient) in males compared to females (Bateman principle). However, in various species females are more competitive than males and males are the more caring sex. Using long term field data from wild populations, we provide a comprehensive comparison on the strength of mating selection of two closely related bird species that despite living in sympatry, exhibit contrasting mating patterns. Black coucals are classical polyandrous with females competing and only males caring for offspring while white-browed coucals are socially monogamous with some females engaging in polyandrous matings. In contrast to the Bateman principle, female black coucals and female white-browed coucals, irrespective of their body sizes, displayed steep Bateman gradients. Conversely, male black coucals exhibited shallow Bateman gradients, even though they sired extra-pair and extra-nest offspring, while male white-browed coucals did not vary in mating success. Our results indicate that females of both species and not males benefit from multiple mating and thus are potential targets of sexual selection.
