Sex, Showing-Off & Relatedness in Helping Decisions of the Cooperatively Breeding Bell Miner
Friday seminar by Jonathan Wright
Kin selection predicts that helpers in cooperative systems should preferentially feed young to whom they are more genetically related, thereby gaining indirect fitness benefits. In family-based groups, this can be accomplished by simply feeding any nearby offspring. In more ‘complex’ societies where both kin and non-kin regularly interact, it requires some mechanism of kin discrimination. We investigated the provisioning behaviour of bell miners (/Manorina melanoprhys/), a cooperative species that lives in large, socially complex colonies. Helpers provision at multiple nests within a colony and positively influence offspring condition. We found that helpers of both sexes fed at a higher rate when the young in the nest were more related to them, and that such individual facultative adjustment in helping effort was linear and fine-scaled with regard to genetic relatedness. The question is: how did helpers recognise more related broods? Adult bell miners give context-specific mew calls at the nest, which are individually distinct and sound gradually more similar with greater genetic relatedness between colony members. By preferentially helping parents according to the similarity of their mew calls relative to themselves (or their own parents) helpers appear to have been able to maximise indirect fitness benefits, despite the social complexity of this system.
Jonathan Wright, Professor
Department of Biology, NTNU