PT  - JOURNAL ARTICLE
AU  - Ryan R. Germain
AU  - Peter Arcese
AU  - Jane M. Reid
TI  - The consequences of polyandry for sibship structures, distributions of relationships and relatedness, and potential for inbreeding in a wild population
AID  - 10.1101/145987
DP  - 2017 Jan 01
TA  - bioRxiv
PG  - 145987
4099  - http://biorxiv.org/content/early/2017/06/06/145987.short
4100  - http://biorxiv.org/content/early/2017/06/06/145987.full
AB  - The evolutionary benefits of simultaneous polyandry, defined as female multiple mating within a single reproductive event, remain elusive. One potential benefit could arise if polyandry alters sibship structures and consequent relationships and relatedness among females’ descendants, and thereby intrinsically reduces future inbreeding risk (the ‘indirect inbreeding avoidance hypothesis’). However such effects have not been quantified in naturally complex reproductive systems that also encompass iteroparity, overlapping generations, sequential polyandry, and polygyny. We used long-term social and genetic pedigree data from song sparrows (Melospiza melodia) to quantify cross-generational consequences of simultaneous polyandry for offspring sibship structures and distributions of relationships and relatedness among possible mates. Simultaneous polyandry decreased full-sibships and increased half-sibships on average, but such effects varied among females and were smaller than would occur in the absence of sequential polyandry or polygyny. Further, while simultaneous polyandry decreased the overall frequencies of possible matings among close relatives, it increased the frequencies of possible matings among distant relatives. These results imply that the intrinsic consequences of simultaneous polyandry for inbreeding risk could cause weak indirect selection on polyandry, but the magnitude and direction of such effects will depend on complex interactions with other mating system components and the form of inbreeding depression.