Abstract
The evolutionary benefits of simultaneous polyandry (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, thereby intrinsically reducing future inbreeding risk (the indirect inbreeding avoidance hypothesis). However such effects have not been quantified in naturally complex mating 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 adult full sibs, it increased the frequencies of possible matings among adult half-sibs and more 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.
Original language | English |
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Pages (from-to) | 1-19 |
Number of pages | 19 |
Journal | The American Naturalist |
Volume | 191 |
Issue number | 5 |
Early online date | 28 Feb 2018 |
DOIs | |
Publication status | Published - May 2018 |
Bibliographical note
We thank the Tsawout and Tseycum First Nations for access to Mandarte Island, Pirmin Nietlisbach, Lukas Keller, Greta Bocedi, Brad Duthie, and Matthew Wolak for helpful discussions, and the European Research Council, National Sciences and Engineering Research Council of Canada, and Swiss National Science Foundation for funding. Field data collected following UBC Animal Care Committee (A07-0309) and Environment Canada (Master banding permit 10596) guidelines.Keywords
- extra-pair reproduction
- inbreeding avoidance
- kinship
- monogamy
- polyandry
- relatedness