Indirect fitness benefits through extra-pair mating are large for an inbred minority, but cannot explain widespread infidelity among red-winged fairy-wrens

Lichtenauer, Wendy, van de Pol, Martijn, Cockburn, Andrew, and Brouwer, Lyanne (2019) Indirect fitness benefits through extra-pair mating are large for an inbred minority, but cannot explain widespread infidelity among red-winged fairy-wrens. Evolution, 73 (3). pp. 467-480.

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Abstract

Extra-pair paternity (EPP) has been suggested to improve the genetic quality of offspring, but evidence has been equivocal. Benefits of EPP may be only available to specific individuals or under certain conditions. Red-winged fairy-wrens have extremely high levels of EPP, suggesting fitness benefits might be large and available to most individuals. Furthermore, extreme philopatry commonly leads to incestuous social pairings, so inbreeding avoidance may be an important selection pressure. Here, we quantified the fitness benefits of EPP under varying conditions and across life-stages. Extra-pair offspring (EPO) did not appear to have higher fitness than within-pair offspring (WPO), neither in poor years nor in the absence of helpers-at-the-nest. However, EPP was beneficial for closely related social pairs, because inbred WPO suffered an overall 75% reduction in fitness. Inbreeding depression was nonlinear and reduced nestling body condition, first year survival and reproductive success. Our comprehensive study indicates that EPP should be favored for the 17% of females paired incestuously, but cannot explain the widespread infidelity in this species. Furthermore, our finding that fitness benefits of EPP only become apparent for a small part of the population could potentially explain the apparent absence of fitness differences in population wide comparisons of EPO and WPO.

Item ID: 69633
Item Type: Article (Research - C1)
ISSN: 1558-5646
Keywords: Compatible genes, cooperative breeding, fitness, good genes, inbreeding avoidance, Malurus, pairwise relatedness
Copyright Information: © 2019 The Author(s). Evolution published by Wiley Periodicals, Inc. on behalf of The Society for the Study of Evolution. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited
Funders: Australian Research Council (ARC)
Projects and Grants: ARC DE130100174, ARC DP0451018, ARC DP1092565, ARC FT120100204
Date Deposited: 19 Oct 2021 01:46
FoR Codes: 31 BIOLOGICAL SCIENCES > 3103 Ecology > 310301 Behavioural ecology @ 100%
SEO Codes: 28 EXPANDING KNOWLEDGE > 2801 Expanding knowledge > 280102 Expanding knowledge in the biological sciences @ 100%
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