Extra-pair mating and sexual selection on male traits across populations

Theory suggests that traits under positive selection may introgress asymmetrically across a hybrid zone, potentially driven by sexual selection. Two subspecies of the red-backed fairy-wren ( Malurus melanocephalus ) differ primarily in a sexual signal used in mate choice—red versus orange male back plumage colour—but phylogeographic analyses suggest asymmetrical introgression of red plumage into the genetic background of the orange subspecies. We hypothesized that this asymmetrical introgression may be facilitated by sexual selection if red males have a mating advantage over orange males. We tested this hypothesis with correlational data and a plumage manipulation experiment where we reddened the back plumage of a subset of orange males to mimic males of the red subspecies. There was no correlational evidence of a mating advantage to naturally redder males in this population. Experimentally reddened males sired a similar amount of within-pair young and lost paternity at the same rate as orange males, but they sired significantly more extra-pair young, leading to substantially higher total reproductive success. Thus, we conclude that sexual selection via extra-pair mating is a likely mechanism responsible for the asymmetrical introgression of plumage colour in this system, and is potentially driven by a sensory bias for the red plumage signal.

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EFFECTS OF SOCIAL AND EXTRA-PAIR MATING ON SEXUAL SELECTION IN BLUE TITS (CYANISTES CAERULEUS)

Evolution ◽

10.1111/evo.12073 ◽

2013 ◽

pp. n/a-n/a ◽

Cited By ~ 7

Author(s):

Emmi Schlicht ◽

Bart Kempenaers

Keyword(s):

Sexual Selection ◽

Cyanistes Caeruleus ◽

Pair Mating ◽

Extra Pair Mating ◽

Blue Tits

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Female and male plumage colour is linked to parental quality, pairing and extra-pair mating in a tropical passerine

10.1101/2020.06.07.125443 ◽

2020 ◽

Author(s):

Ana V. Leitão ◽

Michelle L. Hall ◽

Raoul A. Mulder

Keyword(s):

Sexual Selection ◽

Phenotypic Traits ◽

Plumage Colour ◽

Honest Signal ◽

Sexual Competition ◽

Extra Pair Paternity ◽

Parental Quality ◽

Male Plumage ◽

Pair Mating ◽

Extra Pair Mating

ABSTRACTSexual selection has been proposed to drive the evolution of elaborate phenotypic traits in males, which often confer success in competition or mating. However, in many species both males and females display such traits, although studies reporting selection acting in both sexes are scarce. In this study, we investigated whether plumage ornamentation is sexually selected in female and male lovely fairy-wrens Malurus amabilis, a cooperatively breeding songbird. We found that female and male plumage colour was correlated with parental quality but did not incur survival costs. We also found evidence of positive assortative mating based on plumage colour. Microsatellite analyses of paternity indicated that the lovely fairywren has high levels of extra-pair paternity, with 53% of offspring resulting from extra-pair mating. Female and male plumage colour did not predict reproductive success and female proportion of extra-pair offspring in its own nest, but less colourful males obtained higher extra-pair paternity. We argue that plumage colour may be under sex-specific selection, highlighting the importance of looking at both sexes in studies of sexual selection and ornament evolution. The current findings together with previous study, suggest that plumage colour in female and male lovely fairy-wrens appears to be an honest signal relevant in both intra and inter-sexual competition contexts.

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When mothers make sons sexy: maternal effects contribute to the increased sexual attractiveness of extra-pair offspring

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2011.1543 ◽

2011 ◽

Vol 279 (1731) ◽

pp. 1233-1240 ◽

Cited By ~ 35

Author(s):

Barbara Tschirren ◽

Erik Postma ◽

Alison N. Rutstein ◽

Simon C. Griffith

Keyword(s):

Sexual Selection ◽

Maternal Effects ◽

Genetic Basis ◽

Mating Behaviour ◽

Maternal Investment ◽

Genetic Benefits ◽

The Social ◽

Pair Mating ◽

Extra Pair Mating

Quality differences between offspring sired by the social and by an extra-pair partner are usually assumed to have a genetic basis, reflecting genetic benefits of female extra-pair mate choice. In the zebra finch ( Taeniopygia guttata ), we identified a colour ornament that is under sexual selection and appears to have a heritable basis. Hence, by engaging in extra-pair copulations with highly ornamented males, females could, in theory, obtain genes for increased offspring attractiveness. Indeed, sons sired by extra-pair partners had larger ornaments, seemingly supporting the genetic benefit hypothesis. Yet, when comparing ornament size of the social and extra-pair partners, there was no difference. Hence, the observed differences most likely had an environmental basis, mediated, for example, via differential maternal investment of resources into the eggs fertilized by extra-pair and social partners. Such maternal effects may (at least partly) be mediated by egg size, which we found to be associated with mean ornament expression in sons. Our results are consistent with the idea that maternal effects can shape sexual selection by altering the genotype–phenotype relationship for ornamentation. They also caution against automatically attributing greater offspring attractiveness or viability to an extra-pair mate's superior genetic quality, as without controlling for differential maternal investment we may significantly overestimate the role of genetic benefits in the evolution of extra-pair mating behaviour.

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