Direct fitness benefits explain mate preference, but not choice, for similarity in heterozygosity levels

Abstract

Under sexual selection, mate preferences can evolve for traits advertising fitness benefits. Observed mating patterns (mate choice) are often assumed to represent preference, even though they result from the interaction between preference, sampling strategy and environmental factors. Correlating fitness with mate choice instead of preference will therefore lead to confounded conclusions about the role of preference in sexual selection. Here we show that direct fitness benefits underlie mate preferences for genetic characteristics in a unique experiment on wild great tits. In repeated mate preference tests, both sexes preferred mates that had similar heterozygosity levels to themselves, and not those with which they would optimise offspring heterozygosity. In a subsequent field experiment where we cross fostered offspring, foster parents with more similar heterozygosity levels had higher reproductive success, despite the absence of assortative mating patterns. These results support the idea that selection for preference persists despite constraints on mate choice.

Mutual mate preferences and assortative mating in relation to a carotenoid-based color trait in blue tits

“…We did not measure mate choice per se in our apparatus since birds were not allowed to pair and reproduce together, but rather a sexual, or eventually social (see below), mate preference. Actual mate choice in the wild depends on a number of other parameters than mate preferences, including environmental conditions, availability of preferred phenotypes, time and effort allocated to prospecting mates, time of season and intra-sexual competition (Jennions and Petrie, 1997;Cotton et al, 2006;Botero and Rubenstein, 2012;Kuijper et al, 2012;Auld et al, 2017;Zandberg et al, 2017). Nevertheless, mate choice is the manifestation of a mate preference (Cotton et al, 2006).…”

“…In zebra finches (Taeniopygia guttata), females that were reared in enlarged broods, and that were concomitantly considered as being of poorer quality than females raised in small broods, were shown to prefer males that were themselves of lower quality (Holveck and Riebel, 2010; see Griggio and Hoi, 2010 for a similar example in sparrows; but see Wang et al, 2017). Similarly, male and female great tits (Parus major) have been shown to prefer opposite-sex individuals that were of similar heterozygosity levels as themselves, even if in the case of relatively homozygous individuals it meant having offspring of low heterozygosity level (Zandberg et al, 2017). In the frog and the great tit examples, the authors also showed that these preferences are adaptive because pairing with the preferred phenotypes led to higher fertilization rates and fitter offspring, respectively (Robertson, 1990;Zandberg et al, 2017).…”

“…Similarly, male and female great tits (Parus major) have been shown to prefer opposite-sex individuals that were of similar heterozygosity levels as themselves, even if in the case of relatively homozygous individuals it meant having offspring of low heterozygosity level (Zandberg et al, 2017). In the frog and the great tit examples, the authors also showed that these preferences are adaptive because pairing with the preferred phenotypes led to higher fertilization rates and fitter offspring, respectively (Robertson, 1990;Zandberg et al, 2017). Such kind of selfreferent phenotype matching, leading to assortative mating, could be quite widespread.…”

Water immersion tolerance by larval instars of stable fly, Stomoxys calcitrans, L1758 (Diptera: Muscidae) impairs the fitness performance of their subsequent stages

“…Maintaining its balance is a critical aspect of insect physiology [ 8 ]. The abnormal presence of water in the body of an insect can generate a long-lasting fitness consequence [ 9 ], specifically, in small-bodied insects possessing a high surface area to volume ratio [ 10 ]. In the order Diptera, the majority of studies assessing the impact of water stress on life-history traits have focused on the effects of its loss, namely desiccation (e.g.…”

Implications of nutritional stress as nestling or fledgling on subsequent attractiveness and fecundity in zebra finches (Taeniopygia guttata)

“…Specifically in monogamous species with biparental care, like many songbirds, males should also be choosy, as they need to find a compatible mate ( Griffith, Owens & Burke, 1999 ; Amundsen, 2000 ; Jones, Monaghan & Nager, 2001 ). Yet few experiments have been conducted on male choice ( Holveck, Geberzahn & Riebel, 2011 ; Zandberg et al, in press ) and specifically it remains to be shown if also males discriminate between females with different early developmental backgrounds.…”