Heterozygosity-based assortative mating in blue tits (Cyanistes caeruleus): implications for the evolution of mate choice

Abstract

The general hypothesis of mate choice based on non-additive genetic traits suggests that individuals would gain important benefits by choosing genetically dissimilar mates (compatible mate hypothesis) and/or more heterozygous mates (heterozygous mate hypothesis). In this study, we test these hypotheses in a socially monogamous bird, the blue tit (Cyanistes caeruleus). We found no evidence for a relatednessbased mating pattern, but heterozygosity was positively correlated between social mates, suggesting that blue tits may base their mating preferences on partner's heterozygosity. We found evidence that the observed heterozygosity-based assortative mating could be maintained by both direct and indirect benefits. Heterozygosity reflected individual quality in both sexes: egg production and quality increased with female heterozygosity while more heterozygous males showed higher feeding rates during the broodrearing period. Further, estimated offspring heterozygosity correlated with both paternal and maternal heterozygosity, suggesting that mating with heterozygous individuals can increase offspring genetic quality. Finally, plumage crown coloration was associated with male heterozygosity, and this could explain unanimous mate preferences for highly heterozygous and more ornamented individuals. Overall, this study suggests that non-additive genetic traits may play an important role in the evolution of mating preferences and offers empirical support to the resolution of the lek paradox from the perspective of the heterozygous mate hypothesis.

Environmental and Within-Nest Factors Influencing Nestling-Feeding Patterns of Mediterranean Blue Tits (Cyanistes caeruleus)

“…From these recordings, following a procedure similar to that of Johnsen et al (2005), we extracted feeding rates. We found a strong correlation between parental feeding rates estimated with videotape recording and those obtained by means of this system (García-Navas et al 2009). The similarity of the two sets of estimates shows that the PIT-tag method resulted in realistic estimates of provisioning effort.…”

“…Another possibility is that such a relationship arises as a consequence of the assortative mating of high-quality birds. In the populations of the Blue Tit we have studied, we have found the heterozygosity of social mates to be positively correlated, suggesting that this species may select mates on the basis of the partner's heterozygosity (García-Navas et al 2009). In addition, in males, we observed a positive association between an individual's genetic diversity and feeding rates.…”

Genetic variance components and heritability of multiallelic heterozygosity under inbreeding

“…Theoretical studies have shown that heterozygosity is heritable when allele frequencies are unequal (Borgia, 1979;Mitton et al, 1993;Neff and Pitcher, 2008), and a number of empirical studies have reported parent-offspring correlations in heterozygosity itself (Cothran et al, 1983;Mitton et al, 1993;Richardson et al, 2004;Hoffman et al, 2007;García-Navas et al, 2009;Oh, 2009;Thoß, 2010;Thonhauser et al, 2014), or inferred them from a parent-offspring correlation in inbreeding coefficients (Reid et al, 2006). Although the presence of substantial heritability of heterozygosity has been formally shown for two-allelic loci more than two decades ago (Mitton et al, 1993), this is not well known among evolutionary biologists (e.g., Coulson and Clegg, 2014).…”

Pairing patterns in relation to body size, genetic similarity and multilocus heterozygosity in a tropical monogamous bird species

“…So far, few studies have considered simultaneously the genetic and phenotypic dimensions of individual quality in relation to pairing patterns in socially monogamous species (but see Freeman-Gallant et al 2003;García-Navas et al 2009;Thünken et al 2012). In particular, heterozygosity can influence body size in vertebrates (Hoffman et al 2010;Herdegen et al 2013), such that patterns of assortative mating in relation to both parameters might be more complex than previously thought.…”