The strength of the association between heterozygosity and probability of interannual local recruitment increases with environmental harshness in blue tits

Abstract

The extent of inbreeding depression and the magnitude of heterozygosity–fitness correlations (HFC) have been suggested to depend on the environmental context in which they are assayed, but little evidence is available for wild populations. We combine extensive molecular and capture–mark–recapture data from a blue tit (Cyanistes caeruleus) population to (1) analyze the relationship between heterozygosity and probability of interannual adult local recruitment and (2) test whether environmental stress imposed by physiologically suboptimal temperatures and rainfall influence the magnitude of HFC. To address these questions, we used two different arrays of microsatellite markers: 14 loci classified as neutral and 12 loci classified as putatively functional. We found significant relationships between heterozygosity and probability of interannual local recruitment that were most likely explained by variation in genomewide heterozygosity. The strength of the association between heterozygosity and probability of interannual local recruitment was positively associated with annual accumulated precipitation. Annual mean heterozygosity increased over time, which may have resulted from an overall positive selection on heterozygosity over the course of the study period. Finally, neutral and putatively functional loci showed similar trends, but the former had stronger effect sizes and seemed to better reflect genomewide heterozygosity. Overall, our results show that HFC can be context dependent, emphasizing the need to consider the role of environmental heterogeneity as a key factor when exploring the consequences of individual genetic diversity on fitness in natural populations.

Evidence of opposing fitness effects of parental heterozygosity and relatedness in a critically endangered marine turtle?

“…Several authors have argued for the importance of marker type in HFC studies. MLH measured using microsatellites located in expressed or otherwise conserved regions may be more likely to yield HFCs than MLH using anonymous/nonconserved loci by virtue of, on average, being closer to polymorphic loci under selection (Küpper et al ., ; Olano‐Marin et al ., ,b; Szulkin & David, ; Ferrer et al ., , ). The effect is statistically still a ‘general’ one, as it is the net, cumulative effect of multiple small effects (Szulkin & David, ).…”

Parental genetic similarity and offspring performance in blue tits in relation to brood size manipulation

“…Furthermore, there is evidence that environmental conditions may strengthen the relationship between heterozygosity and fitness, with stronger correlations arising under poor environmental conditions (Ferrer, García‐Navas, Sanz, & Ortego, ; Forcada & Hoffman, ; Voegeli, Saladin, Wegmann, & Richner, ). However, to our knowledge no experimental research has addressed this question.…”

Heterozygosity at neutral and immune loci is not associated with neonatal mortality due to microbial infection in Antarctic fur seals

“…Moreover, the genes themselves could be diverse, or alternatively, they might be related mainly to immunity, with reduced parasite loads and disease leading to greater longevity, enhanced growth, behavioral dominance and attractiveness. There is some evidence to suggest that immune genes do play a disproportionate role, in at least some cases (Luikart, Pilgrim, Visty, Ezenwa, & Schwartz, ; Banks, Dubach, Viggers, & Lindenmayer, ; Assunção‐Franco, Hoffman, Harwood, & Amos, ; Lenz, Mueller, Trillmich, & Wolf, ; Bateson et al, ; Ferrer, García‐Navas, Sanz, & Ortego, ; Brambilla, Keller, Bassano, & Grossen, ). However, in general, it has proven difficult to disentangle the contributions of different genes because the vast majority of studies use neutral microsatellites, whereas studies using markers mined from functional genomic regions (Da Silva et al, ; Olano‐Marin, Mueller, & Kempenaers, ; Laine, Herczeg, Shikano, & Primmer, ; Ferrer et al, ) are still relatively uncommon.…”