Inbreeding depression in morphological and growth traits of wild barn owls (Tyto alba)

Despite its detrimental effects, inbreeding depression in wild populations is relatively under-explored. Here, we use whole-genome sequence data from more than 2700 wild barn owls (Tyto alba) to investigate the presence, severity and genetic architecture of inbreeding depression in three morphological traits. Using linear models (accounting for age) and nonlinear models (measuring growth effects) we show evidence for inbreeding depression. Moreover, by partitioning developmental stages we improve our ability to detect it, as in some traits we find that it manifests during juvenile growth, and in others during adulthood. These trait-specific patterns may reflect changes in environmental influences, as we also find that juvenile heritability is lower. We additionally use two genomic inbreeding coefficients: F_ROH and F_UniW, and while both showed the same direction of effect, the strength of evidence for inbreeding depression differs. This discrepancy offers some insight into the frequency distribution of responsible variants, as the coefficients weight variants differently based on their frequencies. Finally, an assessment of local genomic inbreeding effects highlights a handful of genomic regions with significantly deleterious effects when homozygous, alongside many regions with a smaller contribution. Overall, we provide a detailed examination of inbreeding depression affecting morphological and growth traits in this wild population.