Inbreeding depression can have major negative effects on both individual fitness and population-performance. Complex environmental and genetic factors make explicitly disentangling processes contributing to inbreeding depression challenging, particularly in natural populations where necessary fitness and inbreeding data are only rarely available. As such, studies of inbreeding effects in the wild have been largely limited to insular populations with historical bottlenecks, remnant small population sizes or without gene flow – where population dynamics likely affect accumulation, architecture and expression of inbreeding load. 

In this seminar, I will present three studies on the genomic basis of inbreeding depression in two wild populations of iconic Australian birds, superb fairy-wrens (Malurus cyaneus), and purple-crowned fairy-wrens (Malurus coronatus coronatus). Leveraging genomic inbreeding estimates, I will show how inbreeding depression affects fitness across the full life-history of both species. Then, I will discuss the possible somatic and intergenerational costs of inbreeding in nestling telomere length of purple-crowned fairy-wrens. These studies provide a detailed breakdown of the somatic and lifetime costs of genomic inbreeding in two iconic Australian species. Moreover, they demonstrate that natural populations experiencing high effective population sizes and regular dispersal might be affected by inbreeding depression less than previously assumed.