Sex-specific effects of inbreeding on reproductive senescence

Inbreeding depression plays a significant role in evolutionary biology and ecology. Yet, we lack a clear understanding of the fitness consequences of inbreeding depression. Studies often focus on short-term effects of inbreeding in juvenile offspring whereas inbreeding depression in adult traits and the interplay between inbreeding depression and age is rarely addressed. Inbreeding depression may increase with age and accelerate the decline in reproductive output in ageing individuals (‘reproductive senescence’), which could be subject to sex-specific dynamics. We test this hypothesis with a longitudinal experimental study in a short-lived songbird. Adult inbred and outbred male and female canaries were paired in a 2x2 factorial design and survival and annual reproductive performance were studied for three years. We found inbreeding depression in female egg-laying ability, male fertilization success and survival of both sexes. Annual reproductive success of both males and females declin...