Data from: No evidence of inbreeding depression in sperm performance traits in wild song sparrows

Further, the hypothesis that inbreeding could increase within-ejaculate variation in sperm traits, and thereby further affect male fertilisation success has not been explicitly tested. We used a wild pedigreed song sparrow (Melospiza melodia) population, where frequent extra-pair copulations likely create strong post-copulatory competition for fertilisation success, to quantify effects of male coefficient of inbreeding (f) on key sperm performance traits.

We found no evidence of inbreeding depression in sperm motility, longevity or velocity, and the within-ejaculate variance in sperm velocity did not increase with male f. Contrary to inferences from highly inbred captive and experimental populations, our results imply that moderate inbreeding will not necessarily constrain sperm performance in wild populations. Consequently, the widely observed individual-level and population-level inbreeding depression in male and female fitness may not stem from reduced sperm performance in inbred males.

Usage notes

Data for inbreeding depression in sperm performance (Losdat et al. 2017) Losdat et al_ ID in sperm song sparrows.txt