Molecular paternity determination in captive bonobos and the impact of inbreeding on infant mortality

Inbreeding and the loss of genetic diversity may lower fitness and reduce the potential for a population to adapt to changing environments. In small populations, for example in captive populations or populations of endangered species, this can have considerable consequences for their survival. We investigated the effects of inbreeding on infant mortality in the world captive population of bonobos Pan paniscus. Using a combination of studbook data and high-quality pedigree data from genotyped individuals, inbreeding information was available for 142 captive-born individuals. For the determination of paternities that were unresolved in the studbook, nuclear microsatellite DNA was amplified from hair and blood samples using the Great Ape Kit and PowerPlex((R)) 16 System. In total, 54 bonobos (17 offspring and their putative parents) were genotyped at eight tetranucleotide repeat microsatellite loci. Inbreeding coefficients were calculated for each individual for whom paternity was confirmed by either studbook data or DNA analysis. We found significantly higher infant mortality in inbred offspring compared with non-inbred offspring, suggesting that inbreeding reduces infant survival in captive bonobos. In addition, we argue that the total magnitude of inbreeding depression is probably underestimated in this captive population. In conclusion, even though the breeding programme of captive bonobos is aimed at avoiding inbreeding, closely related individuals do occasionally produce offspring that do show inbreeding depression. There is, however, no indication that this currently threatens the long-time survival of the captive population of bonobos.