Inbreeding depression in non‐human primates: a historical review of methods used and empirical data

Abstract

Offspring born to related parents may show reduced fitness due to inbreeding depression. Although evidence of inbreeding depression has accumulated for a variety of taxa during the past two decades, such analyses remain rare for primate species, probably because of their long generation time. However, inbreeding can have important fitness costs and is likely to shape life-history traits in all living species. As a consequence, selection should have favored inbreeding avoidance via sex-biased dispersal, extra-group paternity, or kin discrimination. In this paper, we review empirical studies on the effects of inbreeding on fitness traits or fitness correlates in primate species. In addition, we report the methods that have been used to detect inbreeding in primate populations, and their development with the improvement of laboratory techniques. We focus particularly on the advantages and disadvantages using microsatellite loci to detect inbreeding. Although the genetic data that are typically available (partial pedigrees, use of microsatellite heterozygosity as an estimate of genomewide inbreeding) tend to impose constraints on analyses, we encourage primatologists to explore the potential effects of inbreeding if they have access to even partial pedigrees or genetic information. Such studies are important because of both the value of basic research in inbreeding depression in the wild and the conservation issues associated with inbreeding, particularly in threatened species, which include more than half of the currently living primate species.

Heritability of digit ratio (2D:4D) in rhesus macaques (Macaca mulatta)

“…The present-day population (about 900 individuals) is directly descended from the founder group, originating from the Indian subcontinent (Rawlings and Kessler 1986). Genetic and behavioural analyses indicate no significant inbreeding effects (McMillan and Duggleby 1981;Mason and Perry 1993;Charpentier et al 2007), although female dispersal patterns may potentially reduce genetic diversity (Chepko-Sade and Sade 1979). The study sample was obtained within a larger, long-term study investigating ageing in rhesus monkeys (unrelated to this study), for which animals had to be anaesthetised.…”

Phenotypic traits of primate hybrids: Recognizing admixture in the fossil record

“…As discussed elsewhere, 42,50 there is also no evidence that inbred matings among primates result in the craniofacial anomalies seen here. 69 Because the commonly observed supernumerary distomolars are not typically erupted into full occlusion with the other molar teeth, it is unlikely that they would be beneficial or detrimental. It is less clear whether the double canines would be detrimental, although they also are not completely erupted.…”

Male dispersal in a provisioned multilevel group ofRhinopithecus roxellanain Shennongjia Nature Reserve, China

“…Inbreeding usually produces negative effects on reproductive success [Charpentier et al, 2007;Pack, 1979;Ralls et al, 1988]. According to the inbreeding avoidance hypothesis, young males are expected to leave near sexual maturity if their female relatives remain in their natal groups (natal dispersal), and breeding males are expected to disperse if their female offspring mature (breeding dispersal).…”