No inbreeding effects on body size in two captive endangered gazelles

Selection for body size is intricate, involving trade-offs between energy costs, reproductive output, foraging efficiency, and interaction with other community members. In dimorphic, polygynous ungulates, body size is highly correlated with reproductive success in both sexes. Body size has been proposed as a potential phenotypic indicator of genetic change, in wild and in captive populations. We analysed the relationship between adult body size and inbreeding in two captive populations of endangered gazelles. Two estimates of inbreeding were used: individual inbreeding coefficient (Fi) and individual increase in inbreeding (Δ Fi). Six cranial traits and eight post-cranial bones were measured in 87 Cuvier’s gazelles and 97 Mohor gazelles. The average level of individual inbreeding found for the alive population of Cuvier’s gazelle was 0.236 and for Mohor gazelle 0.260. Our study demonstrated that within our populations most variability in body size is explained by sex, but we have not found any evidence of inbreeding depression in this morphological trait. Our results are surprising in the light of a widely held belief that from an evolutionary point of view close inbreeding has deleterious effects. The great diversity of factors acting on the effects of inbreeding on trait values make difficult to provide a simple framework to understand them all, hence, we suggest fitness consequences of inbreeding has to be assessed considering the conditions under which one should expect inbreeding depression.