Inbreeding depression in the Speke's gazelle captive breeding program

The Speke's gazelle (Gazella spekei) captive breeding program has been pres ented as one of the few examples of selection reducing the genetic load of a population and as a potential model for the captive breeding of endangere d species founded from a small number of individuals. In this breeding prog ram, three generations of mate selection apparently increased the viability of inbred individuals. We reanalyzed the Speke's gazelle studbook and exam ined potential causes for the reduction of inbreeding depression. Our analy sis indicates that the decrease in inbreeding depression is not consistent with any model of genetic improvement in the herd. Instead, we found that t he effect of inbreeding decreased from severe to moderate during the first generation of inbreeding, and that this change is responsible for almost al l of the decline in inbreeding depression observed during the breeding prog ram, This eliminates selection as a potential explanation for the decrease in inbreeding depression and suggests that inbreeding depression may be mor e sensitive to environmental influences than is usually thought.