SELECTIVE BREEDING PROGRAMS FOR RARE ALLELES - EXAMPLES FROM THE PRZEWALSKI HORSE AND CALIFORNIA CONDOR PEDIGREES

As extinction due to loss of habitat grows more imminent for a wide va riety of species, population management has been recognized as an impo rtant means toward species survival and recovery in the wild. Genetic management practices generally seek to preserve population variation a t the level of the genome. It has been proposed however that such effo rts should instead be directed to specific loci harboring alleles with particular selective benefits. This strategy may in fact result in gr eater loss of variation in the rest of the genome, potentially threate ning population viability. Pedigrees of Przewalski's horse (Equus prez ewalskii) and the California Condor (Gymnogyps californianus) were use d to evaluate a ''rare kinship'' management strategy in which a single individual known to carry a unique allele is repeatedly bred to mates chosen by mean kinship in order to increase the frequency of the rare allele. This strategy led to increased population mean kinship and re duced gene diversity and founder genome equivalents relative to a no-m anagement control pedigree and performed considerably worse than a ped igree managed for mean kinship Reduced success in the breeding program can be directly attributed to significant deviations of founders' rep resentations from their respective target values. As a result, a strat egy for increasing the frequency of rare alleles cannot be generally r ecommended for management of captive populations. Under strict conditi ons, however, limited use of this strategy may be applicable only if u sed for a short time under careful monitoring by pedigree analysis. Ev en if these conditions are met, managing by a more conventional method such as mean kinship is preferable. These results illustrate the util ity of thoughtful analysis of pedigree information to successful popul ation management.