Fitness, genetic load and purging in experimental populations of the housefly

摘要

The relative effects of purging of the genetic load versus the fixation of deleterious alleles, under inbreeding, will influence a population's probability of extinction. The relative contribution of these two phenomena is expected to depend upon the rate of inbreeding. A further complication is due to the fact that a purging of the genetic load in one environment does not necessarily imply a purging of the genetic load in other environment. To address these two issues, we compare fitness and genetic load in populations experiencing similar levels of inbreeding, but occurring as either a short-term bottleneck or as a consequence of long-term reduced population size, over a range of environments. Inbred populations have consistently lower fitness than outbred populations across all environments tested. However, the bottlenecked populations suffer less inbreeding depression for a given level of inbreeding, whether or not challenged by novel environments, than populations kept at a constant small size. The results of this study demonstrate populations initiated from a small number of funders are able to recover fitness and survive novel environmental challenges, provided that habitat is available for rapid population growth.