Genetic variation, inbreeding and chemical exposure—combined effects in wildlife and critical considerations for ecotoxicology

摘要

Exposure to environmental chemicals can have negative consequences for wildlife and even causelocalized population extinctions. Resistance to chemical stress, however, can evolve and the mech-anisms include desensitized target sites, reduced chemical uptake and increased metabolicdetoxification and sequestration. Chemical resistance in wildlife populations can also arise indepen-dently of exposure and may be spread by gene flow between populations. Inbreeding—matingsbetween closely related individuals—can have negative fitness consequences for natural populations,and there is evidence of inbreeding depression in many wildlife populations. In some cases, reducedfitness in inbred populations has been shown to be exacerbated under chemical stress. In chemicaltesting, both inbred and outbred laboratory animals are used and for human safety assessments, iso-genic strains (virtual clones) of mice and rats are often employed that reduce response variation, thenumber of animals used and associated costs. In contrast, for environmental risk assessment, strainsof animals are often used that have been selectively bred to maintain heterozygosity, with theassumption that they are better able to predict adverse effects in wild, genetically variable, animals.This may not necessarily be the case however, as one outbred strain may not be representative ofanother or of a wild population. In this paper, we critically discuss relationships between geneticvariation, inbreeding and chemical effects with the intention of seeking to support more effectivechemical testing for the protection of wildlife.