Alternative life histories and genetic conservation

Ecologically and morphologically polymorphic species pose several difficulties for conservation genetics. First, the genetic relationships among the different phenotypes must be established. Second, the ecological factors maintaining the polymorphism must be understood. Third, intervention to protect threatened populations must integrate population genetic and ecological considerations. Here, I have discussed these issues based on information about the biology and management of salmonid fishes in particular. A number of salmonid species contain coexisting phenotypes which differ in life history, habitat use, and morphology. Population genetic studies of these species typically show that there is less genetic differentiation between coexisting life-history types than between the same life-history type sampled from geographically separate localities. The life-history polymorphisms appear to be one way by which salmonid populations adapt to heterogeneous environments. How can this genetic and ecological knowledge be integrated in the conservation of polymorphic populations? First, anthropogenic activities that lead to the loss of genetic variation within and between populations should be discouraged. Second, anthropogenic activities should be evaluated with respect to their effect on the life history polymorphism itself, even though this aspect is less well understood. Knowledge about the evolutionary response of natural populations to novel selection regimes may lead to a more detailed view about how populations should be managed from the perspective of conservation genetics.