Genetic Erosion: Context Is Key

Genetic erosion is a useful concept for conservationists, collection curators, natural lands managers, and practitioners of restoration and revegetation. However, there is variation in how the term has been used and how faithfully it follows from the genetic concepts upon which it was based. Genetic erosion is the loss of genetic diversity—often magnified or accelerated by human activities. It can result from habitat loss and fragmentation, but it also can result from a narrow genetic base in the original populations or collections or by practices that reduce genetic diversity. Just as loss of diversity is relative (to some baseline condition), so too is the biological significance of that loss, the management implications, and the human-applied value. Thus we emphasize the context in this chapter’s treatment of genetic erosion. Although few species-specific guidelines are available, practitioners can minimize the risk of genetic erosion by being familiar with the biology of the affected species (including breeding system, mode of reproduction, and pattern of genetic diversity). Narrowly based genetic collections should be avoided, providers of plant materials for revegetation projects should offer information on their collection methods, and nursery managers should endeavor to minimize diversity losses at all stages of nursery culture.