Search Results

Genetic management of fragmented populations is one of the major, largely unaddressed issues in biodiversity conservation. Many species across the planet have fragmented distributions with small isolated populations that are potentially suffering from inbreeding and loss of genetic diversity (genetic erosion), leading to elevated extinction risk. Fortunately, genetic deterioration can usually be remedied by augmenting gene flow (crossing between populations within species), yet this is rarely done, in part because of fears that crossing may be harmful (but it is possible to predict when this will occur). Benefits and risks of genetic problems are sometimes altered in species with diverse mating systems and modes of inheritance. Adequate genetic management depends on appropriate delineation of species. We address management of gene flow between previously isolated populations and genetic management under global climate change.

The number and geographic location of genetically differentiated populations must be identified to determine if fragmented populations require genetic management. Clustering of related genotypes to geographic locations (landscape genetic analyses) is used to determine the number of populations and their boundaries, with the simplest analyses relying on random mating within, but not across populations. Evidence of genetic differentiation among populations indicates either that they have drifted apart (and are likely inbred) and/or that the populations are adaptively differentiated. The current response when populations are genetically differentiated is usually to recommend separate management, but this is often ill-advised. A paradigm shift is needed where evidence of genetic differentiation among populations is followed by an assessment of whether populations are suffering genetic erosion, whether there are other populations to which they could be crossed, and whether the crosses would be beneficial, or harmful.

Genetic management of fragmented populations is one of the major, largely unaddressed issues in biodiversity conservation. Many species across the planet have fragmented distributions with small isolated populations that are potentially suffering from inbreeding and loss of genetic diversity (genetic erosion), leading to elevated extinction risk. Fortunately, genetic deterioration can usually be remedied by gene flow from another population (crossing between populations within species), yet this is rarely done, in part because of fears that crossing may be harmful (but we can predict when this will occur). We address management of gene flow between previously isolated populations and genetic management under global climate change.

Adverse genetic impacts on fragmented populations are expected to accelerate under global climate change. Many populations and species may not be able to adapt in situ, or move unassisted to suitable habitat. Management may reduce these threats by augmenting genetic diversity to improve the ability to adapt evolutionarily, by translocation, including that outside the species’ historical range (assisted colonization) and by ameliorating non-genetic threats. Global climate change amplifies the need for genetic management of fragmented populations.

Evidence of population structure and limited gene flow often leads to the questionable conclusion that populations should be managed as separate unit. A paradigm shift is needed where evidence of genetic differentiation among populations is followed by an assessment of whether populations are suffering genetic erosion, whether there are other populations to which they could be crossed, and whether the crosses would be beneficial, or harmful, and if beneficial, whether the benefits would be large enough to justify a genetic rescue attempt. Here we address these questions based on the principles established in the preceding chapters.

Adverse genetic impacts on fragmented populations are expected to worsen under global climate change. Many populations and species may not be able to adapt in situ, or to move unassisted to suitable habitat. Management may reduce these threats by augmenting genetic diversity to improve the ability to adapt evolutionarily, by translocation, including that outside the species’ historical range, and by ameliorating non-genetic threats. Global climate change amplifies the need for genetic management of fragmented populations.