The habitats of most species have been fragmented by human actions, isolating small populations that consequently develop genetic problems. Millions of small, isolated, fragmented populations are likely suffering from inbreeding depression and loss of genetic diversity, greatly increasing their risk of extinction. Crossing between populations is required to reverse these effects, but managers rarely do so. A key reason for such inaction is that managers are often advised to manage populations in isolation whenever molecular genetic methods indicate genetic differences among them. Following this advice will often doom small populations to extinction when the habitat fragmentation and genetic differences were caused by human activities. A paradigm shift is required whereby evidence of genetic differentiation among populations is a trigger to ask whether any populations are suffering genetic problems, and if so, whether they can be rescued by augmenting gene flow. Consequently, there is now an urgent need for an authoritative practical guide to facilitate this paradigm shift in genetic management of fragmented populations.

One of the greatest unmet challenges in conservation biology is the genetic management of fragmented populations of threatened animal and plant species. More than a million small, isolated, population fragments of threatened species are likely suffering inbreeding depression and loss of evolutionary potential, resulting in elevated extinction risks. Although these effects can often be reversed by re-establishing gene flow between population fragments, managers very rarely do this. On the contrary, genetic methods are used mainly to document genetic differentiation among populations, with most studies concluding that genetically differentiated populations should be managed separately, thereby isolating them yet further and dooming many to eventual extinction! Many small population fragments are going extinct principally for genetic reasons. Although the rapidly advancing field of molecular genetics is continually providing new tools to measure the extent of population fragmentation and its genetic consequences, adequate guidance on how to use these data for effective conservation is still lacking. This accessible, authoritative text is aimed at senior undergraduate and graduate students interested in conservation biology, conservation genetics, and wildlife management. It will also be of particular relevance to conservation practitioners and natural resource managers, as well as a broader academic audience of conservation biologists and evolutionary ecologists.

The habitats of most species have been fragmented by human actions, isolating small populations that consequently develop genetic problems. Millions of small, isolated, fragmented populations are likely suffering from inbreeding depression and loss of genetic diversity, greatly increasing their risk of extinction. Crossing between populations is required to reverse these effects, but managers rarely do so. A key reason for such inaction is that managers are often advised to manage populations in isolation whenever molecular genetic methods indicate genetic differences among them. Following this advice will often doom small populations to extinction when the habitat fragmentation and genetic differences were caused by human activities. A paradigm shift is required whereby evidence of genetic differentiation among populations is a trigger to ask whether any populations are suffering genetic problems, and if so, whether they can be rescued by augmenting gene flow. Consequently, there is now an urgent need for an authoritative practical guide to facilitate this paradigm shift in genetic management of fragmented populations.

One of the greatest unmet challenges in conservation biology is the genetic management of fragmented populations of threatened animal and plant species. More than a million small, isolated, population fragments of threatened species are likely suffering inbreeding depression and loss of evolutionary potential, resulting in elevated extinction risks. Although these effects can often be reversed by re-establishing gene flow between population fragments, managers very rarely do this. On the contrary, genetic methods are used mainly to document genetic differentiation among populations, with most studies concluding that genetically differentiated populations should be managed separately, thereby isolating them yet further and dooming many to eventual extinction! Many small population fragments are going extinct principally for genetic reasons. Although the rapidly advancing field of molecular genetics is continually providing new tools to measure the extent of population fragmentation and its genetic consequences, adequate guidance on how to use these data for effective conservation is still lacking. This accessible, authoritative text is aimed at senior undergraduate and graduate students interested in conservation biology, conservation genetics, and wildlife management. It will also be of particular relevance to conservation practitioners and natural resource managers, as well as a broader academic audience of conservation biologists and evolutionary ecologists.