I consider how the study of genetic variation has influenced efforts to conserve natural populations over the last 50 years. Studies with allozymes in the 1970s provided the first estimates of the ...amount of genetic variation within and between natural populations at multiple loci. These early studies played an important role in developing plans to conserve species. The description of genetic variation in mitochondrial DNA in the early 1980s laid the foundation for the field of phylogeography, which provided a deeper look in time of the relationships and connectivity among populations. The development of microsatellites in the 1990s provided much more powerful means to describe genetic variation at nuclear loci, including the ability to detect past bottlenecks and estimate current effective population size with a single temporal sample. In the 2000s, single nucleotide polymorphisms presented a cornucopia of loci that has greatly improved power to estimate genetic and population demographic parameters important for conservation. Today, population genomics presents the ability to detect regions of the genome that are affected by natural selection (e.g. local adaptation or inbreeding depression). In addition, the ability to genotype historical samples has provided power to understand how climate change and other anthropogenic phenomena have affected populations. Modern molecular techniques provide unprecedented power to understand genetic variation in natural populations. Nevertheless, application of this information requires sound understanding of population genetics theory. I believe that current training in conservation genetics focuses too much on the latest techniques and too little on understanding the conceptual basis which is needed to interpret these data and ask good questions.
Genetic data are often used to assess 'population connectivity' because it is difficult to measure dispersal directly at large spatial scales. Genetic connectivity, however, depends primarily on the ...absolute number of dispersers among populations, whereas demographic connectivity depends on the relative contributions to population growth rates of dispersal vs. local recruitment (i.e. survival and reproduction of residents). Although many questions are best answered with data on genetic connectivity, genetic data alone provide little information on demographic connectivity. The importance of demographic connectivity is clear when the elimination of immigration results in a shift from stable or positive population growth to negative population growth. Otherwise, the amount of dispersal required for demographic connectivity depends on the context (e.g. conservation or harvest management), and even high dispersal rates may not indicate demographic interdependence. Therefore, it is risky to infer the importance of demographic connectivity without information on local demographic rates and how those rates vary over time. Genetic methods can provide insight on demographic connectivity when combined with these local demographic rates, data on movement behaviour, or estimates of reproductive success of immigrants and residents. We also consider the strengths and limitations of genetic measures of connectivity and discuss three concepts of genetic connectivity that depend upon the evolutionary criteria of interest: inbreeding connectivity, drift connectivity, and adaptive connectivity. To conclude, we describe alternative approaches for assessing population connectivity, highlighting the value of combining genetic data with capture-mark-recapture methods or other direct measures of movement to elucidate the complex role of dispersal in natural populations.
We will soon have complete genome sequences from thousands of species, as well as from many individuals within species. This coming explosion of information will transform our understanding of the ...amount, distribution and functional significance of genetic variation in natural populations. Now is a crucial time to explore the potential implications of this information revolution for conservation genetics and to recognize limitations in applying genomic tools to conservation issues. We identify and discuss those problems for which genomics will be most valuable for curbing the accelerating worldwide loss of biodiversity. We also provide guidance on which genomics tools and approaches will be most appropriate to use for different aspects of conservation.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Restoring gene flow into small, isolated populations can alleviate genetic load and decrease extinction risk (i.e., genetic rescue), yet gene flow is rarely augmented as a conservation strategy. Due ...to this discrepancy between opportunity and action, a recent call was made for widespread genetic rescue attempts. However, several aspects of augmenting gene flow are poorly understood, including the magnitude and duration of beneficial effects and when deleterious effects are likely to occur. We discuss the remaining uncertainties of genetic rescue in order to promote and direct future research and to hasten progress toward implementing this potentially powerful conservation strategy on a broader scale.
Genetic rescue has helped prevent the extinction of several populations, yet augmented gene flow is rarely used as a conservation strategy.Recent calls have been made for a paradigm shift in the conservation of small, isolated populations away from managing populations in isolation and toward widespread restoration of gene flow.Several aspects of genetic rescue remain poorly understood.Genetic rescue is inherently an eco-evolutionary process, and successful genetic rescue attempts have been part of comprehensive conservation plans that consider habitat, life history, and genetics.Genomics is being increasingly used in the implementation and monitoring of genetic rescue attempts.
Human harvest of phenotypically desirable animals from wild populations imposes selection that can reduce the frequencies of those desirable phenotypes. Hunting and fishing contrast with agricultural ...and aquacultural practices in which the most desirable animals are typically bred with the specific goal of increasing the frequency of desirable phenotypes. We consider the potential effects of harvest on the genetics and sustainability of wild populations. We also consider how harvesting could affect the mating system and thereby modify sexual selection in a way that might affect recruitment. Determining whether phenotypic changes in harvested populations are due to evolution, rather than phenotypic plasticity or environmental variation, has been problematic. Nevertheless, it is likely that some undesirable changes observed over time in exploited populations (e.g., reduced body size, earlier sexual maturity, reduced antler size, etc.) are due to selection against desirable phenotypes—a process we call "unnatural" selection. Evolution brought about by human harvest might greatly increase the time required for over-harvested populations to recover once harvest is curtailed because harvesting often creates strong selection differentials, whereas curtailing harvest will often result in less intense selection in the opposing direction. We strongly encourage those responsible for managing harvested wild populations to take into account possible selective effects of harvest management and to implement monitoring programs to detect exploitation-induced selection before it seriously impacts viability.
How does the 50/500 rule apply to MVPs? Jamieson, Ian G.; Allendorf, Fred W.
Trends in ecology & evolution (Amsterdam),
10/2012, Letnik:
27, Številka:
10
Journal Article
Recenzirano
The 50/500 rule has been used as a guiding principle in conservation for assessing minimum viable effective population size (Ne). There is much confusion in the recent literature about how the 500 ...value should be applied to assess extinction risk and set priorities in conservation biology. Here, we argue that the confusion arises when the genetic basis for a short-term Ne of 50 to avoid inbreeding depression is used to justify a long-term Ne of 500 to maintain evolutionary potential. This confusion can result in misleading conclusions about how genetic arguments alone are sufficient to set minimum viable population (MVP) thresholds for assessing the extinction risk of threatened species, especially those that emphasize that MVPs should be in the thousands to maintain evolutionary potential.
Genomic data have the potential to revolutionize the delineation of conservation units (CUs) by allowing the detection of adaptive genetic variation, which is otherwise difficult for rare, endangered ...species. In contrast to previous recommendations, we propose that the use of neutral versus adaptive markers should not be viewed as alternatives. Rather, neutral and adaptive markers provide different types of information that should be combined to make optimal management decisions. Genetic patterns at neutral markers reflect the interaction of gene flow and genetic drift that affects genome-wide variation within and among populations. This population genetic structure is what natural selection operates on to cause adaptive divergence. Here, we provide a new framework to integrate data on neutral and adaptive markers to protect biodiversity.
Inbreeding depression (reduced fitness of individuals with related parents) has long been a major focus of ecology, evolution, and conservation biology. Despite decades of research, we still have a ...limited understanding of the strength, underlying genetic mechanisms, and demographic consequences of inbreeding depression in the wild. Studying inbreeding depression in natural populations has been hampered by the inability to precisely measure individual inbreeding. Fortunately, the rapidly increasing availability of high‐throughput sequencing data means it is now feasible to measure the inbreeding of any individual with high precision. Here, we review how genomic data are advancing our understanding of inbreeding depression in the wild. Recent results show that individual inbreeding and inbreeding depression can be measured more precisely with genomic data than via traditional pedigree analysis. Additionally, the availability of genomic data has made it possible to pinpoint loci with large effects contributing to inbreeding depression in wild populations, although this will continue to be a challenging task in many study systems due to low statistical power. Now that reliably measuring individual inbreeding is no longer a limitation, a major focus of future studies should be to more accurately quantify effects of inbreeding depression on population growth and viability.
Human harvest of animals in the wild occurs in terrestrial and aquatic habitats throughout the world and is often intense. Harvest has the potential to cause three types of genetic change: alteration ...of population subdivision, loss of genetic variation, and selective genetic changes. To sustain the productivity of harvested populations, it is crucial to incorporate genetic considerations into management. Nevertheless, it is not necessary to disentangle genetic and environmental causes of phenotypic changes to develop management plans for individual species. We recommend recognizing that some genetic change due to harvest is inevitable. Management plans should be developed by applying basic genetic principles combined with molecular genetic monitoring to minimize harmful genetic change.
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