The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Philip W Hedrick - One of the best experts on this subject based on the ideXlab platform.
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understanding inbreeding depression purging and Genetic Rescue
Trends in Ecology and Evolution, 2016Co-Authors: Philip W Hedrick, Aurora GarciadoradoAbstract:Inbreeding depression, the reduction of fitness caused by inbreeding, is a nearly universal phenomenon that depends on past mutation, selection, and Genetic drift. Recent estimates suggest that its impact on individual fitness is even greater than previously thought. Genomic information is contributing to its detection and can enlighten important aspects of its Genetic architecture. In natural populations, purging and Genetic Rescue mitigate fitness decline during inbreeding periods, and might be critical to population survival, thus, both mechanisms should be considered when assessing extinction risks. However, deliberate purging and Genetic Rescue involve considerable risk in the short and medium term, so that neither appears to be a panacea against high inbreeding depression.
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Genetic Rescue in isle royale wolves Genetic analysis and the collapse of the population
Conservation Genetics, 2014Co-Authors: Philip W Hedrick, Rolf O Peterson, Leah M Vucetich, Jennifer R Adams, John A VucetichAbstract:While Genetic Rescue is known to benefit population viability, the duration of that benefit is poorly understood. We document what appears to be the waning benefit of Genetic Rescue after approximately 2–3 generations for the wolf population in Isle Royale National Park. The fitness benefit of Genetic Rescue declined because of inbreeding and population abundance declined when the inbred individuals exhibited low reproduction and survival. Only detailed studies of other cases will reveal what aspects of these dynamics represent general features of Genetic Rescue. We also present evidence indicating that numerous past immigration events have likely gone undetected. This finding is of particular significance because the Isle Royale wolf population has maintained good population viability for decades even though it was small and thought to be isolated from the mainland population of wolves. Past gene flow also suggests that human-assisted gene flow is necessary to conserve the ecosystem services associated with predation, since climate warming has reduced the frequency of ice bridges and with it the only opportunity for unassisted gene flow.
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genomic sweep and potential Genetic Rescue during limiting environmental conditions in an isolated wolf population
Proceedings of The Royal Society B: Biological Sciences, 2011Co-Authors: Jennifer R Adams, Philip W Hedrick, Rolf O Peterson, Leah M Vucetich, John A VucetichAbstract:Genetic Rescue, in which the introduction of one or more unrelated individuals into an inbred population results in the reduction of detrimental Genetic effects and an increase in one or more vital rates, is a potentially important management tool for mitigating adverse effects of inbreeding. We used molecular techniques to document the consequences of a male wolf (Canis lupus) that immigrated, on its own, across Lake Superior ice to the small, inbred wolf population in Isle Royale National Park. The immigrant’s fitness so exceeded that of native wolves that within 2.5 generations, he was related to every individual in the population and his ancestry constituted 56 per cent of the population, resulting in a selective sweep of the total genome. In other words, all the male ancestry (50% of the total ancestry) descended from this immigrant, plus 6 per cent owing to the success of some of his inbred offspring. The immigration event occurred in an environment where space was limiting (i.e. packs occupied all available territories) and during a time when environmental conditions had deteriorated (i.e. wolves’ prey declined). These conditions probably explain why the immigration event did not obviously improve the population’s demography (e.g. increased population numbers or growth rate). Our results show that the beneficial effects of gene flow may be substantial and quickly manifest, short-lived under some circumstances, and how the demographic benefits of Genetic Rescue might be masked by environmental conditions.
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Genetic Rescue guidelines with examples from mexican wolves and florida panthers
Conservation Genetics, 2010Co-Authors: Philip W Hedrick, Richard FredricksonAbstract:In populations or species with low fitness (high Genetic load), a new management strategy called Genetic Rescue has been advocated to help avoid extinction. In this strategy, unrelated individuals from another population are introduced into the population with low fitness in an effort to reduce Genetic load. Here we present ten guidelines that can be used to evaluate when Genetic Rescue is a good management option, the appropriate procedures for Genetic Rescue planning and management, and the potential negative Genetic consequences of Genetic Rescue. These guidelines are then used to evaluate the Genetic Rescue aspects of the recovery programs for the Mexican wolf and the Florida panther.
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Genetic Rescue and inbreeding depression in mexican wolves
Proceedings of The Royal Society B: Biological Sciences, 2007Co-Authors: Richard J Fredrickson, Peter Siminski, Melissa Woolf, Philip W HedrickAbstract:Although inbreeding can reduce individual fitness and contribute to population extinction, gene flow between inbred but unrelated populations may overcome these effects. Among extant Mexican wolves (Canis lupus baileyi ), inbreeding had reduced Genetic diversity and potentially lowered fitness, and as a result, three unrelated captive wolf lineages were merged beginning in 1995. We examined the effect of inbreeding and the merging of the founding lineages on three fitness traits in the captive population and on litter size in the reintroduced population. We found little evidence of inbreeding depression among captive wolves of the founding lineages, but large fitness increases, Genetic Rescue, for all traits examined among F1 offspring of the founding lineages. In addition, we observed strong inbreeding depression among wolves descended from F1 wolves. These results suggest a high load of deleterious alleles in the McBride lineage, the largest of the founding lineages. In the wild, reintroduced population, there were large fitness differences between McBride wolves and wolves with ancestry from two or more lineages, again indicating a Genetic Rescue. The low litter and pack sizes observed in the wild population are consistent with this Genetic load, but it appears that there is still potential to establish vigorous wild populations.
Patricia Gonzalezrodriguez - One of the best experts on this subject based on the ideXlab platform.
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Genetic Rescue of mitochondrial and skeletal muscle impairment in an induced pluripotent stem cells model of coenzyme q10 deficiency
Stem Cells, 2017Co-Authors: Damia Romeromoya, Carlos Santosocana, Julio Castano, Gloria Garrabou, Jose A Rodriguezgomez, Vanesa Ruizbonilla, Clara Bueno, Patricia GonzalezrodriguezAbstract:Coenzyme Q10 (CoQ10) plays a crucial role in mitochondria as an electron carrier within the mitochondrial respiratory chain (MRC), and is an essential antioxidant. Mutations in genes responsible for CoQ10 biosynthesis (COQ genes) cause primary CoQ10 deficiency, a rare and heterogeneous mitochondrial disorder with no clear genotype-phenotype association, mainly affecting tissues with high-energy demand including brain and skeletal muscle (SkM). Here, we report a 4-year old girl diagnosed with minor mental retardation and lethal rhabdomyolysis harboring a heterozygous mutation (c.483G>C (E161D)) in COQ4. The patient's fibroblasts showed a decrease in [CoQ10], CoQ10 biosynthesis, MRC activity affecting complexes I/II+III, and respiration defects. Bona fide induced pluripotent stem cell (iPSCs) lines carrying the COQ4 mutation (CQ4-iPSCs) were generated, characterized and Genetically edited using the CRISPR-Cas9 system (CQ4ed-iPSCs). Extensive differentiation and metabolic assays of control-iPSCs, CQ4-iPSCs and CQ4ed-iPSCs demonstrated a genotype association, reproducing the disease phenotype. The COQ4 mutation in iPSC was associated with CoQ10 deficiency, metabolic dysfunction, and respiration defects. iPSC differentiation into SkM was compromised, and the resulting SkM also displayed respiration defects. Remarkably, iPSC differentiation in dopaminergic or motor neurons was unaffected. This study offers an unprecedented iPSC model recapitulating CoQ10 deficiency-associated functional and metabolic phenotypes caused by COQ4 mutation. This article is protected by copyright. All rights reserved.
Antonio R Castilla - One of the best experts on this subject based on the ideXlab platform.
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Genetic Rescue by distant trees mitigates qualitative pollen limitation imposed by fine scale spatial Genetic structure
Molecular Ecology, 2019Co-Authors: Antonio R Castilla, Pedro J Garrote, Magdalena żywiec, Gemma Calvo, Alberto Suarezesteban, Miguel Delibes, Jose A GodoyAbstract:Restricted seed dispersal frequently leads to fine-scale spatial Genetic structure (i.e., FSGS) within plant populations. Depending on its spatial extent and the mobility of pollinators, this inflated kinship at the immediate neighbourhood can critically impoverish pollen quality. Despite the common occurrence of positive FSGS within plant populations, our knowledge regarding the role of long-distance pollination preventing reproductive failure is still limited. Using microsatellite markers, we examined the existence of positive FSGS in two low-density populations of the tree Pyrus bourgaeana. We also designed controlled crosses among trees differing in their kinship to investigate the effects of increased local kinship on plant reproduction. We used six pollination treatments and fully monitored fruit production, fruit and seed weight, proportion of mature seeds per fruit, and seed germination. Our results revealed positive FSGS in both study populations and lower fruit initiation in flowers pollinated with pollen from highly-Genetically related individuals within the neighbourhood, with this trend intensifying as the fruit development progressed. Besides, open-pollinated flowers exhibited lower performance compared to those pollinated by distant pollen donors, suggesting intense qualitative pollen limitation in natural populations. We found positive fine-scale spatial Genetic structure is translated into impoverished pollen quality from nearby pollen donors which negatively impacts the reproductive success of trees in low-density populations. Under this scenario of intrapopulation Genetic Rescue by distant pollen donors, the relevance of highly-mobile pollinators for connecting spatially and Genetically distant patches of trees may be crucial to safeguarding population recruitment.
Markus Fischer - One of the best experts on this subject based on the ideXlab platform.
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Genetic Rescue persists beyond first generation outbreeding in small populations of a rare plant
Proceedings of The Royal Society B: Biological Sciences, 2007Co-Authors: Yvonne Willi, Stefan Dietrich, Mark Van Kleunen, Markus FischerAbstract:Habitat fragmentation commonly causes Genetic problems and reduced fitness when populations become small. Stocking small populations with individuals from other populations may enrich Genetic variation and alleviate inbreeding, but such artificial gene flow is not commonly used in conservation owing to potential outbreeding depression. We addressed the role of long-term population size, Genetic distance between populations and test environment for the performance of two generations of offspring from between-population crosses of the locally rare plant Ranunculus reptans L. Interpopulation outbreeding positively affected an aggregate measure of fitness, and the fitness superiority of interpopulation hybrids was maintained in the second offspring (F2) generation. Small populations benefited more strongly from interpopulation outbreeding. Genetic distance between crossed populations in neutral markers or quantitative characters was not important. These results were consistent under near-natural competition-free and competitive conditions. We conclude that the benefits of interpopulation outbreeding are likely to outweigh potential drawbacks, especially for populations that suffer from inbreeding.
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Genetic Rescue in interconnected populations of small and large size of the self incompatible ranunculus reptans
Heredity, 2005Co-Authors: Yvonne Willi, Markus FischerAbstract:Small populations of our study species Ranunculus reptans have reduced fitness because of inbreeding, Genetic load, and reduced mate availability; that is, they suffer from a three-fold Genetic Allee effect. Here, we investigate how the effect of interpopulation outbreeding on offspring fitness depends on population size. We performed within- and between-population crosses with plants originating from 15 populations, and measured offspring performance in a common environment. Interpopulation outbreeding led to an increase in population means of clonal performance, which was defined as the number of rooted offspring rosettes produced per maternal ovule. This fitness gain mainly occurred at the life stage of seed set. It was especially pronounced for populations with a long-term history of small size inferred from their low Genetic diversity, estimated from eight allozyme loci. We conclude that in a self-incompatible plant such as R. reptans, interpopulation outbreeding can lead to an immediate Genetic Rescue effect due to increased cross-compatibility and heterosis, and that this Rescue effect is increased as population size decreases.
Gordon Luikart - One of the best experts on this subject based on the ideXlab platform.
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evaluating the outcomes of Genetic Rescue attempts
Conservation Biology, 2021Co-Authors: Zachary L Robinson, Gordon Luikart, Andrew R Whiteley, Donovan A Bell, Tashi Dhendup, Marty KardosAbstract:Augmenting gene flow is a powerful tool for the conservation of small, isolated populations. However, Genetic Rescue attempts have largely been limited to populations at the brink of extinction, in part due to concerns over negative outcomes (e.g., outbreeding depression). Increasing habitat fragmentation may necessitate more proactive Genetic management. Broader application of augmented gene flow will, in turn, require rigorous evaluation to increase confidence and identify pitfalls in this approach. To date, there has been no assessment of best monitoring practices for Genetic Rescue attempts. We used genomically explicit, individual-based simulations to examine the effectiveness of common approaches (i.e., tests for increases in fitness, migrant ancestry, heterozygosity, and abundance) for determining whether Genetic Rescue or outbreeding depression occurred. Statistical power to detect the effects of gene flow on fitness was high (≥0.8) when effect sizes were large, a finding consistent with those from previous studies on severely inbred populations. However, smaller effects of gene flow on fitness can appreciably affect persistence probability but current evaluation approaches fail to provide results from which reliable inferences can be drawn. The power of the metrics we examined to evaluate Genetic Rescue attempts depended on the time since gene flow and whether gene flow was beneficial or deleterious. Encouragingly, the use of multiple metrics provided nonredundant information and improved inference reliability, highlighting the importance of intensive monitoring efforts. Further development of best practices for evaluating Genetic Rescue attempts will be crucial for a responsible transition to increased use of translocations to decrease extinction risk.
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translating effects of inbreeding depression on component vital rates to overall population growth in endangered bighorn sheep
Conservation Biology, 2011Co-Authors: Heather E. Johnson, Thomas R. Stephenson, John D. Wehausen, Scott L Mills, Gordon LuikartAbstract:Evidence of inbreeding depression is commonly detected from the fitness traits of animals, yet its effects on population growth rates of endangered species are rarely assessed. We examined whether in- breeding depression was affecting Sierra Nevada bighorn sheep (Ovis canadensis sierrae), a subspecies listed as endangered under the U.S. Endangered Species Act. Our objectives were to characterize Genetic variation in this subspecies; test whether inbreeding depression affects bighorn sheep vital rates (adult survival and female fecundity); evaluate whether inbreeding depression may limit subspecies recovery; and examine the potential for Genetic management to increase population growth rates. Genetic variation in 4 populations of Sierra Nevada bighorn sheep was among the lowest reported for any wild bighorn sheep population, and our results suggest that inbreeding depression has reduced adult female fecundity. Despite this population sizes and growth rates predicted from matrix-based projection models demonstrated that inbreeding depres- sion would not substantially inhibit the recovery of Sierra Nevada bighorn sheep populations in the next approximately 8 bighorn sheep generations (48 years). Furthermore, simulations of Genetic Rescue within the subspecies did not suggest that such activities would appreciably increase population sizes or growth rates during the period we modeled (10 bighorn sheep generations, 60 years). Only simulations that augmented the Mono Basin population with Genetic variation from other subspecies, which is not currently a management option, predicted significant increases in population size. Although we recommend that recovery activities should minimize future losses of Genetic variation, Genetic effects within these endangered populations—either negative (inbreeding depression) or positive (within subspecies Genetic Rescue)—appear unlikely to dramat- ically compromise or stimulate short-term conservation efforts. The distinction between detecting the effects of inbreeding depression on a component vital rate (e.g., fecundity) and the effects of inbreeding depression on population growth underscores the importance of quantifying inbreeding costs relative to population dynamics to effectively manage endangered populations.
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Genetic Rescue of an insular population of large mammals
Proceedings of The Royal Society B: Biological Sciences, 2006Co-Authors: John T. Hogg, Stephen H Forbes, Brian M Steele, Gordon LuikartAbstract:Natural populations worldwide are increasingly fragmented by habitat loss. Isolation at small population size is thought to reduce individual and population fitness via inbreeding depression. However, little is known about the time-scale over which adverse Genetic effects may develop in natural populations or the number and types of traits likely to be affected. The benefits of restoring gene flow to isolates are therefore also largely unknown. In contrast, the potential costs of migration (e.g. disease spread) are readily apparent. Management for ecological connectivity has therefore been controversial and sometimes avoided. Using pedigree and life-history data collected during 25 years of study, we evaluated Genetic decline and Rescue in a population of bighorn sheep founded by 12 individuals in 1922 and isolated at an average size of 42 animals for 10–12 generations. Immigration was restored experimentally, beginning in 1985. We detected marked improvements in reproduction, survival and five fitness-related traits among descendants of the 15 recent migrants. Trait values were increased by 23–257% in maximally outbred individuals. This is the first demonstration, to our knowledge, of increased male and female fitness attributable to outbreeding realized in a fully competitive natural setting. Our findings suggest that Genetic principles deserve broader recognition as practical management tools with near-term consequences for large-mammal conservation.
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The alluring simplicity and complex reality of Genetic Rescue
Trends in ecology & evolution, 2004Co-Authors: David A. Tallmon, Gordon Luikart, Robin S. WaplesAbstract:A series of important new theoretical, experimental and observational studies demonstrate that just a few immigrants can have positive immediate impacts on the evolutionary trajectory of local populations. In many cases, a low level of immigration into small populations has produced fitness benefits that are greater than those predicted by theoretical models, resulting in what has been termed 'Genetic Rescue'. However, the opposite result (reduced fitness) can also be associated with immigration of Genetically divergent individuals. Central to our understanding of Genetic Rescue are complex interactions among fundamental concepts in evolutionary and population biology, including both Genetic and non-Genetic (environmental, behavioral and demographic) factors. Developing testable models to predict when Genetic Rescue is likely to occur is a daunting challenge that will require carefully controlled, multi-generation experiments as well as creative use of information from natural 'experiments'.