scholarly journals Inferring past demographic changes in a critically endangered marine fish after fishery collapse

2014 ◽  
Vol 71 (7) ◽  
pp. 1619-1628 ◽  
Author(s):  
Fausto Valenzuela-Quiñonez ◽  
John Carlos Garza ◽  
Juan A. De-Anda-Montañez ◽  
Francisco J. García-de-León
Keyword(s):  
Genetic Diversity ◽  
Marine Fish ◽  
Extinction Risk ◽  
Substantial Reduction ◽  
Critically Endangered ◽  
Biological Traits ◽  
Genetic Level ◽  
Loss Of Genetic Diversity ◽  
Fishery Collapse

Several worldwide marine fish stocks need to recover from collapse or overexploitation. However, the effects of a fishery collapse at the genetic level are still largely unknown, as is the extent of reduction in genetic diversity caused by fisheries and the consequences for extinction risk. Here we present a case study of totoaba, the first marine fish considered as critically endangered. We assessed 16 microsatellite loci to determine whether the demographic collapse of the species resulted in a loss of genetic diversity. Our data indicate that genetic diversity of totoaba is in the range of values observed for fish with similar biological traits without a documented fishery collapse. Contemporary demographic analysis indicated no loss of genetic diversity. Long-term genealogical analysis showed a substantial reduction in effective population size. However, the time and causal effects for population decline cannot be inferred because of the large uncertainty in estimates. Our results indicate that the totoaba in the Gulf of California has not suffered a measurable contemporary reduction in genetic diversity, and that genetic diversity is driven by long-term climatic events. Estimates of current effective size indicate that it is large enough that genetic factors may not be a major problem for conservation. We conclude that the recent fishery collapse of totoaba did not have sufficient consequences at the genetic level to increase the risk of extinction from genetic drift. However, selective effects of fishing on the adaptive potential in totoaba remain unclear.

Inbreeding and loss of genetic diversity increase extinction risk

2019 ◽  
pp. 31-48
Author(s):  
Richard Frankham ◽  
Jonathan D. Ballou ◽  
Katherine Ralls ◽  
Mark D. B. Eldridge ◽  
Michele R. Dudash ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Inbreeding Depression ◽  
Environmental Changes ◽  
Extinction Risk ◽  
Raw Material ◽  
Heterozygote Advantage ◽  
Isolated Populations ◽  
Survival And Reproduction ◽  
Loss Of Genetic Diversity ◽  
Harmful Effects

Inbreeding reduces survival and reproduction (i.e. it causes inbreeding depression), and thereby increases extinction risk. Inbreeding depression is due to increased homozygosity for harmful alleles and at loci exhibiting heterozygote advantage. Inbreeding depression is nearly universal in sexually reproducing organisms that are diploid or have higher ploidies. Impacts of inbreeding are generally greater in species that naturally outbreed than those that inbreed, in stressful than benign environments, and for fitness than peripheral traits. Harmful effects accumulate across the life cycle, resulting in devastating effects on total fitness in outbreeding species.Species face ubiquitous environmental change and must adapt or they will go extinct. Genetic diversity is the raw material required for evolutionary adaptation. However, loss of genetic diversity is unavoidable in small isolated populations, diminishing their capacity to evolve in response to environmental changes, and thereby increasing extinction risk.

scholarly journals Shallow gene pools in the high intertidal: extreme loss of genetic diversity in viviparous sea stars ( Parvulastra )

2013 ◽  
Vol 9 (5) ◽  
pp. 20130551 ◽  
Author(s):  
Carson C. Keever ◽  
Jonathan B. Puritz ◽  
Jason A. Addison ◽  
Maria Byrne ◽  
Richard K. Grosberg ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Dna Sequences ◽  
Extinction Risk ◽  
Ancestral Population ◽  
Gene Pools ◽  
Sea Stars ◽  
Isolation With Migration ◽  
Flow Loss ◽  
Loss Of Genetic Diversity ◽  
Intertidal Habitats

We document an extreme example of reproductive trait evolution that affects population genetic structure in sister species of Parvulastra cushion stars from Australia. Self-fertilization by hermaphroditic adults and brood protection of benthic larvae causes strong inbreeding and range-wide genetic poverty. Most samples were fixed for a single allele at nearly all nuclear loci; heterozygotes were extremely rare (0.18%); mitochondrial DNA sequences were more variable, but few populations shared haplotypes in common. Isolation-with-migration models suggest that these patterns are caused by population bottlenecks (relative to ancestral population size) and low gene flow. Loss of genetic diversity and low potential for dispersal between high-intertidal habitats may have dire consequences for extinction risk and potential for future adaptive evolution in response to climate and other selective agents.

Population genetics and conservation of the critically endangered Clematis acerifolia (Ranunculaceae)

2005 ◽  
Vol 83 (10) ◽  
pp. 1248-1256 ◽  
Author(s):  
J. López-Pujol ◽  
F.-M. Zhang ◽  
S. Ge
Keyword(s):  
Genetic Diversity ◽  
Population Genetic ◽  
Critically Endangered ◽  
Ex Situ ◽  
Genetic Structuring ◽  
Long Term Storage ◽  
Hardy Weinberg Equilibrium ◽  
Term Storage

Allozyme electrophoresis was used to evaluate the levels of genetic diversity and population genetic structure of the critically endangered Clematis acerifolia Maximowicz (Ranunculaceae), a narrow endemic species in China. On the basis of variation at 19 putative loci in nine populations covering the entire distribution of this species, low values of genetic diversity were detected (P = 20.5%, A = 1.27, and He = 0.072). A significant deficiency of heterozygotes was found in all populations. Most loci showed deviations from the Hardy–Weinberg equilibrium, probably as a result of population genetic structuring. The high genetic divergence among populations (FST = 0.273) can be interpreted as an effect of the extinction of local populations and genetic drift within extant populations, and has probably been enhanced by habitat fragmentation in recent decades. Threats to this species are mainly anthropogenic (road works, construction of holiday resorts, and extraction activities), although stochastic risks cannot be ignored. Therefore, to preserve extant genetic variation of C. acerifolia, in situ strategies, such as the preservation of its habitat or at least the most diverse populations, and ex situ measures, such as the collection and long-term storage of seeds, should be adopted.

Long-term survival despite low genetic diversity in the critically endangered Madagascar fish-eagle

2008 ◽  
Author(s):  
JEFF A. JOHNSON ◽  
RUTH E. TINGAY ◽  
MELANIE CULVER ◽  
FRANK HAILER ◽  
MICHÈLE L. CLARKE ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Critically Endangered ◽  
Term Survival ◽  
Long Term Survival ◽  
Low Genetic Diversity

scholarly journals Long-term molecular evolutionary rate determines intraspecific genetic diversity

2019 ◽  
Author(s):  
Jiaqi Wu ◽  
Takahiro Yonezawa ◽  
Hirohisa Kishino
Keyword(s):  
Genetic Diversity ◽  
De Novo ◽  
Early Stage ◽  
Morphological Evolution ◽  
Biological Traits ◽  
Gene Trees ◽  
Intraspecific Genetic Diversity ◽  
Molecular Evolutionary Rates ◽  
Species Specific

AbstractWhat determines genetic diversity and how it connects to the various biological traits is unknown. In this work, we offer answers to these questions. By comparing genetic variation of 14,671 mammalian gene trees with thousands of individual genomes of human, chimpanzee, gorilla, mouse and dog/wolf, we found that intraspecific genetic diversity is determined by long-term molecular evolutionary rates, rather than de novo mutation rates. This relationship was established during the early stage of mammalian evolution. Expanding this new finding, we developed a method to detect fluctuations of species-specific selection on genes as the deviations of intra-species genetic diversity predicted from long-term rates. We show that the evolution of epithelial cells, rather than of connective tissue, mainly contributes to morphological evolution of different species. For humans, evolution of the immune system and selective sweeps subjected by infectious diseases are most representative of adaptive evolution.

scholarly journals Founding Events and the Maintenance of Genetic Diversity in Reintroduced Populations

2021 ◽  
Author(s):  
◽  
Kimberly Anne Miller
Keyword(s):  
Genetic Diversity ◽  
Population Size ◽  
Loss Of Heterozygosity ◽  
Genetic Drift ◽  
Reproductive Output ◽  
Introduced Predators ◽  
Reintroduced Population ◽  
Loss Of Genetic Diversity ◽  
Term Maintenance

<p>As habitat loss, introduced predators, and disease epidemics threaten species worldwide, translocation provides one of the most powerful tools for species conservation. However, reintroduced populations of threatened species are often founded by a small number of individuals (typically 30 in New Zealand) and generally have low success rates. The loss of genetic diversity combined with inbreeding depression in a small reintroduced population could reduce the probability of establishment and persistence. Effective management of genetic diversity is therefore central to the success of reintroduced populations in both the short- and long-term. Using population modelling and empirical data from source and reintroduced populations of skinks and tuatara, I examined factors that influence inbreeding dynamics and the long-term maintenance of genetic diversity in translocated populations. The translocation of gravid females aided in increasing the effective population size after reintroduction. Models showed that supplementation of reintroduced populations reduced the loss of heterozygosity over 10 generations in species with low reproductive output, but not for species with higher output. Harvesting from a reintroduced population for a second-order translocation accelerated the loss of heterozygosity in species with low intrinsic rates of population growth. Male reproductive skew also accelerated the loss of genetic diversity over 10 generations, but the effect was only significant when the population size was small. Further, when populations at opposite ends of a species' historic range are disproportionately vulnerable to extinction and background inbreeding is high, genetic differentiation among populations may be an artefact of an historic genetic gradient coupled with rapid genetic drift. In these situations, marked genetic differences should not preclude hybridising populations to mitigate the risks of inbreeding after reintroduction. These results improve translocation planning for many species by offering guidelines for maximising genetic diversity in founder groups and managing populations to improve the long-term maintenance of diversity. For example, founder groups should be larger than 30 for  reintroductions of species with low reproductive output, high mortality rates after release, highly polygynous mating systems, and high levels of background inbreeding. This study also provides a basis for the development of more complex models of losses of genetic diversity after translocation and how genetic drift may affect the long-term persistence of these valuable  populations.</p>

Genetic Management of Fragmented Animal and Plant Populations

2017 ◽  
Author(s):  
Richard Frankham ◽  
Jonathan D. Ballou ◽  
Katherine Ralls ◽  
Mark Eldridge ◽  
Michele R. Dudash ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Gene Flow ◽  
Biological Diversity ◽  
Extinction Risk ◽  
Outbreeding Depression ◽  
Genetic Rescue ◽  
Isolated Populations ◽  
Genetic Management ◽  
Plant Populations ◽  
Loss Of Genetic Diversity

The biological diversity of the planet is being rapidly depleted due to the direct and indirect consequences of human activity. As the size of animal and plant populations decrease and fragmentation increases, loss of genetic diversity reduces their ability to adapt to changes in the environment, with inbreeding and reduced fitness inevitable consequences for many species. Many small isolated populations are going extinct unnecessarily. In many cases, such populations can be genetically rescued by gene flow into them from another population within the species, but this is very rarely done. This novel and authoritative book addresses the issues involved in genetic management of fragmented animal and plant populations, including inbreeding depression, loss of genetic diversity and elevated extinction risk in small isolated populations, augmentation of gene flow, genetic rescue, causes of outbreeding depression and predicting its occurrence, desirability and implementation of genetic translocations to cope with climate change, and defining and diagnosing species for conservation purposes.

scholarly journals Genetic Diversity Despite Population Collapse in a Critically Endangered Marine Fish: The Smalltooth Sawfish (Pristis pectinata)

2011 ◽  
Vol 102 (6) ◽  
pp. 643-652 ◽  
Author(s):  
Demian D. Chapman ◽  
Colin A. Simpfendorfer ◽  
Tonya R. Wiley ◽  
Gregg R. Poulakis ◽  
Caitlin Curtis ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Marine Fish ◽  
Critically Endangered ◽  
Population Collapse ◽  
Pristis Pectinata

scholarly journals Founding Events and the Maintenance of Genetic Diversity in Reintroduced Populations

2021 ◽  
Author(s):  
◽  
Kimberly Anne Miller
Keyword(s):  
Genetic Diversity ◽  
Population Size ◽  
Loss Of Heterozygosity ◽  
Genetic Drift ◽  
Reproductive Output ◽  
Introduced Predators ◽  
Reintroduced Population ◽  
Loss Of Genetic Diversity ◽  
Term Maintenance

<p>As habitat loss, introduced predators, and disease epidemics threaten species worldwide, translocation provides one of the most powerful tools for species conservation. However, reintroduced populations of threatened species are often founded by a small number of individuals (typically 30 in New Zealand) and generally have low success rates. The loss of genetic diversity combined with inbreeding depression in a small reintroduced population could reduce the probability of establishment and persistence. Effective management of genetic diversity is therefore central to the success of reintroduced populations in both the short- and long-term. Using population modelling and empirical data from source and reintroduced populations of skinks and tuatara, I examined factors that influence inbreeding dynamics and the long-term maintenance of genetic diversity in translocated populations. The translocation of gravid females aided in increasing the effective population size after reintroduction. Models showed that supplementation of reintroduced populations reduced the loss of heterozygosity over 10 generations in species with low reproductive output, but not for species with higher output. Harvesting from a reintroduced population for a second-order translocation accelerated the loss of heterozygosity in species with low intrinsic rates of population growth. Male reproductive skew also accelerated the loss of genetic diversity over 10 generations, but the effect was only significant when the population size was small. Further, when populations at opposite ends of a species' historic range are disproportionately vulnerable to extinction and background inbreeding is high, genetic differentiation among populations may be an artefact of an historic genetic gradient coupled with rapid genetic drift. In these situations, marked genetic differences should not preclude hybridising populations to mitigate the risks of inbreeding after reintroduction. These results improve translocation planning for many species by offering guidelines for maximising genetic diversity in founder groups and managing populations to improve the long-term maintenance of diversity. For example, founder groups should be larger than 30 for  reintroductions of species with low reproductive output, high mortality rates after release, highly polygynous mating systems, and high levels of background inbreeding. This study also provides a basis for the development of more complex models of losses of genetic diversity after translocation and how genetic drift may affect the long-term persistence of these valuable  populations.</p>

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