scholarly journals Fitness consequences of targeted gene flow to counter impacts of drying climates on terrestrial-breeding frogs

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Tabitha S. Rudin-Bitterli ◽  
Jonathan P. Evans ◽  
Nicola J. Mitchell
Keyword(s):  
Gene Flow ◽  
Outbreeding Depression ◽  
Hybrid Vigour ◽  
Adaptive Potential ◽  
Isolated Populations ◽  
Northern Population ◽  
Management Actions ◽  
Fitness Consequences ◽  
Frog Species ◽  
East West

AbstractTargeted gene flow (TGF) could bolster the adaptive potential of isolated populations threatened by climate change, but could also lead to outbreeding depression. Here, we explore these possibilities by creating mixed- and within-population crosses in a terrestrial-breeding frog species threatened by a drying climate. We reared embryos of the crawling frog (Pseudophryne guentheri) on wet and dry soils and quantified fitness-related traits upon hatching. TGF produced mixed outcomes in hybrids, which depended on crossing direction (origin of gametes from each sex). North-south crosses led to low embryonic survival if eggs were of a southern origin, and high malformation rates when eggs were from a northern population. Conversely, east-west crosses led to one instance of hybrid vigour, evident by increased fitness and desiccation tolerance of hybrid offspring relative to offspring produced from within-population crosses. These contrasting results highlight the need to experimentally evaluate the outcomes of TGF for focal species across generations prior to implementing management actions.

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.

Evaluating the use of risk assessment frameworks in the identification of population units for biodiversity conservation

2020 ◽  
Vol 47 (3) ◽  
pp. 208
Author(s):  
Erin Liddell ◽  
Carly N. Cook ◽  
Paul Sunnucks
Keyword(s):  
Inbreeding Depression ◽  
Threatened Species ◽  
Outbreeding Depression ◽  
Isolated Populations ◽  
Theoretical Concepts ◽  
Management Actions ◽  
Relevant Evidence ◽  
Relative Risks ◽  
Course Of Action ◽  
Management Recommendations

Abstract ContextManaging small, isolated populations requires conservation practitioners to weigh up the risks of inbreeding depression and outbreeding depression when assessing alternative management actions aimed at preventing species extinction. Accordingly, it is important that research intended to guide these management decisions provides the relevant evidence to inform them. AimsTo determine the extent to which studies that use genetic analyses to characterise population units for conservation consider the key theoretical concepts necessary for making sound management recommendations regarding the desirability of gene flow among units, notably the consequences and relative risks of inbreeding depression and outbreeding depression. MethodsA systematic search was conducted of peer-reviewed literature for studies that attempted to identify population units of threatened birds and mammals. Using content analysis, the theoretical framing of these studies was assessed, based on the discussion of key concepts concerning differences among populations. Key resultsThere has been a significant increase over time in the number of published studies that use genetics to identify population units for conservation. Many do not consider theoretical concepts relevant to the effective management of fragmented populations of threatened species. Mammals were more common than birds as focal species of studies, but the number of concepts used in the framing of the studies was similar for these two taxa, despite differences in their ecology and biology that might be expected to affect perceptions of distinctiveness. Nevertheless, species of greater conservation concern tended to have a slightly more comprehensive theoretical framing. ConclusionsThere is great potential for more studies to implement theoretical guidelines and practical decision support tools when considering the best course of action for identifying appropriate population units for conservation management. ImplicationsThe gap in the identified literature is likely to be impacting the ability of conservation practitioners to make evidence-informed decisions about how to manage the genetic health of threatened species; it would be valuable to improve this situation.

scholarly journals Reducing the Extinction Risk of Populations Threatened by Infectious Diseases

Diversity ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 63
Author(s):  
Gael L. Glassock ◽  
Catherine E. Grueber ◽  
Katherine Belov ◽  
Carolyn J. Hogg
Keyword(s):  
Gene Flow ◽  
Infectious Diseases ◽  
Extinction Risk ◽  
Population Decline ◽  
Outbreeding Depression ◽  
Tasmanian Devil ◽  
Adaptive Potential ◽  
Genetic Management ◽  
Animal Populations ◽  
Devil Facial Tumour Disease

Extinction risk is increasing for a range of species due to a variety of threats, including disease. Emerging infectious diseases can cause severe declines in wild animal populations, increasing population fragmentation and reducing gene flow. Small, isolated, host populations may lose adaptive potential and become more susceptible to extinction due to other threats. Management of the genetic consequences of disease-induced population decline is often necessary. Whilst disease threats need to be addressed, they can be difficult to mitigate. Actions implemented to conserve the Tasmanian devil (Sarcophilus harrisii), which has suffered decline to the deadly devil facial tumour disease (DFTD), exemplify how genetic management can be used to reduce extinction risk in populations threatened by disease. Supplementation is an emerging conservation technique that may benefit populations threatened by disease by enabling gene flow and conserving their adaptive potential through genetic restoration. Other candidate species may benefit from genetic management via supplementation but concerns regarding outbreeding depression may prevent widespread incorporation of this technique into wildlife disease management. However, existing knowledge can be used to identify populations that would benefit from supplementation where risk of outbreeding depression is low. For populations threatened by disease and, in situations where disease eradication is not an option, wildlife managers should consider genetic management to buffer the host species against inbreeding and loss of genetic diversity.

Are there populations suffering genetic erosion that would benefit from augmented gene flow?

2017 ◽  
Author(s):  
Richard Frankham ◽  
Jonathan D. Ballou ◽  
Katherine Ralls ◽  
Mark D. B. Eldridge ◽  
Michele R. Dudash ◽  
...  
Keyword(s):  
Gene Flow ◽  
Genetic Erosion ◽  
Genetic Rescue ◽  
Isolated Populations

Having identified small geographically and genetically isolated populations, we need to determine whether they are suffering genetic erosion, and if so, whether there are any other populations to which they could be crossed. We should next ask whether crossing is expected to be harmful or beneficial, 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.

Outbreeding depression is uncommon and predictable

2017 ◽  
Author(s):  
Richard Frankham ◽  
Jonathan D. Ballou ◽  
Katherine Ralls ◽  
Mark D. B. Eldridge ◽  
Michele R. Dudash ◽  
...  
Keyword(s):  
Natural Selection ◽  
Genetic Differences ◽  
Outbreeding Depression ◽  
Isolated Populations ◽  
Large Populations

Crosses between populations within species sometimes result in reduced fitness, especially in F2 and later generations (outbreeding depression). The primary mechanisms causing outbreeding depression in crosses between populations are fixed chromosomal differences and adaptive genetic differences, especially for long-isolated populations. Outbreeding depression is usually observed after crossing populations with ploidy differences or fixed differences for translocations, inversions or centric fusions: the magnitudes are usually ploidy > translocations and monobrachial centric fusions > inversions and simple centric fusions. Populations adapted to different environments (but with the same karyotype) often exhibit outbreeding depression when crossed, especially in the F2 and later generations. Even if outbreeding depression occurs, it is often only temporary, as natural selection acts to remove it, especially in large populations.

Genetic rescue by augmenting gene flow

2017 ◽  
Author(s):  
Richard Frankham ◽  
Jonathan D. Ballou ◽  
Katherine Ralls ◽  
Mark D. B. Eldridge ◽  
Michele R. Dudash ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Gene Flow ◽  
Inbreeding Coefficient ◽  
Outbreeding Depression ◽  
Genetic Rescue ◽  
Evolutionary Potential ◽  
Beneficial Effects ◽  
The Difference ◽  
Inbred Populations ◽  
Harmful Effects

Inbreeding is reduced and genetic diversity enhanced when a small isolated inbred population is crossed to another unrelated population. Crossing can have beneficial or harmful effects on fitness, but beneficial effects predominate, and the risks of harmful ones (outbreeding depression) can be predicted and avoided. For crosses with a low risk of outbreeding depression, there are large and consistent benefits on fitness that persist across generations in outbreeding species. Benefits are greater in species that naturally outbreed than those that inbreed, and increase with the difference in inbreeding coefficient between crossed and inbred populations in mothers and zygotes. However, benefits are similar across invertebrates, vertebrates and plants. There are also important benefits for evolutionary potential of crossing between populations.

Genetic Differentiation in Isolated Populations of Hakea carinata (Proteaceae)

1998 ◽  
Vol 46 (6) ◽  
pp. 671 ◽  
Author(s):  
G. J. Starr ◽  
S. M. Carthew
Keyword(s):  
Gene Flow ◽  
Habitat Fragmentation ◽  
Gene Diversity ◽  
South Australia ◽  
Similar Species ◽  
Isolated Populations ◽  
Plant Populations ◽  
Evolutionary Condition ◽  
Private Alleles

Fragmentation of the landscape by human activity has created small, isolated plant populations. Hakea carinata F. Muell. ex Meissner, a sclerophyllous shrub, is common in isolated fragments of vegetation in South Australia. This study investigated whether habitat fragmentation has caused restrictions to gene flow between populations. Gene diversity (HT = 0.317) is average for similar species but little is held within populations (HS = 0.168) and 46.9% of gene diversity is accounted for between populations. Estimates of gene flow are NM = 0.270 (based on FST) and NM = 0.129 (based on private alleles). Populations are substantially selfing (t = 0.111). Small isolated populations appears to be a long-term evolutionary condition in this species rather than a consequence of habitat fragmentation; however, population extinctions are occurring. Conservation will require the reservation of many populations to represent the genetic variation present in the species.

scholarly journals Population Genetic Structure of Rhizoctonia oryzae-sativae from Rice in Latin America and Its Adaptive Potential to Emerge as a Pathogen on Urochloa Pastures

2017 ◽  
Vol 107 (1) ◽  
pp. 121-131 ◽  
Author(s):  
Danilo A. dos Santos Pereira ◽  
Paulo C. Ceresini ◽  
Vanina L. Castroagudín ◽  
Lina M. Ramos-Molina ◽  
Edisson Chavarro-Mesa ◽  
...  
Keyword(s):  
Gene Flow ◽  
Genetic Structure ◽  
Reproductive System ◽  
Population Genetic ◽  
Upland Rice ◽  
Adaptive Potential ◽  
Rhizoctonia Oryzae ◽  
Hardy Weinberg Equilibrium ◽  
Two Populations ◽  
Brazilian Populations

The fungus Rhizoctonia oryzae-sativae is an important pathogen that causes the aggregated sheath spot disease on rice. In this study, we investigated the genetic structure of rice-adapted populations of R. oryzae-sativae sampled from traditional rice-cropping areas from the Paraíba Valley, São Paulo, Brazil, and from Meta, in the Colombian Llanos, in South America. We used five microsatellite loci to measure population differentiation and infer the pathogen’s reproductive system. Gene flow was detected among the three populations of R. oryzae-sativae from lowland rice in Brazil and Colombia. In contrast, a lack of gene flow was observed between the lowland and the upland rice populations of the pathogen. Evidence of sexual reproduction including low clonality, Hardy-Weinberg equilibrium within loci and gametic equilibrium between loci, indicated the predominance of a mixed reproductive system in all populations. In addition, we assessed the adaptive potential of the Brazilian populations of R. oryzae-sativae to emerge as a pathogen to Urochloa spp. (signalgrass) based on greenhouse aggressiveness assays. The Brazilian populations of R. oryzae-sativae were probably only incipiently adapted as a pathogen to Urochloa spp. Comparison between RST and QST showed the predominance of diversifying selection in the divergence between the two populations of R. oryzae-sativae from Brazil.

scholarly journals Population Genomics of Bettongia lesueur: Admixing Increases Genetic Diversity with no Evidence of Outbreeding Depression

Genes ◽  
2019 ◽  
Vol 10 (11) ◽  
pp. 851 ◽  
Author(s):  
Kate Rick ◽  
Kym Ottewell ◽  
Cheryl Lohr ◽  
Rujiporn Thavornkanlapachai ◽  
Margaret Byrne ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Threatened Species ◽  
Population Genomics ◽  
Fold Increase ◽  
Recruitment Rate ◽  
Outbreeding Depression ◽  
Nucleotide Polymorphisms ◽  
Isolated Populations ◽  
Genomic Markers ◽  
Founder Populations

Small and isolated populations are subject to the loss of genetic variation as a consequence of inbreeding and genetic drift, which in turn, can affect the fitness and long-term viability of populations. Translocations can be used as an effective conservation tool to combat this loss of genetic diversity through establishing new populations of threatened species, and to increase total population size. Releasing animals from multiple genetically diverged sources is one method to optimize genetic diversity in translocated populations. However, admixture as a conservation tool is rarely utilized due to the risks of outbreeding depression. Using high-resolution genomic markers through double-digest restriction site-associated sequencing (ddRAD-seq) and life history data collected over nine years of monitoring, this study investigates the genetic and fitness consequences of admixing two genetically-distinct subspecies of Bettongia lesueur in a conservation translocation. Using single nucleotide polymorphisms (SNPs) identified from 215 individuals from multiple generations, we found an almost 2-fold increase in genetic diversity in the admixed translocation population compared to the founder populations, and this was maintained over time. Furthermore, hybrid class did not significantly impact on survivorship or the recruitment rate and therefore we found no indication of outbreeding depression. This study demonstrates the beneficial application of mixing multiple source populations in the conservation of threatened species for minimizing inbreeding and enhancing adaptive potential and overall fitness.

Demographic, dispersal, predation and genetic data reveal the potential vulnerability of an endangered rainforest shrub, Triunia robusta (Proteaceae)

2017 ◽  
Vol 65 (3) ◽  
pp. 270 ◽  
Author(s):  
Yoko Shimizu-Kimura ◽  
Scott Burnett ◽  
Alison Shapcott
Keyword(s):  
Gene Flow ◽  
Life Span ◽  
Demographic Data ◽  
Genetic Data ◽  
Seedling Mortality ◽  
Isolated Populations ◽  
Predation Mortality ◽  
Dispersal Vectors ◽  
Limited Gene Flow ◽  
Reproductive Rates

We investigated the population ecology of Triunia robusta (C.T. White) Foreman, an endemic rainforest shrub of south-east Queensland, Australia. Two-time demographic data from 1999 and 2010 were used to estimate the species life span and changes in demographic factors over the 11 year period. The potential dispersal vectors and their activities were monitored, and the effects of predation on seed and seedling mortality were quantified. Published genetic data was used to assess the gene flow distance in years. On average, T. robusta has a life span of 103 years, with a generation time of 44 years. Larger populations (>200) increased in size since 1999, whereas smaller populations retained the same or slightly reduced numbers. Small, isolated populations in the northern distribution range showed substantially lower reproductive rates. Local rodents and marsupials were considered responsible for the majority of observed secondary seed dispersal (<10.3 m) and predation activities. Post-predation mortality was high (82%), with only 12% surviving to become seedlings. The empirical evidence of short-distance dispersal, limited gene flow, high post-predation mortality rates and relatively low reproductive rates, combined with potential absence of primary dispersers suggests that critically small and isolated populations may be highly vulnerable.

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