Take home messages

2017 ◽  
Author(s):  
Richard Frankham ◽  
Jonathan D. Ballou ◽  
Katherine Ralls ◽  
Mark D. B. Eldridge ◽  
Michele R. Dudash ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Gene Flow ◽  
Outbreeding Depression ◽  
Isolated Population ◽  
Low Genetic Diversity ◽  
Financial Costs

We recommend augmentation of gene flow for isolated population fragments that are suffering inbreeding and low genetic diversity, provided that proposed population crosses have low risks of outbreeding depression, and the predicted benefits justify the financial costs.

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.

Weak genetic structuring suggests historically high genetic connectivity among recently fragmented urban populations of the scincid lizard, Ctenotus fallens

2015 ◽  
Vol 63 (4) ◽  
pp. 279 ◽  
Author(s):  
Josef Krawiec ◽  
Siegfried L. Krauss ◽  
Robert A. Davis ◽  
Peter B. S. Spencer
Keyword(s):  
Genetic Diversity ◽  
Gene Flow ◽  
Large Population ◽  
Geographic Distance ◽  
Genetic Erosion ◽  
Genetic Connectivity ◽  
Genetic Structuring ◽  
Low Genetic Diversity ◽  
Population Sizes

Populations in fragmented urban remnants may be at risk of genetic erosion as a result of reduced gene flow and elevated levels of inbreeding. This may have serious genetic implications for the long-term viability of remnant populations, in addition to the more immediate pressures caused by urbanisation. The population genetic structure of the generalist skink Ctenotus fallens was examined using nine microsatellite markers within and among natural vegetation remnants within a highly fragmented urban matrix in the Perth metropolitan area in Western Australia. These data were compared with samples from a large unfragmented site on the edge of the urban area. Overall, estimates of genetic diversity and inbreeding within all populations were similar and low. Weak genetic differentiation, and a significant association between geographic and genetic distance, suggests historically strong genetic connectivity that decreases with geographic distance. Due to recent fragmentation, and genetic inertia associated with low genetic diversity and large population sizes, it is not possible from these data to infer current genetic connectivity levels. However, the historically high levels of gene flow that our data suggest indicate that a reduction in contemporary connectivity due to fragmentation in C. fallens is likely to result in negative genetic consequences in the longer term.

Sperm motility and offspring pre- and post-hatching survival in hybridization crosses among a landlocked and two anadromous Atlantic salmon populations: implications for conservation

2020 ◽  
Author(s):  
Aslak Tiuna Eronen ◽  
Jukka Kekäläinen ◽  
Jorma Piironen ◽  
Pekka Hyvärinen ◽  
Hannu Huuskonen ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Sperm Motility ◽  
First Generation ◽  
Hybrid Vigor ◽  
Outbreeding Depression ◽  
Genetic Rescue ◽  
Low Genetic Diversity ◽  
Salmon Eggs ◽  
Salmon Population ◽  
Lake Saimaa

The landlocked salmon (Salmo salar m. sebago) endemic to Lake Saimaa, Finland, is critically endangered and severely threatened by low genetic diversity and inbreeding. To explore the possibility of increasing the genetic diversity of threatened salmon populations by controlled hybridization (genetic rescue), we studied sperm motility and offspring pre- and post-hatching survival in hybridization crosses of landlocked salmon with two geographically close anadromous salmon populations (Rivers Neva and Tornio) relative to the pure-bred populations. While some degree of gametic incompatibility between landlocked and Tornio salmon cannot be ruled out, there were no indications of outbreeding depression in survival traits in these first-generation hybridizations. Instead, pre-hatching survival of landlocked salmon eggs fertilized with Neva salmon sperm and post-hatching survival of anadromous salmon eggs fertilized with landlocked salmon sperm were higher than in pure-bred landlocked salmon. These differences might imply genetic rescue effects (hybrid vigor), although there were also strong maternal effects involved. Our results on early viability point to the possibility of applying genetic rescue to the landlocked salmon population by hybridization with an anadromous population.

Managing gene flow among isolated population fragments. I. Limited information

2017 ◽  
Author(s):  
Richard Frankham ◽  
Jonathan D. Ballou ◽  
Katherine Ralls ◽  
Mark D. B. Eldridge ◽  
Michele R. Dudash ◽  
...  
Keyword(s):  
Population Genetics ◽  
Gene Flow ◽  
Management Strategies ◽  
Genetic Data ◽  
Outbreeding Depression ◽  
Isolated Population ◽  
Limited Information ◽  
Detailed Data ◽  
Genetic Management ◽  
Better Than

When the decision is made to augment gene flow into an isolated population, managers must decide how to augment gene flow, when to start, from where to take the individuals or gametes to be added, how many, which individuals, how often and when to cease. Even without detailed genetic data, sound genetic management strategies for augmenting gene flow can be instituted by considering population genetics theory, and/or computer simulations. When detailed data are lacking, moving (translocating) some individuals into isolated inbred population fragments is better than moving none, as long as the risk of outbreeding depression is low.

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.

Managing gene flow among isolated population fragments

2019 ◽  
pp. 115-134
Author(s):  
Richard Frankham ◽  
Jonathan D. Ballou ◽  
Katherine Ralls ◽  
Mark D. B. Eldridge ◽  
Michele R. Dudash ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Gene Flow ◽  
Genetic Information ◽  
Management Strategies ◽  
Genetic Data ◽  
Isolated Population ◽  
Detailed Data ◽  
Genetic Management ◽  
Flow Management ◽  
The Status

Even without detailed genetic data, sound genetic management strategies for augmenting gene flow can be instituted by considering population genetics theory, and/or computer simulations. When detailed data are lacking, moving (translocating) some individuals into isolated inbred population fragments is better than moving none, as long as the risk of outbreeding depression is low. With more detailed genetic information, more precise genetic management of fragmented populations can be achieved. Using mean kinship within and between populations (estimated from modeling, pedigrees, genetic markers or genomes), and moving individuals among fragments with the lowest between fragment mean kinships provides the best approach to gene flow management. Populations should then be monitored to confirm that movement of individuals has resulted in the desired levels of gene flow, genetic diversity has been enhanced, and that the status of the population is improving.

Appropriate delineation of species for conservation purposes

2019 ◽  
pp. 85-96
Author(s):  
Richard Frankham ◽  
Jonathan D. Ballou ◽  
Katherine Ralls ◽  
Mark D. B. Eldridge ◽  
Michele R. Dudash ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Reproductive Isolation ◽  
Biological Species ◽  
Species Concepts ◽  
Outbreeding Depression ◽  
Biological Species Concept ◽  
Genetic Rescue ◽  
Low Genetic Diversity ◽  
Inbred Populations ◽  
Species Definitions

The first step in conservation management is to delineate groups for separate versus combined management. However, there are many problems with species delineation, including diverse species definitions, lack of standardized protocols, and poor repeatability of delineations. Definitions that are too broad will lead to outbreeding depression if populations are crossed, while those that split excessively may preclude genetic rescue of small inbred populations with low genetic diversity. To minimize these problems, we recommend the use of species concepts based upon reproductive isolation (such as the Biological Species Concept) and advise against the use of Phylogenetic and General Lineage Species Concepts. We provide guidelines as to when taxonomy requires revision and outline protocols for robust species delineations.

scholarly journals Genetic Diversity and Population Structure of Medemia argun (Mart.) Wurttenb. ex H.Wendl. Based on Genome-Wide Markers

2021 ◽  
Vol 9 ◽  
Author(s):  
Sakina Elshibli ◽  
Helena Korpelainen
Keyword(s):  
Genetic Diversity ◽  
Gene Flow ◽  
Genetic Differentiation ◽  
Conservation Status ◽  
Ex Situ ◽  
Conservation Strategies ◽  
Nucleotide Polymorphisms ◽  
Genetic Structuring ◽  
Ancestral Gene ◽  
Low Genetic Diversity

Medemia argun is a wild, dioecious palm, adapted to the harsh arid environment of the Nubian Desert in Sudan and southern Egypt. There is a concern about its conservation status, since little is known about its distribution, abundance, and genetic variation. M. argun grows on the floodplains of seasonal rivers (wadis). The continuing loss of suitable habitats in the Nubian Desert is threatening the survival of this species. We analyzed the genetic diversity, population genetic structure, and occurrence of M. argun populations to foster the development of conservation strategies for M. argun. Genotyping-by-sequencing (GBS) analyses were performed using a whole-genome profiling service. We found an overall low genetic diversity and moderate genetic structuring based on 40 single-nucleotide polymorphisms (SNPs) and 9,866 SilicoDArT markers. The expected heterozygosity of the total population (HT) equaled 0.036 and 0.127, and genetic differentiation among populations/groups (FST) was 0.052 and 0.092, based on SNP and SilicoDArT markers, respectively. Bayesian clustering analyses defined five genetic clusters that did not display any ancestral gene flow among each other. Based on SilicoDArT markers, the results of the analysis of molecular variance (AMOVA) confirmed the previously observed genetic differentiation among generation groups (23%; p < 0.01). Pairwise FST values indicated a genetic gap between old and young individuals. The observed low genetic diversity and its loss among generation groups, even under the detected high gene flow, show genetically vulnerable M. argun populations in the Nubian Desert in Sudan. To enrich and maintain genetic variability in these populations, conservation plans are required, including collection of seed material from genetically diverse populations and development of ex situ gene banks.

scholarly journals Gene Flow, Recombination, and Selection in Cyanobacteria: Population Structure of Geographically Related Planktothrix Freshwater Strains

2012 ◽  
Vol 79 (2) ◽  
pp. 508-515 ◽  
Author(s):  
Hanne Sogge ◽  
Thomas Rohrlack ◽  
Trine B. Rounge ◽  
Jørn Henrik Sønstebø ◽  
Ave Tooming-Klunderud ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Gene Flow ◽  
Genetic Variants ◽  
Phylogenetic Analyses ◽  
Purifying Selection ◽  
Split Decomposition ◽  
Content Type ◽  
Low Genetic Diversity ◽  
Peptide Synthetase ◽  
Similar Range

ABSTRACTSeveralPlanktothrixstrains, each producing a distinct oligopeptide profile, have been shown to coexist within Lake Steinsfjorden (Norway). Using nonribosomal peptide synthetase (NRPS) genes as markers, it has been shown that thePlanktothrixcommunity comprises distinct genetic variants displaying differences in bloom dynamics, suggesting aPlanktothrixsubpopulation structure. Here, we investigate thePlanktothrixvariants inhabiting four lakes in southeast of Norway utilizing both NRPS and non-NRPS genes. Phylogenetic analyses showed similar topologies for both NRPS and non-NRPS genes, and the lakes appear to have similar structuring ofPlanktothrixgenetic variants. The structure of distinct variants was also supported by very low genetic diversity within variants compared to the between-variant diversity. Incongruent topologies and split decomposition revealed recombination events betweenPlanktothrixvariants. In several strains the gene variants seem to be a result of recombination. Both NRPS and non-NRPS genes are dominated by purifying selection; however, sites subjected to positive selection were also detected. The presence of similar and well-separatedPlanktothrixvariants with low internal genetic diversity indicates gene flow withinPlanktothrixpopulations. Further, the low genetic diversity found between lakes (similar range as within lakes) indicates gene flow also betweenPlanktothrixpopulations and suggests recent, or recurrent, dispersals. Our data also indicate that recombination has resulted in new genetic variants. Stability within variants and the development of new variants are likely to be influenced by selection patterns and within-variant homologous recombination.

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