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.

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.

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 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.

Is the taxonomy appropriate? Delineating species for conservation purposes

2017 ◽  
Author(s):  
Richard Frankham ◽  
Jonathan D. Ballou ◽  
Katherine Ralls ◽  
Mark D. B. Eldridge ◽  
Michele R. Dudash ◽  
...  
Keyword(s):  
Species Concept ◽  
Conservation Management ◽  
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 Clonal Reproduction and Low Genetic Diversity in Northern Australian Santalum lanceolatum (Santalaceae) Populations Highlights the Need for Genetic Rescue of This Commercially Significant Species

Forests ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 741
Author(s):  
Aaron Brunton ◽  
David J. Lee ◽  
Gabriel Conroy ◽  
Steven Ogbourne
Keyword(s):  
Genetic Diversity ◽  
Natural Populations ◽  
Life History Strategy ◽  
Conservation Strategy ◽  
Regional Differentiation ◽  
Genetic Rescue ◽  
Environmental Pressures ◽  
Northern Margin ◽  
Low Genetic Diversity ◽  
Wild Harvesting

Genetic diversity and the extent of clonality in a plant species can significantly influence its reproductive success. Whilst clonality can be an effective life-history strategy, in harsh environments it can lead to low levels of diversity and sexual reproductive failure. Santalum lanceolatum (Santalaceae) is a hemi-parasitic shrub endemic to the monsoonal dry tropics of northern Australia, which was harvested for its oil-rich heartwood from natural populations in Cape York, Australia. Despite wild harvesting ending over 70 years ago, populations in the region are currently declining. The aims of this study were to examine genetic variation, population genetic structure, inbreeding and clonality of six S. lanceolatum populations from this northern margin of the species range. Analyses of twelve microsatellite markers showed S. lanceolatum had low genetic diversity (AR = 2.776, HE = 0.409), evidence of regional differentiation (FST = 0.307–0.424) and negligible inbreeding levels (F = −0.052). Clonality investigations revealed 135 genets among 200 samples, suggesting that the clonal structure of S. lanceolatum may be limiting the potential for sexual reproduction and natural recruitment. We recommend a conservation strategy involving genetic rescue to prevent the further decline and potential local extinction from a variety of environmental pressures and human activities.

Genetic rescue resulting from gene flow

2019 ◽  
pp. 65-80
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 ◽  
Beneficial Effects ◽  
History Of ◽  
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 natural outbreeders. 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. Crossing between populations also enhances the ability to evolve. Outbreeding depression result primarily from populations belonging to different taxa, having fixed chromosome differences, being genetically adapted to different environments, having a long history of isolation, or to combinations of these, and can be avoided by screening out population combinations with these characteristics.

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.

scholarly journals The importance of long-term genetic monitoring of reintroduced populations: inbreeding in the natterjack toad (Epidalea calamita)

2020 ◽  
pp. 159-167
Author(s):  
Susanna Phillips
Keyword(s):  
Genetic Diversity ◽  
Conservation Management ◽  
Genetic Monitoring ◽  
Source Population ◽  
Genetic Rescue ◽  
Management Actions ◽  
Low Genetic Diversity ◽  
Population Structuring ◽  
Epidalea Calamita

Genetic monitoring is an important, but frequently lacking, component of management actions to support long-term persistence in reintroduced populations. Populations that remain small, due to demographic processes and genetic diversity, are more likely to experience a second extinction event. The natterjack toad (Epidelea calamita) is legally protected in Britain and was the subject of a reintroduction programme in the 1990s. However, subsequent genetic assessment has been mostly lacking. The aim of this study was to assess the genetic diversity of two reintroduced populations of natterjack toads in order to inform conservation management. Adults were sampled and nine microsatellites amplified to assess neutral genetic variation within each site and for comparison with the source population. Inbreeding was observed at the reintroduction sites, as evidenced by high FIS values (0.43 and 0.72), low observed compared to expected heterozygosities, and significant deviation from Hardy-Weinberg equilibrium. Observed heterozygosity is currently lower in the reintroduction sites than it was in the source population at the time of the reintroductions (Red Rocks: 0.15±0.20; Talacre: 0.12±0.20; Ainsdale (source): 0.29). Evidence for a bottleneck was not found, although this is likely a result of sampling overlapping generations. No withinsite population structuring was observed. Such low genetic diversity has not previously been recorded in any natterjack population. Genetic rescue, combined with pool creation, is the most viable option for safeguarding the species at these sites into the future. Our work highlights the importance of ongoing genetic monitoring, in collaboration with conservation organisations, to support conservation management.

The Response to Past Climate Perturbations Explains Extremely Low Genetic Diversity in the Genome of an Abundant Ice-Age Remnant, the Alpine Marmot

2018 ◽  
Author(s):  
Toni I. Gossmann​ ◽  
Achchuthan Shanmugasundram​ ◽  
Stefan Börno ◽  
Ludovic Duvaux ◽  
Christophe Lemaire​ ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Ice Age ◽  
Past Climate ◽  
Low Genetic Diversity ◽  
Alpine Marmot

Modified rescue and risk expectations for species with diverse mating systems and modes of inheritance

2017 ◽  
Author(s):  
Richard Frankham ◽  
Jonathan D. Ballou ◽  
Katherine Ralls ◽  
Mark D. B. Eldridge ◽  
Michele R. Dudash ◽  
...  
Keyword(s):  
Mating Systems ◽  
Outbreeding Depression ◽  
Mixed Mating ◽  
Genetic Rescue ◽  
Mode Of Inheritance

The risks of inbreeding and outbreeding depression, and the prospects for genetic rescue are often different in species with alternative mating systems and mode of inheritance (compared to outbreeding diploids), such as self-incompatible, self-fertilizing, mixed mating, non-diploid (haploid, haplodiploid and polyploid) and asexual.

Sign in / Sign up

Export Citation Format

Share Document