scholarly journals Natural selection acts on Atlantic salmon major histocompatibility (MH) variability in the wild

2007 ◽  
Vol 274 (1611) ◽  
pp. 861-869 ◽  
Author(s):  
Elvira de Eyto ◽  
Philip McGinnity ◽  
Sofia Consuegra ◽  
Jamie Coughlan ◽  
Jarle Tufto ◽  
...  
Keyword(s):  
Natural Selection ◽  
Atlantic Salmon ◽  
Balancing Selection ◽  
Natural Populations ◽  
Class Ii ◽  
Major Histocompatibility ◽  
Genotype Frequencies ◽  
Fitness Consequences ◽  
In The Wild ◽  
Class Ii Alpha

Pathogen-driven balancing selection is thought to maintain polymorphism in major histocompatibility (MH) genes. However, there have been few empirical demonstrations of selection acting on MH loci in natural populations. To determine whether natural selection on MH genes has fitness consequences for wild Atlantic salmon in natural conditions, we compared observed genotype frequencies of Atlantic salmon ( Salmo salar ) surviving in a river six months after their introduction as eggs with frequencies expected from parental crosses. We found significant differences between expected and observed genotype frequencies at the MH class II alpha locus, but not at a MH class I-linked microsatellite or at seven non-MH-linked microsatellite loci. We therefore conclude that selection at the MH class II alpha locus was a result of disease-mediated natural selection, rather than any demographic event. We also show that survival was associated with additive allelic effects at the MH class II alpha locus. Our results have implications for both the conservation of wild salmon stocks and the management of disease in hatchery fish. We conclude that natural or hatchery populations have the best chance of dealing with episodic and variable disease challenges if MH genetic variation is preserved both within and among populations.

Natural selection at the class II major histocompatibility complex loci of mammals

1994 ◽  
Vol 346 (1317) ◽  
pp. 359-367 ◽  
Keyword(s):  
Major Histocompatibility Complex ◽  
Natural Selection ◽  
Balancing Selection ◽  
Synonymous Substitution ◽  
Class Ii ◽  
Class I ◽  
Major Histocompatibility ◽  
Class I Mhc ◽  
Histocompatibility Complex ◽  
Class Ii Mhc

The role of natural selection at major histocompatibility complex (MHC) loci was studied by analysis of molecular sequence data from mammalian class II MHC loci. As found previously for the class I MHC molecule and a hypothetical model of the class II molecule, the rate of non-synonymous nucleotide substitution exceeded that of synonymous substitution in the codons encoding the antigen recognition site of polymorphic class II molecules. This pattern is evidence that the polymorphism at these loci is maintained by a form of balancing selection, such as overdominant selection. By contrast, in the case of monomorphic class II loci, no such enhancement of the rate of non-synonymous substitution was observed. Phylogenetic analysis indicates that, in contrast to monomorphic (‘non-classical’) class I MHC loci, some monomorphic class II loci of mammals are quite ancient. The DMA and DMB loci, for example, diverged before all other known mammalian class II loci, possibly before the divergence of tetrapods from bony fishes. Analysis of the patterns of sharing of polymorphic residues at class II MHC loci by mammals of different species revealed that extensive convergent evolution has occurred at these loci; but no support was found for the hypothesis that MHC polymorphisms have been maintained since before the divergence of orders of eutherian mammals.

scholarly journals Defective major histocompatibility complex class II assembly, transport, peptide acquisition, and CD4+ T cell selection in mice lacking invariant chain expression.

1993 ◽  
Vol 177 (6) ◽  
pp. 1699-1712 ◽  
Author(s):  
E K Bikoff ◽  
L Y Huang ◽  
V Episkopou ◽  
J van Meerwijk ◽  
R N Germain ◽  
...  
Keyword(s):  
Major Histocompatibility Complex ◽  
Mhc Class Ii ◽  
Critical Role ◽  
Class Ii ◽  
Intact Protein ◽  
Invariant Chain ◽  
Major Histocompatibility ◽  
Protein Antigens ◽  
Histocompatibility Complex ◽  
Class Ii Alpha

We used gene targeting techniques to produce mice lacking the invariant chain associated with major histocompatibility complex (MHC) class II molecules. Cells from these mice show a dramatic reduction in surface class II, resulting from both defective association of class II alpha and beta chains and markedly decreased post-Golgi transport. The few class II alpha/beta heterodimers reaching the cell surface behave as if empty or occupied by an easily displaced peptide, and display a distinct structure. Mutant spleen cells are defective in their ability to present intact protein antigens, but stimulate enhanced responses in the presence of peptides. These mutant mice have greatly reduced numbers of thymic and peripheral CD4+ T cells. Overall, this striking phenotype establishes that the invariant chain plays a critical role in regulating MHC class II expression and function in the intact animal.

scholarly journals Captive-bred Atlantic salmon released into the wild have fewer offspring than wild-bred fish and decrease population productivity

2020 ◽  
Vol 287 (1937) ◽  
pp. 20201671
Author(s):  
Ronan James O'Sullivan ◽  
Tutku Aykanat ◽  
Susan E. Johnston ◽  
Ger Rogan ◽  
Russell Poole ◽  
...  
Keyword(s):  
Atlantic Salmon ◽  
Natural Populations ◽  
Mixed Population ◽  
Lifetime Reproductive Success ◽  
Wild Relative ◽  
Offspring Survival ◽  
Wild Populations ◽  
Annual Productivity ◽  
In The Wild ◽  
Analyse Data

The release of captive-bred animals into the wild is commonly practised to restore or supplement wild populations but comes with a suite of ecological and genetic consequences. Vast numbers of hatchery-reared fish are released annually, ostensibly to restore/enhance wild populations or provide greater angling returns. While previous studies have shown that captive-bred fish perform poorly in the wild relative to wild-bred conspecifics, few have measured individual lifetime reproductive success (LRS) and how this affects population productivity. Here, we analyse data on Atlantic salmon from an intensely studied catchment into which varying numbers of captive-bred fish have escaped/been released and potentially bred over several decades. Using a molecular pedigree, we demonstrate that, on average, the LRS of captive-bred individuals was only 36% that of wild-bred individuals. A significant LRS difference remained after excluding individuals that left no surviving offspring, some of which might have simply failed to spawn, consistent with transgenerational effects on offspring survival. The annual productivity of the mixed population (wild-bred plus captive-bred) was lower in years where captive-bred fish comprised a greater fraction of potential spawners. These results bolster previous empirical and theoretical findings that intentional stocking, or non-intentional escapees, threaten, rather than enhance, recipient natural populations.

scholarly journals Fitness consequences of a non-recombining sex-ratio drive chromosome can explain its prevalence in the wild

2019 ◽  
Vol 286 (1917) ◽  
pp. 20192529 ◽  
Author(s):  
Kelly A. Dyer ◽  
David W. Hall
Keyword(s):  
Sex Ratio ◽  
Sperm Competition ◽  
Natural Populations ◽  
Theoretical Models ◽  
Host Population ◽  
Gene Drive ◽  
Fitness Consequences ◽  
In The Wild ◽  
And Performance ◽  
Drive Systems

Understanding the pleiotropic consequences of gene drive systems on host fitness is essential to predict their spread through a host population. Here, we study sex-ratio (SR) X-chromosome drive in the fly Drosophila recens , where SR causes the death of Y-bearing sperm in male carriers. SR males only sire daughters, which all carry SR, thus giving the chromosome a transmission advantage. The prevalence of the SR chromosome appears stable, suggesting pleiotropic costs. It was previously shown that females homozygous for SR are sterile, and here, we test for additional fitness costs of SR. We found that females heterozygous for SR have reduced fecundity and that male SR carriers have reduced fertility in conditions of sperm competition. We then use our fitness estimates to parametrize theoretical models of SR drive and show that the decrease in fecundity and sperm competition performance can account for the observed prevalence of SR in natural populations. In addition, we found that the expected equilibrium frequency of the SR chromosome is particularly sensitive to the degree of multiple mating and performance in sperm competition. Together, our data suggest that the mating system of the organism should be carefully considered during the development of gene drive systems.

Novel class II alpha MHC variability in a small peripheral Atlantic salmon population

2017 ◽  
Vol 48 (3) ◽  
pp. 370-372
Author(s):  
Kate L. Ciborowski ◽  
William C. Jordan ◽  
Carlos García de Leániz ◽  
Sofia Consuegra
Keyword(s):  
Atlantic Salmon ◽  
Class Ii ◽  
Salmon Population ◽  
Class Ii Alpha
Sign in / Sign up

Export Citation Format

Share Document