scholarly journals Local adaptation and hybrid failure share a common genetic basis

2019 ◽  
Author(s):  
Greg M. Walter ◽  
J. David Aguirre ◽  
Melanie J Wilkinson ◽  
Thomas J. Richards ◽  
Mark W. Blows ◽  
...  
Keyword(s):  
Genetic Variation ◽  
Reproductive Isolation ◽  
Local Adaptation ◽  
Morphological Traits ◽  
Genetic Basis ◽  
Genetic Variance ◽  
Hybrid Population ◽  
Hybrid Fitness ◽  
Natural Habitats ◽  
Trade Offs

AbstractTesting whether local adaptation and intrinsic reproductive isolation share a genetic basis can reveal important connections between adaptation and speciation. Local adaptation arises as advantageous alleles spread through a population, but whether these same advantageous alleles fail on the genetic backgrounds of other populations remains largely unknown. We used a quantitative genetic breeding design to produce a late generation (F4) recombinant hybrid population by equally mating amongst four contrasting ecotypes of a native Australian daisy for four generations. We tracked fitness across generations and measured morphological traits in the glasshouse, and used a reciprocal transplant to quantify fitness in all four parental habitats. In the glasshouse, plants in the second generation showed a reduction in fitness as a loss of fertility, but this was fully recovered in the following generation. The F4 hybrid lacked extreme phenotypes present in the parental ecotypes, suggesting that genes reducing hybrid fitness were linked to traits specific to each ecotype. In the natural habitats, additive genetic variance for fitness was greatest for habitats that showed stronger native-ecotype advantage, suggesting that a loss of genetic variation present in the parental ecotypes were adaptive in the natural habitats. Reductions in genetic variance for fitness were associated with a loss of ecological trade-offs previously described in the parental ecotypes. Furthermore, natural selection on morphological traits differed amongst the parental habitats, but was not predicted to occur towards the morphology of the parental ecotypes. Together, these results suggest that intrinsic reproductive isolation removed adaptive genetic variation present in the parental ecotypes. The evolution of these distinct ecotypes was likely governed by genetic variation that resulted in both ecological trade-offs and intrinsic reproductive isolation among populations adapted to contrasting environments.

scholarly journals Should I stay or should I go? The Ectodysplasin locus is associated with behavioural differences in threespine stickleback

2009 ◽  
Vol 5 (6) ◽  
pp. 788-791 ◽  
Author(s):  
Rowan D. H. Barrett ◽  
Tim H. Vines ◽  
Jason S. Bystriansky ◽  
Patricia M. Schulte
Keyword(s):  
Positive Selection ◽  
Local Adaptation ◽  
Morphological Traits ◽  
Genetic Basis ◽  
Natural Populations ◽  
Threespine Stickleback ◽  
Adaptive Divergence ◽  
Freshwater Habitats ◽  
Repeated Evolution ◽  
Freshwater Environments

Adaptive divergence may be facilitated if morphological and behavioural traits associated with local adaptation share the same genetic basis. It is therefore important to determine whether genes underlying adaptive morphological traits are associated with variation in behaviour in natural populations. Positive selection on low-armour alleles at the Ectodysplasin ( Eda ) locus in threespine stickleback has led to the repeated evolution of reduced armour, following freshwater colonization by fully armoured marine sticklebacks. This adaptive divergence in armour between marine and freshwater populations would be facilitated if the low allele conferred a behavioural preference for freshwater environments. We experimentally tested whether the low allele is associated with preference for freshwater by measuring the preference of each Eda genotype for freshwater versus saltwater after acclimation to either salinity. We found no association between the Eda low allele and preference for freshwater. Instead, the low allele was significantly associated with a reduced preference for the acclimation environment. This behaviour may facilitate the colonization of freshwater habitats from the sea, but could also hinder local adaptation by promoting migration of low alleles between marine and freshwater environments.

scholarly journals Sympatric, parapatric or allopatric: the most important way to classify speciation?

2008 ◽  
Vol 363 (1506) ◽  
pp. 2997-3007 ◽  
Author(s):  
Roger K Butlin ◽  
Juan Galindo ◽  
John W Grahame
Keyword(s):  
Reproductive Isolation ◽  
Local Adaptation ◽  
Genetic Basis ◽  
Environmental Gradients ◽  
Sympatric Speciation ◽  
Model System ◽  
Littorina Saxatilis ◽  
The Past ◽  
Intertidal Gastropod

The most common classification of modes of speciation begins with the spatial context in which divergence occurs: sympatric, parapatric or allopatric. This classification is unsatisfactory because it divides a continuum into discrete categories, concentrating attention on the extremes, and it subordinates other dimensions on which speciation processes vary, such as the forces driving differentiation and the genetic basis of reproductive isolation. It also ignores the fact that speciation is a prolonged process that commonly has phases in different spatial contexts. We use the example of local adaptation and partial reproductive isolation in the intertidal gastropod Littorina saxatilis to illustrate the inadequacy of the spatial classification of speciation modes. Parallel divergence in shell form in response to similar environmental gradients in England, Spain and Sweden makes this an excellent model system. However, attempts to demonstrate ‘incipient’ and ‘sympatric’ speciation involve speculation about the future and the past. We suggest that it is more productive to study the current balance between local adaptation and gene flow, the interaction between components of reproductive isolation and the genetic basis of differentiation.

scholarly journals Combining population genomics and fitness QTLs to identify the genetics of local adaptation in Arabidopsis thaliana

2018 ◽  
Vol 115 (19) ◽  
pp. 5028-5033 ◽  
Author(s):  
Nicholas Price ◽  
Brook T. Moyers ◽  
Lua Lopez ◽  
Jesse R. Lasky ◽  
J. Grey Monroe ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Local Adaptation ◽  
Genetic Basis ◽  
Population Genomics ◽  
Frequency Spectra ◽  
Population Genomic ◽  
Trade Offs ◽  
Trait Locus ◽  
Genomic Regions ◽  
Transplant Experiments

Evidence for adaptation to different climates in the model species Arabidopsis thaliana is seen in reciprocal transplant experiments, but the genetic basis of this adaptation remains poorly understood. Field-based quantitative trait locus (QTL) studies provide direct but low-resolution evidence for the genetic basis of local adaptation. Using high-resolution population genomic approaches, we examine local adaptation along previously identified genetic trade-off (GT) and conditionally neutral (CN) QTLs for fitness between locally adapted Italian and Swedish A. thaliana populations [Ågren J, et al. (2013) Proc Natl Acad Sci USA 110:21077–21082]. We find that genomic regions enriched in high FST SNPs colocalize with GT QTL peaks. Many of these high FST regions also colocalize with regions enriched for SNPs significantly correlated to climate in Eurasia and evidence of recent selective sweeps in Sweden. Examining unfolded site frequency spectra across genes containing high FST SNPs suggests GTs may be due to more recent adaptation in Sweden than Italy. Finally, we collapse a list of thousands of genes spanning GT QTLs to 42 genes that likely underlie the observed GTs and explore potential biological processes driving these trade-offs, from protein phosphorylation, to seed dormancy and longevity. Our analyses link population genomic analyses and field-based QTL studies of local adaptation, and emphasize that GTs play an important role in the process of local adaptation.

scholarly journals Natural genetic variation underlying tiller development in barley (Hordeum vulgareL)

2019 ◽  
Author(s):  
Allison M. Haaning ◽  
Kevin P. Smith ◽  
Gina L. Brown-Guedira ◽  
Shiaoman Chao ◽  
Priyanka Tyagi ◽  
...  
Keyword(s):  
Genetic Variation ◽  
Genetic Control ◽  
Morphological Traits ◽  
Agronomic Traits ◽  
Developmental Rate ◽  
Tiller Number ◽  
Natural Genetic Variation ◽  
Trade Offs ◽  
Days To Heading ◽  
Lateral Branches

ABSTRACTIn barley (Hordeum vulgareL.), lateral branches called tillers contribute to grain yield and define shoot architecture, but genetic control of tiller number and developmental rate are not well characterized. The primary objectives of this work were to examine relationships between tiller number and other agronomic and morphological traits and identify natural genetic variation associated with tiller number and rate, and related traits. We grew 768 lines from the USDA National Small Grain Core Collection in the field and collected data over two years for tiller number and rate, and agronomic and morphological traits. Our results confirmed that spike row-type and days to heading are correlated with tiller number, and as much as 28% of tiller number variance is attributed to these traits. In addition, negative correlations between tiller number and leaf width and stem diameter were observed, indicating trade-offs between tiller development and other vegetative growth. Thirty-three quantitative trait loci (QTL) were associated with tiller number or rate. Of these, 40% overlapped QTL associated with days to heading and 22% overlapped QTL associated with spike row-type, further supporting that tiller development is influenced by these traits. Despite this, some QTL associated with tiller number or rate, including the major QTL on chromosome 3H, were not associated with any other traits, suggesting that tiller number can be modified independently of other important agronomic traits. These results enhance our knowledge of the genetic control of tiller development in barley, which is important for optimizing tiller number and rate for yield improvement.

scholarly journals Natural Genetic Variation Underlying Tiller Development in Barley (Hordeum vulgare L)

2020 ◽  
Vol 10 (4) ◽  
pp. 1197-1212
Author(s):  
Allison M. Haaning ◽  
Kevin P. Smith ◽  
Gina L. Brown-Guedira ◽  
Shiaoman Chao ◽  
Priyanka Tyagi ◽  
...  
Keyword(s):  
Genetic Variation ◽  
Hordeum Vulgare ◽  
Genetic Control ◽  
Morphological Traits ◽  
Developmental Rate ◽  
Tiller Number ◽  
Hordeum Vulgare L ◽  
Natural Genetic Variation ◽  
Trade Offs ◽  
Days To Heading

In barley (Hordeum vulgare L.), lateral branches called tillers contribute to grain yield and define shoot architecture, but genetic control of tiller number and developmental rate are not well characterized. The primary objectives of this work were to examine relationships between tiller number and other agronomic and morphological traits and identify natural genetic variation associated with tiller number and rate, and related traits. We grew 768 lines from the USDA National Small Grain Collection in the field and collected data over two years for tiller number and rate, and agronomic and morphological traits. Our results confirmed that spike row-type and days to heading are correlated with tiller number, and as much as 28% of tiller number variance was associated with these traits. In addition, negative correlations between tiller number and leaf width and stem diameter were observed, indicating trade-offs between tiller development and other vegetative growth. Thirty-three quantitative trait loci (QTL) were associated with tiller number or rate. Of these, 40% overlapped QTL associated with days to heading and 22% overlapped QTL associated with spike row-type, further supporting that tiller development is associated with these traits. Some QTL associated with tiller number or rate, including the major QTL on chromosome 3H, were not associated with other traits, suggesting that some QTL may be directly related to rate of tiller development or axillary bud number. These results enhance our knowledge of the genetic control of tiller development in barley, which is important for optimizing tiller number and rate for yield improvement.

scholarly journals Characterization of Deleterious Mutations in Outcrossing Populations

Genetics ◽  
1998 ◽  
Vol 150 (2) ◽  
pp. 945-956 ◽  
Author(s):  
Hong-Wen Deng
Keyword(s):  
Genetic Variation ◽  
Genetic Variance ◽  
Estimation Bias ◽  
Deleterious Mutations ◽  
Environmental Variance ◽  
Higher Power ◽  
Sib Mating ◽  
The Mean ◽  
Simulation Results

Abstract Deng and Lynch recently proposed estimating the rate and effects of deleterious genomic mutations from changes in the mean and genetic variance of fitness upon selfing/outcrossing in outcrossing/highly selfing populations. The utility of our original estimation approach is limited in outcrossing populations, since selfing may not always be feasible. Here we extend the approach to any form of inbreeding in outcrossing populations. By simulations, the statistical properties of the estimation under a common form of inbreeding (sib mating) are investigated under a range of biologically plausible situations. The efficiencies of different degrees of inbreeding and two different experimental designs of estimation are also investigated. We found that estimation using the total genetic variation in the inbred generation is generally more efficient than employing the genetic variation among the mean of inbred families, and that higher degree of inbreeding employed in experiments yields higher power for estimation. The simulation results of the magnitude and direction of estimation bias under variable or epistatic mutation effects may provide a basis for accurate inferences of deleterious mutations. Simulations accounting for environmental variance of fitness suggest that, under full-sib mating, our extension can achieve reasonably well an estimation with sample sizes of only ∼2000-3000.

Comparing Mutational Variabilities

Genetics ◽  
1996 ◽  
Vol 143 (3) ◽  
pp. 1467-1483 ◽  
Author(s):  
David Houle ◽  
Bob Morikawa ◽  
Michael Lynch
Keyword(s):  
Life History ◽  
Morphological Traits ◽  
Life History Traits ◽  
Genetic Variance ◽  
Balance Model ◽  
Phenotypic Traits ◽  
Infinite Population ◽  
Persistence Time ◽  
Coefficients Of Variation ◽  
Balance Hypothesis

Abstract We have reviewed the available data on VM, the amount of genetic variation in phenotypic traits produced each generation by mutation. We use these data to make several qualitative tests of the mutation-selection balance hypothesis for the maintenance of genetic variance (MSB). To compare VM values, we use three dimensionless quantities: mutational heritability, the mutational coefficient of variation, CVM; and the ratio of the standing genetic variance to VM, VG/VM. Since genetic coefficients of variation for life history traits are larger than those for morphological traits, we predict that under MSB, life history traits should also have larger CVM. This is confirmed; life history traits have a median CVM value more than six times higher than that for morphological traits. VG/VM approximates the persistence time of mutations under MSB in an infinite population. In order for MSB to hold, VG/VM must be small, substantially less than 1000, and life history traits should have smaller values than morphological traits. VG/VM averages about 50 generations for life history traits and 100 generations for morphological traits. These observations are all consistent with the predictions of a mutation-selection balance model.

scholarly journals The genomics of adaptation

2012 ◽  
Vol 279 (1749) ◽  
pp. 5024-5028 ◽  
Author(s):  
Jacek Radwan ◽  
Wiesław Babik
Keyword(s):  
Genetic Variation ◽  
Natural Selection ◽  
Royal Society ◽  
Genetic Basis ◽  
Genomic Data ◽  
Evolutionary Change ◽  
Introductory Article ◽  
Technological Advances ◽  
A Genome ◽  
Genome Level

The amount and nature of genetic variation available to natural selection affect the rate, course and outcome of evolution. Consequently, the study of the genetic basis of adaptive evolutionary change has occupied biologists for decades, but progress has been hampered by the lack of resolution and the absence of a genome-level perspective. Technological advances in recent years should now allow us to answer many long-standing questions about the nature of adaptation. The data gathered so far are beginning to challenge some widespread views of the way in which natural selection operates at the genomic level. Papers in this Special Feature of Proceedings of the Royal Society B illustrate various aspects of the broad field of adaptation genomics. This introductory article sets up a context and, on the basis of a few selected examples, discusses how genomic data can advance our understanding of the process of adaptation.

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