Balancing Selection on a Floral Polymorphism

Subramaniam, Banu; Rausher, Mark D.

doi:10.1111/j.0014-3820.2000.tb00070.x

Cited by 59 publications

(51 citation statements)

References 22 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Our second example, on a polymorphic stickleback population, adds to a growing number of studies investigating the role of selection in the maintenance of ecologically important genetic polymorphisms (Subramaniam & Rausher 2000;Fitzpatrick et al 2007;Mitchell-Olds et al 2007). It would be difficult if not impossible to make progress on the mechanisms maintaining the polymorphism without knowing the major gene underlying it.…”

Section: Discussionmentioning

confidence: 99%

“…Considerable insight has already been gained into the frequency of directional and nonlinear selection on phenotypic traits in natural populations (Hoekstra et al 2001;Siepielski et al 2009). Direct measurements of selection (or rather, of the effects of selection) on variation at underlying genes are still rare but increasingly within reach (Subramaniam & Rausher 2000;Coberly & Rausher 2008 Schluter (2010, unpublished data) investigated the form of selection on variation at the Ectodysplasin (Eda) locus in a stickleback population polymorphic for lateral plates. The focus of the study is the population of Kennedy Lake, BC, which is one of only a few stickleback populations in the region that are polymorphic for lateral plate armour.…”

Section: The Form Of Selection On a Polymorphic Traitmentioning

confidence: 99%

“…However, knowledge of underlying genes will also permit direct measurements of the fitnesses of alternative genotypes, and so aid the study of the causes of selection (Bradshaw & Schemske 2003;Lexer et al 2003;Barrett et al 2008;Coberly & Rausher 2008;Gratten et al 2008). Direct measurement of selection will additionally illuminate the form of selection on genetic polymorphisms, whether balancing, disruptive or frequency dependent (Subramaniam & Rausher 2000;Fitzpatrick et al 2007), and contribute to our understanding of how genetic variation is maintained in the wild. As a final example, the distribution of the phenotypic effect sizes of genes may reveal aspects of the recent history of natural selection on traits (Orr 1998(Orr , 2005Collins et al 2007;Kopp & Hermisson 2007;Martin et al 2007).…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Natural selection and the genetics of adaptation in threespine stickleback

Schluter

Marchinko

Barrett

et al. 2010

Phil. Trans. R. Soc. B

View full text Add to dashboard Cite

Growing knowledge of the molecular basis of adaptation in wild populations is expanding the study of natural selection. We summarize ongoing efforts to infer three aspects of natural selectionmechanism, form and history-from the genetics of adaptive evolution in threespine stickleback that colonized freshwater after the last ice age. We tested a mechanism of selection for reduced bony armour in freshwater by tracking genotype and allele frequency changes at an underlying major locus (Ectodysplasin) in transplanted stickleback populations. We inferred disruptive selection on genotypes at the same locus in a population polymorphic for bony armour. Finally, we compared the distribution of phenotypic effect sizes of genes underlying changes in body shape with that predicted by models of adaptive peak shifts following colonization of freshwater. Studies of the effects of selection on genes complement efforts to identify the molecular basis of adaptive differences, and improve our understanding of phenotypic evolution.

show abstract

Section: Discussionmentioning

confidence: 99%

Section: The Form Of Selection On a Polymorphic Traitmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Natural selection and the genetics of adaptation in threespine stickleback

Schluter

Marchinko

Barrett

et al. 2010

Phil. Trans. R. Soc. B

View full text Add to dashboard Cite

show abstract

“…Our slightly more complex models, which include variation in productivity, analytically capture a key insight of Templeton and Levin's (1979) simulations-the importance of covariance between seed production and relative fitnesses. Our attempt at understanding the L. parryae polymorphism in terms of a specific model complements Subramaniam and Rausher's (2000) experimental approach to demonstrating that balancing selection maintains the flower-color polymorphism in the morning glory, Ipomoea purpurea.…”

mentioning

confidence: 98%

Stable Two-Allele Polymorphisms Maintained by Fluctuating Fitnesses and Seed Banks: Protecting the Blues in Linanthus Parryae

Turelli¹,

Schemske²,

2001

View full text Add to dashboard Cite

Abstract. Motivated by data demonstrating fluctuating relative and absolute fitnesses for white-versus blue-flowered morphs of the desert annual Linanthus parryae, we present conditions under which temporally fluctuating selection and fluctuating contributions to a persistent seed bank will maintain a stable single-locus polymorphism. In L. parryae, blue flower color is determined by a single dominant allele. To disentangle the underlying diversity-maintaining mechanism from the mathematical complications associated with departures from Hardy-Weinberg genotype frequencies and dominance, we successively analyze a haploid model, a diploid model with three distinguishable genotypes, and a diploid model with complete dominance. For each model, we present conditions for the maintenance of a stable polymorphism, then use a diffusion approximation to describe the long-term fluctuations associated with these polymorphisms. Our protected polymorphism analyses show that a genotype whose arithmetic and geometric mean relative fitnesses are both less than one can persist if its relative fitness exceeds one in years that produce the most offspring. This condition is met by data from a population of L. parryae whose white morph has higher fitness (seed set) only in years of relatively heavy rain fall. The data suggest that the observed polymorphism may be explained by fluctuating selection. However, the yearly variation in flower color frequencies cannot be fully explained by our simple models, which ignore age structure and possible selection in the seed bank. We address two additional questions-one mathematical, the other biological-concerning the applicability of diffusion approximations to intense selection and the applicability of long-term predictions to datasets spanning decades for populations with long-lived seed banks. Through the seminal papers of Epling and Dobzhansky (1942) and Wright (1943a, b), the flower color polymorphism in the diminutive desert annual Linanthus parryae played a central role in shaping population genetic theory and opinions concerning the roles of natural selection, genetic drift, and migration in evolution. In their 1941 survey of 427 sampling locations in the Mojave Desert, California, Epling and Dobzhansky (1942) found a preponderance of monomorphic populations with most having white flowers. About 19% of their 1261 samples were polymorphic, and white flowers predominated in most of these. Wright (1943b; 1978, pp. 194-223) analyzed the spatial pattern of flower color frequencies and concluded that despite some evidence for directional selection favoring white, selection was generally negligible, and drift, migration and, possibly, mutation-selection balance determined allele frequencies in these populations. Wright argued that the effects of drift could explain the spatial pattern of polymorphic frequencies if effective local population sizes were on the order of 100 or less. However, after monitoring these same populations for another 15 years, Epling et al. (1960) found little change ...

show abstract

“…Among the few adaptive genes identified in other organisms to date, several show patterns consistent with the recruitment of alternative alleles at highly variable genes. For instance, loci involved in the parallel reduction of body spines in sticklebacks (Chan et al 2009), crypsis in insects (Reed et al 2011) and vertebrates (Rosenblum and Harmon 2010), as well as genes associated to plant host-pathogen interactions (Caicedo et al 1999;Rose et al 2004;Cronin et al 2007) and flowering time differences (Johanson 2000;Subramaniam and Rausher 2000;Zufall and Rausher 2004;Cooley et al 2011;Smith and Rausher 2011), have been recurrently targeted by selection and are highly variable across the species ranges. In general, these results may arise from selection on recurrent mutations or on old variants present as standing variation .…”

Section: Evidence For the Repeated Recruitment Of Adaptive Variantsmentioning

confidence: 99%

The genomic basis of parallel ecological speciation

Fornaguera¹

View full text Add to dashboard Cite

Ecological speciation, the origin of new species via divergent natural selection, is one of the most fundamental and unresolved processes in evolution. Although the evidence for adaptation of organisms to their environment is abundant, the role of ecological selection in mediating species formation remains controversial. This knowledgegap arises in part from a scarcity of experimental evidence linking environmental selection to the creation of reproductive barriers that ultimately lead to species formation. An experimental framework to investigate ecological speciation consists in studying the genetic architecture of adaptive traits and reproductive isolation in interbreeding populations adapted to contrasting environments. In my thesis I explored the genomics of ecological speciation in plants using the Senecio lautus species complex, a diverse group of plants that have adapted to a broad array of environment across Australia.It has been suggested that local adaptation to different environments will lead to genetic divergence and speciation only if genomic regions controlling adaptive traits are not exchanged between organisms adapted to different niches. This will happen if adaptive genes also mediate reproductive isolation, thus making migration between environments difficult, or leading to poor survival of recombinants. This model of ecological speciation creates testable predictions on the genomic architecture of adaptation: Firstly, genomic divergence between incipient species is expected to be heterogeneous, where a few genomic regions display outlier differentiation. Secondly one expects divergent regions to contain genes affecting fitness in natural environments. Thirdly, these "genomic islands of speciation" will also contain loci controlling adaptive traits and reproduction.In my thesis I tested these predictions using divergent populations of plants from the S. lautus species complex. I used a combination of genomic and ecological approaches to: (i) Describe patterns of genomic differentiation between natural populations across Australia and made inferences about the forces that generated these patterns. Specifically, I tested the repeated and independent evolution of forms to coastal environments and analyzed whether genomic divergence was more heterogeneous between parapatric than allopatric populations. (ii) Demonstrate experimentally that divergent genomic regions contain genes controlling differential survivorship between environments. (iii) Detect QTLs associated to environmentally selected traits and associate their location to genomic regions of high differentiation between parapatric populations. In combination, these experiments were used to test the role of ecology in creating and maintaining the reproductive barriers that ultimately lead to plant speciation. ! ! 3!A phylogenomic study of a continental collection of S. lautus populations showed that these plants have a monophyletic origin and evolved rapidly colonizing a broad array of environments. Importantly, populations adapted...

show abstract

Balancing Selection on a Floral Polymorphism

Cited by 59 publications

References 22 publications

Natural selection and the genetics of adaptation in threespine stickleback

Natural selection and the genetics of adaptation in threespine stickleback

Stable Two-Allele Polymorphisms Maintained by Fluctuating Fitnesses and Seed Banks: Protecting the Blues in Linanthus Parryae

The genomic basis of parallel ecological speciation

Contact Info

Product

Resources

About