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Supergenes and their role in evolution - Coggle Diagram
Supergenes and their role in evolution
Introduction
Adaptation is a universal problem that changes multiple traits to compensate the immediate environement.
Balanced polymorphisms is coexisting phenotypes that are maintained in a population by selection
Polymorphisms led to the concept of the "supergene"
Adaptations can cause recombination between multiple loci imposes selective cost on alleles
Supergenes consists of multiple tightly linked loci that regulate a system of phenotypes
Morphology can be influenced by negative frequency dependent selection and alternative phenotypes
The term supergene was created during Modern Synthesis
Variation categorized as environmental variation, mutations, fluctuations, non-heritable
Supergene architecture can generate diversity
Modelling the origins of a supergene
Selection can modify the recombination rate between two linked loci
Rate of change in recombination was greatest when the modifier was in strong linkage disequilibrium with the loci selected
Selection for genetic linkage of coadapted traits resulted in translocation of genes
Translocation model was more likely that mutations came from linkage with the supergene
Local adaptation lead to the evolution of a single locus genetic architecture by gene translocation
Rearrangements of inversions and translocations may have a role in supergene evolution
A new perspective from developmental genetics
Regulatory linkage alternatively to chromosomal linkage can determine co-expression of genes
Supergenes show high levels of linkage disequilibrium
A new definition
Supergene is a genetic architecture involving multiple linked genetic elements that allow switch between phenotypes
Stable polymorphism in a population is controlled by a single locus that is maintained at intermediate frequency
Supergene qualifications needs to demonstrate complex phenotypes of multiple co-adapted elements with pattern of inheritance to the alternative alleles at a single locus while maintaining polymorphism in a single population
Self-incompatibility and heterostyly
SI describes a multitude of different mechanisms that evolved convergently and outcrossing through prevention of fertilization by self pollen can be considered molecular homomorphic
Tight linkage between genes determining male and female specific responses are crucial to SI maintenance
Homomorphic SI is accomplished through intercellular interactions leading to inhibited growth or death of self pollen
Selection for co-segregation of loci determining complex traits can create supergenes
High sequence diversity with certain halotypes possibly derived by recombination or gene duplication
SI mechanisms in flowering plants represent the best characterized examples of a supergene architecture
Hetero and homomorphic SI show the same type of genetic architecture of tightly linked male and female genes arguing of selection favoring a supergene.
Mimicry
Mimicry leads to negative frequency dependent selection
Hosts can maintain polymorphism and effective mimicry requires a correlated response in several phenotypic characters
Mimetic butterflies wing patterns is maintained by heterogenous selection for locally adapted traits.
Involves supergenes
Social Polymorphism
Supergene architecture required to have tight association of signal and behavior
Designating a supergene must have a mechanism to reduce recombination and a balanced polymorphism of a complex polygenic and co-adapted phenotype
Other adaptive colouration
Selective forces maintaining polymorphism is mixed with several selective factors including predation, climate selection, heterosis, or random processes
Conclusion
Physical linkage reduces trait combinations by recombination
Co-adapted traits increases the linkage becoming advantageous as it maintains favorable combination of traits
Evolution of genetic architectures reduces the recombination between functional elements
Supergene evolution has the potential to have insight in convergent evolution of particular architectures and the role of genome structure have on adaptation
References
Thompson MJ, Jiggins CD. 2014. Supergenes and their role in evolution. Heredity. 113(1):1–8. doi:10.1038/hdy.2014.20.