Genetics and the fitness of hybrids.

@article{Burke2001GeneticsAT,
  title={Genetics and the fitness of hybrids.},
  author={John M. Burke and Michael Lynn Arnold},
  journal={Annual review of genetics},
  year={2001},
  volume={35},
  pages={
          31-52
        }
}
Over the years, the evolutionary importance of natural hybridization has been a contentious issue. At one extreme is the relatively common view of hybridization as an evolutionarily unimportant process. A less common perspective, but one that has gained support over the past decade, is that of hybridization as a relatively widespread and potentially creative evolutionary process. Indeed, studies documenting the production of hybrid genotypes exhibiting a wide range of fitnesses have become… 

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References

SHOWING 1-10 OF 134 REFERENCES
The role of hybridization in evolution
TLDR
Fisher’s model of stabilizing selection on multiple traits, under which reproductive isolation evolves as a side‐effect of adaptation in allopatry, confirms a priori arguments that while recombinant hybrids are less fit on average, some gene combinations may be fitter than the parents, even in the parental environment.
Transgressive segregation, adaptation and speciation
TLDR
Credence is lent to the view that hybridization may provide the raw material for rapid adaptation and provide a simple explanation for niche divergence and phenotypic novelty often associated with hybrid lineages.
The population genetics of speciation: the evolution of hybrid incompatibilities.
TLDR
The number of genic incompatibilities between taxa increases much faster than linearly with time, and it is "easier" to evolve complex hybrid incomp atibilities requiring the simultaneous action of three or more loci than to evolve simple incompatibles between pairs of genes.
The likelihood of homoploid hybrid speciation
TLDR
The model is of recombinational speciation, in which chromosomal rearrangements between parental species result in poor fertility of F1 hybrids, but through recombination, novel homozygous types are formed that have restored fertility.
Hybrid zones and the genetic architecture of a barrier to gene flow between two sunflower species.
TLDR
The utility of hybrid zones for identifying factors contributing to isolation and the prediction of increased resolution relative to controlled crosses are demonstrated and verified.
Genetic Architecture of Physiological Phenotypes: Empirical Evidence for Coadapted Gene Complexes
TLDR
Evidence is provided for the existence of nuclear/nuclear and/or nuclear/mitochondrial coadaptation within natural populations of T. californicus.
GENETIC INTERACTIONS AND NATURAL SELECTION IN LOUISIANA IRIS HYBRIDS
TLDR
The traditional view that interactions between divergent genomes are always deleterious is an oversimplification and it seems likely that crosses between Divergent lineages can lead to the production of both fit and unfit hybrid genotypes.
The Origin of Interspecific Genomic Incompatibility via Gene Duplication
TLDR
It is suggested that duplicate genes, and more generally any kind of genomic redundancies, provide a powerful substrate for the origin of genomic incompatibilities in isolated populations.
Epistatic selection opposed by immigration in multiple locus genetic systems
TLDR
This kind of epistasis, which provides a simple model for a character that requires several components to be present at the same time, is very sensitive to even a small amount of immigration, and the evolution of such characters is likely only in completely rather than partially isolated populations.
Mutation and Conservation
TLDR
The findings suggest that current recovery goals for many threatened and endangered species are inadequate to ensure long-term population viability.
...
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3
4
5
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