Patterns of male sterility in a grasshopper hybrid zone imply accumulation of hybrid incompatibilities without selection

It is now widely accepted that post-zygotic reproductive isolation is the result of negative epistatic interactions between derived alleles fixed independently at different loci in diverging populations (the Dobzhansky-Muller model). What is less clear is the nature of the loci involved and whether...

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Bibliographic Details
Published in:Proceedings of the Royal Society. B, Biological sciences Biological sciences, 2005-12, Vol.272 (1580), p.2491-2497
Main Authors: Shuker, D.M, Underwood, K, King, T.M, Butlin, R.K
Format: Article
Language:English
Subjects:
Acrididae
Alleles
Animals
Body Weights and Measures
Chorthippus parallelus
Chorthippus parallelus erythropus
Chorthippus parallelus parallelus
Clines
Dobzhansky-Muller Incompatibilities
Epistasis
Evolutionary genetics
females
Follicles
France
Genetic loci
Genetic variation
Genetics, Population
Genitalia, Male - anatomy & histology
grasshoppers
Grasshoppers - anatomy & histology
Grasshoppers - genetics
Grasshoppers - physiology
Hybrid Male Sterility
Hybrid Zone
Hybridity
Hybridization, Genetic
hybrids
insect reproduction
Male
male fertility
Male infertility
Models, Statistical
ovarian follicles
Population Dynamics
Population genetics
Reproduction - genetics
Reproduction - physiology
Spain
Speciation
Species Specificity
Statistical variance
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Summary:It is now widely accepted that post-zygotic reproductive isolation is the result of negative epistatic interactions between derived alleles fixed independently at different loci in diverging populations (the Dobzhansky-Muller model). What is less clear is the nature of the loci involved and whether the derived alleles increase in frequency through genetic drift, or as a result of natural or sexual selection. If incompatible alleles are fixed by selection, transient polymorphisms will be rare and clines for these alleles will be steep where divergent populations meet. If they evolve by drift, populations are expected to harbour substantial genetic variation in compatibility and alleles will introgress across hybrid zones once they recombine onto a genetic background with which they are compatible. Here we show that variation in male sterility in a naturally occurring Chorthippus parallelus grasshopper hybrid zone conforms to the neutral expectations. Asymmetrical clines for male sterility have long tails of introgression and populations distant from the zone centre show significant genetic variation for compatibility. Our data contrast with recent observations on 'speciation genes' that have diverged as a result of strong natural selection.
ISSN:0962-8452
1471-2954
DOI:10.1098/rspb.2005.3242