Ecological selection against hybrids in natural populations of sympatric threespine sticklebacks

Experimental work has provided evidence for extrinsic post‐zygotic isolation, a phenomenon unique to ecological speciation. The role that ecological components to reduced hybrid fitness play in promoting speciation and maintaining species integrity in the wild, however, is not as well understood. We...

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Published inJournal of evolutionary biology Vol. 20; no. 6; pp. 2173 - 2180
Main Authors GOW, J. L., PEICHEL, C. L., TAYLOR, E. B.
Format Journal Article
LanguageEnglish
Published Oxford, UK Blackwell Publishing Ltd 01.11.2007
Subjects
admixture
Animals
Ecology
Ecosystem
Evolutionary biology
extrinsic post‐zygotic reproductive isolation
Fish
Gasterosteus aculeatus
Genetic Speciation
Hybridization
Hybridization, Genetic
Life cycles
Microsatellite Repeats
microsatellites
natural selection
Smegmamorpha - genetics
Smegmamorpha - physiology
Species Specificity
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Summary:Experimental work has provided evidence for extrinsic post‐zygotic isolation, a phenomenon unique to ecological speciation. The role that ecological components to reduced hybrid fitness play in promoting speciation and maintaining species integrity in the wild, however, is not as well understood. We addressed this problem by testing for selection against naturally occurring hybrids in two sympatric species pairs of benthic and limnetic threespine sticklebacks (Gasterosteus aculeatus). If post‐zygotic isolation is a significant reproductive barrier, the relative frequency of hybrids within a population should decline significantly across the life‐cycle. Such a trend in a natural population would give independent support to experimental evidence for extrinsic, rather than intrinsic, post‐zygotic isolation in this system. Indeed, tracing mean individual hybridity (genetic intermediateness) across three life‐history stages spanning four generations revealed just such a decline. This provides compelling evidence that extrinsic selection plays an important role in maintaining species divergence and supports a role for ecological speciation in sticklebacks.
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ISSN:1010-061X
1420-9101
DOI:10.1111/j.1420-9101.2007.01427.x