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Related Experiment Video

Updated: Jul 18, 2026

Microinjection for Transgenesis and Genome Editing in Threespine Sticklebacks

Microinjection for Transgenesis and Genome Editing in Threespine Sticklebacks

Published on: May 13, 2016

Reproductive isolation in a threespine stickleback hybrid zone.

F C Jones¹, C Brown, J M Pemberton

¹Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, UK. Felicity.Jones@canterbury.ac.nz

Journal of Evolutionary Biology

|August 17, 2006

Summary

Barriers to gene flow maintain differences between anadromous and freshwater threespine sticklebacks, even when they breed together. Hybridization occurs, but genetic and cytonuclear disequilibrium confirm reproductive isolation in the wild.

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Area of Science:

Evolutionary Biology
Ecology
Genetics

Background:

Morphological and genetic divergence persists between anadromous and freshwater threespine sticklebacks in sympatric estuarine populations.
Understanding the mechanisms maintaining these differences is crucial for evolutionary studies.

Purpose of the Study:

Investigate the maintenance of morphological divergence in a natural hybrid zone of threespine sticklebacks in the River Tyne, Scotland.
Identify distinct genetic clusters and assess barriers to gene flow between anadromous and freshwater morphs.

Main Methods:

Bayesian Markov Chain Monte Carlo (MCMC) approach to identify genetic clusters.
Morphological description of the hybrid zone.
Analysis of heterozygote deficit and cytonuclear disequilibrium in sympatric juvenile populations.

Main Results:

Distinct anadromous and freshwater genetic clusters were identified.
Significant heterozygote deficit and cytonuclear disequilibrium confirmed barriers to gene flow.
Hybridization occurs (33% frequency), but assortative mating is not strong.

Conclusions:

Reproductive isolation barriers, including prezygotic (temporal, spatial, sexual) and postzygotic selection, contribute to maintaining divergence between threespine stickleback morphs.
Gene flow is restricted despite sympatric breeding.