Natural selection and parallel speciation in sympatric sticklebacks

Natural selection plays a fundamental role in most theories of speciation, but empirical evidence from the wild has been lacking. Here the post-Pleist ocene radiation of threespine sticklebacks was used to infer natural select ion in the origin of species. Populations of sticklebacks that evolved unde r different ecological conditions show strong reproductive isolation, where as populations that evolved independently under similar ecological conditio ns lack isolation. Speciation has proceeded in this adaptive radiation in a repeatable fashion, ultimately as a consequence of adaptation to alternati ve environments.