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Contrasting effects of environment and genetics generate a continuum of parallel evolution [Nature Ecology & Evolution]

Keywords : ecological genetics, evolution, evolutionary ecology, genetic variation, ichthyology

par Frédéric Magné - publié le

Parallel evolution of similar traits by independent populations in similar environments is considered strong evidence for adaptation by natural selection. Often, however, replicate populations in similar environments do not all evolve in the same way, thus deviating from any single, predominant outcome of evolution. This variation might arise from non-adaptive, population-specific effects of genetic drift, gene flow or limited genetic variation. Alternatively, these deviations from parallel evolution might also reflect predictable adaptation to cryptic environmental heterogeneity within discrete habitat categories. Here, we show that deviations from parallel evolution are the consequence of environmental variation within habitats combined with variation in gene flow. Threespine stickleback (Gasterosteus aculeatus) in adjoining lake and stream habitats (a lake–stream ‘pair’) diverge phenotypically, yet the direction and magnitude of this divergence is not always fully parallel among 16 replicate pairs.(...)

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