Constraints on Rapid Adaptation in Sticklebacks: availability and maintenance of genetic variation used in adaptation to freshwater environments
JO 1316/1-1
Understanding the mechanisms and constraints influencing rapid adaptation to new or changing environments is an important and significant challenge in evolutionary biology. One major focus centres on the type and source of genetic variation that acts as a substrate for rapid adaptive change. This is of particular interest because evolutionary history and demographic processes can affect the availability of adaptive genetic variation, promoting or constraining the speed of adaptation, and influencing the future evolutionary trajectory a population. Theoretical population genetic models of adaptation have traditionally focused on de novo mutations as the source of adaptive genetic variation. However, in populations exposed to a new environment or subject to environmental change, pre-existing standing genetic variation, as opposed to de novo mutation, may provide a more readily available substrate, potentially pre-screened by historical selection events, that facilitates rapid adaptation. Consistent with this, quantitative genetic experiments and studies of natural populations have revealed rapid phenotypic responses to selection on time scales considered to be too short to be caused by de novo mutations. And more recent population genetic models of adaptation have shown that the speed of adaptation increases significantly when the substrate is standing genetic variation rather than de novo mutation. However, despite these advances and theoretical models, relatively little empirical data is available on the type, source, prevalence and properties of genetic variation underlying rapid adaptation in natural populations. Here, we combine empirical data from state-of-the-art genomic sequencing of threespine stickleback fish with population genetic models of maintenance of standing genetic variation in source marine populations, and selective sweeps in freshwater populations, in order to identify and quantify key factors that shape, promote and constrain rapid adaptation in the natural populations. In addition to estimating the plausible parameter range of factors influencing adaptation, our study will provide valuable insight into the origin, spread and maintenance of genetic variation that is essential for preserving the future adaptive potential of natural populations.
Publikationen
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