Shifting thresholds: rapid evolution of migratory life histories in steelhead/rainbow trout, Oncorhynchus mykiss
- Published
- Accepted
- Subject Areas
- Aquaculture, Fisheries and Fish Science, Ecology, Evolutionary Studies
- Keywords
- anadromy, contemporary evolution, local adaptation, partial migration, threshold traits
- Copyright
- © 2014 Phillis et al.
- Licence
- This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, reproduction and adaptation in any medium and for any purpose provided that it is properly attributed. For attribution, the original author(s), title, publication source (PeerJ PrePrints) and either DOI or URL of the article must be cited.
- Cite this article
- 2014. Shifting thresholds: rapid evolution of migratory life histories in steelhead/rainbow trout, Oncorhynchus mykiss. PeerJ PrePrints 2:e361v1 https://doi.org/10.7287/peerj.preprints.361v1
Abstract
Expression of phenotypic plasticity depends on reaction norms adapted to historic selective regimes; anthropogenic changes in these selection regimes necessitate contemporary evolution or extirpation. Adaptation of conditional strategies following a change in the selection regime requires evolution of either the environmentally influenced cue (e.g. growth rate) or the state (e.g. size threshold) at which an individual switches between conditional strategies. Using a population of steelhead (Oncorhynchus mykiss) introduced above a barrier waterfall in 1910, we evaluate how the conditional strategy to migrate evolves in response to selection against migration. Common garden-raised offspring of parents from the above-barrier population were 11% smaller and 31% lighter than offspring of parents from the below-barrier source population. Using a novel analytical approach we estimate that the mean size at which above-barrier fish switch between the resident and migrant strategy is 43% larger than below-barrier fish. As a result, above-barrier fish were 30% less likely to express the migratory strategy. Our results demonstrate how rapid and opposing changes in growth rate and threshold size contribute to the contemporary evolution of a conditional strategy and indicate that migratory barriers may elicit rapid evolution towards the resident life-history on timescales relevant for conservation and management of conditionally migratory species.