1. Evolutionary stasis of a heritable morphological trait in a wild fish population despite apparent directional selection
- Author
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Paulo A. Prodöhl, Susan E. Johnston, Philip McGinnity, Thomas E. Reed, Russell Poole, Tutku Aykanat, Craig R. Primmer, Ronan O’Sullivan, Ger Rogan, Adam Kane, External Funding, Evolution, Conservation, and Genomics, Organismal and Evolutionary Biology Research Programme, Faculty of Biological and Environmental Sciences, and Helsinki Institute of Sustainability Science (HELSUS)
- Subjects
0106 biological sciences ,Atlantic salmon ,secondary theorem of selection ,INTENSE NATURAL-SELECTION ,FITNESS-RELATED TRAITS ,Biology ,Body size ,010603 evolutionary biology ,01 natural sciences ,SEXUAL SELECTION ,03 medical and health sciences ,lcsh:QH540-549.5 ,phenotypic selection ,14. Life underwater ,Population dynamics of fisheries ,Ecology, Evolution, Behavior and Systematics ,BODY-SIZE ,Original Research ,030304 developmental biology ,Nature and Landscape Conservation ,0303 health sciences ,Ecology ,Directional selection ,pedigree ,NORTH-ATLANTIC ,ADAPTIVE EVOLUTION ,atlantic salmon ,Evolutionary biology ,Sexual selection ,SOCKEYE-SALMON ,1181 Ecology, evolutionary biology ,Breeder’s equation ,lcsh:Ecology ,SALMON SALMO-SALAR ,Morphological trait ,Adaptive evolution ,Breeder's equation - Abstract
Comparing observed versus theoretically expected evolutionary responses is important for our understanding of the evolutionary process, and for assessing how species may cope with anthropogenic change. Here, we document directional selection for larger female size in Atlantic salmon, using pedigree-derived estimates of lifetime reproductive success as a fitness measure. We show the trait is heritable and, thus, capable of responding to selection. The Breeder's Equation, which predicts microevolution as the product of phenotypic selection and heritability, predicted evolution of larger size. This was at odds, however, with the observed lack of either phenotypic or genetic temporal trends in body size, a so-called "paradox of stasis." To investigate this paradox, we estimated the additive genetic covariance between trait and fitness, which provides a prediction of evolutionary change according to Robertson's secondary theorem of selection (STS) that is unbiased by missing variables. The STS prediction was consistent with the observed stasis. Decomposition of phenotypic selection gradients into genetic and environmental components revealed a potential upward bias, implying unmeasured factors that covary with trait and fitness. These results showcase the power of pedigreed, wild population studies-which have largely been limited to birds and mammals-to study evolutionary processes on contemporary timescales.
- Published
- 2019