Evolution of variation and variability under fluctuating, stabilizing, and disruptive selection.
How variation and variability (the capacity to vary) may respond to selection remain open questions. Indeed, effects of different selection regimes on variational properties, such as canalization and developmental stability are under debate. We analyzed the patterns of among- and within-individual variation in two wing-shape characters in populations of Drosophila melanogaster maintained under fluctuating, disruptive, and stabilizing selection for more than 20 generations. Patterns of variation in wing size, which was not a direct target of selection, were also analyzed. Disruptive selection dramatically increased phenotypic variation in the two shape characters, but left phenotypic variation in wing size unaltered. Fluctuating and stabilizing selection consistently decreased phenotypic variation in all traits. In contrast, within-individual variation, measured by the level of fluctuating asymmetry, increased for all traits under all selection regimes. These results suggest that canalization and developmental stability are evolvable and presumably controlled by different underlying genetic mechanisms, but the evolutionary responses are not consistent with an adaptive response to selection on variation. Selection also affected patterns of directional asymmetry, although inconsistently across traits and treatments.
Pélabon
Christophe
C
Department of Biology, Center for Conservation Biology, Norwegian University of Science and Technology, 7491 Trondheim, Norway. christophe.pelabon@bio.ntnu.no
Hansen
Thomas F
TF
Carter
Ashley J R
AJ
Houle
David
D
D000704:Analysis of Variance; D000818:Animals; D005075:Biological Evolution; D001837:Body Weights and Measures; D004331:Drosophila melanogaster; D014644:Genetic Variation; D008957:Models, Genetic; D010641:Phenotype; D012641:Selection, Genetic; D014921:Wings, Animal / Q000033:anatomy & histology