title: Parallel trait adaptation across opposing thermal environments in experimental Drosophila melanogaster populations.
abstract: Thermal stress is a pervasive selective agent in natural populations that impacts organismal growth, survival, and reproduction. Drosophila melanogaster exhibits a variety of putatively adaptive phenotypic responses to thermal stress in natural and experimental settings; however, accompanying assessments of fitness are typically lacking. Here, we quantify changes in fitness and known thermal tolerance traits in replicated experimental D. melanogaster populations following more than 40 generations of evolution to either cyclic cold or hot temperatures. By evaluating fitness for both evolved populations alongside a reconstituted starting population, we show that the evolved populations were the best adapted within their respective thermal environments. More strikingly, the evolved populations exhibited increased fitness in both environments and improved resistance to both acute heat and cold stress. This unexpected parallel response appeared to be an adaptation to the rapid temperature changes that drove the cycling thermal regimes, as parallel fitness changes were not observed when tested in a constant thermal environment. Our results add to a small, but growing group of studies that demonstrate the importance of fluctuating temperature changes for thermal adaptation and highlight the need for additional work in this area.
authors.affiliation: Institut für Populationsgenetik, Vetmeduni Vienna, Veterinärplatz 1, Vienna, A-1210, Austria.|Vienna Graduate School of Population Genetics, Vetmeduni Vienna, Veterinärplatz 1, Vienna, A-1210, Austria.
authors.forename: Ray
authors.initials: R
authors.lastname: Tobler
authors.affiliation: Department of Mathematics, University of Vienna, Nordbergstrasse 15, 1090, Vienna, Austria.|Max F. Perutz Laboratories, Dr. Bohr-Gasse 9, 1030, Vienna, Austria.
authors.forename: Joachim
authors.initials: J
authors.lastname: Hermisson
authors.affiliation: Institut für Populationsgenetik, Vetmeduni Vienna, Veterinärplatz 1, Vienna, A-1210, Austria. christian.schloetterer@vetmeduni.ac.at.
authors.forename: Christian
authors.initials: C
authors.lastname: Schlötterer
mesh_terms: D000220:Adaptation, Biological; D000818:Animals; D003080:Cold Temperature; D004331:Drosophila melanogaster / Q000235:genetics / Q000502:physiology*; D056084:Genetic Fitness; D006358:Hot Temperature; D012641:Selection, Genetic; D013312:Stress, Physiological
keywords: Experimental natural selection; fitness; temperature variation; thermal shock