Artificial selection on chill-coma recovery time in Drosophila melanogaster: Direct and correlated responses to selection.
Artificial selection can be used to create populations with extreme phenotypic responses to environmental stressors. When artificial selection is applied to a single component of a stress response, this selection may result in correlated responses in other stress responses, a phenomenon called cross-tolerance, which is ultimately controlled by the genetic correlations among traits. We selected for extreme responses to cold tolerance by selecting for chill-coma recovery time from a single temperate population of Drosophila melanogaster. Chill-coma recovery time is a common metric of low, but non-lethal, cold temperature tolerance. Replicated divergent artificial selection was applied to a genetically variable base population for 31 generations, resulting in two cold resistant, two cold susceptible, and two unselected control lines. To quantify the relationship between selection on chill-coma recovery and other metrics of thermal performance, we also measured survivorship after acute cold exposure, survivorship after chronic cold exposure, survivorship after cold exposure following a pre-treatment period (rapid cold hardening), starvation tolerance, and heat tolerance. We find that chill-coma recovery time is heritable within this population and that there is an asymmetric response to increased and decreased chill-coma recovery time. Surprisingly, we found no cross-tolerances between selection on chill-coma recovery time and the other environmental stress response traits. These results suggest that although artificial selection has dramatically altered chill-coma recovery time, the correlated response to selection on other stress response phenotypes has been negligible. The lack of a correlated response suggests that chill-coma recovery time in these selection lines is likely genetically independent from measures of cold survivorship tested here.
Division of Biology and The Ecological Genomics Institute, Kansas State University, Manhattan, KS 66506 USA.
Alison R
AR
Gerken
Department of Biological Sciences, Program in Genetics and W. M. Keck Center for Behavioral Biology, North Carolina State University, Raleigh, NC 27695, USA.
Trudy F C
TF
Mackay
Division of Biology and The Ecological Genomics Institute, Kansas State University, Manhattan, KS 66506 USA. Electronic address: tjmorgan@ksu.edu.
Theodore J
TJ
Morgan
D000064:Acclimatization; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D001947:Breeding; D003080:Cold Temperature; D058639:Cold-Shock Response; D004331:Drosophila melanogaster / Q000235:genetics / Q000502:physiology*; D005260:Female; D008297:Male; D010641:Phenotype; D012641:Selection, Genetic; D013312:Stress, Physiological
Artificial selection; Chill-coma recovery; Cross-tolerance; Drosophila melanogaster