title: Physiological mechanisms of evolved desiccation resistance in Drosophila melanogaster.
abstract: We investigated physiological characters associated with water balance in laboratory populations of Drosophila melanogaster selected for resistance to desiccating conditions for over 100 generations. Five replicate, outbred, desiccation-selected (D) populations were compared with their control (C) populations. Water loss rates of female D flies were approximately 40% lower than those of C females. Although excretory water loss was reduced in desiccation-selected flies, it comprised less than 10% of total water loss, indicating that the D populations have evolved reduced cuticular and/or respiratory water loss rates. Total surface lipid amounts did not differ between the C and D flies. Cuticular hydrocarbons from D flies were longer than those from C flies and melted at slightly higher temperatures, possibly contributing to reduced water loss rates. Desiccation-selected flies contained approximately 30% more bulk water than controls, as well as more glycogen. However, total metabolic water stores did not differ between the stocks owing to higher lipid levels in the C populations. The ability to tolerate water loss, as measured by water content at the time of death, did not differ between D and C flies. Thus, evolution of increased desiccation resistance has occurred by multiple physiological mechanisms, but some potential adaptive differences have not evolved.
authors.affiliation: Department of Ecology and Evolutionary Biology, University of California, Irvine 92697, USA. agibbs@uci.edu
authors.forename: A G
authors.initials: AG
authors.lastname: Gibbs
authors.forename: A K
authors.initials: AK
authors.lastname: Chippindale
authors.forename: M R
authors.initials: MR
authors.lastname: Rose
mesh_terms: D000818:Animals; D003681:Dehydration / Q000503:physiopathology; D004331:Drosophila melanogaster / Q000737:chemistry / Q000502:physiology*; D005260:Female; D005828:Genetics, Population; D008055:Lipids / Q000032:analysis; D008297:Male; D013499:Surface Properties; D014882:Water-Electrolyte Balance
chemical_list: D008055:Lipids