A new set of laboratory-selected Drosophila melanogaster lines for the analysis of desiccation resistance: response to selection, physiology and correlated responses.

Artificial selection experiments provide insights into the evolutionary factors that can shape adaptive responses and have previously been utilized to examine the physiological adaptations that can improve survival to desiccation in Drosophila melanogaster. While such studies demonstrate that multiple resistance mechanisms may arise via different base populations and selection regimes, water retention emerges as a key mechanism for desiccation survival. Here, we present the physiological, correlated response and life history data for a new set of selection lines designed for the genetic dissection of desiccation resistance. After 26 generations of selection for desiccation resistance, female survival increased twofold. In contrast to previous studies, the altered resistance was associated primarily with enhanced dehydration tolerance and increased mass and less consistently with decreased rates of water loss. Life history tradeoffs and correlated selection responses were examined and overlap with previously published data. We crossed the resistant selected lines to desiccation-sensitive lines from the same control background to examine how each heterozygous resistant chromosome (excluding four) may improve desiccation resistance and observed that most of the resistance was due to genes on the third and first chromosomes, although interaction effects with the second chromosome were also detected. Results are compared to other selection responses and highlight the multiple evolutionary solutions that can arise when organisms are faced with a common selection pressure, although water loss rate remains a common mechanism in all studies.