Changes in thermotolerance and Hsp70 expression with domestication in Drosophila melanogaster

To examine how the duration of laboratory domestication may affect Drosophi la stocks used in studies of thermotolerance, we measured expression of the inducible heat-shock protein Hsp70 and survival after heat shock in D. mel anogaster strains recently collected from nature and maintained in laborato ry culture for up to 50 or more generations. After an initial increase in b oth Hsp70 expression and thermotolerance immediately after transfer to labo ratory medium, both traits remained fairly constant over time and variation among strains persisted through laboratory domestication. Furthermore, var iation in heat tolerance and Hsp70 expression did not correlate with the le ngth of time populations evolved in the laboratory. Therefore, while enviro nmental variation likely contributed most to early shifts in strain toleran ce and Hsp70 expression, other population parameters, for example genetic d rift, inbreeding, and selection likely affected these traits little. As lon g as populations are maintained with large numbers of individuals, the cult ure of insects in the laboratory may have little effect on the tolerance of different strains to thermal stress.