Antagonistic correlated responses in knockdown resistance to high temperature and chill-coma recovery after selecting for mating success at high temperature

STAZIONE L; SAMBUCETTI P; NORRY FM; GOMEZ FH

Simposio; IEPEP 8th International Symposium on the Environmental Physiology of Ectotherms and Plants; 2019

It is well-known that reproduction and related traits such as mating success are widely affected by thermal stress. Artificial selection for thermal stress tolerance is a useful tool to evaluate adaptation to warming environments. Here we tested correlated responses to artificial selection in replicated lines of Drosophila buzzatii that were successfully selected for mating success at high temperature. Two ecologically relevant traits, knockdown resistance to high temperature (KRHT) and chill-coma recovery (CCR) were tested for correlated selection responses. Selected lines (S lines) were generated in three replicates by allowing virgin flies to mate for four hours from released at 33 °C. Then, females were returned at 25 °C in culture bottles in each selection generation. Other three replicated lines were maintained at 25 °C without any selection as control (C lines). After 15 selection generations, KRHT was measured as the time until the flies were knocked down at 37 ° C in a glass column, and CCR was measured as time until individuals were able to stand on their legs at 25°C after remaining placed for 20 h to 0°C. Both traits were measured in flies that did not receive any hardening pre-treatments as well as in flies that were heat/cold hardened, respectively. Thermotolerance traits showed significant correlated responses with higher KRHT in S than in C lines, both with and without a heat-hardening pre-treatment. CCR time was longer in S than in C lines both with and without a cold-hardening pre-treatment. Thus, KHRT and CCR showed an antagonistic pattern of correlated responses in our selection regime, evidencing a previously suggested trade‐off for adaptation to both temperature extremes in Drosophila. Given that mating success is an important fitness component, their correlated responses on thermotolerance traits such as KRHT and CCR are keys for thermal adaptation.