Laboratory selection of resistance by the Red Flour Beetle,Tribolium castaneum (Herbst), To a carbon dioxide-enriched atmosphere

Adult populations of the red flour beetle,Tribolium castaneum (Herbst), were exposed for 40 generations to an atmosphere containing 65% CO₂, 20% O₂ and 15% N₂ at 95% RH, in order to select a strain resistant to a high carbon dioxide content (HCC) atmosphere. Selection pressure was maintained at between 50% and 70% mortality. At the 40th generation, comparison of sensitivity between the selected strain and the original non-selected strain indicated a resistance factor at the 50% mortality level (LT₅₀) of x 9.2. Throughout the selection process, log-time against probit-mortality lines remained roughly parallel and the slope remained low and similar to that of the non-selected strain until the last generation. Implications are that at a high level of selection, multiple genetic factors continued to act together even at the 40th generation to select for adaptation to survival at high CO₂ concentrations. Removal of selection pressure from a sub-population of the selected strain from the 13th to 21st generation revealed that resistance was partially retained with a decrease of 17% in the resistance factor. The modified atmosphere chosen in this study does not represent real-life situations where O₂ concentrations are reduced by flushing with CO₂, and intergranular relative humidities are generally not above 70%.