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

Abstract

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%.