Predicting parasitoid population dynamics resulting from novel interactions of climate change and selenium pollution

Our research investigated the individual and joint effects of increased temperatures and the anthropogenic pollutant selenium (Se) on the life history on the parasitoid Cotesia marginiventris (Cresson) attacking the beet armyworm, Spodoptera exigua (Hubner). Previous research indicated that parasitoids can be affected detrimentally by environmental pollutants, and that changes in insect-plant interactions due to global climate change are likely to have consequences for higher trophic levels. However, information regarding the effects of these factors on parasitoids is relatively sparse. Our specific objective was to determine in a factorial experiment how three temperatures (constant 28.6°C, constant 33°C and a fluctuating temperature between 28.6 and 33°C) and three concentrations of seleno-DL-methionine (0.00, 10.59, and 21.21 μg/g) affected this parasitoid’s survival, development, and fecundity. Cotesia marginiventris larvae exhibited a significant (temperature by selenium) interaction on development time to adult emergence. There were significant declines due to increased temperature, but not selenium, on adult C. marginiventris female lifespan and number of progeny that survived to adulthood. Mean generation times and the intrinsic rate of increase (r) further show that both of these life table statistics declined under conditions of increasing levels of selenium and temperature. These data will be used as part of a model system to help understand and predict the changes in effectiveness of biological control programs as climate changes in the presence of pollution.