Impact of extreme temperatures on phenotypic plasticity of Trichogramma euproctidis

The effect of temperature on the development of ectothermic organisms is a subject of study which has aroused the interest of many scientists. Recently, climate change threats have reinforced this interest, particularly in assessing the effect of higher temperatures on insect distribution and phenology. Climate change can also contribute to the adaptation of individuals to extreme temperature via phenotypic plasticity. These phenotypic variations can have considerable effects on individual fitness and thus modify the effectiveness of a biological control agent. Here, we evaluated the impact of constant and fluctuating temperatures (including extreme temperatures) on the development of the egg parasitoid Trichogramma euproctidis. Developmental time and traits associated to fitness (size, weight, longevity and fecundity) were measured at mean temperatures of 15, 22 and 30°C, including exposition to 10° and 35°C for the fluctuating temperature treatment. Extreme temperatures did not cause deleterious effects on T. euproctidis fitness, although they were unable to develop at these temperatures under a constant regime. This assumes that either T. euproctidis has a compensation mechanism that does not affect his fitness or that the number of hours at extreme temperatures was not high enough to cause damage. Further experiments with more extreme temperatures will determine which of the two hypotheses applies.