Effects of thermal history on temperature-dependent flight performance in insects : Ceratitis capitata (Diptera: Tephritidae) as a model organism

[摘要] ENGLISH ABSTRACT: Understanding the impact of environmental factors on locomotor performance and flight energetics is of fundamental importance to understanding evolution and ecology. Increased performance that leads to increased dispersal ability can result in increased migration distance to reach optimal habitats, increased gene flow between populations and an overall contribution to the survival of individuals as well as the structuring of species‟ geographic range sizes. The temperature-dependent nature of insects, in conjunction with predicted climate change and shifting optimal climatic ranges, could have important ecological and economic consequences such as increased invasion by alien and pest species. In this study, the influence of thermal history on temperature-dependent flight performance was investigated in a notorious invasive agricultural pest, Ceratitis capitata (Diptera: Tephritidae). Flies were exposed to one of four developmental acclimation temperatures (Tacc: 15, 20, 25, 30°C) during their pupal stage and tested at random at either of those temperatures (Ttest) as adults in a full-factorial experimental design. Major factors influencing flight performance included sex, body mass, Ttest and the interaction between Ttest and Tacc. Performance increased with increasing Ttest across all acclimation groups, e.g. at 15°C only 10% of all flies had successful flight, whereas at 30°C the success rate was 76.5%. Even though Tacc alone did not affect flight performance, it did have an effect in combination with Ttest. The negative interaction term Ttest x Tacc, in combination with a multiple comparison between Tacc groups at each Ttest, indicated that flies acclimated to 15°C and 20°C performed better than those acclimated to 25°C and 30°C when tested at cold temperatures. This provides partial support for the colder is better‟ hypothesis. To explain these results, several key, flight-related traits were examined to determine if Tacc influenced flight performance as a consequence of changes in body or wing morphology, whole-animal metabolic rate or cytochrome c oxidase (CCO) activity. Although significant effects of Tacc could be detected in several of the traits examined, with emphasis on sex-related differences, increased flight performance could not be explained solely on the basis of changes in any one of these traits. To illustrate the potential applied value of this study, the main flight performance outcomes were also coupled with a degree-day (thermal development) model to determine if knowledge of flight ability could improve predicted population dynamics. The results and insights obtained from this study are broadly applicable to a variety of insect species and demonstrate that, by recognising the impact of environmental factors on locomotor performance and flight energetics, an increased understanding of the functioning, biology and evolution of flight-capable arthropods can be obtained.

[发布机构] Stellenbosch University