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In sexually dimorphic species, males and females have different morphological phenotypes. Elaborate ornamental traits, usually possessed by males, impart a selective advantage to mate competition; however, these traits often impose costs on other aspects of fitness. For example, impaired locomotor performance due to unwieldy ornaments has been proposed to increase risk of predation. Teleopsids, also known as stalk-eyed flies, have eyes that protrude laterally from their head on long peduncles. In the dimorphic species Teleopsis dalmanni, the average eyespan of males greatly exceeds that of females. Previous studies have investigated the possibility of impaired flight performance as a cost of elongated eyestalks but have found no biologically significant reduction in either velocity or turning behavior. This project examines the cost of male ornamentation in T. dalmanni from an energetic perspective. Using a method of closed-system respirometry, CO2 production during flight was measured and compared between sexes of T. dalmanni and that of a closely related monomorphic species, T. quinqueguttata. Data for numerous experimental and morphological variables were included in model construction, and model selection was carried out using Information Theoretical (IT) methods. No difference in CO2 production was observed among species or sex. From the data collected, flight index – the measurement of time spent in flight – appeared to have the greatest influence on energetic expenditure, and flight index appeared to be most dependent on the age of the flies. The flight apparatus and method of measuring flight metabolism developed in this project have possible applications in future studies of energetic cost in insects.
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Mayer, Emily M., "Measuring the Energetic Requirements of Flight for Teleopsids: an Investigation of the Cost of Male Ornamentation in Sexually Dimorphic Species" (2012). Senior Projects Spring 2012. 23.