CAREER: Performance and Fitness Consequences of Insect Ornaments

University Of South Dakota Main Campus, Vermillion SD

Investigators

Abstract

CAREER: PERFORMANCE AND FITNESS CONSEQUENCES OF INSECT ORNAMENTS JOHN G. SWALLOW UNIVERSITY OF SOUTH DAKOTA Sexual selection is responsible for much of the morphological diversity among animals and is often expressed in the form of male ornamental displays. Sexual selection theory indicates that these display traits do not come without costs, such that the displays and their costs are countered by natural selection. Stalk-eyed flies provide the ideal model system to test for costs and tradeoffs related to male ornamentation. All species in this extraordinary family display exaggerated head morphology, with eyes and antennae displaced at the end of long stalks, and interspecific variation in eye span can be more than ten-fold. Furthermore, all available evidence indicates that eye stalks are critical sexual signals used in both male-male competition and female choice. This study will examine the effects of elongated eye stalks on flight performance and survivorship of stalk-eyed flies to assess whether these effects run counter to the effects of sexual selection. To achieve this goal, the PI will integrate information from three distinct avenues of research. First, to establish a link between morphology and performance, variation in eye span and locomotor performance will be measured in a single species, Cyrtodiopsis dalmanni, to test for trade-offs between secondary sexual traits and adaptations for flight. For this study, lines of C. dalmanni that have been bidirectionally selected for increased and decreased eye span will be used to increase the natural variation seen in this species. Direct measurements of acceleration, speed and maneuverability during flight will be made using computer-integrated high speed video cameras. Additionally, load lifting capacity and energy used during flight will be measured. Second, the fitness consequences of impaired flight performance will be directly measured in a series of predation avoidance experiments in greenhouse enclosures. Third, patterns of correlated evolution between morphology and flight performance measured on many species within the family Diopsidae will reveal evolutionary consequences of sexual selection. If eye stalks impair locomotor ability, compensatory changes in body design are predicted to evolve within the family to reduce the locomotor cost. Such compensatory changes would indirectly suggest that such reduction in performance was selectively important. This research program incorporates multiple disciplines and will certainly result in new insights regarding interactions between the costs of locomotion and the evolution of secondary sexual ornaments. The PI's educational activities will focus primarily on disadvantaged pre-college students from Native American reservation schools and rural schools. Both of these groups, particularly Native Americans, are traditionally underrepresented in both college and the sciences. South Dakota has both a large Native American population (~ 10%) and a large rural population. Through cooperation with the instructors affiliated with the Mobile Science Laboratory (MSL), the PI will develop a contribution on "Sexual selection and insect diversity: secondary sexual ornaments" for the MSL. Outreach projects developed for the MSL will expose K-12 students from Native American reservation and rural schools to the process of science and discovery. This outreach program has the potential to positively influence thousands of people throughout the state of South Dakota.