Meeting Abstract

37.3  Wednesday, Jan. 5  Compensation for exaggerated eyestalks in stalk-eyed flies (Diopsidae) HUSAK, JF*; RIBAK, G; WILKINSON, GS; SWALLOW, JG; Univ. of South Dakota; Technion University; Univ. of Maryland ; Univ. of South Dakota jerry.husak@usd.edu

Exaggerated male ornaments are hypothesized to be costly. Despite the prediction that ornaments should increase predation risk due to reduced locomotor performance, empirical evidence supporting this is equivocal. However, current costs of ornaments may be difficult to detect in nature due to the evolution of compensatory mechanisms to offset detrimental effects. The exaggerated eyestalks of male stalk-eyed flies increases their moment of inertia compared to females, yet males do not suffer a flight performance decrement. We tested for evidence of compensation within seven species of stalk-eyed flies, examining eyespan and wing morphology in four dimorphic and three monomorphic species. We found that, within species, males had larger wings than females in most species dimorphic for eyespan but not in monomorphic species. In males of the dimorphic species there were positive relationships between relative eyespan and relative wing size measures, indicating compensation, whereas there were no such relationships in females of most dimorphic species or in either males or females of the monomorphic species. We propose a new approach for testing whether ornaments are costly.