HUEY, R.B.*; GILCHRIST, G.W.; Univ. of Washington, Seattle; College of William & Mary: Mutation accumulation, performance and fitness in Drosophila melanogaster

Studies of the �physiology-performance-fitness� paradigm typically monitor natural variation in physiology and/or performance and then search for correlations with indices of fitness. Here we take a very different approach to testing this paradigm. We worked with a set of laboratory lines of Drosophila melanogaster (44 experimentals, 13 control lines) that had undergone mutation accumulation (�MA�) in another laboratory for over 60 generations. These MA lines were already known to have much lower competitive fitness than did the control lines (but see below). Consequently, by measuring performance of these same lines, we could evaluate whether mutation induced variation in competitive fitness correlated with variation in performance. For each line, we measured several �performance� traits of larvae (feeding rate, crawling speed) and of adults [walking speed, knock-down temperature, a �get-a-grip� index] as well as a life history trait (egg viability). MA lines generally had significantly lower performances (and egg viabilities) than did control lines. However, because control lines had been unknowingly contaminated, the conclusion that MA reduces performance is tentative. In any case, only egg viability and one performance trait (get-a-grip) were significantly correlated (positively) with competitive fitness. Two main patterns emerge from this study. First, MA negatively affects diverse aspects of physiological performance, but does so differentially across traits. Second, MA induced variation in performance is at best weakly correlated with variation in competitive fitness.