AERIAL PERFORMANCE OF DROSOPHILA-MELANOGASTER FROM POPULATIONS SELECTED FOR UPWIND FLIGHT ABILITY

A computerized system for three-dimensional tracking of large numbers of individual free-flying insects was used to assess the performance o f Drosophila melanogaster from populations that had undergone 160 gene rations of selection for upwind flight ability. Compared with control lines, the selected lines showed significant increases in mean flight velocity, decreases in angular trajectory and a significant change in the interaction between velocity and angular trajectory. Maximal fligh t velocity was apparent as a sharply defined upper boundary of the dis tribution of horizontal and vertical velocity as a function of angular trajectory; this upper bound (0.85 ms(-1)) differed little between th e selected and control lines, although individuals from the selected l ines attained maximal performance levels much more frequently. Maximum induced power output was calculated directly from the product of maxi mum vertical velocity and body weight, This measure (28 Wkg(-1) muscle ) was closely predicted by a scaling relationship derived from the loa d-lifting limits of larger insects and;vertebrates, as well as tethere d D. melanogaster stimulated via their optomotor reflex to produce max imal lift. These results indicate that selection for flight performanc e can readily alter the relative effort and/or the frequency of phenot ypes capable of attaining population-wise maximal performance levels, but shows little ability to increase population-wise maximal performan ce.