Meeting Abstract
Two factors central to flight mechanics in birds are muscle forces exerted by the pectoralis on the wing and wing shape that governs its aerodynamics. Although the sternum serves as the anchor for the pectoralis, comprehensive morphometric analysis of sternum size and shape across birds has yet to be undertaken. Previous work has shown that birds with a large keel are adept fliers, while birds with a reduced or absent keel typically are flightless, and that avian sterna may be classified into three locomotor modes (swimming, flying, and walking). How sternum shape varies phylogenetically or ecologically remains to be explored. Wing shape in birds is correlated with flight strategy and ecology as shown by a simple aspect ratio: elongate wings are associated with soaring, broad wings with maneuverability, and short, pointed wings with speed. In this study, a series of geometric morphometric analyses were performed on the dorsal, ventral, lateral, and anterior views of a wide range of avian species to better correlate sternal shape with flight strategy. These studies have been compared with geometric morphometric data collected on wing shapes to determine whether there is a correlation between sternum shape and wing shape. Preliminary results show that high aspect ratio wings have evolved multiple times independently with significant phylogenetic signal across the bird tree for wing shape. The morphology of the sternum also clusters strongly in relation to lifestyle and phylogeny with a complementary pattern to that of wing shape analyses. This suggests that although wing shape is important for studying avian evolution and adaptation, sternal morphology should also be taken into account and analyzed in concert with the wing in order to test hypotheses of coevolution among functional traits and convergence across bird phylogeny.
