Meeting Abstract
P3.171 Monday, Jan. 6 15:30 Evolutionary and biomechanical correlates of hummingbird body size SKANDALIS, D.A.*; STILES, F.G.; MCGUIRE, J.A.; ALTSHULER, D.L.; University of British Columbia, Vancouver, BC, Canada; Universidad Nacional de Colombia, Bogotá, Colombia; University of California, Berkeley; University of British Columbia, Vancouver, BC, Canada skandalis@zoology.ubc.ca
Body shape and size are under multiple selective pressures, with major sources of variation including evolutionary history and intraspecific variation. We investigated correlates of sexual and biomechanical selective pressures in hummingbirds using a newly developed phylogeny and recent analytic tools that account for measurement error in interspecific studies. Rensch’s rule is the observation that in small species females are larger while in large species males are larger, and is often taken to reflect sexual selection, especially on males. We tested this hypothesis for body size and for several measurements of wing size and shape, and observed some trends consistent with the predicted pattern, but with wide confidence intervals. Any change in body and wing morphology due to sexual selection should also influence biomechanical performance. For example, moments of wing area, which are frequently used to describe wing shape, are hypothesized to relate to specific components of mechanical power output that could be advantageous for territorial males. We applied a multivariate approach, principal components analysis, to a suite of morphological and physiological parameters. Three components dominated: the first corresponds to wing shape parameters, the second to body mass, wing length and area, as well as wingbeat frequency, and the third to wing stroke amplitude. This suggests that wing shape parameters are not strongly linked to either flight performance or body size across species, and that stroke amplitude is behaviorally, not morphologically, determined. We suggest that in contrast to extravagant tail and bill sexual dimorphism, sexual selection on body and wing size in hummingbirds is limited.
