Meeting Abstract

40.5  Wednesday, Jan. 5  Phenotypic evolution of sexual dimorphism in hummingbird bills BERNS, Chelsea M.*; ADAMS, Dean C.; Iowa State University, Ames; Iowa State University, Ames cmberns@iastate.edu

The ecological and evolutionary importance of sexual dimorphism in hummingbird bill morphology has been studied for over a century. Recent work has examined the functional relationship between bill morphology (mainly curvature), food resource niche, and differences in bill morphology between the sexes in relation to foraging. Most studies of sexual dimorphism in bill shape are limited to a few tropical taxa, and a comparative examination across all species has not been performed. Recently, sexual shape dimorphism was identified in the bills of the Ruby-throated Hummingbird, a temperate migratory species whose breeding range is separate from other hummingbirds. By contrast, its sister species, the Black-chinned Hummingbird, does not exhibit sexual shape dimorphism. Interestingly, this species is also sympatric with several other temperature hummingbirds, leading to the hypothesis that competitive mechanisms (or shared environmental pressures) have constrained the evolution of sexual dimorphism in Black-chinned hummingbirds. Here I used geometric morphometrics to test this, and other related evolutionary hypotheses. I quantified patterns of sexual shape dimorphism in the bills of several species of temperate hummingbirds. I then examined these patterns in a comparative phylogenetic context to determine the extent to which environmental pressures, and shared evolutionary history, have influenced patterns of morphological variation in these taxa. The implications of phenotypic evolution for hummingbird evolution and ecology are discussed.