Evidence for Ecological Causation of Sexual Dimorphism in a Hummingbird
Ethan J. Temeles,*
Irvin L. Pan,
Jillian L. Brennan,
Jedediah N. Horwitt
Unambiguous examples of ecological causes of animal
sexual dimorphism are rare. Here we present evidence for ecological
causation of sexual dimorphism in the bill morphology of a hummingbird, the purple-throated carib. This hummingbird is the sole pollinator of
two Heliconia species whose flowers correspond to the bills of either males or females. Each sex feeds most quickly at the flower
species approximating its bill dimensions, which supports the
hypothesis that floral specialization has driven the evolution of bill
dimorphism. Further evidence for ecological causation of sexual
dimorphism was provided by a geographic replacement of one
Heliconia species by the other and the subsequent
development of a floral dimorphism, with one floral morph matching the
bills of males and the other of females.
Department of Biology, Amherst College, Amherst, MA 01002, USA.
*
To whom correspondence should be addressed. E-mail:
ejtemeles{at}amherst.edu
