title: The effect of mammalian herbivory on inflorescence architecture in ornithophilous Babiana (Iridaceae): implications for the evolution of a bird perch.
abstract: OBJECTIVE
  The showiness of floral displays is usually explained as an adaptation to attract pollinators. However, selection for less attractive displays imposed by non-pollinating agents, particularly herbivores, may balance pollinator-driven selection for highly visible inflorescences. We investigated whether inflorescence architecture, particularly the unusual ground-level flowering associated with a specialized bird perch in Babiana ringens may have originated, in part, as an adaptive response to mammalian herbivory.
  
  
  METHODS
  We measured levels of herbivory by antelope in populations of B. hirsuta, the putative sister species of B. ringens, which possesses the likely ancestral form of inflorescence architecture. To test for position-dependent effects of herbivory on flowers, we compared the herbivory rates and seed production of manipulated inflorescences in a field experiment. We predicted that flowers at the base of inflorescences would suffer less herbivory than those in apical positions.
  
  
  RESULTS
  We found herbivore damage to flowers in 50% of naturally occurring B. hirsuta plants. Manipulated inflorescences with only basal flowers, and consequently similar inflorescence architecture to B. ringens, experienced significantly lower herbivory and higher seed set than inflorescences manipulated to have only apical flowers.
  
  
  CONCLUSIONS
  Our results are consistent with the hypothesis that position-dependent herbivory on inflorescences could have played a role in the evolution of inflorescence design. More specifically, position-dependent herbivory may have selected for the loss of apical flowers. Position-dependent herbivory may have contributed toward the evolution of a naked inflorescence axis, a structure that characterizes B. ringens and functions as a bird perch facilitating cross-pollination by sunbirds.
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, Ontario, Canada M5S 3B2.
authors.forename: Caroli
authors.initials: C
authors.lastname: de Waal
authors.forename: Spencer C H
authors.initials: SC
authors.lastname: Barrett
authors.forename: Bruce
authors.initials: B
authors.lastname: Anderson
mesh_terms: D000818:Animals; D000866:Antelopes / Q000502:physiology; D005075:Biological Evolution; D005247:Feeding Behavior; D060434:Herbivory / Q000502:physiology*; D056626:Inflorescence / Q000502:physiology*; D027621:Iridaceae / Q000145:classification / Q000502:physiology*; D008322:Mammals / Q000502:physiology; D011058:Pollen / Q000502:physiology; D054817:Pollination / Q000502:physiology*; D012098:Reproduction / Q000502:physiology; D012639:Seeds / Q000502:physiology; D013045:Species Specificity