title: Floral function: effects of traits on pollinators, male and female pollination success, and female fitness across three species of milkweeds (Asclepias).
abstract: OBJECTIVE
  Central questions in plant reproductive ecology are whether the functions of floral traits in hermaphrodites create conflict between sexes that could slow evolution, and whether individual floral traits function in pollinator attraction, efficiency, or both. We studied how floral traits affect pollinator visitation and efficiency, and how they affect male and female function and female fitness within and across three Asclepias species that differ in floral morphology.
  
  
  METHODS
  Using separate multiple regressions, we regressed pollen removal, deposition, and fruit number onto six floral traits. We also used path analyses integrating these variables with pollinator visitation data for two of the species to further explore floral function and its effects on fruit production.
  
  
  RESULTS
  Most traits affected male pollination success only, and these effects often differed between species. The exception was increased slit length, which increased pollinia insertion in two of the species. There were no interspecific differences in the effects of the traits on female pollination success. All traits except horn reach affected pollination efficiency in at least one species, and horn reach and two hood dimensions were the only traits to affect pollinator attraction, but in just one species.
  
  
  CONCLUSIONS
  Traits tended to function in only one sex, and more traits affected function through pollinator efficiency than through attraction. There was no significant link between female pollination success and female fitness in any of the three species; this pattern is consistent with fruit production not being limited by pollen deposition.
authors.affiliation: W. K. Kellogg Biological Station, Department of Plant Biology, and Program in Ecology, Evolutionary Biology and Behavior, Michigan State University, 3700 E. Gull Lake Dr., Hickory Corners, Michigan 49060 raffica.larosa@colorado.edu.
authors.forename: Raffica J
authors.initials: RJ
authors.lastname: La Rosa
authors.affiliation: W. K. Kellogg Biological Station, Department of Plant Biology, and Program in Ecology, Evolutionary Biology and Behavior, Michigan State University, 3700 E. Gull Lake Dr., Hickory Corners, Michigan 49060.
authors.forename: Jeffrey K
authors.initials: JK
authors.lastname: Conner
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology; D000704:Analysis of Variance; D000818:Animals; D031108:Asclepias / Q000145:classification / Q000469:parasitology / Q000502:physiology*; D035264:Flowers / Q000033:anatomy & histology / Q000469:parasitology / Q000502:physiology*; D005638:Fruit / Q000033:anatomy & histology / Q000469:parasitology / Q000502:physiology; D007313:Insecta / Q000145:classification / Q000502:physiology; D011058:Pollen / Q000033:anatomy & histology / Q000469:parasitology / Q000502:physiology*; D054817:Pollination / Q000502:physiology*; D012098:Reproduction; D013045:Species Specificity
keywords: floral function; natural selection gradient; path analysis; plant-pollinator interactions