title: Experimental floral and inflorescence trait manipulations affect pollinator preference and function in a hummingbird-pollinated plant.
abstract: OBJECTIVE
  Controversy is ongoing regarding the importance of pollinator-mediated selection as a source of observed patterns of floral diversity. Although increasing evidence exists of pollinator-mediated selection acting on female reproductive success, there is still limited understanding of pollinator-mediated selection on floral traits via male reproductive success. Here we quantify potential selection by the ruby-throated hummingbird, Archilochus colubris, on four floral traits of hermaphroditic Silene exerted through male floral function.
  
  
  METHODS
  In single trait manipulative experiments we quantified hummingbird visitation preference and/or fluorescent dye (a pollen analog) donation as a function of number of flowers displayed (inflorescence size), height of the floral display (inflorescence height), floral color, and corolla tube length.
  
  
  RESULTS
  Hummingbirds preferred to visit larger floral displays and floral displays at greater height, likely representing a general pollinator preference for larger, more visible signals and/or greater rewards. In addition, hummingbirds preferred to visit red flowers, and male function was greater in flowers manipulated to have longer corolla tubes.
  
  
  CONCLUSIONS
  Selection pressures exerted by hummingbirds on S. virginica floral and inflorescence design through male reproductive success are consistent with the contemporary expression of floral traits of S. virginica relative to related Silene species with different pollinators, and they are consistent with the hummingbird syndrome of traits expressed by S. virginica.
authors: Department of Biology, University of Maryland, College Park, Maryland 20742, USA. mdudash@umd.edu
authors: Michele R
authors: MR
authors: Dudash
authors: Cynthia
authors: C
authors: Hassler
authors: Peter M
authors: PM
authors: Stevens
authors: Charles B
authors: CB
authors: Fenster