title: Pollinator-mediated interactions in experimental arrays vary with neighbor identity.
abstract: OBJECTIVE
  Local ecological conditions influence the impact of species interactions on evolution and community structure. We investigated whether pollinator-mediated interactions between coflowering plants vary with plant density, coflowering neighbor identity, and flowering season.
  
  
  METHODS
  We conducted a field experiment in which flowering time and floral neighborhood were manipulated in a factorial design. Early- and late-floweringClarkia unguiculataplants were placed into arrays withC. bilobaneighbors, noncongeneric neighbors, additional conspecific plants, or no additional plants as a density control. We compared whole-plant pollen limitation of seed set, pollinator behavior, and pollen deposition among treatments.
  
  
  RESULTS
  Interactions mediated by shared pollinators depended on the identity of the neighbor and possibly changed through time, although flowering-season comparisons were compromised by low early-season plant survival. Interactions with conspecific neighbors were likely competitive late in the season. Interactions withC. bilobaappeared to involve facilitation or neutral interactions. Interactions with noncongeners were more consistently competitive. The community composition of pollinators varied among treatment combinations.
  
  
  CONCLUSIONS
  Pollinator-mediated interactions involved competition and likely facilitation, depending on coflowering neighbor. Experimental manipulation helped to reveal context-dependent variation in indirect biotic interactions.
authors.affiliation: Department of Biology and Ecology, Yuba College, 2088 North Beale Road, Marysville, California 95946, USA mha@yccd.edu.
authors.forename: Melissa K
authors.initials: MK
authors.lastname: Ha
authors.affiliation: Department of Biological Sciences, California State University, Chico, California 95929, USA.
authors.forename: Christopher T
authors.initials: CT
authors.lastname: Ivey
mesh_terms: D000818:Animals; D001516:Bees / Q000502:physiology*; D031663:Clarkia / Q000145:classification / Q000254:growth & development / Q000469:parasitology*; D017753:Ecosystem; D032601:Erysimum / Q000254:growth & development / Q000469:parasitology; D035264:Flowers / Q000254:growth & development / Q000469:parasitology; D006927:Hymenoptera / Q000502:physiology*; D011058:Pollen / Q000254:growth & development / Q000469:parasitology; D054817:Pollination / Q000502:physiology*; D011156:Population Density; D031224:Raphanus / Q000254:growth & development / Q000469:parasitology; D012098:Reproduction / Q000502:physiology; D012621:Seasons; D013045:Species Specificity
keywords: Clarkia unguiculata; context-dependency; facilitation; indirect interactions; interspecific competition; intraspecific competition; pollination; pollinator-mediated interactions; specialist pollinators