title: Geographic variation in resistance to nectar robbing and consequences for pollination.
abstract: OBJECTIVE
  Floral evolution is frequently ascribed to selection by pollinators, but may also be shaped by antagonists. However, remarkably few studies have examined geographic mosaics in resistance to floral antagonists or the consequences for other floral interactions.
  
  
  METHODS
  Gelsemium sempervirens experiences frequent nectar robbing in northern Georgia, but rarely in southern Georgia. We conducted common-garden experiments in both locations using genotypes from each region and measured robbing, pollinator attraction, floral attractive and defensive traits, and plant reproduction.
  
  
  RESULTS
  Nectar robbing was more than four times higher in the north vs. south, and pollinator visits did not differ between gardens. Across both gardens, northern genotypes were half as likely to be nectar-robbed but received half as many pollinator visits as southern genotypes, suggesting evolution of resistance to robbing at a cost of reduced pollinator attraction. Plant-level traits, such as height and number of flowers, were more closely associated with resistance to robbing than floral size, shape, or chemistry. Northern genotypes had lower female and estimated male reproduction compared to southern genotypes at both locations, which could be due to costs of resistance to nectar robbing, or costs of adaptations to other biotic or abiotic differences between regions.
  
  
  CONCLUSIONS
  Our study indicates that geographic variation can play a strong role structuring interactions with floral antagonists and mutualists and provides evidence consistent with the hypothesis that local resistance to nectar robbing imposes costs in terms of decreased pollinator attraction and reproduction.
authors.affiliation: Department of Biology, 221 Morrill Science Center South, 611 N. Pleasant St., University of Massachusetts, Amherst, Massachusetts 01003 USA lsadler@bio.umass.edu.
authors.forename: Lynn S
authors.initials: LS
authors.lastname: Adler
authors.affiliation: Department of Biology, Georgia Southern University, PO Box 8042-1, Statesboro, Georgia 30460 USA.
authors.forename: Lissa M
authors.initials: LM
authors.lastname: Leege
authors.affiliation: Department of Biological Sciences, Life Science Center, 78 College Street, Dartmouth College, Hanover, New Hampshire 03755 USA.
authors.forename: Rebecca E
authors.initials: RE
authors.lastname: Irwin
mesh_terms: D063147:Animal Distribution; D000818:Animals; D005075:Biological Evolution; D035264:Flowers / Q000502:physiology; D031450:Gelsemium / Q000502:physiology*; D005845:Georgia; D007313:Insecta / Q000502:physiology*; D057048:Plant Nectar / Q000032:analysis; D054817:Pollination; D013559:Symbiosis
chemical_list: D057048:Plant Nectar
keywords: Carolina jessamine; Gelsemium sempervirens; Loganiaceae; common garden experiment; geographic mosaic; nectar robbing; pollination; resistance