title: Diverse ecological relations of male gametophyte populations in stylar environments.
abstract: OBJECTIVE
  Pollen on a stigma represents a local population of male gametophytes vying for access to female gametophytes in the associated ovary. As in most populations, density-independent and density-dependent survival depend on intrinsic characteristics of male gametophytes and environmental (pistil) conditions. These characteristics and conditions could differ among flowers, plants, populations, and species, creating diverse male-gametophyte population dynamics, which can influence seed siring and production.
  
  
  METHODS
  For nine species, we characterized the relations of both the mean and standard deviation of pollen-tube number at the style base to pollen receipt with nonlinear regression. Models represented asymptotic or peaked relations, providing information about the incidence and magnitude of facilitation and competition, the spatial and temporal characteristics of competition, and the intensity and relative timing of density-independent mortality.
  
  
  RESULTS
  We infer that pollen tubes of most species competed sequentially, their tips ceasing growth if earlier tubes had depleted stylar space/resources; although two species experienced simultaneous competition. Tube success of three species revealed positive density dependence (facilitation) at low density. For at least four species, density-independent mortality preceded competition. Tube success varied mostly within plants, rather than among plants or conspecific populations. Pollen quality influenced tube success for two of three species; affecting density-independent survival in one and density-dependent performance in the other.
  
  
  CONCLUSIONS
  The diverse relations of pollen-tube success to pollen receipt evident among just nine species indicate significant contributions of the processes governing pollen germination and tube growth to the reproductive diversity of angiosperms.
authors.affiliation: Department of Biological Sciences, University of Calgary, Calgary, Alberta T2N 1N4 Canada harder@ucalgary.ca.
authors.forename: Lawrence D
authors.initials: LD
authors.lastname: Harder
authors.affiliation: Laboratorio Ecotono, INIBIOMA-CONICET and Centro Regional Bariloche, Universidad Nacional del Comahue, Quintral 1250, 8400 Bariloche, Río Negro, Argentina.
authors.forename: Marcelo A
authors.initials: MA
authors.lastname: Aizen
authors.forename: Shane A
authors.initials: SA
authors.lastname: Richards
authors.affiliation: School of Biological Sciences, Washington State University, PO Box 644236, Pullman, Washington 99164-4236 USA.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Joseph
authors.affiliation: School of Biological Sciences, Washington State University, PO Box 644236, Pullman, Washington 99164-4236 USA.
authors.forename: Jeremiah W
authors.initials: JW
authors.lastname: Busch
mesh_terms: D017753:Ecosystem; D008954:Models, Biological; D017711:Nonlinear Dynamics; D011058:Pollen / Q000502:physiology*; D053205:Pollen Tube / Q000254:growth & development; D012044:Regression Analysis; D013045:Species Specificity
keywords: competition; facilitation; male gametophyte; pollen quality; pollen tube; population ecology; progamic