title: Effective long-distance pollen dispersal in Centaurea jacea.
abstract: BACKGROUND
  Agri-environment schemes play an increasingly important role for the conservation of rare plants in intensively managed agricultural landscapes. However, little is known about their effects on gene flow via pollen dispersal between populations of these species.
  
  
  RESULTS
  In a 2-year experiment, we observed effective pollen dispersal from source populations of Centaurea jacea in restored meadows, the most widespread Swiss agri-environment scheme, to potted plants in adjacent intensively managed meadows without other individuals of this species. Potted plants were put in replicated source populations at 25, 50, 100 m and where possible 200 m distance from these source populations. Pollen transfer among isolated plants was prevented by temporary bagging, such that only one isolated plant was accessible for flower visitors at any one time. Because C. jacea is self-incompatible, seed set in single-plant isolates indicated insect mediated effective pollen dispersal from the source population. Seed set was higher in source populations (35.7+/-4.4) than in isolates (4.8+/-1.0). Seed set declined from 18.9% of that in source populations at a distance of 25 m to 7.4% at 200 m. At a distance of 200 m seed set was still significantly higher in selfed plants, indicating long-distance effective pollen dispersal up to 200 m. Analyses of covariance suggested that bees contributed more than flies to this long-distance pollen dispersal. We found evidence that pollen dispersal to single-plant isolates was positively affected by the diversity and flower abundance of neighboring plant species in the intensively managed meadow. Furthermore, the decline of the dispersal was less steep when the source population of C. jacea was large.
  
  
  CONCLUSIONS
  We conclude that insect pollinators can effectively transfer pollen from source populations of C. jacea over at least 200 m, even when "recipient populations" consisted of single-plant isolates, suggesting that gene flow by pollen over this distance is very likely. Source population size and flowering environment surrounding recipient plants appear to be important factors affecting pollen dispersal in C. jacea. It is conceivable that most insect-pollinated plants in a network of restored sites within intensively managed grassland can form metapopulations, if distances between sites are of similar magnitude as tested here.
authors.affiliation: Institute of Environmental Sciences, University of Zurich, Zurich, Switzerland. matthias.albrecht@uwinst.uzh.ch
authors.forename: Matthias
authors.initials: M
authors.lastname: Albrecht
authors.forename: Peter
authors.initials: P
authors.lastname: Duelli
authors.forename: Martin K
authors.initials: MK
authors.lastname: Obrist
authors.forename: David
authors.initials: D
authors.lastname: Kleijn
authors.forename: Bernhard
authors.initials: B
authors.lastname: Schmid
mesh_terms: D031179:Centaurea / Q000502:physiology*; D004463:Ecology; D011058:Pollen
references.citation: Evolution. 1999 Feb;53(1):63-73
references.pmid: 28565199
references.citation: Oecologia. 2001 Apr;127(2):239-245
references.pmid: 24577655
references.citation: Oecologia. 1990 Jun;83(2):191-6
references.pmid: 22160110
references.citation: Am J Bot. 2002 Aug;89(8):1250-9
references.pmid: 21665726
references.citation: Evolution. 1980 Sep;34(5):934-943
references.pmid: 28581139
references.citation: Am Nat. 1998 Jun;151(6):487-96
references.pmid: 18811371
references.citation: Evolution. 1985 Mar;39(2):418-431
references.pmid: 28564230
references.citation: Ecol Lett. 2008 Jun;11(6):564-75
references.pmid: 18363716
references.citation: Ecology. 2006 Apr;87(4):931-41
references.pmid: 16676537
references.citation: New Phytol. 2006;169(3):615-21
references.pmid: 16411963
references.citation: Nature. 2001 Oct 18;413(6857):723-5
references.pmid: 11607029
references.citation: Oecologia. 2007 Sep;153(3):589-96
references.pmid: 17483965
references.citation: Evolution. 1989 Nov;43(7):1444-1455
references.pmid: 28564243
references.citation: Mol Ecol. 2004 Apr;13(4):937-54
references.pmid: 15012767
references.citation: Oecologia. 1993 Jun;94(3):446-450
references.pmid: 28313684
references.citation: Biol Rev Camb Philos Soc. 2005 Aug;80(3):413-43
references.pmid: 16094807
references.citation: Evolution. 1991 Mar;45(2):398-409
references.pmid: 28567876
references.citation: J Environ Manage. 2004 May;71(1):79-93
references.pmid: 15084362
references.citation: Evolution. 1968 Mar;22(1):130-139
references.pmid: 28564980
references.citation: Oecologia. 1998 Jan;113(3):341-349
references.pmid: 28307818
references.citation: Heredity (Edinb). 2001 Aug;87(Pt 2):136-45
references.pmid: 11703503