title: On the roles of colour and scent in a specialized floral mimicry system.
abstract: OBJECTIVE
  Sexually deceptive orchids achieve cross-pollination by mimicking the mating signals of female insects, generally hymenopterans. This pollination mechanism is often highly specific as it is based primarily on the mimicry of mating signals, especially the female sex pheromones of the targeted pollinator. Like many deceptive orchids, the Mediterranean species Ophrys arachnitiformis shows high levels of floral trait variation, especially in the colour of the perianth, which is either green or white/pinkinsh within populations. The adaptive significance of perianth colour polymorphism and its influence on pollinator visitation rates in sexually deceptive orchids remain obscure.
  
  
  METHODS
  The relative importance of floral scent versus perianth colour in pollinator attraction in this orchid pollinator mimicry system was evaluated by performing floral scent analyses by gas chromatography-mass spectrometry (GC-MS) and behavioural bioassays with the pollinators under natural conditions were performed.
  
  
  RESULTS
  The relative and absolute amounts of behaviourally active compounds are identical in the two colour morphs of O. arachnitiformis. Neither presence/absence nor the colour of the perianth (green versus white) influence attractiveness of the flowers to Colletes cunicularius males, the main pollinator of O. arachnitiformis.
  
  
  CONCLUSIONS
  Chemical signals alone can mediate the interactions in highly specialized mimicry systems. Floral colour polymorphism in O. arachnitiformis is not subjected to selection imposed by C. cunicularius males, and an interplay between different non-adaptive processes may be responsible for the maintenance of floral colour polymorphism both within and among populations.
authors.affiliation: Evolutionary Biology & Ecology, Free University of Brussels/Université Libre de Bruxelles, Av. F.D. Roosevelt 50 CP 160/12, B-1050 Brussels, Belgium. nicolas.vereecken@ulb.ac.be
authors.forename: Nicolas J
authors.initials: NJ
authors.lastname: Vereecken
authors.forename: Florian P
authors.initials: FP
authors.lastname: Schiestl
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D001516:Bees / Q000502:physiology; D035264:Flowers / Q000502:physiology*; D005602:France; D009812:Odorants; D029595:Orchidaceae / Q000502:physiology*; D010858:Pigmentation / Q000502:physiology*; D054817:Pollination / Q000502:physiology; D011157:Population Dynamics
references.citation: Annu Rev Entomol. 2009;54:425-46
references.pmid: 19067636
references.citation: Trends Ecol Evol. 1992 Aug;7(8):255-9
references.pmid: 21236024
references.citation: Evolution. 1997 Jun;51(3):715-723
references.pmid: 28568581
references.citation: Am Nat. 1998 Nov;152(5):696-705
references.pmid: 18811344
references.citation: Ann Bot. 2009 Aug;104(3):497-506
references.pmid: 19001428
references.citation: J Exp Biol. 2007 Apr;210(Pt 8):1398-405
references.pmid: 17401122
references.citation: Evolution. 2005 Jul;59(7):1449-63
references.pmid: 16153031
references.citation: Proc Natl Acad Sci U S A. 2008 May 27;105(21):7484-8
references.pmid: 18508972
references.citation: Ann Bot. 2007 Oct;100(4):757-65
references.pmid: 17684024
references.citation: Trends Ecol Evol. 2000 Apr;15(4):140-143
references.pmid: 10717682
references.citation: J Evol Biol. 2008 Jul;21(4):958-65
references.pmid: 18507700
references.citation: J Chem Ecol. 2005 Aug;31(8):1765-87
references.pmid: 16222807
references.citation: Am J Bot. 2005 Oct;92(10):1624-31
references.pmid: 21646079
references.citation: Am J Bot. 1997 Oct;84(10):1383
references.pmid: 21708546
references.citation: Phytochemistry. 2005 Jan;66(2):203-13
references.pmid: 15652577
references.citation: Oecologia. 1997 Feb;109(3):414-426
references.pmid: 28307539
references.citation: Ann Bot. 2008 Dec;102(6):911-22
references.pmid: 18819948
references.citation: Trends Ecol Evol. 2005 Sep;20(9):487-94
references.pmid: 16701425
references.citation: Proc Natl Acad Sci U S A. 2001 May 22;98(11):6253-5
references.pmid: 11353863
references.citation: Science. 1971 Jan 15;171(3967):203-5
references.pmid: 17751330
references.citation: J Exp Biol. 2009 May;212(Pt 9):1365-70
references.pmid: 19376957
references.citation: J Chem Ecol. 2006 May;32(5):917-27
references.pmid: 16739013
references.citation: Evolution. 1996 Dec;50(6):2207-2220
references.pmid: 28565662
references.citation: Naturwissenschaften. 2005 Jun;92(6):255-64
references.pmid: 15931514
references.citation: Trends Ecol Evol. 2007 Feb;22(2):71-9
references.pmid: 17055107
references.citation: Am J Bot. 2002 Nov;89(11):1772-8
references.pmid: 21665604
references.citation: Oecologia. 2004 Feb;138(3):405-13
references.pmid: 14666418
references.citation: J Chem Ecol. 1981 Mar;7(2):427-36
references.pmid: 24420488
references.citation: Am Nat. 2003 Apr;161(4):537-52
references.pmid: 12776883
references.citation: J Chem Ecol. 2003 Jan;29(1):1-14
references.pmid: 12647849
references.citation: Evolution. 1987 May;41(3):599-606
references.pmid: 28563812