Evolutionary Ecology

, Volume 24, Issue 5, pp 1199–1218

Absence of pollinator-mediated premating barriers in mixed-ploidy populations of Gymnadenia conopsea s.l. (Orchidaceae)

  • Jana Jersáková
  • Sílvia Castro
  • Nicole Sonk
  • Kathrin Milchreit
  • Iva Schödelbauerová
  • Till Tolasch
  • Stefan Dötterl
Original Paper

DOI: 10.1007/s10682-010-9356-7

Cite this article as:
Jersáková, J., Castro, S., Sonk, N. et al. Evol Ecol (2010) 24: 1199. doi:10.1007/s10682-010-9356-7

Abstract

Polyploidy has played a key role in plant evolution and diversification. Despite this, the processes governing reproductive isolation among cytotypes growing in mixed-ploidy populations are still largely unknown. Theoretically, coexistence of diploid and polyploid individuals in sympatric populations is unlikely unless cytotypes are prezygotically isolated through assortative pollination. Here, we investigated the pre-mating barriers involved in the maintenance of three co-occurring cytotypes from the genus Gymnadenia (Orchidaceae): tetraploid and octoploid G. conopsea and tetraploid G. densiflora. We assessed differences in flowering phenology, floral morphology, and visual and olfactory cues, which could lead to assortative mating. Gas chromatography coupled with electroantennographic detection was used to identify scent compounds with physiological activity in the two main pollinators, Deilephila porcellus and Autographa gamma. The importance of olfactory cues was also assessed in the field by analysing the moths’ responses to the olfactory display of the plants, and by following the pollinator’s behaviour on artificial arrays. Our complex approach demonstrated that the coexistence of Gymnadenia cytotypes in mixed-ploidy populations was only partly explained by differences in floral phenology, as cytotypes with overlapping flowering (i.e., octoploid G. conopsea and tetraploid G. densiflora) might freely exchange pollen due to only 1 mm differences in spur lengths and the lack of assortative behaviour of pollinators. While floral colour among the cytotypes was similar, floral scent differed significantly. Though both pollinator species seemed to physiologically detect these differences, and the floral scent alone was sufficient to attract them, pollinators did not use this cue to discriminate the cytotypes in the field. The absence of pre-mating barriers among cytotypes, except partial temporal segregation, suggests the existence of other mechanisms involved in the cytotypes’ coexistence. The genetic differences in ITS sequences among cytotypes were used to discuss the cytotype’s origin.

Keywords

Cytotypes Floral volatiles Fragrant orchid Gas chromatography–electroantennographic detection Matting barriers Polyploidy 

Supplementary material

10682_2010_9356_MOESM1_ESM.doc (1.5 mb)
Supplementary material 1 (DOC 1584 kb)

Copyright information

© Springer Science+Business Media B.V. 2010

Authors and Affiliations

  • Jana Jersáková
    • 1
    • 2
  • Sílvia Castro
    • 3
    • 4
  • Nicole Sonk
    • 5
  • Kathrin Milchreit
    • 5
  • Iva Schödelbauerová
    • 1
    • 2
  • Till Tolasch
    • 6
  • Stefan Dötterl
    • 5
  1. 1.Department of Theoretical Ecology, Institute of System Biology and Ecology AS CRČeské BudějoviceCzech Republic
  2. 2.Faculty of ScienceUniversity of South BohemiaČeské BudějoviceCzech Republic
  3. 3.Centre for Functional Ecology, Department of Life SciencesUniversity of CoimbraCoimbraPortugal
  4. 4.Institute of BotanyAcademy of SciencesPrůhoniceCzech Republic
  5. 5.Department of Plant SystematicsUniversity of BayreuthBayreuthGermany
  6. 6.Institut für Zoologie, Fg. TierökologieUniversität HohenheimStuttgartGermany

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