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Evolutionary Ecology

, Volume 29, Issue 5, pp 703–717 | Cite as

Increased divergence in floral morphology strongly reduces gene flow in sympatric sexually deceptive orchids with the same pollinator

  • Julia Gögler
  • Johannes Stökl
  • Pierluigi Cortis
  • Heinrich Beyrle
  • Maria Rosaria Barone Lumaga
  • Salvatore CozzolinoEmail author
  • Manfred Ayasse
Original Paper

Abstract

In sexually deceptive orchids, pollinator specificity is the main factor responsible for species isolation. The two sexually deceptive orchids Ophrys chestermanii and Ophrys normanii occur sympatrically on Sardinia and attract the same pollinator, males of Bombus vestalis, by producing the same odour bouquets. Since gene flow between these two species has been shown to be almost absent, their genetic distinctness seems to be preserved by other forms of reproductive barrier than pollinator specificity. The aim of this study is to investigate the nature and strength of these isolation barriers which apparently halt gene flow between these two orchids that share the same pollinator. Morphological measurements, combined with observations of cross-pseudocopulations, revealed that, in sympatry, the longer caudicles of O. normanii and the smaller and differently shaped stigmatic cavity in O. chestermanii are the main factors preventing gene flow between these two sympatric species. In contrast, other pre- or post-mating barriers seem to be weak or absent, as the two species have overlapping flowering time and we were able to rear hybrid offspring from interspecific manual crosses. At the same time, genetic analysis of orchid plantlets collected at sympatric sites detected the presence of only two putative hybrid individuals. Thus, the probability of natural cross-pollination between O. normanii and O. chestermanii seems to be strongly limited by divergence in their floral morphology. For some traits, this divergence was found increased between sympatric populations.

Keywords

Ecological character displacement Ophrys chestermanii Ophrys normanii Phenology Pollinia placement Mechanical barriers Reinforcement Reproductive isolation 

Notes

Acknowledgments

We thank Claudia Gack, Manfred Kalteisen, Cesario Giotta and Marcello Piccitto for helping us to collect plant material and Hannes Paulus, Hannah Burger and Heiko Bellmann for their help in producing figures. Financial support by the German Science Foundation (AY12/1-1, AY12/1-2) and the FAZIT-Stiftung is gratefully acknowledged.

Supplementary material

Supplementary video 1: B. vestalis male, carrying pollinaria of O. normanii, pseudocopulating with a flower of O. chestermanii. It could be noted that the O. normanii pollinaria do not fit into the small stigmatic cavity of O. chestermanii. (WMV 1069 kb)

Supplementary video 2: B. vestalis male, carrying pollinaria of O. normanii, pseudocopulating with a flower of O. normanii. It could be noted that the O. normanii pollinaria well fit into the large stigmatic cavity of O. normanii. (WMV 1588 kb)

10682_2015_9779_MOESM3_ESM.tif (4.4 mb)
Supplementary Fig. 1: SEM images of stigmatic cavity of O. normanii (left) and O. chestermanii (right) (bar = 1 mm). (TIFF 4522 kb)
10682_2015_9779_MOESM4_ESM.tif (14.9 mb)
Supplementary Fig. 2: Frontal details of stigmatic cavities of flowers from three individuals of allopatric O. normanii (a–c), sympatric O. normanii (d–f), sympatric O. chestermanii (g–i), close allopatric O. chestermanii (j–l) and far allopatric O. chestermanii (m–o). (TIFF 15209 kb)

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Copyright information

© Springer International Publishing Switzerland 2015

Authors and Affiliations

  • Julia Gögler
    • 1
  • Johannes Stökl
    • 2
  • Pierluigi Cortis
    • 3
  • Heinrich Beyrle
    • 4
  • Maria Rosaria Barone Lumaga
    • 5
  • Salvatore Cozzolino
    • 5
    Email author
  • Manfred Ayasse
    • 1
  1. 1.Institute for Experimental EcologyUniversity of UlmUlmGermany
  2. 2.Institute of ZoologyUniversity of RegensburgRegensburgGermany
  3. 3.Department of Life and Environmental SciencesUniversity of CagliariCagliariItaly
  4. 4.Myorchids Ltd.StadtbergenGermany
  5. 5.Department of BiologyUniversity of Naples Federico IINaplesItaly

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