AOBPreview originally published online on February 23, 2005
Annals of Botany 2005 95(5):763-772; doi:10.1093/aob/mci090
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Pseudocopulatory Pollination in Lepanthes (Orchidaceae: Pleurothallidinae) by Fungus Gnats
1 Department of Botany, University of Florida, 220 Bartram Hall, Gainesville, FL 32611-8526, USA, 2 Jardín Botánico Lankester, Universidad de Costa Rica, Apdo. 1031-7050 Cartago, Costa Rica, 3 Instituto Centroamericano de Investigación Biológica y Conservación, Apdo. 2398-250 San Pedro de Montes de Oca, San José, Costa Rica and 4 Monteverde Orchid Garden, Apdo. 83-5655 Monteverde, Puntarenas, Costa Rica
* For correspondence. E-mail mblanco{at}flmnh.ufl.edu
Received: 4 November 2004 Returned for revision: 30 November 2004 Accepted: 5 January 2005 Published electronically: 23 February 2005
• Background and Aims Lepanthes is one of the largest angiosperm genera (>800 species). Their non-rewarding, tiny and colourful flowers are structurally complex. Their pollination mechanism has hitherto remained unknown, but has been subject of ample speculation; the function of the minuscule labellum appendix is especially puzzling. Here, the pollination of L. glicensteinii by sexually deceived male fungus gnats is described and illustrated.
• Methods Visitors to flowers of L. glicensteinii were photographed and their behaviour documented; some were captured for identification. Occasional visits to flowers of L. helleri, L. stenorhyncha and L. turialvae were also observed. Structural features of flowers and pollinators were studied with SEM.
• Key Results Sexually aroused males of the fungus gnat Bradysia floribunda (Diptera: Sciaridae) were the only visitors and pollinators of L. glicensteinii. The initial long-distance attractant seems to be olfactory. Upon finding a flower, the fly curls his abdomen under the labellum and grabs the appendix with his genitalic claspers, then dismounts the flower and turns around to face away from it. The pollinarium attaches to his abdomen during this pivoting manoeuvre. Pollinia are deposited on the stigma during a subsequent flower visit. The flies appear to ejaculate during pseudocopulation. The visitors of L. helleri, L. stenorhyncha and L. turialvae are different species of fungus gnats that display a similar behaviour.
• Conclusions Lepanthes glicensteinii has genitalic pseudocopulatory pollination, the first case reported outside of the Australian orchid genus Cryptostylis. Since most species of Lepanthes have the same unusual flower structure, it is predicted that pollination by sexual deception is prevalent in the genus. Several morphological and phenological traits in Lepanthes seem well suited for exploiting male fungus gnats as pollinators. Correspondingly, some demographic trends common in Lepanthes are consistent with patterns of male sciarid behaviour.
Key words: Bradysia floribunda, Lepanthes glicensteinii, Lepanthes helleri, Lepanthes stenorhyncha, Lepanthes turialvae, mimicry, Orchidaceae, Pleurothallidinae, pollination, pseudocopulation, Sciaridae, sexual deception
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  R. J. Waterman and M. I. Bidartondo Deception above, deception below: linking pollination and mycorrhizal biology of orchids J. Exp. Bot., March 2, 2008; (2008) erm366v1. [Abstract] [Full Text] [PDF]
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