Facultative autogamy in Cyrtopodium polyphyllum (Orchidaceae) through a rain-assisted pollination mechanism
Ludmila Mickeliunas Pansarin A C , Emerson Ricardo Pansarin B and Marlies Sazima AA Universidade Estadual de Campinas, Instituto de Biologia, Departamento de Botânica, Caixa Postal 6109, 13083-970 Campinas, SP, Brazil.
B Universidade de São Paulo, FFCLRP, Departamento de Biologia, 14040-901, Ribeirão Preto, SP, Brazil.
C Corresponding author. Email: colax@pop.com.br
Australian Journal of Botany 56(4) 363-367 https://doi.org/10.1071/BT07135
Submitted: 17 July 2007 Accepted: 15 January 2008 Published: 16 June 2008
Abstract
Cyrtopodium includes ~42 species, among which is Cyrtopodium polyphyllum (Vell.) Pabst ex F. Barros that occurs in a rainforest in south-eastern Brazil. Its non-rewarding flowers, which attract Centridini bees by deceit, are rain-assisted self-pollinated, a phenomenon rarely found in orchids and other plant families. In addition, self-pollination has never been reported in Cyrtopodiinae and data on the pollination of South American orchids are scarce. Flowers were observed at different times of the day, on both sunny and rainy days, to record floral morphology, visitors and the effects of rainfall on flowers. On rainy days, water accumulates on the stigma and dissolves the adhesive substance of the stigmatic surface. A viscous drop thus forms, which contacts the pollinarium. When evaporation makes the viscous drop shrink, the drop moves the pollinarium with the anther onto the stigmatic surface and promotes self-pollination. Fruit set in natural habitat was low, with 2.4% at one study site, where a similar value (2.2%) was recorded in flowers self-pollinated by rain. In C. polyphyllum, facultative self-pollination assisted by rain is thus an important strategy that guarantees fruit set when pollinator’s visits are scarce, which is common in species pollinated by deceit.
Acknowledgements
We thank the Núcleo Picinguaba, Instituto Florestal, for granting permissions for field work, Leonardo Galetto, Silvana Buzato and Mardiori T. P. dos Santos for valuable suggestions and Alain François for improving our English. This study is part of the Master’s Degree dissertation of LMP at the Departamento de Botânica, Pós-Graduação em Biologia Vegetal, Universidade Estadual de Campinas, São Paulo, Brazil. This research was supported by the State of São Paulo Research Foundation (FAPESP) as part of the Thematic Project Functional Gradient (Process Number 03/12595–7), within the BIOTA/FAPESP Program - The Biodiversity Virtual Institute (http://www.biota.org.br), as well as by FAPESP (grant 04/12531–1) and CNPq. COTEC/IF 43.703/2004 permit.
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