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Acta Amazonica

Print version ISSN 0044-5967On-line version ISSN 1809-4392

Acta Amaz. vol.11 no.1 Manaus Mar. 1981

http://dx.doi.org/10.1590/1809-43921981111013 

BOTÂNICA

Sistemas de polonização de duas espécies simpátricas de Dalechampia (Euphorbiaceae) no Amazonas, Brasil (*)

W. Scott Armbruster** 

G. L. Webster** 

**— Department of Botany, University of California, Davis, CA 95816, U.S.A.


Resumo

Dalechampia affinis (Euphorbiaceae) e D. scandens crescem simpaticamente nos arredores de Manaus, Amazonas, Brasil. Durante uma pesquisa, realizada em setembro de 1978, observou-se que as duas espécies diferiam uma da outra no tamanho da glândula floral que secreta resina (o atrativo do polinizador), na disposição das flores estaminadas e pistiladas na inflorescência, e no periodo do dia que as brácteas da inflorescência se abrem. Tais diferenças resultam de ser D. affinis polinizada principalmente por Euglossa (Apidae) e D. scandens principalmente por Hypanthidium (Megachilidae). Como uma conseqüência dessas diferenças há. provavelmente, pouco fluxo de pólen entre as duas espécies observadas.

Summary

During September, 1978 observation were made near Cacau Pirêra, in the vicinity of Manaus, Amazonas, Brazil, on the pollination systems of two sympatric species of Dalechampia (Euphorbiaceae). The flowers of Dalechampia are unisexual; three pistillate and usually 9-10 staminate flowers are aggregated into a functionally bisexual inflorescence which is subtended by two large showy bracts. The two sympatric species which occur near Manaus, D. affinis and D. scandens differ from each other in time of day that the inflorescences are open for pollination, size of bracts, the distances from the flowers to the gland which secretes resin (the pollinator attractant), and the amount of resin secreted. D. affinis secretes a larger amount of resin than D. scandens, attracting Euglossa sp. and Hypanthidium nr. melanopterum. Because the distance between the gland and stigma is relatively great, only the larger bee, Euglossa, pollinates D. affinis. D. scandens secretes a smaller amount of resin and attracts only small bees, Hypanthidium nr. melanopterum, which do pollinate this small-flowered species. The attraction of different bees by such similar plant species is probably the result of the tendency for the larger bees i.e. Euglossa) to forage resin only from sources with large amounts of resin, "ignoring" inflorescences with small amounts of resin. Although both D. affinis and D. scandens are visited by Hypanthidium, the pollen flow between the two species is probably fairly low. Hypanthidium pollinates D. scandens early in the day before the inflorescences of D. affinis are open. It is too small a bee to transfer any pollen to the stigmas of D. affinis when inflorescences of that species are open in the late afternoon.

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*— Este estudo foi financiado pela bolsa do NSF DEB 77-24263 (U.S.A.).

Creative Commons License  This is an Open Access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.