Insect pollination and inflorescence structure in two species of Spiranthes orchids
Orchids of the genus Spiranthes are also called "ladies' tresses" because of the spiral arrangement of the vertical row of flowers. We studied the two species present in the Mediterranean region, i.e. Spiranthes aestivalis and S. spiralis , which bloom in June and October respectively. Both species are generally pollinated by hymenopterans (e.g. honeybees and bumblebees) all of which visit the spiral row of flowers from bottom to the top. We observed that flower visiting behaviour of varied depending on the morphology of the inflorescence. Insects were observed either walking between two subsequent flowers separated by an acute angle or flying between two subsequent flowers separated by a broad angle. In the second case, pollination was performed more slowly and a smaller frequency of flowers was pollinated. We also observed that a very broad angle (more than 120°) between two subsequent flowers resulted in the insect stopping its visit and flying away. We then studied the variation of several parameters (direction of the spiral, number of flowers per turn, angle between two subsequent flowers) characterising the spiral inflorescence in different populations of the two Spiranthes species. These orchids thus provide a good example of a direct relationship between the inflorescence structure and visitation behaviour of pollinators.
| Main Authors: | , , |
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| Format: | conference_item biblioteca |
| Language: | eng |
| Published: |
CIRAD-AMAP
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| Subjects: | F63 - Physiologie végétale - Reproduction, F50 - Anatomie et morphologie des plantes, |
| Online Access: | http://agritrop.cirad.fr/523905/ |
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