Pollination Panel Session having Aline Raynal-Roques as moderator with the participation of Y. Sell, Günter Gerlach, Mark Whitten and Norris H. Williams, M. Démares, Jean Claessens et Jacques Kleynen, Thierry Pailler

Reward or not ?
By Aline Raynal-Roques

For more than two centuries, it has been admitted that the flower rewards its pollinator. The attractors found in the orchidaceous flowers are most numerous and diverse. Many of them are puzzling to us. We recognize attractors useful to the visitor, misleading it, harmful to it or looking as having no consequence. Can we consider an atractor, even an useful one, as a reward? The pollinator is unaware of its polllinating role; the plant has no will of thanking it. Conceiving a compensation help-reward sounds to limite the relationship Orchid-pollinator to an anthropomorphic and restrictive view.

Aline Raynal-Roques is a teacher at the Museum National d'histoire naturelle (Paris) and expert in tropical flore and floral biology.

Fragrance festival in orchids
By Y. Sell

Odour emitted by flowers is the main attractant for insects. Attractive fragrances as well as pheromones from the orchid are mixtures, in well determined specific amounts, of various chemical compounds. These fragrances, issued from tissues mainly located in the labellum, generally constitute an olfactory guidance towards reproducing organs. A priviledged relationship is created between flower and insect, that may end into exclusivity and mainly leads towards orchid pollination.

Yves SELL is master of lecturer in Vegetal Biology at the College of Life at the 'Université Louis Pasteur, Strasbourg, retired. Expert in compared and experimented morfophology mainly floral ecology. President of the section of the orchidists of the Amis du Jardin Botanique de Strasbourg since 1984.

Pollination and fragrances in the tribe Maxillarieae
By Günter Gerlach - Botanischer Garten München - Nymphenburg - Germany

Tribe Maxillarieae circumscribes subtribes Coeliopsidinae, Maxillariinae, Oncidiinae, Stanhopeiane and Zygopetalinae with often ornamental species. Pollination systems present here are manifold, rewarding ones are also present as deceptive ones. Among the rewarding ones there exist oil flowers, offering fatty oils for brood provision and perfume flowers. Members of the subtribes Stanhopeinae and Coeliopsidinae are exclusively, members of Zygopetalinae and Maxillariinae partly pollinated by perfume collecting male euglossine bees. The mechanisms involved here belong to the most spectacular ones in plant kingdom. The fragrances serve to select one or very few bee species of the species inventary present in the respective aerea. The bees are so special in their preferences that so an efective barrier against hybridisation evolved. Fragrance analyses of flowers from subtribes with perfume syndrome are helpful to distinguish the species even when they are very similar, they give very informative hints for taxonomy but fail in generic level. To avoid intergeneric hybrids a mechanical barrier evolved, glueing the pollinaria genus specific at different parts of the bees body.

Günter Gerlach is a botanical curator at the Botanical Garden Munich in Germany. His research topics are broadly arranged: from systematics and taxonomy of the Stanhopeinae and Zygopetalinae going over to pollination biology, analysis and chemistry in the involved fragrances and floral oils of several neotropical plant groups and the ecology of the pollinating bees.

Evolutionary Relationships within Tribe Maxillarieae: Lessons from Molecules, Morphology, and Pollination Biology
By Mark Whitten and Norris H. Williams

The neotropical tribe Maxillarieae contains about 10% of the Orchidaceae and includes some of the most spectacular and horticulturally important genera (Oncidium, Odontoglossum, Stanhopea, Zygopetalum, Maxillaria). Like most Orchidaceae, the classification of these orchids has been problematic during the last 300 years, in both defining genera and in grouping these genera into higher categories. DNA sequence data give us a relatively objective set of data for reconstructing evolutionary relationships and for constructing a classification system. These DNA-based phylogenies indicate that gross floral shape and color is often misleading in constructing classifications, and that shifts to different pollinators or convergence in pollination systems has confounded earlier classification systems. In general, the DNA data support traditional classifications within subtribes that produce legitimate floral rewards (e.g., Stanhopeinae). In subtribes that contain many species with deceit-based pollination systems (e.g. Oncidiinae), the DNA-based trees conflict strongly with traditional classifications. Convergent evolution may produce very similar floral morphologies in unrelated orchids; classifications based primarily upon gross floral characters may be misleading.

Photo by M Whitten

Trigonidium grande
Photo by M Whitten

Maxillaria huancabambae

Mark Whitten is a botanist at the Florida Museum of Natural History in Gainesville Florida. His research interests include molecular systematics of orchids and chemical ecology of orchids Euglossine bees. He is presently working on the molecular systematics of Maxillaria in collaboration with colleagues in Mexico, Costa Rica, Ecuador and Brazil.

Pollination in native French orchids
By M. Démares

At first, giving some definitions about general morphology of the orchid flower and that of an insect, the author approaches pollination
1 – from a descriptive viewpoint,
- at plant level, studying different types of flowers (with long spur, with medium/short spur, without spur, with hypochile, Ophrys) and their gynostemium :
- at insect level, surveying with examples the main concerned Orders (Lepidoptera, Hymenoptera, Coleoptera, Diptera),
2 – from a dynamic viewpoint, describing the behaviours of insects towards flowers.
Then he will emphasize the relationship between insect and orchid and will show the reciprocal adaptation.

The gynostemium of the European orchids. Form and function”
By Jean Claessens et Jacques Kleynen

During the last decade we intensively studied the gynostemium of the European orchids. The gynostemium is not only important in taxonomy, but its morphology also determines the way pollination takes place. Most descriptions of gynostemia of European orchids are based on alcohol preparates. By examining fresh flower material we gathered many facts, not only about the morphology of the gynostemia, but also about their function.
In our lecture we will present several European orchid genera, e.g. Cephalanthera, Corallorhiza, Epipogium and Ophrys in various ways: we made photographs of habitus, flower, gynostemium, longitudinal sections of the flower and microscopic sections of the gynostemium. Form and function of the flower are closely connected. Examples are given to show how minor changes in the construction plan of a gynostemium can determine the way pollination takes place. For maximum insight and comparison we will present two dia slides on two screens simultaneously.

Jean Claessens et Jacques Kleynen are nature photographers specialised in extreme macrophotography.

Orchid pollinator interactions in an oceanic Island.
By Thierry Pailler

Universiteé de la Réunion - Peuplements Vegetaux Et Bioagresseurs En Milieu Tropical
The orchid flora of Réunion Island mainly originated from Madagascan colonists. At present, it contains more than 120 native species, half of which are endemics. The sub-tribe angraecinae is represented by 7 genera and 62 species. Jumellea is one of these genera which contains 9 endemic species. Four species are short spurred (8-50 mm in length), which is a feature of the phalenophilous pollination syndrome and five are long-spurred (90-150 mm in length), which is a feature of the sphingophilous pollination syndrome. A set of experiments (hand pollinations, pollinator exclusion experiments and emasculation in natural conditions) on the reproductive biology of 8 species of Jumellea revealed that short-spurred species need pollen vectors to reproduce successfully, while long-spurred species are self-fertile and do not require any pollinators to achieve reproduction. The study of floral features of both short and long spurred species shows the loss of odour and shorter floral duration in long spurred species. The study assumes the lack of long tongue pollinators (hawkmoth) during the long spurred orchids colonization event. The breakdown of the orchid - sphingid co-evolution will be discussed in the context of island existence and Baker’s law.

T. Pailler. Dr in Plant Reproductive Biology. Lecturer at La Réunion University (France, Indian Océan). Member of the Orchid Specialist Group of IUCN. Member of La Réunion Island Herbarium.
Main interest: Orchid biology, orchid ecology and plant conservation.

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