Pollination Effectiveness and Pollen Dispersal in a Rhododendron ferrugineum (Ericaceae) Population

N. Escaravage; J. Wagner

doi:10.1055/s-2004-821143

Plant Biology, Table of Contents

Plant Biol (Stuttg) 2004; 6(5): 606-615
DOI: 10.1055/s-2004-821143

Original Paper

Georg Thieme Verlag Stuttgart KG · New York

Pollination Effectiveness and Pollen Dispersal in a Rhododendron ferrugineum (Ericaceae) Population

N. Escaravage¹ , J. Wagner²

¹Evolution et Diversité Biologique UMR 5471, CNRS/UPS, 118, route de Narbonne, Bât. 4R3, 31062 Toulouse cedex 4, France
²Institute of Botany, University of Innsbruck, Sternwartestraße 15, 6020 Innsbruck, Austria

Abstract

Many alpine plants are predominantly outcrossing, thus plant reproductive success is highly dependent on effectiveness of pollinators. How pollinators transfer pollen from one flower to another is of great interest in understanding the genetic structure in plant populations. We studied (1) the role and effectiveness of insect visitors for pollination, and (2) their contribution as pollen vectors for gene dispersal in a Rhododendron ferrugineum population. Various insect visitors were recorded, including Hymenoptera, Diptera, Coleoptera, and Lepidoptera. The most frequent and effective insects were honey bees and bumblebees. Muscid flies were considered as important pollinators, particularly due to their relatively high visitation rate. Syrphid flies, Formicidae, and Coleoptera were ineffective in transporting pollen, while the effectiveness of Lepidoptera and Empididae was negligible. A fluorescence labelling experiment revealed that pollen dispersal was restricted (0 - 2 m) in a dense R. ferrugineum stand and decreased in a leptokurtic fashion. This might lead to geitonogamous self-pollination that could explain the close relationship between individuals found in genetic studies of R. ferrugineum. However, some pollen grains may travel 40 - 45 m, which implies the occurrence of cross-pollination through the foraging activities of bumblebees and honey bees.

Key words

Alpine plant - pollination effectiveness - pollen dispersal - pollen flow - Rhododendron ferrugineum.

Full Text

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N. Escaravage

Evolution et Diversité Biologique UMR 5471, CNRS/UPS

118, route de Narbonne, Bât. 4R3

31062 Toulouse cedex 4

France

Email: nathalie.escaravage@cict.fr

Section Editor: K. Clay