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RESEARCH PRODUCT

Pollination: An Integrating Factor of Biocenoses

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A survey is given of the ecological constraints which affect the process of pollen transfer — and hence the gene flow — within a biocenosis. Wind pollination (anemophily) plays a dominant role in species-poor communities only. The quantity of zoophilous species increases equator-ward to up to 100 % and so does the degree of integration in animal-plant interactions. Biotic pollination is pinpointed. Manifoldness and specifity of methods reduce pollen waste and mispollinations. Saturated ecosystems dispose of a complete set of pollination syndromes and the respective pollinator guilds, narrow niche widths, a high percentage of eutropic flowers, shorter flowering times, and a temporal and spatial partitioning of floral resources. In pioneer communities generalists (allotropic flowers) or autogamy prevail. Flowering times are extended and there is less biotic integration. — Usually, floral contrivances favour allogamy. Genetic heterogeneity of potential sexual partners is effected by seed dispersal while gene flow results from pollen transfer. The mean range of the latter and thus the sizes of an individual’s interaction sphere within a population (neighbourhood) are species-specific and depend on, e.g., gregariousness; efficiency of the pollination apparatus; nectar quantity; kind of pollinator, its flying range, and flight direction as well as terrain features. Usually, it amounts to a few meters only. Anemophilic and generalist species suffer from a more intense pollen waste than do specialists, but compensate for it by high pollen/ovule ratios. Habitually sparse species are pollinated by trapliners or benefit synergistically from the presence of a similar dominating species. Synergism by vicariating flowering times secures the continuity of a common pool of polylectic pollinators. An oligolectic pollinator’s dependency of certain flowers is often more obligatory than vice versa. Establishment of species with specialized flowers requires additional prerequisites for the existence of respective oligolectic pollinators: nectar and pollen in due proportion, nesting facilities, foodplants or prey for the larvae, climatic conditions, etc. These dependencies and minimum population sizes are critical factors for the survival of a biocenosis.