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Pollination by a Guild of Fluctuating Moth Populations: Option for Unspecialization in Silene Vulgaris
M. W. Pettersson
Journal of Ecology
Vol. 79, No. 3 (Sep., 1991), pp. 591-604
Published by: British Ecological Society
Stable URL: http://www.jstor.org/stable/2260655
Page Count: 14
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(1) The pollinating efficiency of moths was examined during four seasons by counting the number of pollen grains that individual moths deposited on the stigmas of virgin female flowers of Silene vulgaris. (2) Experimental pollination showed that c. 150 pollen grains per flower were required to achieve the average natural full seed-set in the plant population. Although 57% of the flower-visiting moths deposited pollen, only about 10% of the moth visits delivered ⩽ 150 pollen grains in one visit to virgin female flowers, indicating that seed-set usually originated from multiple pollinator visits. (3) Pollen receipt indicated pollination by a guild of noctuid and sphingid moths. The abundance of the dominating pollinator species varied strongly between years. (4) Most species deposited about the same mean number of pollen grains, although they were taxonomically diverse and had different flower-visiting behaviours and proboscis lengths. Even noctuid moths of the genus Hadena, known as associated larval seed predators of S. vulgaris, were not especially frequent or efficient pollinators despite the fact that these moths influence their larval food resource through pollination. (5) The annual and seasonal variation in abundance among pollinator species and lack of variation in pollination efficiency among them are factors which counteract specializational trends and control evolutionary retention of plastic and unspecialized floral traits in S. vulgaris. They thereby provide an option for opportunistic responses in this species.
Journal of Ecology © 1991 British Ecological Society