Pollination, Predation and Seed Set in Linaria vulgaris (Scrophulariaceae)

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Abstract
L. vulgaris, a self-incompatible perennial herb, has a complex of adaptations related to insect-pollination. These include: the production of conspicuous yellow flowers, each with a bright orange palate, arranged in vertical inflorescences of 15-20 flowers; the production of multiple inflorescences by individuals. These flower in a staggered, but temporally overlapping, sequence suggesting a trade-off between maximum showiness and maximum blooming period; the production of nectar containing 37% sugar, as sucrose equivalents. Despite these adaptations, however, L. vulgaris has low seed set when compared to most other self-incompatible perennials that have been studied. The success of ovules declined from .apprx. 1.6% in early Aug. (the height of the season for this species) to .apprx. 0.3% in early September, although individuals continued to produce new flowers until the end of Sept. The declining seed set occurred at a time when pollinator activity was declining. Predispersal seed predation by insect larvae was important in limiting seed set. Heavy predation of ovaries, however, made it difficult to assess the relative importance of pollinator availability as an additional limiting factor.