Abstract
Most flowering plants are colour monomorphic, while within-population flower colour variation is rare. Multiple selection agents on flower colour, each favouring a different colour morph, may drive such uncommon polymorphisms. We tested the role of biotic antagonistic interactions in maintaining flower colour variation in Anemone coronaria (Ranunculaceae), in colour-polymorphic populations comprised of red, purple, and white flowers. We estimated the extent of leaf herbivory and petal florivory in each flower colour morph in three populations over two flowering seasons. We categorized types of damage to four groups of herbivores and estimated the plant maternal fitness. We tested pollinator response to different levels (0-30%) of simulated florivory in experimental flower arrays. Leaf and petal damage did not differ between white- and purple-flowering plants. Red-flowering plants had higher leaf damage than white-flowering plants and higher petal damage than purple-flowering plants. Nevertheless, all colour morphs had similar fitness. Red flowers exhibited more petal scratches (attributed to glaphyrid beetles), but fewer petal bites (attributed to caterpillars or grasshoppers), than white and purple flowers. Experimentally induced florivory did not reduce visits by potential pollinators in any colour morph. Glaphyrid beetles are the major pollinators of red anemone flowers, suggesting that their service to red flowers as mutualists (pollinators) should be weighed against their disservice as antagonists (florivores). A balance between pollination service and petal scratch damage of red flowers, both mediated by Glaphyird beetles, may equalize fitness between the red and the purple/white colour morphs, contributing to colour polymorphism.