Protective floral structures may evolve in response to the negative effects of floral herbivores. For example, water calyces—liquid-filled, cup-like structures resulting from the fusion of sepals—may reduce floral herbivory by submerging buds during their development. Our observations of a water-calyx plant, Chrysothemis friedrichsthaliana (Gesneriaceae), revealed that buds were frequently attacked by ovipositing moths (Alucitidae), whose larvae consumed anthers and stigmas before corollas opened. Almost 25% of per-plant flower production was destroyed by alucitid larvae over two seasons, far exceeding the losses to all other floral herbivores combined. Experimental manipulation of water levels in calyces showed that a liquid barrier over buds halved per-flower alucitid egg deposition and subsequent herbivory, relative to buds in calyces without water. Thus, C. friedrichsthaliana’s water calyx helps protect buds from a highly detrimental floral herbivore. Our findings support claims that sepal morphology is largely influenced by selection to reduce floral herbivory, and that these pressures can result in novel morphological adaptations.
The benefits of bathing buds: water calyces protect flowers from a microlepidopteran herbivore
Publication: Biology Letters