Abstract
Insect-pollinated carnivorous plants are expected to have higher fitness if they resolve pollinator-prey conflicts by sparing insects pollinating their flowers while trapping prey insects. We examined whether separation between flowers and traps of the carnivorous sundew species or pollinator preferences for colours of flowers enable these plants to spare pollinators. In addition, we collected odours from flowers and traps of each carnivorous species in order to identify volatile chemicals that are attractive or repellent to pollinators and prey insects. In Drosera spatulata and D. arcturi, no volatiles were detected from either their flowers or traps that could serve as kairomone attractants for insects. However, behavioural experiments indicated white colour and spatial separation between flowers and traps aid in reducing pollinator entrapment while capturing prey. In contrast, D. auriculata have flowers that are adjacent to their traps. In this species we identified chemical signals emanating from flowers that comprised an eight-component blend, while the plant’s traps emitted a unique four-component blend. The floral odour attracted both pollinator and prey insects, while trap odour only attracted prey. This is the first scientific report to demonstrate that carnivorous plants utilize visual, spatial, and chemical signals to spare flower visitors while trapping prey insects.
Highlights
Pollinators and lessen the pollinator-prey conflict[9,10]
The flower-trap separation in D. spatulata was the greatest followed by D. arcturi and D. auriculata, respectively (Fig. 2)
In spite of differences in spatial separation between flowers and traps in the three species, only a small proportion of flower visitors were caught in traps of each species
Summary
Anderson[11] found no pollinators were captured by two Drosera species with either long or short scapes, and flowers on long scapes attracted more insect visitors than flowers on short scapes. He proposed that sundew have evolved long scapes as an adaption to place their flowers in the flight path of pollinators rather than to protect them from traps. Most plants attract insects to flowers for pollination with visual and olfactory cues[14,16], and there would be strong selection pressure for competing carnivorous and non-carnivorous plants to have evolved similar means for attracting pollinators. We hypothesized there may be qualitative and quantitative differences in the volatiles between flowers and traps, perhaps in conjunction with visual and spatial mechanisms, that elicit different responses of pollinators and prey to traps and flowers, and optimize fitness for carnivorous plants and their pollinators
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