Mechanisms that improve prey richness in carnivorous plants may involve three crucial phases of trapping:attraction, capture and retention. Nepenthes rafflesiana var. typica is an insectivorous pitcher plant that is widespread in northern Borneo. It exhibits ontogenetic pitcher dimorphism with the upper pitchers trapping more flying prey than the lower pitchers. While this difference in prey composition has been ascribed to differences in attraction,the contribution of capture and retention has been overlooked. This study focused on distinguishing between the prey trapping mechanisms, and assessing their relative contribution to prey diversity. Arthropod richness and diversity of both visitors and prey in the two types of pitchers were analysed to quantify the relative contribution of attraction to prey trapping. Rate of insect visits to the different pitcher parts and the presence or absence of a sweet fragrance was recorded to clarify the origin and mechanism of attraction. The mechanism of retention was studied by insect bioassays and measurements of fluid viscosity. Nepenthes rafflesiana was found to trap a broader prey spectrum than that previously described for any Nepenthes species,with the upper pitchers attracting and trapping a greater quantity and diversity of prey items than the lower pitchers. Capture efficiency was low compared with attraction or retention efficiency. Fragrance of the peristome,or nectar rim,accounted mainly for the observed non-specific, better prey attraction by the upper pitchers, while the retentive properties of the viscous fluid in these upper pitchers arguably explains the species richness of their flying prey. The pitchers of N. rafflesiana are therefore more than simple pitfall traps and the digestive fluid plays an important yet unsuspected role in the ecological success of the species.
Summary1. Nepenthes rafflesiana is a carnivorous vine from Borneo characterized by an ontogenetic pitcher dimorphism with aerial (upper) and ground (lower) pitchers of different morphologies. Previous studies have shown that fragrant upper pitchers of climbing parts of the plant are more effective in trapping flying insects than non-fragrant lower pitchers, which are essentially restricted to an ant diet. We tested the hypotheses that odours are effective cues for prey attraction in this carnivorous plant and that upper pitchers biochemically mimic flowers in their olfactory cues. 2. The visitor diversity and the scent composition of each pitcher type were determined for different sites and periods during field studies in Borneo. Olfactometer bioassays were conducted using fruit flies and ants as models for flying flower-visitors and non-flying visitors, respectively. 3. Fifty-four volatile compounds were identified and the analysis of their relative quantities in the blends showed significant differences between pitcher types. The blends of lower pitchers contained some aliphatics and terpenoids but were poor in benzenoids. Upper pitchers differed from lower ones in that they attracted a greater quantity and diversity of insects, including a guild of flower-visitors absent from the visitor spectrum of lower pitchers. Upper pitchers also emitted a greater quantity of odours and a larger spectrum of volatiles, including some terpenoids and benzenoids that often characterize the sweet scents classically found in flower blends. Choice bioassays showed that, in absence of any visual cue, the scents of the nectariferous pitcher rim (peristome) were particularly attractive to ants and flies, and those of upper pitchers were more attractive to flies than those of lower pitchers. 4. Synthesis. This study demonstrates the use of scent by Nepenthes carnivorous plants to mediate prey attraction. The climbing part of the plant produces pitcher-modified leaves that mimic flower olfactory cues and suggest an evolutionary convergent strategy with that of generalist pollination systems.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.