Multiple signalling increases both prey response and diversity in a carnivorous pitcher plant

Abstract Organisms across the tree of life use multiple signals such as colour, movement sound, and many types of chemical signals to convey seemingly the same information. These signals are potentially costly, yet the repeated evolution of multiple signalling across systems suggests an adaptive value. Using prey attraction by a carnivorous pitcher plant ( Sarracenia purpurea ), we tested two non‐mutually exclusive hypotheses of how multiple signalling may be adaptive: (1) the receiver variability hypothesis that different signals reach different receivers, increasing the diversity of the receiver response and (2) the redundant signal hypothesis that additional signals increase the probability of signal transmission to relevant receiver(s). We used artificial pitcher plant models with red coloration, nectar and volatile organic compound signals to examine both the receiver variability and redundant signal hypotheses in a manipulative, full factorial field experiment in S. purpurea native habitat. Like pitcher plants, models captured visiting arthropods, which pitcher plants digest to cope with nutrient‐poor bog soils. We found support for both the receiver variability and redundant signal hypotheses; both colour and nectar additively increased prey diversity, as well as increased the capture of the bog specialist ant Myrmica lobifrons . Our results suggest that increasing both signal redundancy and diversity of respondents is a substantial benefit that balances the costs of multiple signalling. Read the free Plain Language Summary for this article on the Journal blog.