Many organisms use multiple signals to attract conspecifics, mutualists or prey. For example, flowering plants may use both visual and olfactory cues to entice pollinators. As maintaining signals is costly, having multiple signals must bring benefits. A study published in Functional Ecology shows that two distinct mechanisms explain multiple signalling by the pitcher plant Sarracenia purpurea. Sylvie Martin-Eberhardt and colleagues tested whether multiple signals make these carnivorous plants better at capturing certain prey, able to capture a wider range of prey, or both. They set up a controlled experiment, replicated at four sites, using centrifuge tubes modified to capture and retain insects, with all combinations of up to three cues expected to attract prey: volatile organic compounds, red venation and nectar. Comparisons with real pitcher plants indicated that the model plants were realistic enough to attract typical prey species. Volatile compounds appeared to have no role, whereas both nectar and (to a lesser extent) red venation independently increased prey capture. Both signals attracted a wider range of arthropods as well as more individuals of a key prey species (the ant Myrmica lobifrons), and their combination maximized both measures of prey capture. These findings indicate that maintaining two signals helps the pitcher plants to attract a wider audience and to increase the probability of reaching an important receiver. This study illustrates how rigorous experimental design and a bit of creativity can overcome challenges in testing mechanistic hypotheses.
Original reference: Funct. Ecol. https://doi.org/10.1111/1365-2435.70239 (2025)
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