TY - JOUR T1 - Floral humidity as a signal – not a cue – in a nocturnal pollination system JF - bioRxiv DO - 10.1101/2022.04.27.489805 SP - 2022.04.27.489805 AU - Ajinkya Dahake AU - Piyush Jain AU - Caleb Vogt AU - William Kandalaft AU - Abraham Stroock AU - Robert A. Raguso Y1 - 2022/01/01 UR - http://biorxiv.org/content/early/2022/04/29/2022.04.27.489805.abstract N2 - Although visual and olfactory floral signals attract pollinators from a distance, at the flower’s threshold, pollinators can use floral humidity as an index cue for nectar presence. We evaluate the role of floral humidity in the Datura wrightii-Manduca sexta nocturnal pollination system. In addition to our finding that M. sexta shows strong innate attraction toward humid flowers, we identify the hygrosensing sensillum on their antennae, demonstrate its extreme sensitivity to minute changes in RH, and observe the elimination of moths’ behavioral preference towards humid flowers following experimental occlusion of the sensilla. Despite Manduca’s attraction toward humid flowers, we find that floral humidity is not a reliable cue for nectar presence in this system. While Datura floral headspace sustains an enormous humidity gradient, it is not a consequence of nectar evaporation, but an outcome of gas exchange through floral stomata and is decoupled from nectar presence. Using interdisciplinary tools, we demonstrate the function of floral humidity as an attractive signal, not a cue, in this pollination system, thus showcasing an underappreciated modality by which flowers may manipulate their visitors.Competing Interest StatementThe authors have declared no competing interest. ER -