While Prosopanche (Hydnoraceae) flowers gently heat: mutualistic pollination relationships among the perianth-bearing Piperales

ROCAMUNDI, N.; ARCE MILLER, M; MAUBECIN, CC; MARTEL, C; MORÉ, M; MARVALDI, AE; COCUCCI, AA

BOTANICAL JOURNAL OF THE LINNEAN SOCIETY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2023

0024-4074

Flowers of most Piperales do not reward pollinators. However, a few mutualistic pollination relationships have been proposed among perianth-bearing species. To test the hypothesis of a mutualistic relationship between Prosopanche and their beetle pollinators, we studied the pollination biology of three species (P. americana, P. bonacinae, P. panguanensis). We recorded flower visitors and flower volatile organic compounds (VOCs), and only for P. americana we also investigated flower phases, thermogenesis, visitors´ behaviour and viability of transported pollen. Using a behavioural experiment, we identified the role of flower heat and fragrance in pollinator attraction. We recorded two sap beetle species (Nitidulidae) as main pollinators and two weevil species (Belidae) as occasional pollinators of Prosopanche. Thermogenic female flowers heat up to 8ºC above the ambient temperature. Flowers only trap the small-sized sap beetles in the stigmatic chamber. The VOC profile was dominated by methyl-3-methyl-2-butanoate. This was a powerful attractant for sap beetles in controlled bioassays. We conclude that pollination in Prosopanche is mutualistic. It is observed through a pollinator-size-based access limit to the stigmatic chamber and a strong olfactory attractant. Mutualism in Prosopanche therefore contrasts with that of most perianth-bearing Piperales, suggesting it is a novel pollination relationship in early-diverging angiosperms.