Consistency in floral volatiles impacts plant-pollinator interactions in the face of environmental change in the Eastern Himalayas

Abstract

Floral scents are an important mediator of many plant-pollinator interactions. However, environmental and ecological change could affect the synthesis and emission of volatile chemicals that constitute floral scents, potentially influencing pollinator perception of scents. We investigated the effects of elevation and warming on the floral scents of multiple co-occurring alpine meadow plant species along an elevational gradient in the Eastern Himalayas (3000 - 4000 masl). We also investigated pollinator responses in the same locations using 3-D printed floral models that replicated the differing volatile constituents. Finally, we assessed how pollinator preferences changed with variations in elevation, flowering season and location. We found that elevation and in-situ warming using Open Top Chambers (OTC) led to significant intraspecific variation in the composition of floral scents, both in terms of quality and quantity of volatiles released. Nevertheless, conspecific floral scents across elevations were more similar to each other than to other species. Cafeteria assays using artificial floral models revealed that pollinator preferences were driven by a small number of volatiles (p-cymene, 2-pentylfuran and -pinene), but these preferences were abolished in a novel plant-pollinator community where the same floral volatiles were not detected. Our results suggest that the local odourscape established by the floral community present plays a key role in plant-pollinator interactions. This emphasizes the need to incorporate ecological impacts such as changes in community into climate change analyses to understand the long-term impacts of human activity on co-evolutionary relationships like pollination. Significance StatementFloral scents are important for most plant-pollinator interactions, and can be affected by environmental factors like elevation and temperature. Our study shows that elevation and simulated in situ warming change the composition of floral scents, yet scents from the same species were more similar to each other across elevations and temperatures than to other species. Further, pollinator preferences to these scents replicated in artificial models persisted in spite of variation in temperature and elevation, but not in a novel plant-pollinator community containing floral species not releasing those volatiles. This emphasizes the need to incorporate factors such as floral community composition into our understanding of the long-term impacts of climate change and human activity on co-evolutionary relationships like pollination.