With warming temperatures and altered precipitation regimes, among other components of climate change, we anticipate numerous effects on plant-pollinator interactions through both direct and indirect pathways. One understudied pathway by which climate change may alter plant-pollinator interactions is via shifts in floral scent and pollinator attraction. Over three years, we sampled the floral volatile organic compounds (VOCs), phenologies, and pollinator visitors from naturally-growing plants in a montane meadow in order to acquire a base understanding of how floral VOCs and other plant traits may structure plant-pollinator interactions across the growing season.
We hypothesized that floral VOCs would influence interactions with pollinators and influence community-wide dynamics. We expected floral species with floral VOCs that were original (far from the community mean) and unique (far from the nearest neighbor) would have few pollinating partner (i.e., specialists), while forbs with non-original floral VOCs would form the generalist core. We expected the degree of overlap of forb species in floral VOC trait space would contribute to the degree of nestedness in plant-pollinator interaction network structure across the growing season and across years. We expected additional seasonal dynamics, with floral VOC functional diversity correlating with species diversity in the community, peaking in mid-summer.
Our preliminary results indicate that floral VOC richness was positively correlated to the richness of bee visitors, except for the most abundant forb species in this community (i.e., Potentilla, Geranium, and Arnica). These patterns suggest a strong influence of floral VOCs on pollinator attraction as well as the potential for trade-offs among plant traits (e.g., floral display size) in structuring plant-pollinator interactions. Second, forbs varied in the originality, uniqueness, and dispersion of floral VOCs, indicating the potential for different functional roles in plant-pollinator networks. Interestingly, both very specialist and very generalist plants (i.e., very few or very many floral visitors, respectively) often produced original scents, but only very specialist plants produced unique scents. Plants with intermediate levels of floral visitors produced scents that were frequently close to the community mean (un-original). Third, species blooming in early spring emitted small amounts of similar VOC blends containing generalist attractants (e.g., benzaldehyde), whereas VOC abundance and complexity was highest in midsummer. We highlight implications of these results for plant-pollinator interactions across the growing season and as phenologies shift due to climate change.