One of the most ubiquitous signals of climate change across ecosystems is the changing of life event timing or phenology. When species interactions depend on synchronous phenology, anthropogenic ecosystem change may induce phenological mismatch. Uncoupling of abiotic cues governing pollinator activity and plant blooming may disrupt pollination network structure and function. While several studies have experimentally altered phenology in one or a few species (both pollinators and plants), we are unaware of any work that has manipulated phenology at the whole-network level. We conducted a pilot assessment of the effects of snowmelt acceleration on network structure and functioning (plant seed production) of pollination networks. We experimentally accelerated timing of snowmelt within three pairs of accelerated and control plots (each plot 10 x 14m) at the Rocky Mountain Biological Laboratory, Colorado, USA. We assessed fine scale plant and pollinator phenology weekly. In addition, we constructed plant-pollinator networks based on floral visitation within each plot and compared key network structural metrics such as specialization and nestedness for each paired site. Lastly, we assessed pollinator-dependent seed production with hand pollination experiments.
Results/Conclusions
We were able to experimentally accelerate snowmelt timing by two weeks within all manipulated plots. Fine resolution results on flower phenology are still under analysis but snowmelt manipulations led to accelerated flowering phenology in two of three sites. We found idiosyncratic effects on network structure. Specialization (H2’) increased with snowmelt acceleration in all 3 sites. Pollinator identification is still underway and many groups are currently identified only to gross category. Network level metrics may be sensitive to taxonomic resolution. We found increased seed production in Delphinium nuttalianum in accelerated plots, which was contrary to our predictions. This may have been due to an unseasonably dry June that flowers in the accelerated plots avoided. Plant-pollinator networks are thought to be buffered to future climate change because of network structural components that lend robustness to species loss. However, it is unclear if these network metrics are sensitive to phenological mismatch. This is the first assessment on the community level that we are aware of investigating the impact of phenological mismatch on network structure.