Arctic and alpine ecosystems have been found to be highly susceptible to changes in global climate trends. It is therefore important to study both the plants and the pollinators within these vulnerable ecosystems in order to best hypothesize how their mutualistic relationships may be affected by predicted, future climates. Pedicularis groenlandica (Orobanchaceae) is a nectarless, buzz-pollinated flower that is often found in wet habitats from the montane into the alpine of the western U.S. With these characteristics, this species may serve as a model species for examining the impacts of climate change on plant-pollinator interactions. Our project was conducted in the summer of 2016 with a population of P. groenlandica on Pennsylvania Mountain (Alma, Colorado). The two main goals of this study were to, first, fill in some of the gaps in our understanding of the reproductive strategies of this species. This was investigated with hand-pollination treatments in the field. Second, this project tested the technique of bioacoustic monitoring as a means of detecting pollinator visits. Microphones were used to record the acoustics of bumblebee flight buzzes in order to see how the number of buzzes within a patch of flowers related to the seedset of those flowers.
Results/Conclusions
Through various pollination treatments, it was found that pollen may be limiting to the seedset of these flowers. Flowers that were hand-pollinated with extra, out-crossed pollen tended to have more mature fruits and slightly heavier seeds than those which were pollinated by bees alone. While other environmental factors may be limiting the reproductive output of these plants, pollen may specifically be limiting the number of fruits that mature and the weight of the subsequent seeds. It was also found that the height of an inflorescence predicted the ratio of mature fruits to total fruits on that plant. This finding may be a result of reproductive allocation within the plant or it may be related to pollination efforts. When controlled for factors of visibility (such as the number of inflorescences within the patch), the number of recorded buzzes predicted the average seed weight of the flowers within that patch. With more work, this technique of bioacoustic monitoring could be applied to a broad range of pollination studies. P. groenlandica is a useful model plant for these studies due to the possibility of recording and quantifying pollinator visitations via the acoustics of flight buzzes as well as (potentially) pollination buzzes.