The Clarkia of the Kern Canyon are interesting because they share a group of specialist bee pollinators which are necessary for outcrossing and reproduction. The pollinators are specialists on the genus, but we do not know the extent to which the pollinators specialize on any one species. How Clarkia share pollinators is important for understanding the negative effects that plants can incur when living in communities of congeners (via heterospecific pollen transfer) versus the positive effects (via joint attraction of pollinators). To understand the level of meaningful pollinator sharing that happens in Clarkia communities, I am estimating pollinator constancy, or the amount of switching between Clarkia species, and pollinator preference, or the relative amount that they visit each Clarkia species, by quantifying the amount of each species of Clarkia pollen I captured in Clarkia communities with various species composition.
Though not often studied, the relationship between plant diversity, abundance, and pollinator foraging choice is important for understanding how diversity in biotic communities is generated and sustained in the two interdependent guilds of plants and pollinators. In this study, I ask if Clarkia benefit from joint pollinator attraction because they are in abundant communities, high-diveristy communities, or both. In the summers of 2015 and 2016, I set up experimental arrays of plants wherein I vary both Clarkia richness and abundance and observe the amount of pollinators that visit, as well as their visitation patterns while in the experimental patch.
Pollinator Sharing and Coexistence
A key for incorporating pollinator sharing into coexistence theory is to determine the extent to which it changes the competitive interactions between plants. To do so, competition between plants must be measured before and after being exposed to pollinators. In this experiment, I will be measuring the effect that pollinators have on Clarkia interactions by measuring the pre- and post- pollination performance of Clarkia plants in meter-squared experimental plots that I seeded in the fall of 2016.
Most empirical studies of coexistence in plant communities estimate the probability of coexistence by measuring the per-capita effects of competition in small experimental neighborhoods or averaging per-capita effects over large areas, leaving spatial heterogeneity out of the coexistence picture. In this project slated for summer 2018, I explore the spatial component of coexistence in four species of Clarkia by measuring how each species' fitness changes with: 1. the location on the landscape and 2. the density and richness of their local Clarkia neighborhoods.