Neutral or Asymmetric Dispersal? Exploring the relationship between microbial communities in adjacent flowers of Sticky Monkeyflower

Dispersal, the spread of individuals from one community to a new environment, is a key factor in the assembly of metacommunities, sets of communities linked by dispersal. In the sticky monkeyflower plant, Diplacus aurantiacus, microbes that inhabit floral nectar are dispersed by hummingbirds and insects, continuously leading to the establishment of microbial communities in new, blooming flowers. This may create similarity and persistence in the types of microbial communities that occur in these plants, considered as metacommunities. However, at the scale of pairs of adjacent flowers, the relationship between the microbial communities of these flowers has not been directly studied. Moreover, the role of bacteria and yeast in differing pollinator nectar preferences is well-documented in D. aurantiacus, but it is uncertain how the dominant nectar microbial community present impacts dispersal to nearby flowers. Additionally, it is uncertain how similar the microbial communities of adjacent flowers are. Through a field experiment at the Stanford Dish trail, this project explores the relationship between pairs of adjacent flowers, inoculating either bacteria, yeast, or a sham control into the nectar of one flower in a pair. Comparing the types of microbial communities present in each flower by using nectar pH as a proxy, the data provides support for similarity of microbial communities of adjacent flowers. Moreover, it is difficult to conclude that the linkage between flowers was altered by the type of inoculation, suggesting that the dispersal of microbes at this scale tends to be neutral. This finding, although limited by its spatial scale, contributes to our understanding of how plant-pollinator interactions promote metacommunity assembly and how these interactions can lead to other observed patterns of a population’s spatial distribution. Furthermore, if this relationship between adjacent flowers is able to expand beyond the flower-pair scale, there could be downstream effects on the health of the overall plant and/or patches of plants.