A model tallgrass prairie plant, Echinacea angustifolia, grows in small, isolated patches of varying size and shape. Echinacea is pollinated by solitary bees with diverse foraging ranges. Reproductive success is influenced by mating opportunity, which depends on the flowering synchrony of potential mates. However, we do not understand which potential mates are spatially connected. Here, we define Echinacea clusters using a connection distance, d. If an individual has neighbors within d, they are in the cluster, and neighbors of those plants that are within d are also included. (1) How does phenological synchrony within clusters vary with d? (2) How do cluster characteristics such as size (number of plants), area, and shape (longest length of cluster) depend on d? We used a 3-year dataset including precise spatial coordinates, and first and last day of flowering for 2836 flowering Echinacea individuals within a 6400 ha study site in western Minnesota. We calculated synchrony using Augspurger’s method (1983).
Results/Conclusions
Flowering synchrony is lower in clusters defined by larger d (p = 0.03). From the pollinator’s perspective, bee species with smaller foraging distances experience more synchronously flowering clusters of Echinacea and more variation in synchrony, while bee species with larger foraging distances experience less synchronously flowering clusters. Lower synchrony at larger d may result from clusters encompassing heterogeneous environments or genetically differentiated patches. d is also highly correlated with number of plants, area, and length per cluster. These findings indicate that the scale defining clusters determines interpretation of synchrony, a general phenomenon that affects mating opportunities.