Both flowering time and distance to conspecific plants affect reproduction in Echinacea angustifolia, a common prairie perennial

1. In small fragmented plant populations, reproductive failure due to pollen limitation is often attributed to spatial isolation of individuals. While flowering time has been shown to affect seed set, its role in pollen limited fragmented populations is less understood. 2. In this study, we quantified near-neighbour distances, flowering phenology, and how they interact to affect seed set in individual plants. We followed the daily flowering phenology of over 2,400 heads on over 500 Echinacea angustifolia individuals and quantified the resulting seed set during three consecutive flowering seasons. The study was conducted in an experimental plot where we randomised planting locations to eliminate spatial patterns of mate availability which are common in fragmented populations of Echinacea, a self-incompatible plant. 3. We found that individual flowering time had a larger and more consistent effect on seed set than did spatial location. Seed set in the earliest flowering plants exceeded se...