Summary Small and low‐density populations often suffer significant reductions in reproduction, as exemplified by studies on rare and threatened species. While this phenomenon is less studied in common species, if general, it should not be restricted to those in peril. We addressed this assertion by examining the effects of plant abundance, measured at population‐level (population size, density) and local‐level (local neighbourhood size, LNS) spatial scales, on fruit set, seed set and subsequent reproductive success (RS) across 19 natural populations of the widespread biennial Sabatia angularis (Gentianaceae). We also examined stigmatic pollen loads across a subset of populations to address whether changes in reproduction were related to reduced pollination. Effects of plant abundance on reproduction were evident at both spatial scales. At the population level, population size – but not density – affected fruit set significantly. This effect was non‐linear. Fruit set in populations larger than 15 individuals was relatively constant, but dropped abruptly in populations below that size. This relationship did not prevail between population size and RS. Instead, RS declined significantly with population density. At the local level, increases in LNS between 1‐m and 4‐m radii from study plants increased fruit set significantly. In contrast, increases within 1 m significantly reduced seed set. Both of these effects prevailed at different spatial scales for RS; increases in 1‐m LNS reduced RS, but increases beyond that distance and within 4 m increased RS. Although non‐significant, trends in the data are consistent with facilitative interactions for pollination influencing local‐level effects on fruit set. However, negative interactions, presumably because of competition for resources, are more important for determining seed set at local scales. Both interactions influence RS, but the effect of competition appears to dominate at the population level. Synthesis . This study demonstrates that although significant ...