Interactions between species are strong drivers of both diversification and maintenance of biodiversity. According to the geographic mosaic theory of coevolution, an interaction between the same species pair can have different outcomes when occurring in different environments. Several recent studies indicate that a key factor affecting the coevolutionary outcome is the local species community composition. For example, the interaction between Woodland Star plants (Lithophragma spp., Saxifragaceae) and the highly specialized nursery pollinator Greya politella (Prodoxidae) can be affected by the local presence of other Greya species. In some populations of the species L. parviflorum, high abundance of co-pollinators also affects the interaction, because the plants in these populations are no longer depending on the nursey pollinator for reproduction. In the remaining Greya-pollinated Lithophragma species, however, the plant-moth interaction has traditionally been considered a close to obligate mutualism. Therefore, it is interesting that recent data report tremendous among- and within-species variation in several floral traits important for Greya moth attraction. This contrasts with predictions from coevolutionary theory, which suggest that selection should act stabilizing on traits important for tight mutualisms in stable environments. Here, I investigate whether spatial variation in the presence of co-pollinators could help explain this variation, focusing on the species L. bolanderi. To do this, I utilize that G. politella oviposition leave readily detectable traces in the Lithophragma capsules. This unique feature provides the possibility to score the contribution of G. politella oviposition to pollination post-flowering. In total, I collected developing capsules from nine L. bolanderi populations distributed across its Sierra Nevadan range to investigate the importance of G. politella versus co-pollinators for seed set. In addition, using two of these populations, I first conducted laboratory pollination efficacy experiments to determine the Greya moth contribution to pollination during nectaring. Second, I conducted repeated flower visitor observations to assess among-population variation in visitation rate by Greya moths and more generalized pollinators. Together, my results show (i) that the importance of G. politella pollination varies dramatically among L. bolanderi populations, (ii) that nectaring Greya moths are probably only weakly contributing to pollination, and (iii) that the contribution to pollination by generalist co-pollinators, such as solitary bees, is spatially variable and may outweigh the pollination by G. politella in some populations. This suggests that the large among-population variation in the floral display traits of L. bolanderi could be generated in a selection mosaic of populations relying to different extents on pollination by G. politella and more generalized co-pollinators.