Flowering segregation and pollinator distinctiveness contribute to coexistence in an extremely generalist plant group

ABSTRACT Background Flowering time determines potential plant mates, and it is related to gene flow within and among plant populations arising from different selective forces and interspecific interactions between plants with similar pollination niches. However, these effects on the flowering phenology of plants with generalist pollination systems have received little attention and hence our knowledge of the contribution of generalised pollination systems on the evolution of adaptative traits, such as the flowering time containing lacunae. Aims To verify the effective contribution of interspecific plant interactions in a generalised pollination system to the structuring of flowering phenology. Methods We recorded the reproductive phenophases of four Baccharis species in a subtropical grassland. We evaluated their flowering patterns by a niche overlap index and compared it with a null model. We used ecological network metrics from insect visitors recorded to determine the pollinator network structure. Results A staggered flowering pattern and distinctiveness of insect pollinators with non-signalling modularity and a variation in the Baccharis-pollinators network structure throughout the year were observed. The distinctiveness on pollinators with a strong bee-dependence added to temporal divergence on flowering among the species leads to no negative effects on fruit set. Conclusion The temporal segregation on flowering peaks and low pollinator similarity appear to underlie to coexistence of Baccharis species studied in southern Brazil.