The importance of floral signals in the establishment of plant-ant mutualisms

摘要

Visual and olfactory floral signals are essential for the establishment of plant-pollinator mutualisms. Different batteries of floral features attract different pollinators and may achieve specific relationships that are essential for the immediate plant reproductive success, and at an evolutionary time scale have been of vital importance in the radiation of Angiosperms. We have found that mutualistic services by ants, insects traditionally considered ineffective pollinators, are essential for the pollination of Cytinus hypocistis (Cytinaceae), a Mediterranean root holoparasitic plant. Diverse floral signals, mainly nectar characteristics and floral scent could be playing a key role in the attraction of different species of ants, which pollinate effectively the flowers. Surprisingly, the abundance of other insects foraging in this parasite was very low and, although this scarcity could be due in part to the presence of ants, we suggest that different floral features exhibited by C. hypocistis couldbe evolving for attracting ants. Based on some current findings, we suspect that the study of floral signals in Cytinaceae is critical in the understanding the divergence of pollination systems in this fascinating family of parasitic plants.