Uncovering plant-pollinator interactions and breeding systems of native Brazilian species in Tigridieae (Iridaceae)

Iridaceae is one of the largest families of monocots and possesses species with a wide range of flower colors and shapes, which may serve as signals to pollinators. Several South American species of Iridaceae, especially those of Tigridieae, produce floral oils as rewards and are pollinated by oil-collecting bees. The present study aimed to contribute to a deeper understanding of the reproductive biology, pollination ecology and specialization level of interactions of species encompassed in Tigridieae. Data were acquired from breeding and pollination systems of six species native to Southern Brazil. Visitation frequency and pollen load of two functional groups of bees were also investigated. The results strongly suggest that the studied species are distributed along a specialization-generalization continuum. Three oil-producing taxa, namely Cypella herbertii, C. pusilla and C. amplimaculata were pollinated by oil-bees, while in the other two studied species, namely Kelissa brasiliensis, Herbertia pulchella, oil-bees presented a surprisingly distinct behavior which indicate a possible failure as pollinators during oil foraging. New insights into aspects of the pollination systems and breeding systems in this tribe are provided and a continuum of specialization is suggested. This continuum of specialization resulted from the differences in pollinator behavior during oil and pollen foraging at the species studies. Furthermore, the results provide a significant contribution towards a better understanding of specialized plant-pollinator interactions between Iridaceae and oil-collecting bees.