Asynchronous Diversification in a Specialized Plant-Pollinator Mutualism

• Published in: Science (American Association for the Advancement of Science) 2011-09, Vol.333 (6050), p.1742-1746
• Main Authors: Ramírez, Santiago R., Eltz, Thomas, Fujiwara, Mikiko K., Gerlach, Günter, Goldman-Huertas, Benjamin, Tsutsui, Neil D., Pierce, Naomi E.
• Format: Article
• Language: English
• Subjects: Angiosperms; Animal and plant ecology; Animal, plant and microbial ecology; Animals; Autoecology; Bees; Bees - anatomy & histology; Bees - classification; Bees - genetics; Bees - physiology; Biological and medical sciences; Biological Evolution; Coevolution; Ecosystem; Evolutionary biology; Extinction, Biological; Female; Flowers - anatomy & histology; Fossils; Fundamental and applied biological sciences. Psychology; Genera; Genetic Speciation; Genetics of eukaryotes. Biological and molecular evolution; Insect genetics; Insect pollination; Insect reproduction; Male; Male animals; Molecular Sequence Data; Mutualism; Odorants; Orchidaceae; Orchidaceae - anatomy & histology; Orchidaceae - classification; Orchidaceae - genetics; Orchidaceae - physiology; Phylogenetics; Phylogeny; Plant ecology; Plant reproduction; Plants and fungi; Pollinating insects; Pollination; Protozoa. Invertebrata; Selection, Genetic; Specialization; Symbiosis
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.1209175

Most flowering plants establish mutualistic associations with insect pollinators to facilitate sexual reproduction. However, the evolutionary processes that gave rise to these associations remain poorly understood. We reconstructed the times of divergence, diversification patterns, and interaction networks of a diverse group of specialized orchids and their bee pollinators. In contrast to a scenario of coevolution by race formation, we show that fragrance-producing orchids originated at least three times independently after their fragrance-collecting bee mutualists. Whereas orchid diversification has apparently tracked the diversification of orchids' bee pollinators, bees appear to have depended on the diverse chemical environment of neotropical forests. We corroborated this apparent asymmetrical dependency by simulating co-extinction cascades in real interaction networks that lacked reciprocal specialization. These results suggest that the diversification of insect-pollinated angiosperms may have been facilitated by the exploitation of preexisting sensory biases of insect pollinators.