ReviewBiology of the Neotropical orchid genus Catasetum: A historical review on floral scent chemistry and pollinators

- Pollinators of more than 85% of all Catasetum species remain unknown.
- Flower scents of ca. 90% of all Catasetum species await chemical characterization.
- Evolution of floral scents is mediated by olfactory preferences of pollinators.
- Daily fluctuation in floral scents matches the foraging activity of pollinators.
- Possible sexual dimorphism in floral scents awaits experimental investigations.

The Neotropical genus Catasetum is one of the most notable orchids because of its unusual reproductive strategy. In contrast to most orchids, all of the ca. 170 Catasetum species have sexually dimorphic, unisexual flowers involved in a highly specialized pollination mechanism. Flowers of Catasetum produce strong floral perfumes that act as both attractant and reward for male euglossine bees. While collecting perfumes, euglossine males may remove the pollinarium from a male flower and subsequently deposit it in the stigmatic slit of a female flower, resulting in pollination. Here we present an overview of the existing literature on floral scent chemistry and pollinators of Catasetum and add new reports on the pollinators of some species. We provide some insights into the ecology and evolution of floral scents in the genus Catasetum and suggest directions for future research. We hope this review will stimulate research not only on the ecology and evolution of Catasetum but also of the about 1000 species of fragrance-rewarding plants that are found in the Neotropics.