Intraspecific variation in floral color and odor in orchids

Abstract

Many flowering plant species are characterized by a large variation in floral traits at the population or individual levels. Among these traits, colors and odors are particularly important for pollinator attraction, yet they appear to be highly variable among conspecifics. Orchids are famous for their great taxonomic and floral diversity, as well as for their complex pollination strategies. Many species of this family achieve pollination through deception, which may promote floral polymorphism. In this review, we compile and analyze 115 studies investigating floral colors and scents in 184 different orchid species. We particularly focus on studies that have documented variation in color and/or odor traits among or within conspecific populations. We describe the different types of variation that have been reported for floral colors and scents, and we examine the factors that likely contribute to such variation, with a focus on the role of pollinators, comparing orchid species using different pollination strategies. We also show that color-odor associations are frequent in orchids but may result from processes other than biochemical constraints. Finally, we underline the current gaps in our understanding of intraspecific variation of floral color and scent in orchids, and we identify several stimulating topics for future research.