Abstract Detail

Pollination Biology

Arevalo , Rafael E [1], Cameron, Kenneth [2].

Floral fragrance differentiation among species of Mormolyca (Orchidaceae): what floral scent profiles can tell us about pollination.

Floral scents constitute an important communication system between flowering plants and their pollinators. Fragrance is a highly complex component of floral phenotype, and can promote specialization in plant-pollinator relationships through specific compounds or unique ratios of widespread compounds. There is no doubt that floral scents have played an important role in orchid evolution and speciation, and their variations tend to be reflected in the evolutionary history of the species. Consequently, scent data may be used to infer phylogenetic relationships, or alternatively, evolutionary trends of floral scents might be studied by optimizing biochemical characters onto phylogenetic reconstructions inferred from independent data. Within the orchid subtribe Maxillariinae, the genus Mormolyca Fenzl, with ca. 27 species, exhibits enough floral diversity that species can be clustered in three morphologically distinct groups (i.e., Hedwigiae, Ringens and Rufescens). This diversity could be the result of pollinator- mediated selection that has shaped the evolution of their flower morphology, particularly their labella. Each type of labellum is characterized by its shape/form, appearance, and particular type of papillae and/or secretions, which all seem to have a roll in the pollination system of each group. While flowers from the Hedwigiae group have ephemeral and relatively faint, fruity fragrances, those from the Rufescens group exhibit a conspicuous diversity of strong long-lasting sweet fragrances that range from a combination of coconut, chocolate and/or vanilla, to a citrus-like refreshing fragrance. Given that these species are suspected to have reward-offering flowers, scent could not only be related to presence of floral rewards, but also be responsible for long-distance pollinator attraction. In the Ringens group, where labellum shape and indumentum superficially resemble an insect, the phenomenon of pseudocopulation has been described in one species. The induced pseudocopulation activity has been attributed to the similarity in chemical composition of the flower volatiles and non-volatiles to the waxes and cephalic extracts of virgin queen bees. To date, the scent chemistry of most Mormolyca species of is unknown. Studies in scent chemistry from related species within a lineage provide primary information about the phylogenetic distribution of floral scent chemistry and promote the testing of alternative hypotheses about how such patterns evolved. Thus, the objectives of this study are to: (1) examine and discriminate the chemical composition of floral scents emitted from selected species of Mormolyca; (2) how chemical distinctness relates to phylogeny; and (3) to what extent scent profiles support groups of species based on hypothetical pollination systems.

1 - University Of Wisconsin, Botany, 244 Birge Hall, 430 Lincoln Dr., Madison, WI, 53706, USA
2 - University Of Wisconsin, Department Of Botany, 154 Birge Hall, 450 Lincoln Drive, Madison, WI, 53706, USA

Keywords:
floral traits
Orchidaceae
pollination
Phylogeny.

Presentation Type: Oral Paper:Papers for Topics
Session: 32
Location: Firs South/Boise Centre
Date: Wednesday, July 30th, 2014
Time: 8:15 AM
Number: 32002
Abstract ID:741
Candidate for Awards:None