Molecular Systematics, Floral Micro-Morphology, Rewards, and Scent Variation in the Neotropical Orchid Genus Mormolyca Fenzl (Orchidaceae)

The Neotropical orchid genus Mormolyca Fenzl, with at least 28 species, consists of epiphytic plants distributed from southern Mexico to Bolivia and Northern Brazil, including the Greater Antilles. For a relatively small genus, species exhibit considerable flower diversity, possibly correlated with different pollination systems, which include both sexual deception and mutualism (rewards). To study the mechanisms and evolution of pollination systems in the group, a phylogenetic inference based on multiple DNA markers is constructed for use as a framework. The phylogenetic tree, which had good resolution and support, reveals patterns of evolution that are likely related to pollination systems. At the same time, confirms classification of new species that were discovered during this study.;To better understand the characters involved in the attraction of insect pollinators, floral micro-morphological traits were studied among species of Mormolyca. Labella of flowers were sectioned and examined for micro-morphological and anatomical characters, as well as for the presence of possible food rewards (e.g., starch, lipids, and proteins). Species were found to cluster into three morphological groups, the Hedwigiae, Ringens and Rufescens groups, based on a combination of labellar papillae, the presence/absence of secretions, nutrients, and scents. The presence of capillary papillae is restricted to the Ringens group, which includes the sexually deceptive species, whereas the Hedwigiae and Rufescens groups (the rewarding species) have papillae with distended apices that produce aromatic amino acids. Labellar papillae, in conjunction with osmophores (glandular tissue), provide the flowers the ability to attract, guide, feed, and/or deceive pollinators through a combination of visual, tactile, and/or olfactory cues.;To further understand the possible olfactory cues, floral fragrance composition was investigated for six species of Mormolyca representing the three morphologically distinct groups. Volatile and nonvolatile constituents of flower extracts were identified with Gas Chromatograph-Mass Spectrometry. The species that are sexually deceptive contain alkanes and alkenes known to be involved with sexual mimicry in Orchidaceae. Species that are thought to offer rewards in the form of nutrient-rich labellar secretions or papillae were distinctively scented. These species release volatiles that are characteristic of euglossophilous flowers (flowers pollinated by euglossine bees).