Variation in Floral Fragrances and Morphology: Incipient Speciation in Cycnoches?

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Abstract
Variation in flower color, labellum morphology and fragrance are described for 4 Panamanian species of Cycnoches previously considered to be C. egertonianum Batem. A lack of odor detectable by nose or gas chromatography (GC) from C. aureum Lindl. and distinct odor profiles obtained for C. dianae Rchb. f., C. densiflorum Rolfe and C. stenodactylon Schltr. indicate that each should be recognized as a well-defined species. Odor profiles were calculated from fragrances produced by lamella within 8 h of excision from the plants. These profiles did not differ appreciably from those obtained from excised whole inflorescences or from flowers maintained on the plants. Labella reliably produced copious amounts of fragrance compounds that were easy to concentrate within 1 h in small containers. Male and female flowers of each species produced the same scent. Differences in odor profiles among individual plants occurred within sample populations. Two fragrance chemotypes were detected by GC for C. densiflorum and C. dianae. In the former, half the clones produced .alpha.- and .beta.-pinene as 37% or more (mean = 67.7 .+-. 6.8) of their profiles; the other half had odors with 49.5% or less .alpha.- and .beta.-pinene (mean = 43.6 .+-. 5.3). Of the clones of C. Dianae, 35% produced neither .alpha.- nor .beta.-pinene. Microevolution and possible sympatric speciation in these orchids are discussed.

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