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Systematics of the Triphoreae (Epidendroideae: Orchidaceae)

My PhD. dissertation research is a systematic study of the orchid tribe, Triphoreae, of the subfamily Epidendroideae. These orchids are small, elusive, terrestrial, mycotrophic herbs. One aspect of this research will be to monograph species and the genera of the Triphoreae as a means to determine both generic and specific boundaries. The tribe, as it is currently described, consists of three genera, Triphora, Psilochilus, Monophyllorchis and 28 species (Dressler 1981;Dressler 1993). While molecular data supports the phylogenetic position of the tribe as basal within the Epidendroids (Cameron et al. 1999;Chase et al. 2001), not all previous phylogenetic representations of relationships within the tribe were constructed using cladistic methodology (Chase et al. 2001), and it is unclear at this point what the phylogenetic relationships are. Another aspect of this study will be to elucidate relationships among the genera and species of the Triphoreae.

The tribe is distributed exclusively in the western hemisphere, from central America and northern South America, including the Caribbean (Nir, 2000) and Florida (Luer, 1972, 1975) with a single species, Triphora trianthophora (three-birds orchid; pictured at right) extending its range north into the eastern United States and southern Ontario and Maine. There are 19 species currently described in the genus Triphora. Triphora trianthophora is the best known species of the tribe, and  the one for which the genus is named. This species is one of the United States native species and can be found in the northern part of its range in beach-maple forests and in Florida, it is found in the mixed hardwood-oak hammocks in association with saw palmetto. In its northern distribution, it blooms from late July through the end of August, and may be found blooming as late as November in more southern regions of its range.  As a whole, the Triphoreae are rather elusive, generally small plants,  having been described by some as "plants which you don't find, but rather find you." For example, T. trianthophora is short, about 7-20 cm tall, and is found scattered or sometimes clustered in small groups on the forest floor among the leaf litter. Finding this species is often a combination of luck and observation, but when it is observed it is generally only because you see the small 1-2cm bright white or slightly pink flowers which have a very characteristic orchid like appearance. The tribe as a whole exhibits what is called synchronous or gregarious blooming which means that under right blooming conditions all flowers in a population, usually 1 per plant, open at the same time. It has been reported that T. trianthophora is pollinated by Halicitid bees, and such a blooming strategy could enhance the possibility of  pollination, given the scattered distribution of these plants in the forest under-story.

The genus Psiolochilus is composed of 7-8 species found throughout the Caribbean, central and Northern South America. Psilochilus macrophyllus, illustrated at left (from Ackerman, 1995), is probably the most common species of this genus.

Monophyllorchis is a small genus, with at most 2 species, however some authors have suggested that what has been described as two species is really the variation observed in one species Monophyllorchis macualta (right; from Dressler, 1993). This genus is found almost exclusively in South America, reaching as far as Panama and Costa Rica. Of all the species in the tribe, the members of the genus  Monophyllorchis have the largest plants, approaching 40 cm tall with 1-2 large leaves (17 x 13cm). The large heart-shaped leaves are quite distinctive with a dark greenish purple color and streaked with silvery white. These flowers remain closed and the species is probably self-fertilizing.

SELECTED LITERATURE CITED

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