Ryan, Angela; (2001) A phylogenetic assessment of Lycaste and Anguloa (Orchidaceae). Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

Parsimony analysis has been used to examine the phylogenetic relationships of two genera of Neotropical orchids, Lycaste and Anguloa. Within these genera, difficulties occur when assigning names to plants using traditional morphological techniques. Many herbarium specimens are in bad condition and some descriptions are incomplete. To date, infrageneric classifications have been based on very few diagnostic characters. Here, three approaches have been evaluated: A systematic analysis of the morphology, an examination of two regions of DNA sequence and an analysis of the chemical composition of the floral fragrances. Morphological analysis showed that Lycaste is not monophyletic. There was a clear division between species currently ascribed to sect. Fimbriatae and the other species of the genus. Selection of characters introduced an element of subjectivity into the analysis and it was shown that exclusion of a single character could significantly affect the topology of relationships. Parsimony analysis of the sequences of both ITS and matK placed Lycaste sect. Fimbriatae closer to Anguloa than to the other species of Lycaste. Neomoorea was identified as nearest neighbour to Lycaste and Anguloa. A combined analysis of ITS and morphological data gave congruent results. Morphological and sequence analyses also indicated that the single pendent species, L. dyeriana, should remain within sect. Fimbriatae and that the taxonomic status of the subspecies of L. macrophylla should be revised. None of the analyses provided sufficient resolution to address the sectional treatment of the remaining Lycaste species. To answer this question, comparison of sequence data from a faster evolving region of DNA will be required. The floral fragrance composition of 28 species and subspecies of Lycaste and Anguloa was determined. In its current form, the data was found to be unsuitable for addressing phylogenetic relationships at species level and above but may prove useful for population studies.

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