A phylogenetic analysis of subtribe Pleurothallidinae (Orchidaceae)

A cladistic analysis of subtribe, Pleurothallidinae (Orchidaceae) is based on 45 anatomical/morphological characters. The ingroup members comprise 24 genera; the large genus Pleurothallisconsists of two subgenera and ten species complexes. Three taxa representing subtribes Laeliinae and Arpophyllinae are designated as outgroup. Eight most parsimonious trees were discovered using computer assisted software (length = 230; CI = 0.27). The hypothesis that subtribe Pleurothallidinae has undergone a unilinear reduction in the number of pollinia is not supported by this study. Although the eight-pollinia state as represented by Octomeriaapparently is plesiomorphic, the two-pollinia and four-pollinia states arose early in the phylogeny of the subtribe. Both two-and four-pollinia states subsequently reappeared as parallelisms. The six-pollinia state exhibited in Brachionidiumis autapomorphic. This cladistic analysis suggests that Pleurothallisis not a natural genus and, perhaps may be divided into several discrete genera.