A phylogenetic analysis of Diurideae (Orchidaceae) based on plastid DNA sequence data

DNA sequence data from plastid matK and trnL-F regions were used in phyloge netic analyses of Diurideae, which indicate that Diurideae are not monophyl etic as currently delimited. However, if Chloraeinae and Pterostylidinae ar e excluded from Diurideae, the remaining subtribes form a well-supported. m onophyletic group that is sister to a "spiranthid" clade. Chloraea, Gavilea , and Megastylis pro parte (Chloraeinae) are all placed among the spiranthi d orchids and form a grade with Pterostylis leading to a monophyletic Crani chideae. Codonorchis, previously included among Chloraeinae, is sister to O rchideae. Within the more narrowly delimited Diurideae two major lineages a re apparent. One includes Diuridinae, Cryptostylidinae, Thelymitrinae, and an expanded Drakaeinae; the other includes Caladeniinae s.s.. Prasophyllina e, and Acianthinae. The achlorophyllous subtribe Rhizanthellinae is a membe r of Diurideae, but its placement is otherwise uncertain. The sequence-base d trees indicate that some morphological characters used in previous classi fications, such as subterranean Storage organs, anther position, growth hab it, fungal symbionts, and pollination syndromes have more complex evolution ary histories than previously hypothesized. Treatments based upon these cha racters have produced conflicting classifications, and molecular data offer a tool for reevaluating these phylogenetic hypotheses.