| Piperia Rydberg includes nine species and two subspecies, and is a section of Platanthera s.l. Piperia has been studied to a limited extent and is considered by orchidologists as a model system for terrestrial orchid studies. Scientific interest for Piperia has intensified because of its taxonomic placement within other terrestrial orchid genera, including its controversial placement within Platanthera.;The results of ITS, combined plastid, and morphology data analyses strongly support the monophyly of Piperia, and some support for the sequential sister relationships: ((Piperia, Platanthera obtusata), P. hookeri). Parsimony and Bayesian analyses of morphological data also support Piperia: synapomorphies include securicular stigma shape, tuber shape and function, fall-winter growth initiation, and caudicle sheath absence. Investigation of perianth-lobe color evolution rejects the hypothesis that green-flowered Piperia are more closely related to one another, than to white flowered taxa; that homoplasy is common in this character; and that small green flowered taxa such as P. leptopetala are polyphyletic species assemblages. Study of comparative morphology reveals that Piperia column and viscidia shapes are consistent at the species level. The hypothesized basal members within Piperia, and P. obtusata have highly reduced auricles. Basal bulges are prominent in Piperia , and their placement and shape support the hypothesis that they are vestigial anther tissue.;The main goals of this study are to: (1) assess monophyly of Piperia, determining the phylogenetic relationships among Piperia and their close relatives; (2) phylogenetically evaluate labellum color to determine whether green-flowered species are conspecific, and whether homoplasy and cryptic species are the source of some identification problems within the group; (3) characterize the column structures of Piperia and close relatives; (4) document timing of leaf growth in sections Piperia, Blephariglottis and Limnorchis; (5) investigate leaf, root, and tuber anatomy in search of synapomorphic characters for Piperia; (6) reappraise the taxonomic importance of morphological characters used by previous authors. This study reports sequences from five molecular regions (ITS, trnS GCU-trnG2S, partial ndhF, rpl14-rpl36, and petA- psbJ) and comparative morphology, analyzed employing parsimony, Bayesian inference, and maximum likelihood methods. |
