Molecular phylogeny of Cypripedium (Orchidaceae: Cypripedioideae) inferred from multiple nuclear and chloroplast regions

A molecular analysis was performed on 56 taxa in the orchid genus Cypripedium using nrDNA ITS and five
chloroplast regions (trnH-psbA, atpI-atpH, trnS-trnfM, trnL-F spacer, and the trnL intron). The genus Cypripedium
was confirmed as monophyletic. Our data provided strong support for monophyletic grouping
of eight infrageneric sections (Subtropica, Obtusipetala, Trigonopedia, Sinopedilum, Bifolia, Flabelinervia,
Arietinum, and Cypripedium) defined in earlier taxonomic treatments, and paraphyletic grouping of two
sections (Irapeana and Retinervi). Within the genus Cypripedium, the first divergent lineage consisted of
two Mesomaerican species, and subsequently the Cypripedium debile lineage from eastern Asia was split.
Our study did not support the notion that two Asian species (Cypripedium subtropicum and Cypripedium
singchii) were closely related to either Mesoamerican Cypripedium irapeanum or North American Cypripedium
californicum, as indicated by previous interpretations based on morphological evidences. In addition,
one pair of vicariant species, Cypripedium plectrochilum (eastern Asia) and Cypripedium arietinum
(North America), unique to section Arietinum, was confirmed. Furthermore, within the monophyletic
section Cypripedium two previously recognized subsections, Cypripedium and Macrantha, were shown
to be paraphyletic. Our results suggested that this section split into two groups based on distribution
(North America vs. Eurasia) instead of such previously used, morphological traits as flower color, and
the shape of the lips (labellum) and lateral petals.