Biosystematics of the genus Piperia Rydb. (Orchidaceae)

Piperia is a North American segregate of Habenaria consisting of 5 taxa (4 species and 1 subspecies). The genus is defined and differentiated from other North American genera of the Habenaria alliance by its morphology and pollination mechanism. All taxa have n = 21 chromosomes. Thin-layer chromatography of fresh leaf extracts and a morphological assessment revealed discrete, but variable, taxa. All species are partially interfertile; however, a high degree of sympatry suggests these species are reproductively isolated. One new combination is proposed: P. elongata subsp. michaelii.