The evolution of parasitism in Scrophulariaceae/ Orobanchaceae: Plastid gene sequences refute an evolutionary transition series

Parasitic plants in Scrophulariaceae and Orobanchaceae have been traditiona lly depicted as forming a linear evolutionary series beginning with hemipar asitism and ending with holoparasitism. The genera Lathraea, Harveya, and H yobanche have been viewed as transitional links between the parasitic membe rs of Scrophulariaceae and the strictly holoparasitic habit of the traditio nal Orobanchaceae. Phylogenetic analyses of plastid rps2 and matK sequences were performed. The transitional genera are not transitional to the tradit ional Orobanchaceae, but represent multiple independent origins of holopara sitism, Within Scrophulariaceae. the two traditional subfamilies Rhinanthoi deae and Antirrhinoideae are defined by the arrangement of the corolla lobe s during aestivation. However, neither of the two subfamilies is monophylet ic in our analyses, suggesting that corolla lobe position is a homoplastic character. While the traditional Orobanchaceae are monophyletic, tribes Buc hnereae and Rhinantheae are clearly not, and genus Orobanche probably is no t. Clades of parasitic genera correspond well with biogeographic provinces. One strongly supported clade contains the parasitic Scrophulariaceae. the traditional Orobanchaceae, anti Lindenbergia. It is proposed that this clad e be defined as the Orobanchaceae.