Phylogenetic Relationships and Evolutionary Trends in Orobanchaceae

Molecular analyses of the last decade have greatly changed our understanding of phylogenetic relationships of Orobanchaceae. This family now includes all photosynthetic and non-photosynthetic parasitic members of former Scrophulariaceae and Orobanchaceae, in addition to a single non-parasitic genus. Although phylogenetic relationships among genera are not fully understood, there is consensus recognition of several major clades. However, due to the lack of correspondence with traditionally defined higher taxa, morphological characterization of these clades and identification of their synapomorphies are still largely lacking. Molecular data support phylogenetic placement of the major weedy species as suggested by morphology, but so far failed in identifying their most closely related wild congeners. A sound phylogenetic framework forms the necessary basis for studying evolutionary trends connected to parasitism, and a few trends are briefly discussed, including host range, genome evolution, horizontal gene transfer and association of polyploidy with holoparasitism.