Phylogeny of the parasitic plant family Orobanchaceae inferred from phytochrome A

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Abstract
Partial sequences of the nuclear gene encoding the photoreceptor phytochrome A (PHYA) are used to reconstruct relationships within Orobanchaceae, the largest of the parasitic angiosperm families. The monophyly of Orobanchaceae, including nonphotosynthetic holoparasites, hemiparasites, and nonparasiticLindenbergiais strongly supported. Phytochrome A data resolve six well‐supported lineages that contain all of the sampled genera exceptBrandisia, which is sister to the major radiation of hemiparasites. In contrast to previous plastid and ITS trees, relationships among these major clades also are generally well supported. Thus, the robust phylogenetic hypothesis inferred from thePHYAdata provides a much better context in which to evaluate the evolution of parasitism within the group. Ninety‐eight species of Orobanchaceae, representing 43 genera, are included andBrandisia,Bungea,Cymbaria,Esterhazya,Nesogenes,Phtheirospermum,Radamaea,Siphonostegia, andXylocalyxare confirmed as members of Orobanchaceae. The earliest diverging lineage of hemiparasites is identified for the first time; it containsBungea,Cymbaria,Monochasma,Siphonostegia, and the monotypicSchwalbea, which is federally endangered. This basal clade is marked by the presence of two novel introns. A second, apparently independent gain of one of these introns marks a clade of largely European taxa. There is significant rate heterogeneity amongPHYAsequences, and the presence of multiplePHYAin some taxa is consistent with observed ploidy levels.
Funding Information
  • National Science Foundation (DEB‐0215780)