Phylogenetic origins of parasitic angiosperm lineages have been difficult to study using DNA sequence data used previously because plastid genes and 18S rDNA may be lost or evolve at greatly accelerated rates making inferences uncertain. We present results of a large-scale sequencing study of conserved mitochondrial genes present in all plants regardless of their photosynthetic status. cox1 and atpA sequences were obtained from every order of angiosperm (recognized by APG, 1998), including every widely recognized hemi- and holoparasitic family. Phylogenetic analyses unambiguously place 12 major parasitic lineages within the context of angiosperm phylogeny. Origins of Balanophoraceae and Mitrastemonaceae are still uncertain and await further sampling. Several of the parasites appear to have arisen within lineages of plants they parasitize. This completely unexpected result suggests cases of adelophoparasitism or horizontal gene transfer from host to parasite.

Key words: adelphoparasitism, atpA, cox1, mitochondrial DNA, parasitic plant