BARKMAN, TODD J., JOEL R. MCNEAL, NELSON D. YOUNG, AND CLAUDE W. DEPAMPHILIS.* Department of Biology and Institute of Molecular Evolutionary Genetics, Penn State University, University Park, PA 16802 and Department of Biology, Trinity University, San Antonio, TX 78212. - Multiple origins of parasitism within angiosperms.
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