XVI International Botanical Congess

Cuscuta plants are stem parasites whose rudimentary root system is lost soon after it makes a haustorial connection to a suitable host plant. Although vascular and seed capsule structure indicate Cuscuta is a close relative of Convolvulaceae (morning glories), its unique form and eccentric life history have prompted placement in its own family, Cuscutaceae. Through DNA sequencing of selected nuclear, plastid, and mitochondrial genes (ITS, matK, rps2, coxI), placement of Cuscuta within a paraphyletic Convolvulaceae may be resolved. In coxI, an intron that occurs sporadically in angiosperms was abnormally altered in Cuscuta with a large deletion and then repeated insertion of a 15 bp microsatellite. Intron length varies greatly, even between closely related Cuscuta, indicating that analysis of intron evolution will help resolve species relationships and the evolution of traits such as host-specificity.