XVI International Botanical Congess

The dwarf mistletoes (Arceuthobium spp.) comprise some 40 species of vascular plant parasites. Arceuthobium americanum infects 2 principal hosts, Pinus banksiana and P. contorta, and has the most extensive range of any N. American dwarf mistletoe. Surprisingly, A. americanum has been the subject of limited genetic and taxonomic research. Based on a lack of apparent morphological and phenological differences among populations, past researchers have found no evidence for undetected taxa. However, genetic differentiation seems likely due to the adaptation of A. americanum to different host populations over its extensive geographic range. We have used a new genetic tool, AFLP, to analyze the population structure of this species. Our preliminary findings suggest that A. americanum consists of two distinct genetic races, one that infects P. banksiana, and another that infects P. contorta.