Quantitative and Experimental Studies of the Systematics of Arctostaphylos Uva-Ursi (Ericaceae) in North America.

Arctostaphylos uva-ursi (L.) Spreng., a common shrub with a circumboreal distribution, has caused botanical controversy in North America. Recently Packer and Denford (1974) recognized 6 infraspecific taxa, differing from one another in the pubescence of young stems and petioles (presence and various combinations of short and long, gl and ular and non-gl and ular trichomes), but concluded that many taxonomic, phytogeographical, and ecological problems remained. I conducted both field and garden studies to evaluate these taxa and the characters on which they were based. The former concerned 394 specimens r and omly obtained throughout much of the continent, for which determinations of pubescence, exposure to sunlight, edaphic moisture, and substrate pH were made. Leaves, pollen, and somatic chromosomes were also studied. Garden studies involved the outdoor growth of 364 cuttings of 60 specimens and the indoor growth of 154 cuttings of 149 specimens, under conditions which varied in exposure, moisture, and pH; 405 seedlings of 110 specimens were also grown under the same conditions indoors. In general, the determinations mentioned above were made for the cuttings and seedlings as well. Field studies showed that other morphological features were loosely correlated with pubescence and that ecological affinities were reflected in geographic differences. For example, gl and ular entities seemed best adapted to moist and basic substrates, and were not represented in coastal regions, where occupied sites were dry and acidic. Garden studies showed that the slight morphological distinctions were even less pronounced under uniform conditions, and the ecological affinities were partially substantiated. In addition, 26% of the cuttings acquired the phenotypes of variants other than those of the specimens from which they were propagated, and 69% of the seedlings for which the maternal parents were other than var. coactilis were assigned to this entity after 14 to 24 months. I concluded that although genetic divergence exists in this species, it does not merit recognition even at the level of variety: the entities are less than distinct and the characters traditionally employed taxonomically are subject to significant environmental modification, so that naming them even at an infravarietal level would serve no purpose.Ph.D.BotanyUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/159447/1/8314348.pd