ARS | Publication request: REPRODUCTION AND DEMOGRAPHY OF TOWNSENDIA APRICA (ASTERACEAE), A RARE ENDEMIC OF THE SOUTHERN UTAH PLATEAU

Submitted to: Western North American Naturalist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 20, 2004
Publication Date: October 29, 2004
Citation: Tepedino, V.J., Sipes, S.D., Griswold, T.L. 2004. Reproduction and demography of townsendia aprica (asteraceae), a rare endemic of the southern Utah plateau. Western North American Naturalist. 64(4):465-470

Interpretive Summary: Last Chance Townsendia is a small-but-showy, appressed-to-the-ground, daisy-like plant that occurs at high elevations in central Utah and nowhere else in the world. It was listed as threatened under the U. S. Endangered Species Act in August, 1985. Little was known about the plant at the time of its listing and little is known today, 18 years later. We undertook our study to determine how this rare species reproduces, whether it requires pollinators to assist it in reproduction, whether low numbers of those pollinators are limiting its reproduction, and what those pollinators might be. We found that, unlike some other species of its genus and family, Last Chance Townsendia cannot produce seeds unless pollinators carry its pollen from flower-to-flower. We found these pollinators to be bees native to North America (not honeybees), some of which nest in the ground among the Townsendia plants. There was no indication that Last Chance Townsendia would produce more seeds if pollinator numbers were increased. There was a suggestion that Last Chance Townsendia depends primarily on one native bee species for pollination and that this bee depends on other plant species as well as Townsendia for its food resources. Thus, conservation of this rare plant depends not only on conservation of bees, but on the other plants that those bees require as well.

Technical Abstract: Townsendia aprica, a rare pulvinate perennial of the southern Utah plateau, was listed as threatened under the U. S. Endangered Species Act in August, 1985. Little is known about the demography or reproduction of this species. Here we report on the reproductive biology and pollination, and provide an estimate, for a single site-year, of size-specific reproductive effort. Last Chance Townsendia appears to be a short-lived perennial that begins reproducing in its second year when about 1.5-2.0 cm diameter. Maximum reproductive effort is not attained until plants age and become larger: 38% of the plants (2.5-4 cm diameter) produced 84% of the flower heads. Few plants survive past the 4 cm size class. The species is primarily self-incompatible: neither autogamous nor geitononogamous breeding system treatments produced a significant number of achenes. In the Ivie Creek population, the species is not apomictic, as are some populations of some of its congeners. Outcrossing is the primary means of reproduction and native solitary bees are the pollinators of record. Most important are several species in the genus Osmia, and the ground-nesting species Synhalonia fulvitarsis, which nests among the T. aprica plants. S. fulvitarsis also visits a contemporaneous blooming Phlox (P. austromontana) which may facilitate pollination of the rare Townsendia. The Townsendia-Pholx-Synhalonia interaction may represent another example of why we must consider communities rather than individual species in our conservation efforts.