Pollination ecology of the rare orchid, Spiranthes diluvialis: Implications for conservation

Abstract

We examined the pollination ecology of Spiranthes diluvialis Sheviak, Ute ladies-tresses, a federally listed, threatened orchid species known only from small, isolated populations in the western United States. The pollinator composition, male and female reproductive success, and demography of S. diluvialis populations were examined in 1995,1997, and 1999. Spiranthes diluvialis sets fruit only when visited by pollinators and observations indicate that native bees, predominantly bumblebees (Bombus spp.), are the most important pollinators. Comparisons of male and female reproductive success were made between populations and years. Significant declines in fruit production and pollinia removal that occurred in 1999 in the Diamond Fork population may be related to changes in pollinator composition. Significant increases in fruit production were recorded in the Brown's Park population, an area in which native pollinators were released in 1999. Management plans to conserve this threatened orchid must provide for the pollinators, their nesting habitat, and pollen-producing plants (S. diluvialis provides no pollen to pollinators). We identified important pollen sources for pollinators in the Diamond Fork population and supplied several types of semi-natural nesting materials to promote nesting by Anthophora terminalis, another species thought to be an important pollinator. Successful preservation of this threatened orchid requires a comrnunity-level conservation plan.

Parent Publication

• Southwestern rare and endangered plants: Proceedings of the Third Conference

Citation

Pierson, Kim; Tepedino, Vincent J.; Sipes, Sedonia; Kuta, Kim. 2001. Pollination ecology of the rare orchid, Spiranthes diluvialis: Implications for conservation. In: Maschinski, Joyce; Holter, Louella, tech. eds. Southwestern rare and endangered plants: Proceedings of the Third Conference; 2000 September 25-28; Flagstaff, AZ. Proceedings RMRS-P-23. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. p. 153-164.