but unconfirmed at one of them (EO#004). It is an associated species that is 

 locally dominant at one of the Idaho occurrences. 



Population biology of the taxon. 



A. General summary: Spiranthes diluvialis is an herbaceous perennial that is long- 

 lived and has fluctuations in flowering stem numbers from year to year; primarily 

 due to the shift between flowering and non-flowering states (Arft 1 995a). Most of 

 the non-flowering plants are in vegetative condition represented by basal leaves, but 

 they also persist underground in season-long dormancy (Arft 1995a, Riedel, in litt., 

 1993), as has been documented for other species of plants including orchids (Tamm 

 1972, reviewed in Lesica and Steele 1994). The season-long dormancy state is 

 actually a mycotrophic state dependent on endocycorrhize (e.g. Gill 1996, in Allen 

 1996). Efforts to propagate Spiranthes diluvialis are underway by Denver Botanic 

 Gardens and the Red Butte Gardens of Salt Lake City, which will help elucidate early 

 stages of life history. 



Monthly data collected in a Colorado population indicated that Spiranthes diluvialis 

 usually produced an overwintering rosette dviring late summer or fall (Arft 1995b). 

 Leaf growth occurred during the growing season following rosette formation. 

 Inflorescence buds were produced as early as June, followed by flowers fi-om mid- 

 July to mid-August (at least two weeks earlier than in Montana). Fruits matured and 

 dehisced fi-om mid- August into September. Mature vegetative plants average 

 between 10-15 cm in height. Mature plants may remain dormant for at least one 

 growing season without producing any above-ground shoot, but the vegetative shoot 

 condition was much more common than the dormant condition overall for 

 populations monitored in Colorado and Utah (Arft 1995a). Studies of Spiranthes 

 magnicamporum in western Kansas and Nebraska report that the incidence of orchid 

 flowering may be as infrequent as once in 20 years (Magrath 1973 in U.S. Fish and 

 Wildlife Service 1995b). Studies of Cypripedium acaule energy allocation document 

 that flowering represents up to 18% of the plant dry weight, reducing the probability 

 of flowering the following year. A similar pattern is suggested for Spiranthes 

 diluvialis as supported by preliminary monitoring results in which only 30% of the 

 plants flowering in 1996 flowered in 1997 (Appendix D). Species' longevity has not 

 been determined. 



B. Demography. 



1. Known populations: The most important demographic parameters in long- 



lived perennials, as identified in conservation of Spiranthes spiralis, are 

 recruitment, mortality, survivorship, longevity and turn-over (Wells 1981). 

 Preliminary population projections have been made for Spiranthes diluvialis 

 at Colorado and Utah occurrences with information to suggest that the "life 

 history bottleneck" may vary depending on the land management practice 



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