1997-06-13_REPORT - M1981302 (11)

Home Browse Search

winter months. Two or more plants often occur in clumps. It is not known whether these clumps are composed of separate individuals or whether all arise from a single underground organ. Reproduction appears to be strictly sexual , with bumble bees (Bombus spp.) as the primary pollinators (Dresler 1981, Sheviak 1984, Sipes at al . , 1993) . Flowers are protandrus (functionally male first and then female) . The inflorescence always begins blooming with the bottom flower and proceeds upwards, sequentially. These features tend to maximize outcrossing due to the tendency of bees to visit the bottommost flower first and then proceed vertically up the spike. Successful conservation of the orchid will require protecting pollinator habitat in and around orchid populations and suitable habitat. The apparent tendency for populations of the Ute ladies'-tresses to fluctuate dramatically from one year to the next makes it difficult to assess the population status and distribution. Due to the difficulty in finding vegetative individuals, monitoring is typically done by counting the number of flowering individuals. Monitoring at the Van Vleet population by the City of Boulder Open Space Department has been conducted since its discovery in 1986, with the exception of 1991 . During that time, apparent population size, as indicated by the number of flowering individuals, has gone from a high of 5,435 in 1986 to a low of 1,137 in 1989 (Arft 1993) . Previous work by Wells (1981) on S. sspiralis indicated that population size did not fluctuate when both flowering and vegetative plants were surveyed. Preliminary results examining both vegetative and flowering individuals at the Van Vleet site and at Dinosaur National Monument suggest that population size of the Ute ladies'-tresses is more stable than indicated by monitoring only flowering individuals (Arft 1993, Riedel 1992) . Research is necessary to elucidate the early life history stages of the Ute ladies'-tresses (from seed dispersal to seedling emergence and from seedling emergence to mature reproducing individual ) , identify limiting or vulnerable stages, and understand factors influencing successful completion of each life history stage. No matter what the original cause(s) of reductions in population that resulted in listing as a federally threatened species, improving population status will require identifying vulnerable and limiting life history stages and implementing measures to enhance the successful passage of individuals through those stages (Schemske at al . 1994) . E. Habitat/Ecology S. diluvialis is endemic to moist soils in mesic or wet meadows near springs, Takes, or perennial streams. The elevational range of known orchid occurrences is 4,300 and 7,000 feet (1 ,310 to 2,134 meters) (Stone 1993) . Most of the occurrences are along riparian edges, gravel bars, old oxbows, and moist to wet meadows along perennial streams, but some localities in the eastern Great Basin are in similar situations near freshwater lakes or springs (U.S. Fish and Wildlife Service 1991) . Jennings (1990) and Coyner (1989, 1990) observed that the orchid seems to require "permanent sub-irrigation", indicating a close affinity with floodplain areas where the water table is 7