Regularity: Regularly occurring
Regularity: Regularly occurring
Global Range: Adapted from Fertig et al. (2005): Known from northern and south-central Utah, central to north-central and northwestern Colorado, east-central and southeastern Wyoming, eastern Idaho, southwestern Montana, eastern Nevada, western Nebraska, and central to north-central Washington, as well as British Columbia, where recently discovered (J. Penny, pers. comm. 2008). Occurs in at least 33 counties in the United States as well as at one site in British Columbia. Utah has the largest number of extant EOs and the highest number of reported plants, followed by Colorado. Using a minimum convex polygon to estimate the range (i.e. without attempting to exclude "extreme discontinuities"), range extent is approximately 900,000 square km.
U.S.A. (CO, ID, MT, NE, NV, UT, WA, WY)
Spiranthes diluvialis has characteristics intermediate between S. romanzoffiana and S. magnicamporum. Adapted from Fertig et al. (2005): S. diluvialis is distinguished from S. romanzoffiana by its whitish, stout, ringent (gaping at the mouth) flowers, by its oval to lance-shaped, narrowed-at-the-middle lip petal with crispy-wavy margins that is exposed in lateral view (compared to the deeply constricted, fiddle-shaped lip petals of S. romanzoffiana), by its sepals being free or connate at the base for a short distance rather than fused to form a hood above the lip, and by its sparsely pubescent inflorescence (S. romanzoffiana has pubescence of short hairs along the stem and inflorescence). S. romanzoffiana occurs in montane wetlands (up to 3400 m) throughout the Rocky Mountains. S. magnicamporum and S. cernua have strap-shaped, wavy-margined lip petals (compared to S. diluvialis' oval to lance-shaped, narrowed-at-the-middle lip petal with crispy-wavy margins), lack leaves at flowering time (leaves of S. diluvialis persist at flowering time), and occur in low-elevation (to 1900 m) wetlands of the Great Plains east of the known range of S. diluvialis (except in Nebraska). S. porrifolia has pale yellow flowers with sepals fused for about half their length but not forming a hood (compared to the white flowers with sepals free or connate for a short distance of S. diluvialis), strap-shaped lip petals with peg-like hairs on the upper surface (compared to S. diluvialis' oval to lance-shaped, narrowed-at-the-middle lip petal with crispy-wavy margins), and glabrous stems. It occurs primarily along the Pacific Coast inland to Idaho and western Nevada in wetlands from 100-2600 m. S. infernalis has yellowish-white flowers with a green lip that is widest near the middle before tapering to the base and is endemic to the Ash Meadows of southern Nevada.
From CNHP Wetland Guide 2012:
·Tepals distinct or united only at the base, not forming a hood above the lip, outer lateral tepals spreading
Flowers diverging at about a 90 degree angle or higher from rachis
·Inflorescence looser, rachis usually visible
Comments: Adapted to early- to mid-seral, moist to wet conditions, where competition for light, space, water, and other resources is normally kept low by periodic or recent disturbance events. Major occupied habitat types include (1) alluvial banks, point bars, floodplains, or ox-bows associated with perennial streams, with a high water table and short, perennial graminoid- and forb-dominated vegetation maintained by grazing, periodic flooding, or mowing; (2) river floodplain habitats which experience regular spring flooding and/or frequent large scale floods but maintain relatively stable, moist to wet soil in summer, within moist meadow, riparian woodland, or riparian shrubland communities; (3) shores of lakes and reservoirs, in mesic meadow-type vegetation maintained by lake level fluctuations or seasonal flooding of gravel bars; (4) groundwater-fed springs, sometimes in desert settings, or subirrigated meadows where edaphic characteristics (e.g. high water table and calcic soil), fire, and/or grazing are sufficient to prevent invasion of later seral vegetation; and (5) human-influenced habitats, including perennial stream, river, lakeshore, and spring sites directly associated with human-developed dams, levees, reservoirs, irrigation ditches, reclaimed gravel quarries, roadside barrow pits, and irrigated meadows. More than half of documented populations occur in sites in which natural hydrology has been influenced by dams, reservoirs, or supplemental irrigation, and many populations occur within agricultural or urban settings. 550 - 2100 m. (adapted from Fertig et al. 2005)
Number of Occurrences
Note: For many non-migratory species, occurrences are roughly equivalent to populations.
Estimated Number of Occurrences: 21 - 80
Comments: Based on standardized EO delineation criteria, 61 EOs were known in 2005, of which 52 were extant (Fertig et al. 2005). Since then, at least one new extant occurrence has been discovered in Colorado (J. Handwerk pers. comm. 2008) and one new extant occurrence has been discovered in British Columbia (J. Penny pers. comm. 2008).
Life History and Behavior
Across its range Spiranthes diluvialis blooms from early July to late October. Asynchronous maturation of flowers promotes outcrossing, but flowers are self-compatible (Fertig et al. 2005).
National NatureServe Conservation Status
Rounded National Status Rank: N1 - Critically Imperiled
Rounded National Status Rank: N2 - Imperiled
NatureServe Conservation Status
Rounded Global Status Rank: G2 - Imperiled
Reasons: Known from approximately 63 sporadic occurrences in lower-elevation wet, herbaceous-dominated habitats in interior western North America. The species was Federally listed (U.S.) in 1992 when it was only known from Colorado, Utah, and Nevada. Since that time, it has been found in Wyoming, Montana, Nebraska, Idaho, Washington, and British Columbia. Utah and Colorado have the most plants and occurrences. Most occurrences are small, with 81% having less than 1000 plants and 95% occupying less than 50 acres. Approximately 12 occurrences are considered protected and appropriately managed. Although trends are difficult to determine, habitat condition is known to be deteriorating at at least some sites. Several historic populations in Utah and Colorado are presumed extirpated. The riparian habitat on which this species depends has been drastically modified by urbanization and stream channelization for agriculture and development. Habitat loss or alteration from competition from non-native plants and vegetation succession appear to be the most widespread threats.
Environmental Specificity: Narrow to moderate.
Comments: Requires stable moisture throughout growing season as well as a seasonal reduction or season-long sparse vegetation cover within wet meadow habitat, i.e., dynamic or low-competition conditions for which too little disturbance can have as great a long-term impact as too much disturbance in an already fragile wetland setting.
Date Listed: 01/17/1992
Lead Region: Mountain-Prairie Region (Region 6)
Listing status: T
For most current information and documents related to the conservation status and management of Spiranthes diluvialis, see its USFWS Species Profile
Global Short Term Trend: Decline of 10-30%
Comments: Population monitoring studies in Colorado and Utah have projected long-term declines if not extirpations in both riparian corridor and wet meadow settings and under current land use practices without conservation intervention. In Idaho, long-term monitoring has detected local extirpation of subpopulations as habitat condition deteriorates through flooding or vegetative succession. Nevertheless, new monitoring and demographic research have documented that populations are more stable than originally suspected, because most past monitoring studies had focused on counts of flowering plants, which are more likely to fluctuate than counts that include more cryptic vegetative, fruiting, and dormant plants (Fertig et al. 2005). Most of the multi-year monitoring studies based on flowering plants exhibit an oscillating trend, alternating between periods of increase and decrease around a relatively stable mean (Fertig et al. 2005). This species also appears more tolerant of human-induced disturbances than originally supposed, based on the discovery of additional populations in significantly human-modified habitats (Fertig et al. 2005).
Global Long Term Trend: Relatively stable to decline of 50%
Comments: Presumed extirpated at several collection sites in parts of range, but with limited historical data for gauging losses. Rocky Mountain Front habitat in Colorado may have been the most extensively converted.
Degree of Threat: Very high - high
Comments: Threats include (by descending number of individual plants affected): competition from invasive species, vegetation succession, hydrology change (including conversion of irrigation water to municipal use, flood control, water development/redevelopment, and stream/riparian restoration [where plants are depedent on current, altered conditions]), flooding, road and other construction, recreation-associated impacts, natural herbivory (e.g. by voles), urbanization, loss of pollinators (reduction in the quantity and suitability of available pollinators, particularly certain bees), grazing by livestock, drought, and haying/mowing (Fertig et al. 2005). Approximately 60% of occurrences are affected by one or more "current threats", while an additional 12% of occurrences are not affected by any "current threats" but have one or more "potential threats" listed, bringing the total to 72% of occurrences thought to be threatened in the present or near future. Competition from invasive species, the most widespread single threat, affects 62% of occurrences and 84% of individual plants (Fertig et al. 2005). Although this species is now thought to be more resilient to human-influenced environments than was originally supposed, many threats remain high.
Relevance to Humans and Ecosystems
Stewardship Overview: Adapted from Arft (1995) and Fertig et al. (2005): Historically, patchy and episodic disturbance events created areas suitable for establishment of new colonies as existing sites became less hospitable over time. In current fragmented ecosystems, human manipulation may be necessary to create early- to mid-successional habitats, while maintaining adequate soil moisture levels. Studies have found that winter grazing and early season mowing or haying can reduce competing vegetation cover and increase plant survival and reproduction, while grazing or haying after flower production (i.e. in summer) can be detrimental. Prescribed burning does not appear to be as effective as winter grazing or early season mowing/haying. In addition, invasion of sites by non-native plants needs to be monitored and curtailed, as these species are frequently adapted to similar environments and act as highly effective competitors with S. diluvialis.
Spiranthes diluvialis is a rare species of orchid known by several common names, including Ute lady's tresses (also, Ute ladies'-tresses). The species name diluvialis means "of the flood". It is native to the western United States, where there are scattered, mostly small occurrences in the states of Colorado, Idaho, Montana, Nebraska, Nevada, Utah, Washington, and Wyoming. An occurrence was recently discovered in southern British Columbia. The plant faces a number of threats to its existence. It is a federally listed threatened species of the United States.
Specimens of this orchid were first collected in 1856 and have been labeled with the names of several species, including Spiranthes romanzoffiana, S. cernua, and S. porrifolia before the plant was finally described as a new species in 1984. Morphological and genetic analysis suggest that the orchid is a hybrid of S. romanzoffiana and S. magnicamporum and is tetraploid, with four sets of chromosomes resulting from the combination of a pair from each parent species. It is a perennial terrestrial orchid with an erect stem growing 20 to 62 centimeters in height. The narrow lance-shaped leaves are arranged around the base of the stem and are up to 28 centimeters in length. The inflorescence is a spiral of many flowers on a stalk coated in glandular hairs. The flower has narrow white or ivory-colored petals. Blooming occurs in July and August, and sometimes into September, and October. The plant reproduces sexually by seed and vegetatively by sprouting from broken-off pieces of root. The seeds are so small they are like dust; one plant can produce 100,000 individual seeds. Like other orchids, this species depends on mycorrhizal fungi to help the seeds germinate. The flowers are pollinated by bees of genus Anthophora, especially Anthophora terminalis, as well as bumblebees (Bombus spp.).
This plant grows in moist wetland habitat, including bogs and riparian areas such as riverbanks, floodplains, lakeshores, riverside woodlands and forest, desert springs, and meadows, and human-made habitat such as ditches, reservoirs, and irrigated agricultural settings. In 2005 there were about 52 occurrences. The population size is difficult to count or estimate because the plant spends most of its time in a vegetative or dormant state, in which there are few or no aboveground plant parts and these may be hidden in dense surrounding vegetation or hard to identify. Some plants may be dormant underground for years at a time. What appear on paper to be larger populations are actually areas that have been more often and intensely surveyed.
Threats to this species include habitat loss and degradation via a many processes. Urban development has led to the extirpation of a number of populations, including some within the Salt Lake City and Colorado Springs metropolitan areas. It continues to be a threat in many areas, including the vicinity of Boulder, Colorado. Threats associated with urban development include the introduction of weeds into the habitat and the loss of pollinating insects. Construction and maintenance of roads and other infrastructure, such as dams and pipelines, damages habitat. Recreational activities in the plant's riparian habitat, such as boating and off-road vehicle use, can be damaging. Some populations grow in irrigated fields and are susceptible to mowing and other farm activity, and the conversion to agricultural use consumes natural areas. As much as 65% of the plant's known habitat is affected by cattle and horse grazing; this can be harmful but it may also be beneficial in some ways, especially if the animals eat competing weeds. The orchid grows in wetland habitat, which is degraded by any process that alters the local hydrology; one estimate had 52% of all individuals in areas threatened by hydrological change. Water is diverted for irrigation and municipal use. The orchid grows in flood-prone river habitat and flood suppression via levees and other structures affects and prevents this natural process. River restoration activities have been known to negatively affect orchid populations that have become established or re-established in previously altered river habitat.
Invasive species of plants considered threats include redtop (Agrostis stolonifera), musk thistle (Carduus nutans), spotted knapweed (Centaurea maculosa), Russian knapweed (Acroptilon repens), creeping thistle (Cirsium arvense), Fullers teasel (Dipsacus fullonum), oleaster (Elaeagnus angustifolia), quickgrass (Elytrigia repens), leafy spurge (Euphorbia esula), peppergrass (Lepidium latifolium), purple loosestrife (Lythrum salicaria), reed canary grass (Phalaris arundinacea), sow thistle (Sonchus arvensis), and saltcedar (Tamarix chinensis).
This plant grows in many types of habitat reliant on natural cycles of disturbance, such as flooding and occasional wildfire. Without these processes, the habitat becomes overgrown and large and woody vegetation types move in as ecological succession causes overall change. When flooding is controlled and fire suppression is implemented, the orchid may face inadequate conditions, such as too much shade or thick layers of built-up leaf litter.
Other threats include herbivory by native animals such as bighorn sheep, voles, and rabbits. The loss of pollinating bees is a threat, as is the loss of other wildflowers that attract the bees. Other documented threats include drought, pesticides, pollution, and poaching.
- Fertig, W., et al. (2005). Rangewide status review of Ute Ladies'-Tresses (Spiranthes diluvialis). Prepared for the USFWS and Central Utah Water Conservancy District. Retrieved August 6, 2011.
- Spiranthes diluvialis. The Nature Conservancy. Retrieved August 6, 2011.
- Sheviak, C. J. (1984). Spiranthes diluvialis (Orchidaceae), a new species from the western United States. Brittonia 36(1) 8-14. Retrieved August 6, 2011.
- Arft, A. M. and T. A. Ranker. (1998). Allopolyploid origin and population genetics of the rare orchid Spiranthes diluvialis. Am J Bot 85(1) 110-22. Retrieved August 6, 2011.
- Szalanski, A. L., et al. (2001). Origin and conservation genetics of the threatened Ute ladies'-tresses, Spiranthes diluvialis (Orchidaceae). Am J Bot 88(1) 177-80. Retrieved August 6, 2011.
- Spiranthes diluvialis. Flora of North America. Retrieved August 6, 2011.
- Spiranthes diluvialis. Center for Plant Conservation. Retrieved August 6, 2011.
Names and Taxonomy
Comments: Taxonomic studies have confirmed hybrid origin and taxonomic distinctiveness (Arft and Ranker 1998, Szalanski et al. 2001).
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