Spiranthes diluvialis

Spiranthes diluvialis Sheviak:
United States (North America)

Note: This information is based on publications available through Tropicos and may not represent the entire distribution. Tropicos does not categorize distributions as native or non-native.

Colo., Idaho, Mont., Nebr., Nev., Utah, Wash., Wyo.

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

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.

Historic Range:
U.S.A. (CO, ID, MT, NE, NV, UT, WA, WY)

Plants 20–62 cm. Roots few–several, horizontal to descending, slenderly tuberous, to 1 cm diam. Leaves persisting through anthesis, usually restricted to base of stem, ascending, linear-lanceolate, to 28 × 1.5 cm. Spikes usually tightly spiraled, 3 flowers per cycle of spiral, rarely loosely spiraled with more than 4 flowers per cycle; rachis sparsely (rarely densely) pubescent, some trichomes capitate, glands obviously stalked (longest trichomes 0.2–0.4 mm). Flowers white or ivory, ascending, strongly gaping from near base (lip prominently diverging from sepals and petals); sepals distinct or connate at base, 7.5–15 mm; lateral sepals broadly spreading to loosely incurved, often raised above rest of flower or often appressed; petals linear, apex acuminate; lip often yellow centrally, ovate, lanceolate, or oblong, with variably evident median constriction, occasionally subpandurate, 7–12 × 2.5–6.8 mm, margins crisped, entire, or apically dentate, distal surface mostly glabrous adaxially; basal calli prominent; veins few to several, branches parallel to wide-spreading; viscidia linear to linear-lanceolate; ovary mostly 4–10 mm. Seeds monoembryonic. 2n = 74.

Spiranthes romanzoffiana Chamisso var. diluvialis (Sheviak) S. L. Welsh

S. 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.

Mesic to wet riparian meadows, marshes, stream banks; of conservation concern; 1300--1800m.

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)

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).

Flowering Jul--Aug(--Sep).

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).

Current Listing Status Summary

Status: Threatened
Date Listed: 01/17/1992
Lead Region:   Mountain-Prairie Region (Region 6) 
Where Listed:

Population detail:

Listing status: T

For most current information and documents related to the conservation status and management of Spiranthes diluvialis, see its USFWS Species Profile

Canada

Rounded National Status Rank: N1 - Critically Imperiled

United States

Rounded National Status Rank: N2 - Imperiled

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.

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.

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.