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Margaritifera falcata

(Gould, 1850)

Western Pearlshell

G3Vulnerable (G3G4) Found in 45 roadless areas NatureServe Explorer →
G3VulnerableGlobal Rank
Near threatenedIUCN
HighThreat Impact
Identity
Unique IDELEMENT_GLOBAL.2.107100
Element CodeIMBIV27020
Record TypeSPECIES
ClassificationSpecies
Classification StatusStandard
Name CategoryInvertebrate Animal
IUCNNear threatened
Endemicoccurs (regularly, as a native taxon) in multiple nations
KingdomAnimalia
PhylumMollusca
ClassBivalvia
OrderUnionoida
FamilyMargaritiferidae
GenusMargaritifera
Other Common Names
Mulette perlière de l'Ouest (FR)
Concept Reference
Turgeon, D. D., J. F. Quinn, Jr., A. E. Bogan, E. V. Coan, F. G. Hochberg, W. G. Lyons, P. M. Mikkelsen, R. J. Neves, C. F. E. Roper, G. Rosenberg, B. Roth, A. Scheltema, F. G. Thompson, M. Vecchione, and J. D. Williams. 1998. Common and scientific names of aquatic invertebrates from the United States and Canada: Mollusks. 2nd Edition. American Fisheries Society Special Publication 26, Bethesda, Maryland. 526 pp.
Taxonomic Comments
The family Margaritiferidae is recognized based on the recent work of Smith (1986) and Smith and Wall (1984). The monotypic genus Cumberlandia has generally has been classified in the family Margaritiferidae; however, preliminary analyses of electrophoretic data led Davis and Fuller (1981) to lump the margaritiferids with the Unionidae. Smith and Wall (1984) reinstated the Margaritiferidae to familial rank following and extensive examination and analysis of morphological characters. Some anatomical data on stomach anatomy (Smith, 1986) indicates Cumberlandia may require reduction to subgeneric level. This is supported by Davis and Fuller (1981), Ziuganov et al. (1994), Smith (2001), and Huff et al. (2004). Smith (2001) analyzied the taxonomic placement of the margaritiferid genera, recognizing Pseudunio, Margaritifera, and Margaritinopsis as valid based largely on morpological characters; with Margaritifera margaritifera the only species in the genus Margaritifera. Contrary to Smith (2001), Huff et al. (2004) investigated phylogenetic relationships using sequence data from five molecular markers and concluded recognition of of at least Margaritifera margaritifera, Margaritifera laevis, Margaritifera falcata, and Margaritifera auricularia with the following relationships: Cumberlandia + Margaritifera auricularia; Margaritifera falcata (Margaritifera marrianae + Margaritifera laevis); and to a lesser degree Dahurinaia dahurica + Margaritifera margaritifera. More recently, to monophyletic clades have been identified within Margaritiferidae based on COI data: one including M. margaritifera, M. dahurica, M. falcata, and M. laevis; and a second comprising M. auricularia and M. marocana (Araujo et al., 2009).
Conservation Status
Rank Method Rank calculation - Biotics v2
Review Date2024-05-31
Change Date2024-05-31
Edition Date2024-05-31
Edition AuthorsK. Jurist (1996); rev. Cordeiro, J. (2009); rev. T. Cornelisse (2024)
Threat ImpactHigh
Range Extent>2,500,000 square km (greater than 1,000,000 square miles)
Number of Occurrences> 300
Rank Reasons
Despite having a large range and many recent occurrences, this species is experiencing ongoing population declines due to several threats.
Range Extent Comments
This species occurs in British Columbia, Canada and in the western United States from Washington to Montana, south through Wyoming and Utah to California and in Alaska (Blevins et al. 2016; GBIF 2024).
Occurrences Comments
This species is known from at least approximately 375 occurrences using a 2 km separation distance and records from 1994-2024 (Blevins et al. 2017; GBIF 2024).
Threat Impact Comments
This species is threatened by habitat loss and degradation associated with dams and other waterway barriers, channelization, mining, and dredging operations; pollutants in wastewater discharges, including from sewage treatment plants and industrial operations; runoff of silt, fertilizers, pesticides, and other pollutants from land disturbance activities, such as development and agriculture implemented without adequate measures to control runoff; and drought conditions that reduce habitat, elevated water temperature, and reduce dilution of pollutants and sediment runoff (Blevins et al. 2017).
Ecology & Habitat

Habitat

This species prefers cold clean creeks and rivers that support salmonid populations. It can inhabit headwater streams less than a few feet wide, but is more common in larger rivers. It can even be found in some irrigation ditches in Oregon. Sand, gravel, and cobble are preferred substrates, especially in stable areas of the streambed. Large boulders hellp create stable enviroments by anchoring the substrate and creating a refuge from strong currents on the downstream side. (Nedeau et al., 2005). Vannote and Minshall (1982) note the best developed communities in central Idaho are found in areas with large stable cobble and boulder channel gravels.

Reproduction

Glochidial host fish include chinook salmon (Oncorhynchus tschawytscha), rainbow trout (Oncorhynchus mykiss), coho (Oncorhynchus kisutch), cutthroat trout (Salmo clarki), and steelhead trout (Salmo gairdneri) (Fuller, 1974; Karnat and Millemann, 1978).
Other Nations (2)
CanadaN5
ProvinceRankNative
British ColumbiaS5Yes
United StatesN3
ProvinceRankNative
UtahS1Yes
WyomingS3Yes
OregonS3Yes
CaliforniaS1Yes
NevadaS1Yes
WashingtonS3Yes
IdahoS2Yes
AlaskaSNRYes
MontanaS2Yes
Threat Assessments
ThreatScopeSeverityTiming
2 - Agriculture & aquacultureLarge - restrictedModerate or 11-30% pop. declineHigh (continuing)
2.3 - Livestock farming & ranchingLarge - restrictedModerate or 11-30% pop. declineHigh (continuing)
3 - Energy production & miningRestricted (11-30%)Serious or 31-70% pop. declineHigh (continuing)
3.2 - Mining & quarryingRestricted (11-30%)Serious or 31-70% pop. declineHigh (continuing)
7 - Natural system modificationsLarge (31-70%)Moderate or 11-30% pop. declineHigh (continuing)
7.2 - Dams & water management/useLarge (31-70%)Moderate or 11-30% pop. declineHigh (continuing)
9 - PollutionLarge - restrictedModerate or 11-30% pop. declineHigh (continuing)
9.1 - Domestic & urban waste waterRestricted (11-30%)Moderate or 11-30% pop. declineHigh (continuing)
9.3 - Agricultural & forestry effluentsRestricted (11-30%)Moderate or 11-30% pop. declineHigh (continuing)
11 - Climate change & severe weatherLarge (31-70%)Moderate or 11-30% pop. declineHigh (continuing)
11.2 - DroughtsLarge (31-70%)Moderate or 11-30% pop. declineHigh (continuing)

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Roadless Areas (45)
California (20)
AreaForestAcres
Bell QuinbyShasta-Trinity National Forest11,556
ChinquapinShasta-Trinity National Forest22,040
Cow CreekShasta-Trinity National Forest22,627
Devils RockShasta-Trinity National Forest16,209
Domeland Add.Sequoia National Forest3,046
KelseyKlamath National Forest3,237
Little French CShasta-Trinity National Forest11,529
MonarchSierra National Forest697
Orleans Mtn. CSix Rivers National Forest15,589
PacksaddleSix Rivers National Forest3,862
PantherShasta-Trinity National Forest12,016
PattisonShasta-Trinity National Forest29,299
Pilot CreekSix Rivers National Forest9,192
RinconSequoia National Forest54,610
SoliderSix Rivers National Forest14,918
South SierraInyo National Forest41,853
South SierraSequoia National Forest8,008
Tom MartinKlamath National Forest9,031
UnderwoodSix Rivers National Forest6,591
WoodpeckerSequoia National Forest11,936
Idaho (6)
AreaForestAcres
Bighorn - WeitasNez Perce-Clearwater National Forest254,845
Italian PeakCaribou-Targhee National Forest141,158
Lemhi RangeSalmon-Challis National Forest308,533
North Lochsa SlopeNez Perce-Clearwater National Forest117,662
Peace RockBoise National Forest191,734
SeceshPayette National Forest248,088
Montana (6)
AreaForestAcres
Allan Mountain (01946)Bitterroot National Forest104,184
Bear - Marshall - Scapegoat - SwanHelena National Forest51,360
Cube Iron - SilcoxLolo National Forest36,998
Italian PeakBeaverhead-Deerlodge National Forest90,401
Selway - Bitterroot (01067)Bitterroot National Forest114,953
Stony MountainLolo National Forest32,796
Oregon (10)
AreaForestAcres
Baldy MountainMalheur National Forest6,416
Coleman RimFremont National Forest10,638
Dixie ButteMalheur National Forest12,208
Drift CreekSiuslaw National Forest6,333
Hebo 1aSiuslaw National Forest13,930
HellholeUmatilla National Forest65,679
Limpy RockUmpqua National Forest6,782
Lookout MountainOchoco National Forest14,115
PotamusUmatilla National Forest5,389
Sky Lakes AWinema National Forest3,940
Utah (1)
AreaForestAcres
Stump CreekCaribou National Forest355
Washington (2)
AreaForestAcres
Black CanyonOkanogan National Forest9,681
PressentinMt Baker-Snoqualmie National Forest14,545
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