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Home/Species/ Slender-stemmed Monkeyflower

Erythranthe filicaulis

(S. Watson) G.L. Nesom & N.S. Fraga

Slender-stemmed Monkeyflower

G2Imperiled Found in 2 roadless areas NatureServe Explorer →
G2ImperiledGlobal Rank
HighThreat Impact
Identity
Unique IDELEMENT_GLOBAL.2.1253170
Element CodePDPHR012H0
Record TypeSPECIES
ClassificationSpecies
Classification StatusStandard
Name CategoryVascular Plant
Endemicendemic to a single state or province
KingdomPlantae
PhylumAnthophyta
ClassDicotyledoneae
OrderLamiales
FamilyPhrymaceae
GenusErythranthe
Synonyms
Mimulus filicaulisS. Wats.
Other Common Names
slenderstem monkeyflower (EN)
Concept Reference
Flora of North America Editorial Committee (FNA). 2019. Flora of North America north of Mexico. Vol. 17: Magnoliophyta: Tetrachondraceae to Orobanchaceae. Oxford Univ. Press, New York. xxiv + 737 pp.
Taxonomic Comments
Flora of North America Editorial Committee (2019) recognizes Erythranthe filicaulis in a broad sense, including Mimulus biolettii as a synonym. In contrast, Kartesz (1994, 1999) recognized M. filicaulis and M. biolettii as distinct species.
Conservation Status
Rank Method Rank calculation - Biotics v2
Review Date2026-03-03
Change Date1990-01-16
Edition Date2026-03-03
Edition AuthorsRusso, Mary (TNC WRO), rev. D. Gries, rev. A. Treher (2012), rev. Soteropoulos (2026)
Threat ImpactHigh
Range Extent250-1000 square km (about 100-400 square miles)
Number of Occurrences21 - 80
Rank Reasons
Erythranthe filicaulis is an annual herb found in open areas, though generally in partial shade, in disturbed, moist or vernally mesic, loamy soil on in meadows, cismontane woodland, lower montane coniferous forest, upper montane coniferous forest, and roadsides. It is endemic to the western United States in the central High Sierra Nevada of east-central California (Mairposa and Tuolumne counties). There are at least 22 occurrences, which face threats from development, including road and trail construction, logging, reforestation projects (especially those including herbicides), recreational activities (off road vehicles as well as campground and trails near sites), roadside and related maintenance, and grazing. Monitoring of populations should be conducted to improve our understanding of reproduction, plant abundance, threats, and trends, as well as continuing conservation measures to protect the taxon.
Range Extent Comments
Erythranthe filicaulis is endemic to the western United States in the central High Sierra Nevada of east-central California (Mairposa and Tuolumne counties) (FNA 2019, Jepson Flora Project 2026). Range extent was estimated to be 625 square kilometers using herbarium specimens, photo-based observations, and NatureServe Network occurrence data documented between 1994 and 2025 (RARECAT 2025, GBIF 2026, iNaturalist 2026, NatureServe 2026, SEINet 2026).
Occurrences Comments
By applying a 1 km separation distance to herbarium specimens, photo-based observations, and NatureServe Network occurrence data documented between 1994 and 2025, it is estimated that there are 22 occurrences rangewide (RARECAT 2025, GBIF 2026, iNaturalist 2026, NatureServe 2026, SEINet 2026). CNPS (2026) estimates that there are 49 occurrences presumed extant, including 36 occurrences that have not been observed for over 20 years.
Threat Impact Comments
This species faces threats from development, including road and trail construction, logging, reforestation projects (especially those including herbicides), recreational activities (off road vehicles as well as campground and trails near sites), roadside and related maintenance, and grazing (CNPS 2026).
Ecology & Habitat

Habitat

Erythranthe filicaulis grows in open areas, though generally in partial shade, in disturbed, moist or vernally mesic, loamy soil on in meadows, cismontane woodland, lower montane coniferous forest, upper montane coniferous forest, and roadsides (FNA 2019, CNPS 2026, Jepson Flora Project 2026).

Reproduction

This species flowers from April to August (CNPS 2026).
Terrestrial Habitats
Forest/WoodlandForest - ConiferForest - MixedWoodland - ConiferWoodland - MixedGrassland/herbaceous
Other Nations (1)
United StatesN2
ProvinceRankNative
CaliforniaS2Yes
Threat Assessments
ThreatScopeSeverityTiming
1 - Residential & commercial developmentRestricted (11-30%)Serious or 31-70% pop. declineHigh (continuing)
1.1 - Housing & urban areasSmall (1-10%)Serious or 31-70% pop. declineHigh (continuing)
1.3 - Tourism & recreation areasRestricted (11-30%)Serious - moderateHigh (continuing)
2 - Agriculture & aquacultureRestricted (11-30%)Moderate or 11-30% pop. declineHigh (continuing)
2.3 - Livestock farming & ranchingRestricted (11-30%)Moderate or 11-30% pop. declineHigh (continuing)
4 - Transportation & service corridorsLarge - restrictedModerate or 11-30% pop. declineHigh (continuing)
4.1 - Roads & railroadsLarge - restrictedModerate or 11-30% pop. declineHigh (continuing)
5 - Biological resource useRestricted (11-30%)Moderate or 11-30% pop. declineHigh (continuing)
5.3 - Logging & wood harvestingRestricted (11-30%)Moderate or 11-30% pop. declineHigh (continuing)
6 - Human intrusions & disturbanceRestricted (11-30%)Moderate or 11-30% pop. declineHigh (continuing)
6.1 - Recreational activitiesRestricted (11-30%)Moderate or 11-30% pop. declineHigh (continuing)
9 - PollutionSmall (1-10%)Serious - moderateHigh (continuing)
9.3 - Agricultural & forestry effluentsSmall (1-10%)Serious - moderateHigh (continuing)

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Plant Characteristics
DurationANNUAL
Economic Value (Genus)No
Roadless Areas (2)
California (2)
AreaForestAcres
Ferguson RidgeSierra National Forest6,104
North MountainStanislaus National Forest7,856
References (10)
  1. Barker, W.R., G.L. Nesom, P.M. Beardsley, and N.S. Fraga. 2012. A taxonomic conspectus of Phrymaceae: A narrowed circumscriptions for <i>Mimulus</i>, new and resurrected genera, and new names and combinations. Phytoneuron 39:1-60.
  2. California Native Plant Society (CNPS), Rare Plant Program. 2026. Inventory of Rare and Endangered Plants of California, online edition, v9.5. Online. Available: https://www.rareplants.cnps.org (accessed 2026).
  3. Flora of North America Editorial Committee (FNA). 2019. Flora of North America north of Mexico. Vol. 17: Magnoliophyta: Tetrachondraceae to Orobanchaceae. Oxford Univ. Press, New York. xxiv + 737 pp.
  4. Global Biodiversity Information Facility (GBIF). 2026. Global Biodiversity Information Facility (GBIF) data portal. Online. Available: https://www.gbif.org/ (accessed 2026).
  5. Jepson Flora Project (eds.) 2026. Jepson eFlora. Online. Available: https://ucjeps.berkeley.edu/eflora/ (accessed 2026).
  6. Kartesz, J.T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. 2nd edition. 2 vols. Timber Press, Portland, OR.
  7. NatureServe. 2026. NatureServe Network Biodiversity Location Data. NatureServe, Arlington, Virginia.
  8. <p>NatureServe's Rapid Analysis of Rarity and Endangerment Conservation Assessment Tool (RARECAT). 2025. Version: 2.1.1 (released April 04, 2025).</p>
  9. Skinner, M.W., and B.M. Pavlik, eds. 1997 (1994). Inventory of rare and endangered vascular plants of California. 1997 Electronic Inventory Update of 1994 5th edition, California Native Plant Society, Special Publication No. 1, Sacramento.
  10. Southwest Environmental Information Network (SEINet). 2026. Collections Databases. Online. Available: https://swbiodiversity.org/seinet/collections/index.php (accessed 2026).