Cardamine micranthera - Rollins
Small-anther Bittercress
Taxonomic Status: Accepted
Related ITIS Name(s): Cardamine micranthera Rollins (TSN 22803)
Unique Identifier: ELEMENT_GLOBAL.2.145351
Element Code: PDBRA0K0P0
Informal Taxonomy: Plants, Vascular - Flowering Plants - Mustard Family
 
Kingdom Phylum Class Order Family Genus
Plantae Anthophyta Dicotyledoneae Capparales Brassicaceae Cardamine
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Concept Reference
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Concept Reference: 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.
Concept Reference Code: B94KAR01HQUS
Name Used in Concept Reference: Cardamine micranthera
Taxonomic Comments: Occasional plants are found in the field that look somewhat intermediate between C. micranthera and C. rotundifolia; however, they appear to be environmentally influenced individuals of C. micranthera growing in mucky conditions. Given the very close genetic similarity of these two Cardamine species (Wieboldt 2002), it would be nice to better understand the effect of environment on morphology and to see whether it correlates with the small genetic differences so far known to exist or whether intermediacy is solely attributable to environmental effects. At present, the taxonomic question seems to be resting on the identity of these intermediate individuals (T. Wiebolt, pers. comm.).
Conservation Status
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NatureServe Status

Global Status: G2
Global Status Last Reviewed: 13Jun2017
Global Status Last Changed: 31Jan2006
Ranking Methodology Used: Ranked by calculator
Rounded Global Status: G2 - Imperiled
Reasons: Endemic to North Carolina and Virginia and with 32-35 extant occurrences; locally abundant at some sites. Some populations are in watersheds that have been severely altered by residential development and agricultural use, and at least some are threatened by continued conversion of habitat, encroachment of exotic species, beaver activity, runoff and livestock-related erosion and trampling. All but two occurrences are on private land without adequate protection.
Nation: United States
National Status: N2

U.S. & Canada State/Province Status
Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
United States North Carolina (S1), Virginia (S2)

Other Statuses

U.S. Endangered Species Act (USESA): LE: Listed endangered (21Sep1989)
U.S. Fish & Wildlife Service Lead Region: R4 - Southeast

NatureServe Global Conservation Status Factors

Range Extent Comments: All extant occurrences are in the Dan River drainage in North Carolina (Stokes and historically, Forsyth County) and Virginia (Patrick County) (USFWS 2016).

Area of Occupancy: 26-125 4-km2 grid cells
Area of Occupancy Comments:  

Number of Occurrences: 21 - 80
Number of Occurrences Comments: There are between 32 and 37 extant occurrences (EOs). In North Caronlina, there are 17 extant EOs, 5 with no plants seen during the last survey, and one occurrence is extirpated. In Virginia, there are 15 extant EOs.

Population Size Comments: Population sizes range from 1 to 8,000 or 10,000 per element occurrence. These population number may appear to be substantial but like other annuals, population size can vary from year to year.

Number of Occurrences with Good Viability/Integrity: Some (13-40)

Overall Threat Impact: Very high - high
Overall Threat Impact Comments: The primary threat to this taxon is habitat alteration through continued conversion and degradation of habitat. Increased land disturbances (conversion, impoundment, channelization) particularly from silviculture and residential development within the Dan River watershed are a threat to the long-term survival of this species due to resulting degradation (sedimentation, canopy loss, invasive species) of stream and seepage habitats (USFWS 2016). Some extant populations are in close proximity to agricultural fields and pastures where accidental herbicide drift or runoff from these areas or from adjacent powerline maintenance could destroy the populations. Plants may also be trampled by livestock (Murdock and Weakley 1991) contribute to erosion from stream banks. Additional threats include flooding and encroachment of exotic species such as Japanese honeysuckle or Japanese Stiltgrass. Persistent drought is a potential threat because C. micranthera inhabits moist areas with a cool microclimate (Murdock and Weakley 1991).

Short-term Trend: Decline of <50% to Relatively Stable
Short-term Trend Comments: Given the available information on plant numbers, most occurrences are believed to have a declining trend and 2-5 are extirpated or no plants were found during the last survey (USFWS 2016). Only two occurrences have had an increase in population size. Populations in North Carolina are believed to be in decline as they are locally endemic to an area heavily impacted by agriculture and residential development. The situation in Virginia is unclear as inventories for this species have generally focused on exploring new habitat to more fully assess the distribution of the species and less on any consistent monitoring of existing populations. An absence of plants was noted in 1999 in one area where it was seen in 1990 (Van Alstine and Killeffer 1999) and another population in streamside and seepage habitat within a pasture suffered a decline from 1998 to 2004, possibly due to a combination of drought conditions and cattle trampling. Beaver activity has also been cited as a threat (USFWS 2016).

Long-term Trend: Unknown

Intrinsic Vulnerability Comments: Little is known about the age of maturity and fecundity of this species; however the plant is a perennial and flowers and fruits annually.

Environmental Specificity: Narrow. Specialist or community with key requirements common.
Environmental Specificity Comments: C. micranthera occupies moist soils of the upper Piedmont that are fully to partially shaded (Murdock and Weakley 1991). More specifically, it is typically found in wet, boggy soils of deciduous woodlands and moist to wet soils along the edge of small to intermediate sized streams (NCA 1996). Within the stream bed plants also inhabit sand and gravel bars and wet rock crevices (Murdock and Weakley 1991).

Other NatureServe Conservation Status Information

Distribution
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Global Range: All extant occurrences are in the Dan River drainage in North Carolina (Stokes and historically, Forsyth County) and Virginia (Patrick County) (USFWS 2016).

U.S. States and Canadian Provinces

Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
Color legend for Distribution Map

U.S. & Canada State/Province Distribution
United States NC, VA

Range Map
No map available.


U.S. Distribution by County Help
State County Name (FIPS Code)
NC Forsyth (37067)*, Stokes (37169)
VA Patrick (51141)
* Extirpated/possibly extirpated
U.S. Distribution by Watershed Help
Watershed Region Help Watershed Name (Watershed Code)
03 Upper Dan (03010103)+
+ Natural heritage record(s) exist for this watershed
* Extirpated/possibly extirpated
Ecology & Life History
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Basic Description: A slender, erect perennial herb with fibrous roots and one (rarely more) simple or branched stem(s), growing up to 4 dm tall, that produce white flowers in April and May.

Diagnostic Characteristics: Basal leaves are 1 to 5 cm long (occasionally longer), 0.5 to 2.0 cm wide, crenate, with one (rarely two) pairs of small lateral lobes or leaflets. Stem leaves are alternate and mostly unlobed, 1 to 1.5 cm long, crenate and cuneate. Flowering and fruiting occur in April and May. Flowers are subtended by leafy bracts, have 4 white petals, 6 stamens, and small round anthers. Fruit is a silique, 0.8 to 1.2 cm long and approximately 1 mm in diameter, with a beak 1 to 1.2 mm long (Rollins 1940).

The most similar species is Cardamine rotundifolia; however, Cardamine micranthera can be distinguished by its much smaller (0.5 mm vs. 1.2 to 1.6 mm long) anthers that are nearly orbicular instead of oblong, smaller flower (petals 1.2 to 2 mm wide vs. 2.5 to 3.5 mm wide), and more angulate and nonclasping leaves. Cardamine rotundifolia is typically branched from the base, the decumbent stems later developing proliferating branches from the main axis and from the inflorescence. In contrast, Cardamine micranthera is typically erect and only occasionally has decumbent stems, but these do not develop proliferating branches (Murdock and Weakley 1991).

Cardamine pennsylvanica sometimes resembles Cardamine micranthera but the former typically has three to five pairs of lateral leaflets that have more definitively toothed margins and a terminal leaflet comprising ¼ to 1/3 of the total leaf length; C. micranthera has one to two pairs of lateral leaflets (or none) with the terminal leaflet nearly ½ of the total length (Murdock and Weakley 1991).

Duration: BIENNIAL, PERENNIAL
Reproduction Comments: Appears not to be limited by seed dispersal ability. It is noted that healthy metapopulations seem to be maintained by seed from upstream sites, implying dispersal is water driven and can likely carry the tiny (1mm) seeds significant distances (USFWS 2016).
Riverine Habitat(s): CREEK
Palustrine Habitat(s): Riparian
Terrestrial Habitat(s): Forest - Hardwood, Forest/Woodland
Habitat Comments: On the upper Piedmont, it occupies seepages, wet rock crevices, streambanks, sandbars, and wet woods along small streams that are fully to partially shaded (Murdock and Weakley 1991).  More specifically, the wet, boggy soils where it is typically found are in deciduous woodlands and in moist to wet soils along the edge of small to intermediate sized streams (NCA 1996) and within the stream bed plants also inhabit sand and gravel bars and wet rock crevices (Murdock and Weakley 1991).
Economic Attributes Not yet assessed
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Management Summary
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Stewardship Overview: The habitat management for this species involves protecting the seepages, streambanks, and gravel/sandbars from destruction or degradation due to erosion and sedimentation, livestock trampling, impoundments, either human-created or from beaver activity, and competition from invasive plant speices. Erosion and sedimentation within the range of this species arises from land uses including silviculture, agriculture, and increasingly from residential development.

Population/Occurrence Delineation Not yet assessed
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Population/Occurrence Viability
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Excellent Viability: 500+ plants in high quality natural habitat.
Good Viability: 201-500 plants in high quality natural habitat or 500+ plants in habitat subject to livestock trampling, silviculture, or highly influenced by invasive species.

Fair Viability: 101-200 plants in high quality natural habitat or 201-500 plants in habitat subject to livestock trampling, silviculture, or highly influenced by invasive species.

Poor Viability: <100 plants in any condition or 101-200 plants in habitat subject to livestock trampling, silviculture, or highly influenced by invasive species.

Justification: Natural habitat includes wet, boggy soils of deciduous woodlands and moist to wet soils along the edge of small to intermediate sized streams undisturbed by livestock trampling, silviculture, or highly influenced by invasive species. Populations in areas subject to livestock or silvicultural practices are downgraded by 1 rank due to threats to habitat integrity resulting from these pressures.

Key for Ranking Species Element Occurrences Using the Generic Approach (2008).
Date: 31Jan2006
Author: North Carolina Natural Heritage Program
U.S. Invasive Species Impact Rank (I-Rank) Not yet assessed
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Authors/Contributors
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NatureServe Conservation Status Factors Edition Date: 13Jun2017
NatureServe Conservation Status Factors Author: S. Mason and N. Van Alstine, rev. A. Treher (2017)
Management Information Edition Date: 31Jan2006
Management Information Edition Author: S. Mason and N. Van Alstine
Element Ecology & Life History Edition Date: 31Jan2006
Element Ecology & Life History Author(s): S. Mason and N. Van Alstine

Botanical data developed by NatureServe and its network of natural heritage programs (see Local Programs), The North Carolina Botanical Garden, and other contributors and cooperators (see Sources).

References
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  • CPC [Center for Plant Conservation]. 2005. National Collection Plant Profile: Cardamine micranthera. Center for Plant Conservation, Missouri Botanical Garden, St. Louis Missouri. http://www.centerforplantconservation.org/

  • Fowler, J. 2016. Specialist Bees of the Mid-Atlantic: Host Plants and Habitat Conservation. The Maryland Entomologist 6(4):2-40.

  • 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.

  • Murdock, N., and A. Weakley. 1991. Recovery plan for small-anthered bittercress (Cardamine micranthera Rollins). U.S. Fish and Wildlife Service, Southeast Region, Atlanta, GA. 22 pp.

  • NCA. 1996. Annual Report for the Center for Plant Conservation Taxa in the National Collection. The North Carolina Arboretum. p.5.

  • Radford, A.E., H.E. Ahles, and C.R. Bell. 1968. Manual of the vascular flora of the Carolinas. Univ. North Carolina Press, Chapel Hill, NC. 1183 pp.

  • Rollins, R.C. 1940. A new Cardamine from North Carolina. Castanea 5(5): 87-88.

  • Rollins, R.C. 1993a. The Cruciferae of continental North America: Systematics of the mustard family from the Arctic to Panama. Stanford Univ. Press, Stanford, California. 976 pp.

  • U.S. Fish and Wildlife Service (USFWS). 2016. Small-anthered bittercress (Cardamine micranthera) 5-year review: Summary and Evaluation. USFWS Southeast Region, Asheville Ecological Field Services Office, Asheville, North Carolina.

  • U.S. Fish and Wildlife Service. 1989. Small anthered bittercress determined to be endangered. Federal Register 54(182): 38947-38949.

  • Van Alstine, N.E. and S.E. Killeffer. 1999. Status survey for Cardamine micranthera Rollins (small-anthered bittercress) in Virginia. Natural Heritage Tech. Rept. 99-23. Virginia Department of Conservation and Recreation, Division of Natural Heritage, Richmond, VA. 45 pp.

  • Wieboldt, T. F. 2002. Molecular study of small-anthered bittercress, Cardamine micranthera. Final Report, Dec. 14, 2002, prepared for Virginia Department of Agriculture and Consumer Services, Office of Plant and Pest Services. 9 pp.

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