Najas minor - All.
Brittle Naiad
Other English Common Names: Brittle Waternymph
Other Common Names: brittle waternymph
Taxonomic Status: Accepted
Related ITIS Name(s): Najas minor All. (TSN 39002)
French Common Names: petite naļade
Unique Identifier: ELEMENT_GLOBAL.2.157427
Element Code: PMNAJ01070
Informal Taxonomy: Plants, Vascular - Flowering Plants - Other flowering plants
 
Kingdom Phylum Class Order Family Genus
Plantae Anthophyta Monocotyledoneae Najadales Najadaceae Najas
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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: Najas minor
Conservation Status
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NatureServe Status

Global Status: GNR
Global Status Last Changed: 22Mar1994
Rounded Global Status: GNR - Not Yet Ranked
Nation: United States
National Status: NNA
Nation: Canada
National Status: NNA (04Nov2017)

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 Alabama (SNA), Arkansas (SNA), Delaware (SNA), Florida (SNA), Georgia (SNR), Illinois (SNA), Indiana (SNA), Iowa (SNA), Kentucky (SNA), Louisiana (SNA), Massachusetts (SNR), Michigan (SNA), Minnesota (SNA), Mississippi (SNA), New Hampshire (SNA), New York (SNA), North Carolina (SNA), Ohio (SNA), Oklahoma (SNA), Pennsylvania (SNA), South Carolina (SNA), Tennessee (SNA), Vermont (SNA), Virginia (SNA), West Virginia (SNA)
Canada Ontario (SNA)

Other Statuses

NatureServe Global Conservation Status Factors

Other NatureServe Conservation Status Information

Distribution
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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
NOTE: The distribution shown may be incomplete, particularly for some rapidly spreading exotic species.

U.S. & Canada State/Province Distribution
United States ALexotic, ARexotic, DEexotic, FLexotic, GA, IAexotic, ILexotic, INexotic, KYexotic, LAexotic, MA, MIexotic, MNexotic, MSexotic, NCexotic, NHexotic, NYexotic, OHexotic, OKexotic, PAexotic, SCexotic, TNexotic, VAexotic, VTexotic, WVexotic
Canada ONexotic

Range Map
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Ecology & Life History Not yet assessed
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Economic Attributes Not yet assessed
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Management Summary Not yet assessed
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Population/Occurrence Delineation Not yet assessed
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Population/Occurrence Viability
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U.S. Invasive Species Impact Rank (I-Rank)
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Disclaimer: While I-Rank information is available over NatureServe Explorer, NatureServe is not actively developing or maintaining these data. Species with I-RANKs do not represent a random sample of species exotic in the United States; available assessments may be biased toward those species with higher-than-average impact.

I-Rank: High/Medium
Rounded I-Rank: High
I-Rank Reasons Summary: Najas minor is an annual rooted, submersed aquatic plant established throughout the eastern US. It inhabits shallow waters of ponds, lakes, reservoirs, marshes, and slow-moving streams and rivers. It can form thick, dense, monospecific mats and stands and can out-compete native vegetation; these dense mats can reduce light availability, deplete oxygen, and increase sedimentation. It is apparently more tolerant of turbid and eutrophic conditions than native Najas species, providing it a competitive advantage at heavily-modified sites. This species is very easily fragmented, with fragments capable of forming new colonies. Waterfowl and boat traffic aid in long-distance transport of fragments and seeds. This species appears to be spreading, both westward in the US and locally within areas already occupied. Fragmentation makes mechanical management difficult; although herbicides are effective, they can have significant impacts on co-occurring native species.
Subrank I - Ecological Impact: Medium
Subrank II - Current Distribution/Abundance: High/Low
Subrank III - Trend in Distribution/Abundance: Medium
Subrank IV - Management Difficulty: High/Medium
I-Rank Review Date: 24Sep2007
Evaluator: Gravuer, K.
Native anywhere in the U.S?
Native Range: Eurasia, including France, Portugal, Austria, Belgium, Czechoslovakia, Germany, Hungary, Poland, the European part of the Russian Federation, Ukraine, Bulgaria, Italy, Romania, Yugoslavia, Morocco, Turkey, India, and Japan (USDA-ARS 2007).

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Screening Questions

S-1. Established outside cultivation as a non-native? YES
Comments: This species is a non-native that is established outside of cultivation (Kartesz 1999).

S-2. Present in conservation areas or other native species habitat? Yes
Comments: Found in ponds, lakes, and reservoirs/artificial lakes, especially in the shallow waters along the shore; in streams and rivers, especially when slow-moving; and in marshes with deep enough water to submerge the plants (Braun 1967, Radford, Ahles, and Bell 1968, Godfrey and Wooten 1979, Mohlenbrock 1986, Voss 1972, Gleason and Cronquist 1991, Yatskievych 1999, Flora of North America Editorial Committee 2000, Rhoads and Block 2000, USACE 2002, Mehrhoff et al. 2003, Wunderlin and Hansen 2003, Robinson 2004, Jones 2005, Selsky 2006, Weakley 2007).

Subrank I - Ecological Impact: Medium

1. Impact on Ecosystem Processes and System-wide Parameters:Moderate significance
Comments: This species can form thick, dense, monospecific mats and stands (USACE 2002, Mehrhoff et al. 2003), reducing light availability for other submerged plants (Robinson 2004). Decay of dense mats can deplete oxygen levels in the water, to the detriment of aquatic animals such as fish (Robinson 2004). Sediment levels often increase with increasing abundance of this species (Robinson 2004)

2. Impact on Ecological Community Structure:Moderate significance
Comments: Can form thick, dense, monospecific mats and stands (USACE 2002, Mehrhoff et al. 2003), aided by its ability to grow rapidly early in the season and shade out native plants (OHDNAP 2001). Can out-compete native vegetation, especially native Najas species, and drive out the animals that depend on the native species (Robinson 2004). Sometimes found in mixed stands with other invasive exotics (NCSU 2003).

3. Impact on Ecological Community Composition:High/Moderate significance
Comments: More tolerant of turbidity and eutrophic conditions than some of the native species of Najas and has replaced them in many instances (Wentz and Stuckey 1971 cited in USACE 2002, Robinson 2004). Can form thick, dense, monospecific mats and stands (USACE 2002, Mehrhoff et al. 2003), aided by its ability to grow rapidly early in the season and shade out native plants (OHDNAP 2001). Can out-compete native vegetation and drive out the animals that depend on the native species (Robinson 2004). Decay of dense mats can deplete oxygen levels in the water, to the detriment of aquatic animals such as fish (Robinson 2004).

4. Impact on Individual Native Plant or Animal Species:Medium/Low significance
Comments: Effects on native Najas species appear somewhat disproportionate, as this species occupies a very similar ecological niche with the exception of its increased tolerance of turbidity and eutrophic conditions, which has provided it an advantage over its native congeners in human-modified systems (Wentz and Stuckey 1971 cited in USACE 2002, Robinson 2004).

5. Conservation Significance of the Communities and Native Species Threatened:Medium/Low significance
Comments: Probably only occasionally threatens high-quality communities, since the species appears to be at greatest advantage compared to natives in eutrophic and/or turbid conditions (Wentz and Stuckey 1971 cited in USACE 2002, Robinson 2004).

Subrank II. Current Distribution and Abundance: High/Low

6. Current Range Size in Nation:High/Moderate significance
Comments: Established throughout the eastern United States, west to Oklahoma, Kansas, and Nebraska (USGS 2007). Several sources note that differentiating this species from several similar Najas species can be difficult, leaving open the possibility that its distribution has been incompletely recorded (Les and Mehrhoff 1999, USACE 2002).

7. Proportion of Current Range Where the Species is Negatively Impacting Biodiversity:Medium/Low significance
Comments: Although this species is clearly perceived as a threat to aquatic ecosystems in some areas (OHDNAP 2001, USACE 2002) and has been declared noxious in several states (USDA-ARS 2007), it has not yet caused major problems in New England (Eliopoulos and Stangel 2001, Mehrhoff et al. 2003) and is considered a "low threat to native plant communities" and "may become a problem in the future" by agencies in North Carolina and Tennessee (Franklin 2005, TN-EPPC 2004).

8. Proportion of Nation's Biogeographic Units Invaded:Moderate significance
Comments: Between 20-50% of HUCs are invaded, based on visual comparison of the generalized range and HUCs map (USGS 2002).

9. Diversity of Habitats or Ecological Systems Invaded in Nation:Medium/Low significance
Comments: Found in ponds, lakes, and reservoirs/artificial lakes, especially in the shallow waters along the shore; in streams and rivers, especially when slow-moving; and in marshes with deep enough water to submerge the plants (Braun 1967, Radford, Ahles, and Bell 1968, Godfrey and Wooten 1979, Mohlenbrock 1986, Voss 1972, Gleason and Cronquist 1991, Yatskievych 1999, Flora of North America Editorial Committee 2000, Rhoads and Block 2000, USACE 2002, Mehrhoff et al. 2003, Wunderlin and Hansen 2003, Robinson 2004, Jones 2005, Selsky 2006, Weakley 2007). Plants are rooted and grow submersed and are typically found in water from 2 to 15 feet deep (Mehrhoff et al. 2003). This species is often found in waters that are alkaline and is more tolerant of turbidity and eutrophic conditions than some of the native species of Najas (Wentz and Stuckey 1971 cited in USACE 2002, Hellquist and Crow 1980, Gleason and Cronquist 1991).

Subrank III. Trend in Distribution and Abundance: Medium

10. Current Trend in Total Range within Nation:Moderate significance
Comments: USGS (2007) reports several new state records (e.g. IA, KS) within the past few years, suggesting that the generalized range is expanding westward. Wisconsin, where the species has not yet established, perceives it as a potential threat due to range expansion (IPAW 2003). Spread is apparently ongoing in some areas of the southeast as well (Yatskievych 1999, NCSU 2003, South Carolina Aquatic Invasive Species Task Force 2007). However, spread eastward into New England from New York and western Massachusetts appears to be limited (Hellquist and Crow 1980, Mehrhoff et al. 2003). Notably, the true spread dynamics of this species are somewhat obscured by the difficulty of differentiating it from several similar Najas species (Les and Mehrhoff 1999, USACE 2002).

11. Proportion of Potential Range Currently Occupied:Low significance
Comments: Establishment throughout the eastern US and current spread westward suggests that many aquatic habitats of the western US, as-yet uninvaded, may be suitable (Yatskievych 1999). However, limitations on its spread eastward into New England from New York (Hellquist and Crow 1980, Mehrhoff et al. 2003) suggests that some of its habitat requirements (e.g. preference for alkaline waters) may not be met throughout the as-yet uninvaded range.

12. Long-distance Dispersal Potential within Nation:High/Moderate significance
Comments: The primary method of dispersal is fragmentation, as plants are extremely brittle and can break into fragments capable of regenerating new plants with little perturbation (Mehrhoff et al. 2003). Dispersal also frequently occurs by seed (Les and Mehrhoff 1999, Selsky 2006). Waterfowl are an important dispersal agent, consuming seeds and transporting plant fragments (Mehrhoff et al. 2003, Robinson 2004, MIPAG 2005, Selsky 2006). Najas is a choice waterfowl food, and fruits are consumed by 20 American duck species at quantities that can exceed 4000 per bird (Martin and Uhler 1939 and McAtee 1939, cited in Les and Mehrhoff 1999). In the 1930s, governmental agencies deliberately introduced Najas minor for waterfowl food in the Great Lakes and possibly elsewhere (Mills et al. 1993 cited in Kolar and Lodge 2000, Les and Mehrhoff 1999); however, that practice apparently lasted only a few years. Other important means of long-distance dispersal include boats and boating gear (Mehrhoff et al. 2003, NCSU 2003, Robinson 2004, Selsky 2006) and water currents (USACE 2002, NCSU 2003, Robinson 2004). Some initial spread may also have occurred from aquaria being dumped into local waterbodies. (Les and Mehrhoff 1999); however, this is not an important means of dispersal for this species today (NRCS 2007).

13. Local Range Expansion or Change in Abundance:Moderate significance
Comments: Becoming more abundant in eastern North America (Haynes 1979 cited in Weakley 2007, NCSU 2003); specifically noted to be spreading rapidly in Missouri, Connecticut, and South Carolina (Yatskievych 1999, Capers et al. 2005, South Carolina Aquatic Invasive Species Task Force 2007).

14. Inherent Ability to Invade Conservation Areas and Other Native Species Habitats:Medium/Low significance
Comments: Apparently can inhabit sites with only moderate disturbance (i.e. significant disturbance not necessary for establishment) (IPAW 2003). Disturbance can facilitate rapid expansion, however; for example, in North Carolina it has been observed to replaces other exotics (e.g., hydrilla) following management operations (NCSU 2003).

15. Similar Habitats Invaded Elsewhere:Low significance
Comments: Also established in Ontario, Canada (Kartesz 1999) and in China (Randall 2002), apparently in similar habitats.

16. Reproductive Characteristics:High significance
Comments: Reproduces both by seed and vegetatively, with fragments capable of dispersing and subsequently founding populations in new locations (Mehrhoff et al. 2003, NCSU 2003, Robinson 2004). Les and Mehrhoff (1999) note that annual Najas species, such as N. minor, typically produce prodigious quantities of seed. Data collected from reservoirs in the Tennessee River system have shown seed banks to be tens of millions of seed per hectare at productive sites (USACE 2002). Growth rate appears to be rapid (NRCS 2007).

Subrank IV. General Management Difficulty: High/Medium

17. General Management Difficulty:Moderate significance
Comments: Harvesting (manual removal) of this species can greatly reduce biomass at a site, but can be challenging because the brittle plants fragment so easily (with fragments capable of dispersing and regenerating) (OHDNAP 2001, Robinson 2004). Several herbicides have been used with success (OHDNAP 2001, Robinson 2004). Benthic barriers have also been used (USACE 2002, Robinson 2004).

18. Minimum Time Commitment:Medium/Low significance
Comments: The presence of a significant seed bank up (USACE 2002) may require several years of follow-up. Follow-up may also be necessary if manual control methods are used, to check for fragments that escaped the initial treatment.

19. Impacts of Management on Native Species:High/Moderate significance
Comments: Herbicide appears to be the most effective means of control; however, this could have significant detrimental impacts on any co-occurring natives. Co-occurring natives might also be damaged by large-scale harvesting operations. Benthic barriers are known to be detrimental to benthic organisms (Robinson 2004).

20. Accessibility of Invaded Areas:Medium/Low significance
Comments: Because this species is aquatic, some invaded areas may be difficult to reach.
Authors/Contributors
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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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  • Braun, L.E. 1967. The Monocotyledoneae: cat-tails to orchids. Vol. One. Ohio State Univ. Press, Columbus, Ohio. 464 pp.

  • Capers, R. S., R. Selsky, G. J. Bugbee, and J. C. White. 2005. Aquatic plants among most destructive invasives. Frontiers of Plant Science: A report from the Connecticut Agricultural Experiment Station, New Haven 55(2): 7-9.

  • Catling, P.M., and S.M. McKay. 1980. Halophytic plants in southern Ontario. Canadian Field-Naturalist 94(3):248-258.

  • Eliopoulos, C. and P. Stangel. 2001. Lake Champlain 2000: Status of aquatic nuisance species. Final Report, May 2001. Prepared for the Lake Champlain Basin Program. Waterbury, VT.

  • Flora of North America Editorial Committee. 2000. Flora of North America north of Mexico. Vol. 22. Magnoliophyta: Alismatidae, Arecidae, Commelinidae (in part), and Zingiberidae. Oxford Univ. Press, New York. xxiii + 352 pp.

  • Franklin, M., compiler. 2005. Invasive exotic plants in NC 2005. Online: http://www.ncwildflower.org/invasives/invasives.htm. Accessed 2005.

  • Hellquist, C. B. and J. Straub. 2002. A guide to selected invasive non-native aquatic species in Massachusetts. Massachusetts Department of Environmental Management, Lakes and Ponds program. Online. Available: http://fishkillcreekwatershed.org/pubs/MA_Aquatic_Invasive_Species_Guide.pdf

  • Hellquist, C.B. and G.E. Crow. 1980. Aquatic vascular plants of New England: Part 1. Zosteraceae, Potamogetonaceae, Zannichelliaceae, Najadaceae. New Hampshire Experiment Station, Durham, New Hampshire. 66 p.

  • Invasive Plants Association of Wisconsin (IPAW). 2003. IPAW working list of the invasive plants of Wisconsin: a call for comments and information. Plants Out of Place, Issue 4. Online. Available: http://www.ipaw.org/newsletters/issue4.pdf (accessed 2006).

  • 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.

  • Kartesz, J.T. 1996. Species distribution data at state and province level for vascular plant taxa of the United States, Canada, and Greenland (accepted records), from unpublished data files at the North Carolina Botanical Garden, December, 1996.

  • Kartesz, J.T. 1999. A synonymized checklist and atlas with biological attributes for the vascular flora of the United States, Canada, and Greenland. First edition. In: Kartesz, J.T., and C.A. Meacham. Synthesis of the North American Flora, Version 1.0. North Carolina Botanical Garden, Chapel Hill, N.C.

  • Kolar, C. S. and D. M. Lodge. 2000. Freshwater nonindigenous species: Interactions with other global changes. pg. 3-30 in Mooney, H. A. and R. J. Hobbs, eds. Invasive species in a changing world. Island Press, Washington, DC.

  • Les, D. H. and L. J. Mehrhoff. 1999. Introduction of nonindigenous aquatic vascular plants in southern New England: a historical perspective. Biological Invasions 1: 281-300.

  • Massachusetts Invasive Plant Advisory Group (MIPAG). 2005, April 1 last update. The evaluation of non-native plant species for invasiveness in Massachusetts. Online. Available: http://www.mnla.com/pdf/invasive/MIPAG_final_050325_rev.pdf (Accessed 2005)

  • Mehrhoff, L.J., J.A. Silander, Jr., S.A. Leicht and E. Mosher. 2003. IPANE: Invasive Plant Atlas of New England. Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, CT. Online. Available: http://invasives.eeb.uconn.edu/ipane/.

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  • Ohio Department of Natural Areas and Parks (OHDNAP). 2001. Invasive Plants of Ohio: Lesser Naiad and Curly Pondweed. Fact Sheet 18. Online. Available: http://www.dnr.state.oh.us/Portals/3/invasive/pdf/invasivefactsheet18.pdf (Accessed 2007).

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  • Selsky, R. 2006. Minor naiad (Najas minor) in Connecticut. Online. Available: http://www.hort.uconn.edu/cipwg/invader_month/Najas_minor_invader.pdf (Accessed 2007).

  • South Carolina Aquatic Invasive Species Task Force. 2007. State management plan for aquatic invasive species in South Carolina. South Carolina Deparment of Natural Resouces. Online. Available: http://www.dnr.sc.gov/water/envaff/aquatic/aisfiles/draftscmgmtplan8092007.pdf

  • Tennessee Exotic Pest Plant Council. 2004. Invasive exotic pest plants in Tennessee - 2004. Available: http://www.tneppc.org/TNEPPC2004PlantList-8x11.pdf. Accessed 2005.

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  • Voss, E.G. 1972. Michigan flora: A guide to the identification and occurrence of the native and naturalized seed-plants of the state. Part I. Gymnosperms and monocots. Cranbrook Institute of Science and Univ. Michigan Herbarium. Ann Arbor. 488 pp.

  • Weakley, A.S. 2007. Flora of the Carolinas, Virginia, Georgia, and surrounding areas. Working draft of 11 January 2007. University of North Carolina Herbarium (NCU), North Carolina Botanical Garden, University of North Carolina at Chapel Hill. [http://www.herbarium.unc.edu/flora.htm (accessed 2007)]

  • Yatskievych, G. 1999. Steyermark's Flora of Missouri, Volume 1. Revised edition. Missouri Department of Conservation, Jefferson City and Missouri Botanical Garden Press, St. Louis.

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