Hydrocharis morsus-ranae - L.
Common Frogbit
Other English Common Names: European Frogbit
Other Common Names: common frogbit
Taxonomic Status: Accepted
Related ITIS Name(s): Hydrocharis morsus-ranae L. (TSN 503098)
French Common Names: hydrocharide grenouillette
Unique Identifier: ELEMENT_GLOBAL.2.155546
Element Code: PMHYD06010
Informal Taxonomy: Plants, Vascular - Flowering Plants - Other flowering plants
 
Kingdom Phylum Class Order Family Genus
Plantae Anthophyta Monocotyledoneae Hydrocharitales Hydrocharitaceae Hydrocharis
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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: Hydrocharis morsus-ranae
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 (22Mar1994)

U.S. & Canada State/Province Status
United States New York (SNA)
Canada Ontario (SNA), Quebec (SNA)

Other Statuses

NatureServe Global Conservation Status Factors

Other NatureServe Conservation Status Information

Distribution
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U.S. States and Canadian Provinces
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NOTE: The distribution shown may be incomplete, particularly for some rapidly spreading exotic species.

U.S. & Canada State/Province Distribution
United States NYexotic
Canada ONexotic, QCexotic

Range Map
No map available.

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: Established in and around the Great Lakes region (Lake Ontario, Lake Erie, New York, Vermont [incl. Lake Champlain], and Michigan) and in Washington state. First recorded in the United States in 1974; spread since that time has been relatively rapid and appears to be ongoing. This species forms large, dense free-floating mats which limit the penetration of light and (to a lesser extent) nutrients, reduce growth of native submerged aquatic plants, and can fill the water column in shallow areas, strongly affecting much native aquatic life. The cover value for aquatic animals greatly declines in infested areas, and mats can also hinder the movement of fish and waterfowl. This species can become locally dominant within five years of establishment at a site; within its range, this species often dominates the wetlands within which it occurs. It prefers shallow, quiet, or slow-moving, more or less open, slightly alkaline water, and invades a range of aquatic/wetland communities (lakes, ponds, rivers, streams, marshes, swamps, ditches and canals). Vegetative reproduction by stolons and turions (overwintering buds) has aided this species in its rapid spread; it is also spread through commercial availability (horticulture), water, birds, and boat traffic. Hand-pulling or mechanical harvest, which does not provide efficient, lasting control, is the only known management technique.
Subrank I - Ecological Impact: High/Medium
Subrank II - Current Distribution/Abundance: Medium/Low
Subrank III - Trend in Distribution/Abundance: High/Medium
Subrank IV - Management Difficulty: Unknown
I-Rank Review Date: 24Jul2007
Evaluator: Gravuer, K.
Native anywhere in the U.S?
Native Range: Native to Eurasia, including Denmark, Finland, Sweden, United Kingdom, Austria, Belgium, Czechoslovakia, Germany, Netherlands, Poland, Portugal, Spain, Bulgaria, Italy, Yugoslavia, Belarus, Estonia, Latvia, Lithuania, Ukraine, Iran, Turkey, Azerbaijan, Georgia, Russian Federation (Siberia), and Uzbekistan (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: Invades lakes, ponds, rivers, and streams (especially coves, shallow areas, and quiet edges); marshes (especially open areas); and swamps (especially standing water pools) (White et al. 1993, Flora of North America Editorial Committee 2000, Jacono 2002, Mehrhoff et al. 2003, VTANR 2003, Czarapata 2005, INDNR 2005, WIDNR 2005, ISSG 2006, St. Lawrence Centre 2007, Whitinger 2007).

Subrank I - Ecological Impact: High/Medium

1. Impact on Ecosystem Processes and System-wide Parameters:High/Moderate significance
Comments: Forms large, dense free-floating mats of intertwining plants, roots, and stolons (Catling and Porebski 1995, Halpern et al. 2003, Mehrhoff et al. 2003, Czarapata 2005, WIDNR 2005). These mats dominate wetlands, significantly limiting the penetration of light and (to a lesser extent) nutrients (Catling et al. 1988, Catling and Porebski 1995, Halpern et al. 2003, Mehrhoff et al. 2003, Czarapata 2005). When plants die in the fall, depleted dissolved oxygen is possible (INDNR 2005).

2. Impact on Ecological Community Structure:High significance
Comments: Forms large, dense free-floating mats of intertwining plants, roots, and stolons (Catling and Porebski 1995, Halpern et al. 2003, Mehrhoff et al. 2003, Czarapata 2005, WIDNR 2005). These mats limit the penetration of light and (to a lesser extent) nutrients, reduce growth of native submerged aquatic plants, and can fill the water column in shallow areas, strongly affecting much native aquatic life (Catling and Porebski 1995, Halpern et al. 2003, Mehrhoff et al. 2003, Czarapata 2005). Catling et al. (1988) provided statistical evidence showing that mats cause significant declines in co-occurring native plant species. The cover value for aquatic animals greatly declines in infested areas because of suppressed growth of submerged vegetation (INDNR 2005), and mats can also hinder the movement of fish and waterfowl (WIDNR 2005). When plants die in the fall, depleted dissolved oxygen is possible, which can impact native animal populations (INDNR 2005). This species can become locally dominant within five years of establishment at a site (Catling and Porebski 1995) and can remain dominant for many years (Urban Forest Associates 2002). Within its range, this species often dominates the wetlands within which it occurs (White et al. 1993).

3. Impact on Ecological Community Composition:High significance
Comments: Forms large, dense free-floating mats of intertwining plants, roots, and stolons (Catling and Porebski 1995, Halpern et al. 2003, Mehrhoff et al. 2003, Czarapata 2005, WIDNR 2005). These mats limit the penetration of light and (to a lesser extent) nutrients, reduce growth of native submerged aquatic plants, and can fill the water column in shallow areas, strongly affecting much native aquatic life (Catling and Porebski 1995, Halpern et al. 2003, Mehrhoff et al. 2003, Czarapata 2005). Catling et al. (1988) provided statistical evidence showing that mats cause significant declines in co-occurring native plant species. The cover value for aquatic animals greatly declines in infested areas because of suppressed growth of submerged vegetation (INDNR 2005), and mats can also hinder the movement of fish and waterfowl (WIDNR 2005). When plants die in the fall, depleted dissolved oxygen is possible, which can impact native animal populations (INDNR 2005). This species can become locally dominant within five years of establishment at a site (Catling and Porebski 1995) and can remain dominant for many years (Urban Forest Associates 2002). Within its range, this species often dominates the wetlands within which it occurs (White et al. 1993).

4. Impact on Individual Native Plant or Animal Species:Insignificant
Comments: No reports of disproportionate impacts were found, although this species has been relatively well-studied.

5. Conservation Significance of the Communities and Native Species Threatened:Moderate significance
Comments: Invades a wide range of aquatic communities/settings, especially where its preferred conditions (shallow, quiet, or slow-moving, more or less open, slightly alkaline water) are found. Appears able to invade such microsites within relatively high-quality lakes, rivers, streams, marshes, and swamps (White et al. 1993, Flora of North America Editorial Committee 2000, Jacono 2002, Mehrhoff et al. 2003, VTANR 2003, Czarapata 2005, INDNR 2005, WIDNR 2005, ISSG 2006, St. Lawrence Centre 2007, Whitinger 2007).

Subrank II. Current Distribution and Abundance: Medium/Low

6. Current Range Size in Nation:Low significance
Comments: Established in and around the Great Lakes region (incl. Lakes Erie and Ontario) and in Washington state. The first US collection was in 1974 along the St. Lawrence River in New York (St. Lawrence County), to which the species was thought to have spread from populations in the Rideau Canal, Ontario, where it was first noted as an escape in the 1930s (Roberts et al. 1981). Within New York, the species then spread to inland sites south of the St. Lawrence River (late 1970s - early 1980s), bays and marshes along Lake Ontario (late 1980s - early 1990s), and the eastern part of the state (southern Lake Champlain, 1990s) (Lumsden and McLachlin 1988, Catling and Porebski 1995, Jacono 2002). In Vermont, it was first found in Lake Champlain in 1993; by 1999, it had moved south to several other Vermont sites, including Benson, Orwell and West Haven (Jacono 2002, Mehrhoff et al. 2003). Found in Michigan in 2000, at which time two sites were known (Lake St. Clair marshes and Detroit River marshes), both of which drain the Detroit River (Jacono 2002). Recently found at a site in Snohomish County, Washington as well, where natural outflow through the wetlands appears to be somewhat restricting spread (Jacono 2002). Overall, the species is relatively common throughout much of the invaded region (esp. New York) in smaller streams, lakes, and beaver ponds (Catling and Porebski 1995).

7. Proportion of Current Range Where the Species is Negatively Impacting Biodiversity:High/Moderate significance
Comments: Appears to be problematic at most sites where established (Catling and Porebski 1995, Jacono 2002). Within its range, this species often dominates the wetlands within which it occurs (White et al. 1993).

8. Proportion of Nation's Biogeographic Units Invaded:Low significance
Comments: Approximately 9 HUCs are within the generalized range, based on visual comparison of the generalized range and subregion HUCs map (USGS 2002).

9. Diversity of Habitats or Ecological Systems Invaded in Nation:Moderate significance
Comments: A free-floating aquatic plant inhabiting shallow, quiet, or slow-moving more or less open water, preferable slightly alkaline, within a wide range of settings (10 - 50 m). Invaded wetlands may be isolated. Invades lakes, ponds, rivers, and streams (especially coves, shallow areas, and quiet edges); marshes (especially open areas); swamps (especially standing water pools); and ditches and canals (White et al. 1993, Flora of North America Editorial Committee 2000, Jacono 2002, Mehrhoff et al. 2003, VTANR 2003, Czarapata 2005, INDNR 2005, WIDNR 2005, ISSG 2006, St. Lawrence Centre 2007, Whitinger 2007).

Subrank III. Trend in Distribution and Abundance: High/Medium

10. Current Trend in Total Range within Nation:High significance
Comments: Has spread south (in New York and Vermont), east (in New York), and west (to Michigan and Washington) since initial establishment in the US (Jacono 2002); studies of this species' spread have found that spread appears to be ongoing (Catling and Porebski 1995, Delisle et al. 2003, Eichler 2006). Rates of spread up to 15 km/year have been reported in some parts of the range (Catling and Porebski 1995, Delisle et al. 2003).

11. Proportion of Potential Range Currently Occupied:High/Moderate significance
Comments: Based on climatic tolerance and distribution of habitat, Catling and Porebski (1995) estimated that this species could spread throughout much of southern and western New York State; further west into southern Great Lakes basin of Illinois, Indiana, Michigan, Ohio, and Wisconsin; and to other areas of the northern midwest and prairie regions of North America such as Minnesota and the Dakotas. Apparently, it can be grown for horticultural purposes as far south as hardiness zone 9b (Whitinger 2007), but it is unclear how far south it may be able to spread outside of cultivation.

12. Long-distance Dispersal Potential within Nation:High significance
Comments: A popular water garden plant available for purchase through the commercial aquatic plant trade (Hamel and Parsons 2001, INDNR 2005); plants were ordered and received in Minnesota even though possession, import, purchase, transport, or introduction of the species is prohibited there by state law (Maki and Galatowitsch 2004). Once established, because plants are free-floating, whole plants can be dispersed as well as turions (overwintering buds) and seeds (ISSG 2006), with dispersal vectors including water, birds, and boats/trailers (Catling and Porebski 1995, Jacono 2002, Delisle et al. 2003, INDNR 2005, WIDNR 2005). Some known long-distance dispersal events are thought to have resulted from ornamental use (Halpern et al. 2003) (especially since owners may opt to dispose of the plant in natural waterways when it takes over their small artificial ponds or aquariums [Duggan et al. 2003, INDNR 2005]) or from movement of seeds or turions by birds (Catling and Dore 1982, Catling and Porebski 1995).

13. Local Range Expansion or Change in Abundance:High/Moderate significance
Comments: Increasing local abundance has been noted in multiple parts of the invaded range. Catling and Dore (1982) noted that the species was "becoming much more frequent in areas from which it has been known for 10-20 years", and Jacono (2002) found that in Michigan, one or two plants were observed at Lake St. Clair in 1996; within two years, plants had become "abundant throughout the marsh and formed dense mats in cut ponds." The species continues to be found in additional lakes in New York state (Eichler 2006), and Delisle et al. (2003) noted rapid local spread as well. Catling and Porebski (1995) state that "in general, it has been rare and present as a few isolated patches when first discovered in an area, but has become a dominant or co-dominant of local aquatic ecosystems within five years."

14. Inherent Ability to Invade Conservation Areas and Other Native Species Habitats:High/Moderate significance
Comments: Invades a wide range of aquatic communities/settings, especially where its preferred conditions (shallow, quiet, or slow-moving, more or less open, slightly alkaline water) are found. Appears able to invade such microsites within relatively undisturbed lakes, rivers, streams, marshes, and swamps (White et al. 1993, Flora of North America Editorial Committee 2000, Jacono 2002, Mehrhoff et al. 2003, VTANR 2003, Czarapata 2005, INDNR 2005, WIDNR 2005, ISSG 2006, St. Lawrence Centre 2007, Whitinger 2007).

15. Similar Habitats Invaded Elsewhere:Low significance
Comments: Appears to have invaded only Canada and the US so far (Randall 2002); invaded habitats in Canada are similar to those in the US (Catling and Porebski 1995).

16. Reproductive Characteristics:High/Moderate significance
Comments: Asexual reproduction is predominant and occurs by two means. First, long, cord-like stolons spread rapidly during the growing season, generating floating mats of interconnected plants (Mehrhoff et al. 2003). Multiple plantlets develop along the stolons of each plant (ISSG 2006), and these daughter plants can break free and float to new locations (WIDNR 2005). Second, plants produce overwintering buds called turions; a single plant can produce up to 100 turions (White et al. 1993). Turions develop in the fall, separate from the plant, sink to the bottom of the water body where they overwinter, and then rise to the surface in the spring to form a new plant (Delisle et al. 2003, VTANR 2003, WIDNR 2005); one turion can grow to cover an area of one meter in diameter in one season (Haynes 1988). Insect pollination of flowers to produce seeds also occurs (Haynes 1988), but is often limited and sometimes non-existent (Mehrhoff et al. 2003), in part because many population of this dioecious species are dominated by one sex (INDNR 2005). Therefore, sexual reproduction by seed is of lesser importance for this species' spread in North America (White et al. 1993, ISSG 2006).

Subrank IV. General Management Difficulty: Unknown

17. General Management Difficulty:Moderate significance
Comments: Currently, it appears that the only known control method is removal by hand or other harvesting methods (VTANR 2003, Czarapata 2005, INDNR 2005). Care must be taken to prevent plant fragments from escaping the infestation site (WIDNR 2005). Herbicidal spraying of the floating mats is inefficient and costly and can have undesirable environmental impacts (Halpern et al. 2003). Three native arthropods may have potential as biological control agents; research on this topic is ongoing (Halpern et al. 2003).

18. Minimum Time Commitment:Unknown
Comments: No reports of control attempts could be found.

19. Impacts of Management on Native Species:Unknown
Comments: Even hand-pulling may have some impact on co-occurring native species, as boat traffic may perturb some aquatic communities. Catling and Porebski (1995) noted that since this species forms turions and forms dense intertwining floating mats, it has the potential to become a major weed of irrigation systems; if this occurs, it may require management that could have substantial environmental impact.

20. Accessibility of Invaded Areas:Unknown
Comments: Some invaded water bodies may be difficult to reach by boat.
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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  • Lumsden, Harry G. and David J. McLachlin. 1988. European frog-bit, Hydrocharis morsus-ranae, in Lake Ontario marshes. Canadian Field-Naturalist. 102(2):261-263.

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