Water Pennywort (Hydrocotyle ranunculoides)

Present distribution

Scientific name:	Hydrocotyle ranunculoides L. f.
Common name(s):	Water Pennywort, Floating Pennywort

This weed is not known to be naturalised in Victoria

Habitat:

Native to North America, Africa & the Middle East &naturalised in Central & South America, parts of Europe (Sheppard et al 2006, Newman 2004) & Western Australia. A potential weed of all freshwater environments occurring in still & slow moving water (Richardson et al 2006). Inhabits rivers, creeks, marshes, wetlands, eutrophic & mesotrophic water bodies, ‘fenland pools’ ditches, ponds & lake margins, (Newman 2004, EPPO 2006, WADE 2003) & able to grow on over-watered or wet/moist ground (DiTomaso & Healy 2003). In south-west WA it occurs in rivers, creeks & freshwater streams of the coastal plains (Csurhes & Edwards 1998, Spooner 1999) & has spread through the drainage system into the Canning River & nearby wetlands (EPPO 2006). In Uganda, it occurs to an altitude of 2000 m in lake & wetland habitats (Denny 1973, Kalema & Ssegawa 2007).

Potential distribution

Potential distribution produced from CLIMATE modelling refined by applying suitable landuse and vegetation type overlays with CMA boundaries

Map Overlays Used

Land Use:

Broad vegetation types
Aquatic areas including; Riparian Strip, 10 m Rivers, 5 m Creeks; Irrigation Canals, 3 m Major, 2 m Minor; Wetlands excluding permanently saline and saltworks, swamp scrub

Colours indicate possibility of Hydrocotyle ranunculoide infesting these areas.

In the non-coloured areas the plant is unlikely to establish as the climate, soil or landuse is not presently suitable.

Map showing the potential distribution of Hydrocotyle

Red= Very high	Orange = Medium
Yellow = High	Green = Likely

Impact

QUESTION	COMMENTS	RATING	CONFIDENCE
Social
1. Restrict human access?	Dense growth can smother static or slowly flowing waterways (Csurhes & Edwards 1998) and mats can grow to such a density that they may impede water flow (Harrell & Bohn 1996). Leaf matter can extend to 40cm above the water surface and the interwoven mat of roots and stems can sink up to 50cm into the water (Newman 2005). It is likely that boat access along waterways infested with H. ranunculoides would be restricted, however, no information was found specifically documented.	M	ML
2. Reduce tourism?	‘Strongly invaded waters loose their attractiveness and safety for recreation (EPPO 2006)’. In the Canning River near Perth it has spread across the river from bank to bank, killing off fish and encouraging blue-green algae (ABC 2001). Likely to impact on recreational uses such as boating, fishing and swimming.	MH	M
3. Injurious to people?	No information was found to suggest that H. ranunculoides possesses any properties injurious to humans.	L	M
4. Damage to cultural sites?	H. ranunculoides can damage waterworks (EPPO 2006). The degree of damage was not clear from the information available but is likely to be moderate.	MH	M
Abiotic
5. Impact flow?	Leaf matter can extend 40cm above the water surface and the interwoven mat of roots and stems can sink 50cm into the water (Newman 2005). Mats can grow to such a density that they impede water flow in canals & ditches (Harrell & Bohn 1996) and flooding may be caused by heavy infestations choking drainage systems and sluices (Kelly 2006). As an attached emergent aquatic, it could have serious impacts on both surface and subsurface flow.	H	M
6. Impact water quality?	Forms dense interwoven vegetation mats that cover the water surface causing loss of light and reduction in dissolved oxygen content of water affecting fish and invertebrate populations (Kelly 2006, EPPO 2006). In the Canning River near Perth it has spread across the river from bank to bank, killing off fish and encouraging blue-green algae (ABC 2001). Has high affects on dissolved oxygen and light with evidence of eutrophication through increasing blue-green algae and fish deaths.	H	M
7. Increase soil erosion?	Flooding may be caused by heavy infestations chocking drainage systems and sluices (EPPO 2006, Kelly 2006). Due to its ability to increase flooding, there is potential for a high probability of large scale soil movement to occur. Off site implications are likely to be variable though, as the degree of erosion that occurs is likely to be related to the amount of bank vegetation that exists at the site.	MH	M
8. Reduce biomass?	Forms dense interwoven vegetation mats, rapidly covering the water surface (Kelly 2006, EPPO 2006) and leading to infestations up to 10km in length (Sheppard et al 2006). Leaf matter can extend to 40cm above the water surface and the interwoven mat of roots and stems can sink up to 50cm into the water (Newman 2005). Biomass may increase.	L	MH
9. Change fire regime?	It is unlikely to cause a change to the fire regime as it is primarily an aquatic species growing in habitats that a not significantly affected by fire.	L	M
Community Habitat
10. Impact on composition (a) high value EVC	It covers the water surface and out-competes most native plant species forming monospecific stands. It displaces floating, submerged and edge plant species through shading by its dense floating mats of vegetation (Kelly 2006, EPPO 2006). Potential to displace all species within a layer and forms monocultures.	H	M
(b) medium value EVC	It covers the water surface and out-competes most native plant species forming monospecific stands. It displaces floating, submerged and edge plant species through shading by its dense floating mats of vegetation (Kelly 2006, EPPO 2006). Potential to displace all species within a layer and forms monocultures.	H	M
(c) low value EVC	It covers the water surface and out-competes most native plant species forming monospecific stands. It displaces floating, submerged and edge plant species through shading by its dense floating mats of vegetation (Kelly 2006, EPPO 2006). Potential to displace all species within a layer and forms monocultures.	H	M
11. Impact on structure?	It covers the water surface and out-competes most native plant species forming monospecific stands (EPPO 2006, Kelly 2006) leading to infestations up to 10km in length (Sheppard et al 2006). It displaces floating, submerged and edge plant species through shading by its dense floating mats of vegetation (EPPO 2006). Major affect on all layers, forms monocultures.	H	MH
12. Effect on threatened flora?	It competes with and displaces native floating, submerged and edge plant species through shading by its dense floating mats of vegetation. Keystone species, endangered species and biodiversity can be reduced. (EPPO 2006). There is potential for it to have a comparable impact on native flora species in Victorian aquatic habitats, however, it does not have a present distribution in Victoria and the impact it would have specifically on threatened flora species is unknown.	MH	L
Fauna
13. Effect on threatened fauna?	H. ranunculoides causes habitat modification which impacts on fauna (EPPO 2006), and is documented as causing a decrease in diving birds (Swarrbrick & Skarratt 1994). Dense mats reduce light penetration leading to de-oxygenation of the water, which affects invertebrate populations and can induce high fish mortality (EPPO 2006, Kelly 2006). In the Canning River near Perth it has spread across the river from bank to bank, killing off fish and encouraging blue-green algae (ABC 2001). It could have a similar impact on fauna in Victorian habitats, resulting in habitat modification and reduced numbers of fauna species. However, it does not have a present distribution in Victoria and the impact it would have specifically on threatened fauna species is unknown.	MH	L
14. Effect on non-threatened fauna?	H. ranunculoides causes habitat modification which impacts on fauna (EPPO 2006), and is documented as causing a decrease in diving birds (Swarrbrick & Skarratt 1994). Dense mats reduce light penetration leading to de-oxygenation of the water, which affects invertebrate populations and can induce high fish mortality (EPPO 2006, Kelly 2006). In the Canning River near Perth it has spread across the river from bank to bank, killing off fish and encouraging blue-green algae (ABC 2001). Although it does not currently have a distribution in Victoria, its presence in local aquatic habitats would likely have similar impact on fauna, resulting in habitat modification and reduced numbers of fauna species.	MH	M
15. Benefits fauna?	Has moderate value to wildlife as protective habitat for small fish, invertebrates and animals such as snakes. The seeds and foliage are often consumed by waterfowl (WADE 2003, Harrell & Bohn 1996) and it is described as having the potential to increase numbers of birds, amphibia & crustacea (Swarrbrick & Skarratt 1994). Likely to provide some assistance in food and/ or shelter to desirable species.	MH	M
16. Injurious to fauna?	No information was found to suggest that H. ranunculoides possesses any properties injurious to fauna.	L	M
Pest Animal
17. Food source to pests?	No information was found documented to suggest that H. ranunculoides would provide a food source to pest animals.	L	ML
18. Provides harbor?	H. ranunculoides can provide protective habitat to small fish (Harrell & Bohn 1996) and, although no information was found specifically documented, it would have the capacity to provide general harbour to pest fish species such as juvenile European Carp, Cyprinus carpio or Mosquito fish, Gambusia spp.	ML	ML
Agriculture
19. Impact yield?	Described as having the ability to impede water flow in drainage canals & ditches that can affect irrigation (Harrell & Bohn 1996) but this is unlikely to lead to a reduction in agricultural cropping yield.	L	ML
20. Impact quality?	Described as having the ability to impede water flow in drainage canals & ditches that can affect irrigation (Harrell & Bohn 1996) but this is unlikely to impact on the agricultural quality of irrigated crops.	L	M
21. Affect land value?	As an aquatic weed it is unlikely to have an impact on agricultural land value.	L	M
22. Change land use?	Although it has the ability to impede water flow in drainage canals & ditches that can affect irrigation (Harrell & Bohn 1996), as an aquatic weed it is unlikely to have enough impact to cause a change in land use.	L	M
23. Increase harvest costs?	H. ranunculoides is described as having the ability to impede water flow in drainage canals & ditches that can affect irrigation (Harrell & Bohn 1996) and also damage waterworks (EPPO 2006). Its spread in some areas is regarded as ‘unstoppable’ and it is documented as having some resistance to Glyphosate (EPPO 2006). In the Netherlands, the high cost of control is expected to lead to a significant rise in water board taxes (Van der Krabben & Rotteveel in EPPO 2006). The presence of this species in irrigation sources has the potential to cause a major increase in production costs through damage it could cause to irrigation machinery and the labour required to control the weed.	H	ML
24. Disease host/vector?	No information was found documented to suggest that H. ranunculoides is a host for any diseases or pests of agriculture.	L	M

Invasive

QUESTION	COMMENTS	RATING	CONFIDENCE
Establishment
1. Germination requirements?	It over winters in the margins and on the banks and then quickly re-grows into new plants in Spring (Torrens 2003, Newman 2005). It appears that warmer seasonal temperatures trigger vegetative regeneration but no information was found regarding the requirements for seed germination.	M	L
2. Establishment requirements?	Planting trees to create shade is considered an effective method of control of H. ranunculoides, as it does not establish well in shaded conditions (Newman 2005). Has more specific establishment requirements, e.g., access to light.	ML	M
3. How much disturbance is required?	Invades freshwater streams, rivers, wetlands, marshes and lake margins (Csurhes & Edwards 1998, EPPO 2006). Establishes in minor disturbed natural ecosystems, e.g. riparian & wetland habitats.	MH	MH
Growth/Competitive
4. Life form?	Stoloniferous, perennial aquatic plant, with floating and emergent leaves (EPPO 2006).	H	MH
5. Allelopathic properties?	Documented as displacing native aquatic species, but this is largely the result of shading by its dense floating mats of vegetation (EPPO 2006), and no information was found to suggest it is due to the presence of any allelopathic properties in the plant.	L	L
6. Tolerates herb pressure?	One beetle species is described as consuming leaves, but with the damage it causes not being severe enough to reduce growth, and the leaves being replaced by new ones at the same node after a period of 4 weeks (Newman 2005). “[Cutting] will only offer a short term reduction in the local extent of the plant as it is capable of growing back rapidly from the nodes” (Newman 2005). Consumed but recovers quickly.	MH	M
7. Normal growth rate?	Rapid growth rate (Newman 2005) with stolons capable of reaching a length of 15m in a single season, growing at approximately 20cm per day (Sheppard et al . 2006). It forms dense vegetation mats, rapidly covering the water surface, out competing most native plant species (EPPO 2006; Kelly 2006). “In Australia, H. ranunculoides doubles its biomass in 3 days” (Newman 2005). Rapid growth rate.	H	MH
8. Stress tolerance to frost, drought, w/logg, sal. etc?	It is described as remaining green and persisting during Winter (WADE 2003, Teels et al. 1976), and if sheltered by other plants, hardy to even the most severe frosts in Europe (Bass & Duistermaat 1999). As an aquatic it is therefore tolerant of waterlogging. Drought would not have a major impact if the water body it occupied was large enough to remain wet during the drought period. It can also persist within mud and is capable of growing back rapidly from a single node (WADE 2003; Newman 2005). The habitats it occupies are unlikely to be significantly affected by fire. Its tolerance to salinity was not found documented. Tolerant of frost and waterlogging and potentially drought and fire.	MH	M
Reproduction
9. Reproductive system	“The plant establishes from seed or by rooting from nodes, root and stem fragments” (Sheppard et al. 2006). “In Britain, floating pennywort plants rooted in the substrate produce seeds, while floating colonies primarily reproduce vegetatively” (DiTomaso & Healy 2003). Both vegetative and sexual reproduction.	H	MH
10. Number of propagules produced?	Inflorescences contain 5-13 flowers (Sheppard et al. 2006) and each flower produces a fruit that splits in half, with each half containing one seed (DiTomaso & Healy 2003). Stolons can grow 15 m in length (Sheppard et al. 2006), so there is potential for the occurrence of numerous inflorescences on a single plant. However, no information was found documented on the number of flowers or propagules produced per plant.	M	L
11. Propagule longevity?	This species is documented as reproducing primarily by vegetative means (Newman 2005) and its seed ecology is generally poorly described. No information was found documented on the longevity of seed propagules.	M	L
12. Reproductive period?	Forms monospecific stands (EPPO 2006) with infestations up to 10km in length being described (Sheppard et al. 2006). Has potential to form self-sustaining monocultures.	H	M
13. Time to reproductive maturity?	H. ranunculoides roots freely from nodes at approximately 40-60mm intervals (Newman 2005) with a new plant being able to develop from a single node (Sheppard et al. 2006). Stolons can grow 15m within a season (Sheppard et al. 2006) and with each rooted node along the stolon technically capable of becoming an individual plant, vegetative propagules have the potential to become separate individuals in under a year.	H	M
Dispersal
14. Number of mechanisms?	Its main mode of spread has been via the aquatic nursery trade through the dumping of aquaria and garden pond waste and the contamination of other aquatic plants with fragments of H. ranunculoides (EPPO 2006). “Seeds and stem fragments disperse with water, substrate movement, animals, and human activities” (DiTomaso & Healy 2003). Propagules spread by deliberate human dispersal, water and attachment to animals.	MH	M
15. How far do they disperse?	H. ranunculoides is capable of regeneration from very small plant fragments containing just a single node (Newman 2005). Human transportation, water or the attachment of small fragments to water birds could disperse viable vegetative propagules or seeds greater than one kilometre.	H	M

References

Australian Broadcasting Corporation (ABC) 2001, Aquatic Weeds Factsheet- Gardening Australia, ABC, viewed: 22/5/07, http://www.abc.net.au/gardening/stories/s276766.htm

Baas WJ & Duistermaat LH 1999, ‘The invasion of floating pennywort (Hydrocotyle ranunculoides L.F.) in the Netherlands, 1996-1998’, Gorteria, vol. 25, no. 4, pp. 77-82.

Csurhes S & Edwards R 1998, Potential Environmental Weeds in Australia, Candidate Species for Preventative Control, Biodiversity Group, Environment Australia, Canberra, ACT.

Denny P 1973, ‘Lakes of south-western Uganda: II. Vegetation studies on Lake Bunyonyi’, Freshwater Biology, vol. 3, pp. 123-135.

Di Tomaso JM & Healy EA 2003, Aquatic and Riparian Weeds of the West, University of California, Division of Agriculture and Natural Resources, Oakland, California.

European & Mediterranean Plant Protection Organisation (EPPO) 2006, Data sheets on quarantine pests: Hydrocotyle ranunculoides, EPPO Bulletin, vol. 36, no. 1, pp. 3-6.

Harrell RM & Bohn RE 1996, Aquatic Plant Identification and Management: Water Pennywort, University of Maryland, Sea Grant Publication UM-SG-MAP-96-20.

Kalema J & Ssegawa P 2007, ‘The flora of highly degraded and vulnerable wetland ecosystems of Nyamuriro and Doho, Uganda’, African Journal of Ecology, vol. 45, no. (supp.) 1, pp. 28-33.

Kelly A 2006, ‘Removal of invasive floating pennywort Hydrocotyle ranunculoides from Gilingham Marshes, Suffolk, England’, Conservation Evidence, vol. 3, pp. 52-53. http://www.conservationevidence.com/Attachments/PDF415.pdf

Newman JR 2005, Information Sheet 24: Floating Pennywort, Centre for Aquatic Plant management, Centre for Ecology & Hydrology, Natural Environment Research Council, Wallingford, UK.

Richardson F.J, Richardson R.G. & Shepherd R.C.H., 2006, Weeds of the south-east. An identification guide for Australia. R.G. and F.J. Richardson. Meredith.

Sheppard AW, Shaw RH & Sforza R 2006, ‘Top 20 environmental weeds for classical biological control in Europe: a review of opportunities, regulations and other barriers to adoption’, Weed Research, vol. 46, pp. 93-117.

Spooner A 1999, Flora of Western Australia- Hydrocotyle ranunculoides L. f., Flora Base: the Western Australian Flora, viewed: 22/5/2007, http://florabase.calm.wa.gov.au/

Swarbrick JT & Skarratt DB 1994, The Bushweed 2 Database of Environmental Weeds in Australia, University of Queensland Gatton College.

Teels BM, Anding G, Arner DH, Norwood ED & Wesley DE 1976, ‘Aquatic plant-invertebrate and waterfowl associations in Mississippi’, Proc. Annual Conf. Southeast Assoc. Game Fish Comm., vol. 30., pp. 610-616.

Torrens R 2003, ‘Hydrocotyle ranunculoides’, Ponds & Water Life -PAWL, viewed: 22/5/07, http://www.4qd.org/Aqua/HR/index.html

Van der Krabben KPM & Rotteveel AJW 2003, Draft report of a pest risk assessment of Hydrocotyle ranunculoides, Plant Protection Service, Wageningen (NL).

Washington State Department of Ecology (WADE) 2003, ‘Floating Mat Rooted Plants: Hydrocotyle ranunculoides’, WADE, Water Quality program, viewed: 22/5/2007, http://www.ecy.wa.gov/programs/wq/plants/plantid2/descriptions/hydran.html

Global present distribution data references

Australian National Herbarium (ANH) 2007, Australia’s Virtual Herbarium, Australian National Herbarium, Centre for Plant Diversity and Research, viewed 22/5/2007, http://www.anbg.gov.au/avh/

Global Biodiversity Information Facility (GBIF) 2007, Global biodiversity information facility: Prototype data portal, viewed 22/5/2007, http://newportal.gbif.org/welcome.htm

Missouri Botanical Gardens (MBG) 2007, w3TROPICOS, Missouri Botanical Gardens Database, viewed 22/5/2007, http://mobot.mobot.org/W3T/Search/vast.html

National Biodiversity Network 2004, NBN Gateway, National Biodiversity Network, UK viewed 22/5/2007,
http://www.searchnbn.net/index_homepage/index.jsp

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