Salvinia (Salvinia natans)

Present distribution

Scientific name:	Salvinia natans (L.) All.
Common name(s):	Salvinia

This weed is not known to be naturalised in Victoria

Habitat:

As a free floating fern it is reported to occur in lakes and ponds in India and Kashmir where it is also reportedly a problem in rice paddies (Mukherjee & Kumar 2005; Zutshi & Vass 1971). Rainfall therefore is not important for a climate match as the plant is always in water.

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, 10m Rivers, 5m Creeks; Irrigation Canals, 3m Major, 2m Minor; Wetlands excluding permanently saline and saltworks.

Colours indicate possibility of Salvinia natans infesting these areas.

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

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

Impact

QUESTION	COMMENTS	RATING	CONFIDENCE
Social
1. Restrict human access?	Reported to form dense mats especially in sheltered positions, similar dense mats of S.molesta have been reported to restrict the use of water preventing activities such as fishing, transport and other recreation (Parsons & Cuthbertson 2001; Zutshi & Vass 1971). As the plant dies back in winter however this restriction would be on a seasonal basis and therefore have a high nuisance value (Zutshi & Vass 1971).	mh	mh
2. Reduce tourism?	Reported to form dense mats especially in sheltered positions, similar dense mats of S.molesta have been reported to restrict the use of water preventing activities such as fishing, transport and other recreation (Parsons & Cuthbertson 2001; Zutshi & Vass 1971).	h	mh
3. Injurious to people?	Salvinia species are not reported to cause any injuries or physiological issues.	l	m
4. Damage to cultural sites?	Large infestations can result in some impact upon aesthetics (Zutshi & Vass 1971). Salvinia auriculata has been reported as a threat to the operation of turbines (Zutshi & Vass 1971).	mh	mh
Abiotic
5. Impact flow?	An a free floating aquatic it can form dense mats which would impacting surface flow (Zutshi & Vass 1971). As it decays each year it has been suggested that this will gradually raise the level of the substrate which could have some impact on subsurface flow (Zutshi & Vass 1971).	mh	h
6. Impact water quality?	When mats develop, water temperature and dissolved oxygen below the mat is reduced (Zutshi & Vass 1971). As the plant decays each year it has also been noted to increase the nutrient levels, which then aid reinvasion the next season (Parsons & Cuthbertson 2001; Zutshi & Vass 1971). It is not reported however to result in eutrophication.	mh	mh
7. Increase soil erosion?	As it can form dense mats on the water surface it can alter the composition of the submerged vegetation, which then may leave the substratum exposed to erosion (Zutshi & Vass 1971). As the plant mainly form dense mats in sheltered positions and most often occurs on still to slow moving water, it is thought to have a low probability of causing large scale erosion (Zutshi & Vass 1971).	l	h
8. Reduce biomass?	It grows and reproduces quickly and can form dense mats which can then effect the submerged vegetation biomass as the mat restricts light, this is however likely still going to be a net increase in biomass (Zutshi & Vass 1971). A the plant decays each year it has also been reported to have potential to raise the substratum, which would also act as a carbon sink (Zutshi & Vass 1971).	l	h
9. Change fire regime?	Aquatic species; therefore not in an environment exposed to fire and unlikely to have any impact on the fire regime.	l	m
Community Habitat
10. Impact on composition (a) high value EVC	EVC= Billabong Wetland (E); CMA= Goulburn Broken; Bioreg= Murray Fans; VH CLIMATE potential. Especially in sheltered potions it is known to form extensive mats creating a monoculture on the waters surface (Zutshi & Vass 1971).	h	h
(b) medium value EVC	Aquatic species. All Victorian water bodies considered to comprise high value EVCs only (Weiss pers. com).	l	m
(c) low value EVC	Aquatic species. All Victorian water bodies considered to comprise high value EVCs only (Weiss pers. com).	l	m
11. Impact on structure?	Especially in sheltered potions it is known to form extensive mats creating a monoculture on the waters surface (Zutshi & Vass 1971). This then has implications on the submerged vegetation which if it is not eliminated is likely to be altered to another species with lower light requirements and therefore salvinia will have some effect on all the strata but no to the extent that no other layers are present (Zutshi & Vass 1971).	mh	h
12. Effect on threatened flora?	Unknown.	mh	l
Fauna
13. Effect on threatened fauna?	Unknown.	mh	l
14. Effect on non-threatened fauna?	It effect on water temperature and especially dissolved oxygen content is reported to have a detrimental effect on fish and aquatic insects (Zutshi & Vass 1971). It is not known to what extent it degrades the habitat.	m	m
15. Benefits fauna?	In Australia, the native insects including Hedotettix bolivari, Nymphula tenebralis and Rhopalosiphum nymphaea are reported to feed on the similar plant S.molesta and many other insects and arachnids are reported to hide and hunt amongst the floating leaves (Groves et al 1995).	m	m
16. Injurious to fauna?	Salvina has not been reported to have toxic or injurious properties.	l	m
Pest Animal
17. Food source to pests?	Not known as a food source to pests.	l	m
18. Provides harbor?	Salvinia has been reported to provide habitat for mosquitoes (Parsons & Cuthbertson 2001).	ml	m
Agriculture
19. Impact yield?	Reported to invade rice paddies and in Kashmir and its effect on the growth of the rice is considered a serious problem (Zutshi & Vass 1971). Unknown to what extent any reduction in yield would be.	m	m
20. Impact quality?	No impact on quality reported.	l	m
21. Affect land value?	May have some impact on rice growers in particular, and other users of irrigation in general, there is no evidence of this however.	m	l
22. Change land use?	May result in growing rice to become unviable, like S.molesta invaded paddies in Sri Lanka (Parsons & Cuthbertson 2001). There is no evidence of this occurring however.	m	l
23. Increase harvest costs?	May cause some interference with irrigation systems and therefore increase labour or maintenance costs. There is no evidence of this occurring however.	m	l
24. Disease host/vector?	Not known as a host or vector for agricultural pests or diseases.	l	m

Invasive

QUESTION	COMMENTS	RATING	CONFIDENCE
Establishment
1. Germination requirements?	New plants develop from the sporangia in spring (Mühlberg 1982).	mh	mh
2. Establishment requirements?	Its presents notably increased in the lakes of Kashmir with the addition of nutrients from near by land use (Zutshi & Vass 1971). It is not however known if high nutrient levels are a requirement for establishment or if the higher nutrient levels have just aided its competitive ability. Can grow under deep shade (Zutshi & Vass 1971). However it is not considered a problem under shade (Frazer pers comm. 2007). This would indicate poor establishment of either new plants from the sporangia or through vegetative reproduction and therefore a requirement for higher light levels.	ml	m
3. How much disturbance is required?	Occurs in lakes and ponds, may need additional nutrients to become abundant (Mühlberg 1982; Zutshi & Vass 1971).	mh	mh
Growth/Competitive
4. Life form?	Floating aquatic fern (Zutshi & Vass 1971).	h	h
5. Allelopathic properties?	Unknown.	m	l
6. Tolerates herb pressure?	Reported to be effected by the biocontrol released for S.molesta with inconsistent results (Frazer pers comm. 2007).	mh	m
7. Normal growth rate?	Described as having rapid growth and rapid vegetative propagation (Zutshi & Vass 1971). Therefore it is assumed to be competitive with species of similar life form.	mh	mh
8. Stress tolerance to frost, drought, w/logg, sal. etc?	Aquatic species therefore tolerant of waterlogging (Zutshi & Vass 1971). Aquatic species therefore not likely to be exposed to fire. Salinity, other Salvinia species have been reported in slightly brackish water (Parsons & Cuthbertson 2001). Drought; can tolerate lakes drying up during winter in Kashmir (Zutshi & Vass 1971). Tolerant of low temperatures in Kashmir, (Zutshi & Vass 1971).	mh	mh
Reproduction
9. Reproductive system	Can reproduce vegetatively as well as sexually with spores (Mühlberg 1982).	h	mh
10. Number of propagules produced?	Each plant is reported to produce between 5 and 8 sporocarps and each sporocarp is said to contain between 6 and 7 sporangia (Zutshi & Vass 1971). This means each plant has the potential to produce between 30 and 56 sporangia. A sporangia can either be a Megasporangia and contain one large female megaspore or a Microsporangia and contain on average 64 small male microspores (Mühlberg 1982). Therefore the potential number of sexual propagules is effectively the number of megasporangia produced, which could be as many as 55 and there would still be enough male spores to ensure fertilisation. Zutshi & Vass (1971) report vegetative reproduction to occur rapidly, therefore assuming exponential growth and maximum sexual reproductive output of 55 fertilised sporangia, within one growing season a population could go from a single plant to more than 2000 propagules with only six vegetative generations.	h	m
11. Propagule longevity?	Unknown.	m	l
12. Reproductive period?	Can form self sustaining monocultures (Zutshi & Vass 1971).	h	h
13. Time to reproductive maturity?	An annual species, it will reproduce vegetatively through the growing season and then sexually producing sporangia (Mühlberg 1982).	h	mh
Dispersal
14. Number of mechanisms?	As both the plants and propagules float dispersal within a catchment would be aided by water (Mühlberg 1982). While dispersal between catchments has been suggested to be through migrating waterbirds and human aided (Mühlberg 1982). Reported to be dispersed by duck species (Frazer pers comm. 2007).	h	mh
15. How far do they disperse?	Dispersal by water and by migratory birds both have the potential of dispersal of many kilometres.	h	m

References

Groves R.H., Shepherd R.C.H. & Richardson R.G., 1995, The biology of Australian weeds. Vol 1, R.G. and F.J. Richardson, Melbourne.

Mühlberg H., 1982, The complete Guide to Water Plants. EP Publishing Limited

Mukherjee S. & Kumar S., 2005, Absorptive uptake of arsenic (V) from water by aquatic fern Salvinia natans. Aqua. 54: 47-53.

Parsons W.T. & Cuthbertson E.G. 2001, Noxious weeds of Australia, 2nd ed., CSIRO Publishing, Collingwood.

Zutshi D.P. & Vass K.K., 1971, Ecology and production of Salvinia natans Hoffim; in Kashmir. Hydrobiologia. 38: 303-320.

Global present distribution data references

Global Biodiversity Information Facility (GBIF) 2007, Global biodiversity information facility: Prototype data portal, viewed 30 Mar 2007, http://www.gbif.org/

Missouri Botanical Gardens (MBG) 2007, w³TROPICOS, Missouri Botanical Gardens Database, viewed 29 Mar 2007, http://mobot.mobot.org/W3T/Search/vast.html

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