|Scientific Name:||Wolffia arrhiza (L.) Horkel ex Wimm.|
Lemna arrhiza L.
Wolffia michelii Schleid.
|Taxonomic Notes:||According to Royal Botanic Gardens, Kew WCSPF (World Checklist of Selected Plant Families), this genus belongs to the Araceae Family.|
|Red List Category & Criteria:||Least Concern ver 3.1|
|Assessor(s):||Gupta, A.K. & Beentje, H.J.|
This species covers a wide geographic range and it is known from many sites. No significant threats have been reported.
|Previously published Red List assessments:|
The main distribution centre for W. arrhiza is in Europe, with populations scattered throughout Africa south of the Sahara, as well as a few populations in North Africa and Asia. It is also known from one locality near Rio de Janeiro, Brazil (Landolt 1986) where it has been introduced.
Native:Albania; Algeria; Angola; Austria; Belarus; Belgium; Benin; Bhutan; Bosnia and Herzegovina; Botswana; Brazil (Rio de Janeiro); Bulgaria; Burundi; Congo, The Democratic Republic of the; Côte d'Ivoire; Croatia; Czech Republic; France; Germany; Ghana; Guinea-Bissau; Hungary; India (Jammu-Kashmir); Iran, Islamic Republic of; Italy (Italy (mainland), Sicilia); Kenya; Lebanon; Liechtenstein; Luxembourg; Macedonia, the former Yugoslav Republic of; Madagascar; Malawi; Moldova; Montenegro; Morocco; Mozambique; Netherlands; Nigeria; Palestinian Territory, Occupied; Philippines; Poland; Portugal; Russian Federation (Central European Russia, East European Russia, European Russia); Rwanda; Senegal; Serbia; Slovenia; South Africa (Eastern Cape Province, Free State, KwaZulu-Natal, Limpopo Province, Northern Cape Province, Western Cape); Spain; Syrian Arab Republic; Taiwan, Province of China (Taiwan, Province of China (main island)); Tanzania, United Republic of; Togo; Uganda; Ukraine; United Kingdom (Great Britain)
|Range Map:||Click here to open the map viewer and explore range.|
This species naturally undergoes massive population fluctuations and when it occurs at low abundance it is extremely easy to overlook. There is no information on global population trends. In Europe populations seem to be stable. It can form large populations in suitable habitats.
|Current Population Trend:||Stable|
|Habitat and Ecology:|
W. arrhiza typically occurs in base-rich lowland ditches and ponds (Preston and Croft 1997) in mesotrophic to eutrophic water. It sometimes occurs with Wolfiella and Lemna minor, or with Pistia; it can be abundant enough to form a scum.
|Continuing decline in area, extent and/or quality of habitat:||No|
|Use and Trade:||Where it grows with Pistia in Africa it is sometimes collected and used as a manure.|
There are no known past, ongoing, or future threats to this species.
There are no conservation measures in place nor likely to be needed.
|Citation:||Gupta, A.K. & Beentje, H.J. 2017. Wolffia arrhiza. The IUCN Red List of Threatened Species 2017: e.T164241A84301916.Downloaded on 22 March 2018.|
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