Index to Genera
Synonymy of Waltheria
Waltheria is a genus of plants belonging to tribe Hermannieae of subfamily Byttneroideae of the angiosperm family Malvaceae sensu APG. It is distinguished from the other genera of the tribe by the possession of a single carpel, rather than 5 as in Melochia and Hermannia, and 2 as in Dicarpidium. However 2 carpels are occasionally found in Waltheria.
Waltheria is pan-tropical, but is most diverse in the Americas, especially in Mexico and Brasil.
Species and Distributions
Kubitzki and Bayer, in their revision of Malvaceae , say that there are 50 to 60 species of Waltheria. Waltheria was revised by Janice Saunders in 1995 [a], and if this was more readily available I would have used this revision, and her subsequent papers, as a based for identifying the recognised species of Waltheria. From examination of various floras, checklists, papers and databases I have identified 55 species.
A recent paper by Janice Saunders gives a figure of 60 species .
The species Waltheria indica is a pan-tropical weed. It is probably native to the New World, where it can be found from the southern United States (Arizona, Texas, Alabama and Florida)  to the north of Argentina, including most Caribbean islands , Mexico , Central America , Peru , Brasil  and Paraguay . However it is now also widespread in the Old World tropics, where it is found over nearly all of Africa (absent from Western Cape, Eastern Cape and Orange Free State in the south, and from Mauritania, Morocco, Algeria, Tunisia and Libya in the north) , in Madagascar , in Macaronesia (Cape Verde and Canary Islands) , in India , in Sri Lanka , in the Philippine Islands, in southern China (Fujian, Guangdong, Guangxi, Taiwan, Yunnan) , in northern Australia  and Hawaii , and probably in other regions.
Waltheria is most diverse in Brasil, where 22 species are found. These are, in addition to Waltheria indica, Waltheria ackermanniana, Waltheria albicans, Waltheria aspera, Waltheria brachypetala, Waltheria bracteosa, Waltheria carpinifolia, Waltheria cinerescens, Waltheria communis, Waltheria douradinha, Waltheria erioclada, Waltheria excelsa, Waltheria ferruginea, Waltheria glazioviana, Waltheria macropoda, Waltheria maritima, Waltheria operculata, Waltheria petiolata, Waltheria polyantha, Waltheria rotundifolia, Waltheria selloana and Waltheria viscosissima . Many of these species are also found in other countries. Waltheria viscosissima has a broad distribution from Mexico to southern Brasil and Bolivia. Waltheria operculata has a broad distribution from Mexico to Brasil and Paraguay. Waltheria rotundifolia is found from Mexico to Brasil. 
Waltheria glomerata is found from Mexico to Columbia. In addition to Waltheria indica, Waltheria glomerata, Waltheria operculata, Waltheria rotundifolia and Waltheria viscosissima, 10 species (Waltheria acapulcensis, Waltheria acuminata, Waltheria brevipes, Waltheria bicolor, Waltheria conzattii, Waltheria fryxellii, Waltheria lundelliana, Waltheria preslii, Waltheria pringlei and Waltheria tridentata) are found in Mexico; to the best of my knowledge they are all endemic to Mexico .
Waltheria arenicola, Waltheria nipensis and Waltheria ovalifolia are endemic to Cuba. Waltheria bahamiensis is endemic to the Bahamas. Waltheria calcicola is endemic to the West Indies (Jamaica, Hispaniola and Puerto Rico). Waltheria glabra is endemic to the West Indies (Guadeloupe, Marie-Galante, Martinique and Hispaniola) .
In addition to Waltheria indica, Waltheria glomerata, Waltheria operculata, and Waltheria viscosissima, 7 species (Waltheria albicans, Waltheria berteroi, Waltheria carmensarae, Waltheria collina, Waltheria involucrata, Waltheria microphylla and Waltheria paniculata) are found in the Guiana Shield. Here the greatest diversity is in the Bolivar province of Venezuela, where 9 species are found, but Waltheria microphylla and Waltheria paniculata are only found in Guyana. Waltheria indica is the only species recorded from Surinam and French Guiana. 
Waltheria carmensarae has a disjunct distribution in Argentina, Paraguay and Venezuela. Waltheria berteroi is found in Columbia and Venezuela
Waltheria boliviensis is endemic to Bolivia. Waltheria ovata is found in Peru and Ecuador (including the Galapagos Islands). Waltheria procumbens and Waltheria macrophylla are endemic to Paraguay .
Waltheria belizensis is endemic to Belize .
One additional species is present in Africa - Waltheria lanceolata of Senegal, Guinea, Sierra Leone and Liberia . Madagascar also has one additional species - the endemic Waltheria madagascarensis .
[Note: While the African Flowering Plants Database  accepts Waltheria laxa, Flora Somalia  identifies it as a teratological specimen of Waltheria indica.]
One additional species is present in Australia - Waltheria virgata  of the Northern Territory and Western Australia.
Waltheria tomentosa is endemic to the Marquesas.
Waltheria pyrolifolia is endemic to the Hawaiian island of Maui . It may be extinct.
Index to Genera
Synonymy of Waltheria
© 2010, 2011 Stewart R. Hinsley