Melanthera

Melanthera (common name: squarestem), is a genus of perennial flowering plants in the family Asteraceae, native to North and South America, as well as Africa, Asia and Oceania, including Hawaii.

The most common species of this genus is Melanthera biflora, found in the coastal areas and islands of the tropical belt of the Indo-Pacific region. Together with Portulaca oleracea, Ipomoea pes-caprae and Digitaria ciliaris, Melanthera biflora is usually one of the first species colonizing degraded or altered environments in tropical zones of the planet.

Despite their general hardiness, leaves of Melanthera species are often attacked by rusts such as Uromyces columbianus and Uromyces martinii.

Taxonomy
There are difficulties regarding the classification of this genus for its affinities are uncertain. Further studies are needed to clarify its taxonomic and phylogenetic relationships.

Species
This is a list of species.
 * Melanthera abyssinica (Sch.Bip. ex A.Rich.) Vatke - tropical Africa from Ethiopia to Tanzania + Sierra Leone
 * Melanthera angustifolia A.Rich. - Central America, Cuba, Yucatán, Bahamas, southern Florida
 * Melanthera biflora (L.) Wild. Indo-Pacific
 * Melanthera bryanii (Sherff) W.L.Wagner & H.Rob. – Pili Nehe; Hawaii
 * Melanthera buchii Urb. - Haiti
 * Melanthera cinerea Schweinf. ex Schweinf. - Africa
 * Melanthera discoidea S.F.Blake - Amazonas State in Brazil
 * Melanthera elliptica O.Hoffm. - central Africa
 * Melanthera fauriei (H. Lév.) W.L.Wagner & H.Rob. – Olokele Canyon Nehe; Hawaii
 * Melanthera felicis C.D.Adams - Guinea in West Africa
 * Melanthera gambica Hutch. & Dalziel - Gambia, Senegal, Guinea-Bissau in West Africa
 * Melanthera hastata (Walt.) Rich. - Michoacán in Mexico, Islas de la Bahía in Honduras, Bahamas, El Salvador
 * Melanthera integrifolia (Nutt.) W.L.Wagner & H.Rob. – Kure Atoll Nehe; Hawaii
 * Melanthera kamolensis (O.Deg.) & Sherff) W.L.Wagner & H.Rob. – Maui Nehe; Maui
 * Melanthera latifolia (Gardner) Cabrera - Brazil, Bolivia, Paraguay, Uruguay, Argentina
 * Melanthera lavarum (Gaudich.) W.L. Wagner & H.Rob. – Coastal Nehe; Hawaii.
 * Melanthera micrantha (Nutt.) W.L.Wagner & H.Rob. - Hawaii
 * Melanthera nivea (L.) Small – Pineland Squarestem, Snow Squarestem, Yerba de Cabra; SE United States (LA MS AL GA FL SC TN KY IL), Caribbean, Mexico (from Tamaulipas to Quintana Roo), Central America, South America (Colombia, Venezuela, Ecuador, Guianas, northern Brazil)
 * Melanthera parvifolia Small – Small-leaf Squarestem - southern Florida
 * Melanthera perdita (Sherff) W.L.Wagner & H.Rob. – Kookoolau; Hawaii
 * Melanthera populifolia (Sherff) W.L. Wagner & H.Rob. – Grassland Nehe; Hawaii
 * Melanthera prostrata (Hemsl.) W.L.Wagner & H.Rob. - China, Japan, Korea, Thailand, Vietnam
 * Melanthera pungens Oliv. & Hiern - tropical Africa
 * Melanthera remyi (A.Gray) W.L.Wagner & H.Rob. – Annual Nehe; Hawaii
 * Melanthera scandens (Schumach.) Roberty
 * Melanthera rhombifolia O.Hoffm. & Muschl. - West Africa
 * Melanthera richardsae Wild - tropical Africa
 * Melanthera robinsonii Wild - tropical Africa
 * Melanthera robusta (Makino) K.Ohashi & H.Ohashi - Japan, Taiwan
 * Melanthera scaberrima Hiern - Angola
 * Melanthera scandens (Schumach. & Thonn.) Roberty - tropical Africa
 * Melanthera subcordata (A.Gray) W.L.Wagner & H.Rob. - Hawaii
 * Melanthera tenuifolia (A.Gray) W.L.Wagner & H.Rob. – Waianae Range Nehe; Oahu
 * Melanthera tenuis (O.Deg. & Sherff) W.L.Wagner & H.Rob. – Streambed Nehe; Hawaii
 * Melanthera triternata (Klatt) Wild - southern Africa
 * Melanthera venosa (Sherff) W.L. Wagner & H.Rob. – Spreading Nehe; Hawaii
 * Melanthera waimeaensis (H.St.John) W.L. Wagner & H.Rob. – Waimea Canyon Nehe; Kauai