Helicia

Helicia is a genus of 115 species of trees and shrubs, constituting part of the plant family Proteaceae. They grow naturally in rainforests throughout tropical South and Southeast Asia, including India, Sri Lanka, Indochina, Peninsular Malaysia to New Guinea and as far south as New South Wales.

Many Helicia species are threatened to various degrees, as officially recognised by the International Union for Conservation of Nature (IUCN) and by continental, national and local governments. Seventeen species have official IUCN global conservation statuses of either critically endangered, endangered, vulnerable or near threatened (see Species list for details).

In 1790, notable pioneer botanist João de Loureiro described this genus as Helicia in his publication Flora Cochinchinensis. The type species for the genus was Helicia cochinchinensis, the type specimen of which was collected in Cochinchina, Vietnam. The genus name derives from the Greek word "έλιξ" (élix), which refers to the petals, now called tepals, spirally revolving or simply rolling or coiling up on themselves, at anthesis (the flowering time when the anthers open).

In 1831, botanist Nathaniel Wallich named Helicia robusta for a dried specimen of a cultivated plant in India, based on the specimen's earlier 1814 name Roupala robusta by William Roxburgh. Roxburgh's Calcutta botanic gardens cultivated the plant.

From the 1850s to the 1860s notable German–Australian botanist Ferdinand von Mueller formally described several new Australian species. In the late 1800s and early 1900s Frederick M. Bailey concentrated further on additional Queensland species, writing descriptions of them in numerous scientific papers.

In 1939, Hermann O. Sleumer described many additional Malesian species, especially in New Guinea. In 1955, he published a revision of the genus. In 1956, his treatment of the genus in Flora Malesiana was published. From 1969 to the late 1990s botanist Don B. Foreman, who was based in Papua New Guinea and Australia, collected numerous additional species, which he formally described before he wrote the comprehensive reviews and flora treatments for the two regions; notably in the authoritative Handbooks of the Flora of Papua New Guinea (1978–1995, to date 3 volumes), he wrote the chapters for Proteaceae and other families; and in the authoritative Flora of Australia (1981–, 60 volume series) he wrote the treatment of Helicia.

From the 1990s botanist Richard C. K. Chung, based in Malaysia, published new species formal descriptions and a revision of the 13 species occurring in Borneo. In total, approximately 100 species have been formally scientifically described.

Lawrie Johnson and Barbara G. Briggs grouped Helicia with Xylomelum in the subtribe Heliciinae, tribe Helicieae, and subfamily Grevilleoideae in their 1975 monograph "On the Proteaceae: the evolution and classification of a southern family". However, genetics studies showed these two to be relatively unrelated, instead finding the closest genetic correlations between Hollandaea and Helicia, and therefore classifying them both in the subtribe Heliciinae within the tribe Roupaleae.