Flora of Singapore. Volume 13: Gentianales. 2019. illus. X, 654 p. Hardcover.

GENTIANALES: RUBIACEAE (K.M. Wong et al.)GENTIANACEAE (K.M. Wong & M. Sugumaran)LOGANIACEAE (C. Puglisi)GELSEMIACEAE (D.J. Middleton)APOCYNA. -

Volume 13 of the Flora of Singapore includes only one order of plants - the Gentianales. The order has five families: Rubiaceae, Gentianaceae, Loganiaceae, Gelsemiaceae and Apocynaceae. The Loganiaceae and Gelsemiaceae are more or less exclusively tropical and subtropical; the Rubiaceae and Apocynaceae are primarily tropical and subtropical but have small numbers of species in temperate regions; and the Gentianaceae is most diverse in the tropics but also has very large numbers of species in the temperate-alpine regions. In Singapore, they are primarily woody plants and range from subshrubs and epiphytes to large lianas and emergent trees.Globally, the Gentianales has about 1110 genera and about 20,725 species (Bittrich & Kadereit, Fam. Gen. Vasc. Pl. 15 (2018) 5). In Singapore, where all five families are present, there are 93 genera, of which 5 are known only from introduced species, and 253 species, of which 15 are casual or naturalised introduced species. At 6% of the total, this is a fairly low percentage of introduced species compared to many other orders.