Decaspermum (Myrtaceae) in New Guinea

Abstract

This article reviews the fourteen species of Decaspermum recognized in the Moluccas, New Guinea and the Bismarck Archipelago. Two earlier articles described the species of Decaspermum in Southeast Asia (Scott 1980) and Australia and the Pacific region (Scott 1979b). Eleven species are endemic to New Guinea, D. urvillei is endemic to the Bismarck Archipelago, D. bracteatum is found in the Moluccas and New Guinea, and D. humile is found in New Guinea and eastern Australia. Within New Guinea the species are found from the coastal forests up to the alpine grasslands, giving New Guinea the largest number of species with the greatest diversity in the genus. The first study of the genus was provided by Blume (1850) using the generic name Nelitris. Blume recognized three species from the Moluccas; alba Blume, bracteata (Roxb.) Blume, and rubra Blume, the latter with a variety rigida Blume. Two species, coriandri Blume and laxiflora Blume, were described from New Guinea. A critical assessment of the useful characters in Decaspermum was made by Diels (1922) who recognized eleven species in New Guinea; lorentzii Lauterb. (with a variety microphyllum Diels), leptanthelium Diels, arfakense Diels, laxiflorum (Blume) Diels, prunoides Diels, nitidum Lauterb., humifusum Diels, petraeum Diels, coriandri (Blume) Diels, rhodoleucum Diels and neurophyllum Lauterb. & K. Schum. Diels (1924) described a further three species: iodochnoum Diels, lamii Diels, and prostratum Diels. The number of collections seen by Diels was small, often only a single collection for a species. Consequently there was little known about the variation within species, especially in characters such as indumentum and leaf shape. Also the types of the species described by Blume were not available to Diels. Emphasis was given by Diels to the number of locules in the ovary, a character which is more variable within species than Diels allowed for.