Evolutionary Relationships of Araliaceae in the Malesian Region:a Preliminary Analysis

Abstract

We employ the nuclear ribosomal ITS sequences to assess the evolutionary relationships of Araliaceae in the Malesian region. Malesian Araliaceae consist of 14 genera and about 500 species. Our analysis suggests a diffuse origin of Araliaceae taxa, with many genera belong to the Asian palmate clade or the tribe Hedereae. The Malesian endemic Harmsiopanax is morphologically unique and its phylogenetic position is not well resolved at present. Several morphologically diverse species of Brassaiopsis perhaps have a relatively recent origin in the Malay Peninsula and Sumatra, as suggested by their monophyly as well as their low ITS sequence divergence. Wardenia is not supported as W.simplex (=B.simplex) is nested within Brassaiopsis. The Malayan region is important for the development of Schefflera, and available evidence suggests that Schefflera in the region forms a clade with the Heptapleurum group. Dendropanax lancifolius does not form a clade with the core group of Dendropanax, and its status needs to be further analyzed. Macropanax maingayi was considered to be a highly distinct member comprising the monotypic genus Hederopsis. Our analysis clearly places it in Macropanax. Aralia merrillii was once considered to be the sole member of the genus Acanthophora because of its unusual climbing habit. The ITS data support its placement in Aralia. Our expanded sampling of Arthrophyllum continues to support its monophyly. Osmoxylon has a primary distribution in the Malesian region and it is a hylogenetically isolated member of Araliaceae.