Biochemical evidence of a former link between Australia and the Mascarene Islands

Abstract

THE land masses destined to become Australia, Madagascar and the associated Mascarene Islands are thought to have separated from the old southern continent of Gondwanaland after the establishment of an angiosperm flora¹. Similarities in the present floras of the areas, as exemplified by Cohnia and Cossinia which occur in Australia and New Caledonia but have their most westerly habitats in the Mascarene Islands, are consistent with this belief². The legume genus Acacia which is widely represented in America, Africa, Asia, Australia and many oceanic islands is thought to have originated in what is now northern South America and to have spread through Gondwanaland³. A survey of non-protein amino acids in the seeds of 123 species of Acacia has shown that the genus is divisible into four discrete biochemically defined sub-genera⁴. All 67 species from Australia which were analysed showed a single characteristic amino acid pattern. This Australian pattern was found in only one non-Australian species. A. heterophylla (Lam.) Willd. a native of the Mascarene Islands and one of the few phyllodinous species found outside Australia. In this communication we suggest that the seed chemistry of A. heterophylla and of the Australian species is the seed chemistry which characterised the original Acacia species of Gondwanaland.