One hundred grams of mature leaves were collected from 2 to 10 widely spaced trees per site and sent to Sydney for analysis as soon as possible after collection. Samples usually arrived in the laboratory within 48 h of collection. The majority of the sampling was done between December 1998 and October 1999. Seasonal trends in oil yields and composition are confounded in the data on geographic variation, but these were considered minor in the context of this study.

Chemotype 1 is comprised of E-nerolidol (74-95%) and linalool (14-30%) and is found from Sydney, north along the east coast of Australia to Selection Flat, New South Wales, with an isolated occurrence near Maryborough, Queensland. Two divisions occur in this chemotype which are based on the presence or absence of significant proportions of linalool (14-40%). Chemotype 2 contains 1,8-cineole (10-75%), viridiflorol (13-66%), alpha-terpineol (0.5-14%) and beta-caryophyllene (0.5-28%) in varying proportions and order of dominance in the oils. It is found throughout the distribution of the species, from Sydney to Papua New Guinea and New Caledonia. Within chemotype 2 there appears to be a continuous spread of oil composition without formation of any further discrete divisions as in chemotype 1. Analyses have shown that M. quinquenervia trees that occur at latitudes south of 25d S have high oil yields (1-3% w/w%, fresh leaves) and comprise chemotypes 1 and 2. North of 25d S, however, chemotype 1 does not occur and oil yields amongst the Australian populations are uniformly low (0.1-0.2%).

Leaves of M. quinquenervia were collected from January to October at seven different locations across New Caledonia: Yate, Mont Panie, Tiebaghi, Temrock, Farino, Martin and Mont Mou.

Niaouli essential oils from New Caledonia were classified into three chemotypes, using principal component analysis (PCA). Of these three chemotypes, found co-occurring in the harvesting locations across the island, chemotype 2, already characterized in Madagascar, is rich in 1,8-cineole (up to 80%) and is widespread (65.4% of the overall samples); chemotype 1 (24.8% of samples) is rich in terpinene derivatives; and chemotype 3 (9.8% of samples) is rich in alpha-pinene and viridiflorol.