Botanic Gardens Trust, Sydney, Australia

Tristaniopsis in south-east Asia

Studies in the genus Tristaniopsis (Myrtaceae) in south-east Asia

Dr Peter Wilson - Senior Research Scientist

Tristaniopsis is a capsular genus of Myrtaceae, with the next most extensive range of any capsular genus after Metrosideros. Its distribution extends from Burma and Thailand, through Malaysia and parts of Indonesia, to the Philippines and Papua New Guinea, extending to New Caledonia and Australia.

In the past year, I have had a close association with Berhaman Ahmad, a senior lecturer in the School of International Tropical Forestry at the Universiti Malaysia Sabah, who has been studying the genus in Borneo for his PhD at the University of Aberdeen. With the support from a grant from the Friends of the Botanic Gardens, I was able to spend two weeks in the field in Sabah with Berhaman and collect most of the species, including many unnamed ones.

Australia has only three species of Tristaniopsis, confined to the coast and tablelands of the eastern seaboard. In contrast to this, Borneo has many types of forest habitats (including fresh water swamp forests and peat swamps, mixed dipterocarp forests and montane forests and forests on limestone and ultramafic soils) and these are home to over 20 species. These species show much variation, particularly in bark and inflorescence type. The species pictured above shows inflorescences with stout axes and crowded, white flowers but other species have long, slender inflorescence axes bearing yellow flowers on relatively long pedicels.

I am working with Berhaman to augment his sampling of the genus for analyses of relationships in the genus using DNA sequence data.

Berhaman’s analyses of Bornean species show that they are quite closely related and further sampling is desirable to test species concepts (some names have been applied to plants with ranges extending from Burma to Borneo). So far, we have added a sample of one of these species from near the type in Singapore. Another interesting question is whether the biogeography of the genus reflects the geological history of the region in some way. To this end, samples of all three Australian species, plus two New Caledonian species, were sequenced so that these data can be included in future anlayses. Further samples, preferably from intermediate areas (e.g. Papua New Guinea and the Philippines), will be sought to improve investigation of biogeographic hypotheses.



Tristaniopsis sp. nov.
Tristaniopsis sp. nov. (Gunung Alab, Sabah)

Berhaman Ahmad
Berhaman Ahmad

All photos: Peter Wilson