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[ Extracted from the Newsletter of the Friends of the Australian National Botanic Gardens, May 1993. The technical paper on this species is also available. ]


Leptospermum namadgiensis
a New Species of Tea-tree from the Southern ACT

Andrew Lyne

The genus Leptospermum is in the family Myrtaceae and comprises about 83 species. Commonly known as tea-tree or ti-tree, they are distributed in Australia, South East Asia, New Guinea and New Zealand. Leptospermums occupy a variety of habitats and are usually (but not always) found in wet or periodically damp substrates.

During the course of applying a revision of the genus Leptospermum to the ANBG Herbarium collection, two specimens collected by Phil Gilmour (an ANBG associate collector) from the Scabby Range in the southern part of the ACT during the summer of 1987-88 were obviously "a bit different". After much checking of keys and descriptions, detailed comparisons against available herbarium specimens of known species of Leptospermum and discussions with colleagues, the possibility that the two collections represented a new species became apparent.

To determine whether these collections really did represent a new species it was necessary to undertake field work and make further collections of material from all stages of development - buds, flowers, fruit and seed. Field work allows botanists to see the plant in its living state, gain some understanding of the species ecology and habitat preferences, delimit the distribution of the species and sample variation in the population.

Between December 1991 and April 1992, four trips to the Scabby Range in the southern ACT were made by Herbarium and Gardens staff to collect material and other information. As a more complete set of material became available, it was obvious that the Leptospermum from the Scabby Range was indeed a new species and one of very limited distribution and habitat preference, essentially being restricted to a few exposed mountain summits - Mts. Scabby, Kelly and Namadgi and Sentry Box Mtn. in Namadgi National Park and Scabby Range Nature Reserve. The plant itself grows as a shrub, 20 - 50cm high in exposed sites and to 1m in sheltered sites. It has small leaves that are usually covered in white hairs that give the plant a silvery appearance. The flowers are about 1cm in diameter with white or soft pink petals.

Having established that this Leptospermum was a new species, it had to be given a name, described, illustrated and have its conservation status assessed. All of these details and more are written up as a scientific paper to be formally published in a botanical journal.

A name that referred to some aspect of the species geography was thought most appropriate. Leptospermum scabbiensis - meaning literally the Leptospermum from or of the Scabby area - was an obvious contender. This was rather appropriate geographically speaking but did unfortunately conjure up an unpleasant image of what the plant looked like and as such was dismissed - it is after all a particularly beautiful plant! Thus, Leptospermum namdgiensis - meaning the Leptospermum from or of the Namadgi area - became the choice. Namadgi is the name given to the mountains south-west of Canberra by the local Aborigines.

The description is an attempt to put into words all the important details - such as leaf size, shape and pubescence, flower size and seed patterning for example - that define the new species. This initially involves examining and measuring many characters from all of the available collections - e.g., many leaves were measured from all of the herbarium collections before stating that Leptospermum namadgiensis has leaves from 3.5 to 9mm long and from 1.5 to 3.7mm wide.

Along with this written description is an illustration showing details of the species habit and anatomy. An illustration makes it a lot easier for readers to visualise what the the written description is saying.

It is now accepted practice when naming a species that an assessment of its conservation status be made. Many plants are under threat of extinction, imminent or otherwise, and as such it is important that details of potential threats, distribution and adequacy of reservation be published. This acts to alert managers of conservation reserves and other authorities to the existence of a rare or threatened species and prompts action to be taken to ensure its continued survival. In this instance, Leptospermum namadgiensis was coded as 2RCat. The "2" means that the species has a very restricted distribution with a maximum distribution of less than 100km (Leptospermum namadgiensis has a distribution of some 15km), "R" refers to the species being rare but not currently considered vulnerable or endangered, "C" denotes that the species is represented within a National Park or other proclaimed Reserve (in this case Namadgi National Park and Scabby Range Nature Reserve), "a" indicates the presence of more than 1000 plants within the Park and Reserve and "t" indicates that the entire known population of the species is within these conservation Reserves. Even though Leptospermum namadgiensis has an extremely limited distribution, the fact that all the individuals occur in rugged, mountainous country within the boundaries of a National Park and Nature Reserve mean that it is in no immediate threat of extinction.

Finally, the paper was published in the March, 1993 edition of Telopea, the National Herbarium of New South Wales (Sydney) journal dealing with systematic botany.

Some work remains to be done with this Leptospermum. There are a few other promising sites to be explored for the presence or absence of Leptospermum namadgiensis - e.g. Mt. Morgan and Yaouk Bill Peak. Also to be done is to examine the phylogenetic relationships between this and other related species of Leptospermum - essentially how this and other Leptospermum "fit in" with each other. In fact, another new Leptospermum from Alpine National Park in Victoria has been discovered. This one occupies a similar type of habitat and shares many similar characters with Leptospermum namadgiensis - just how similar these two are and their relationship with each other is still unclear. This work is continuing.

Cuttings of Leptospermum namadgiensis were taken during the course of the field work and brought back to the Nursery for propagation. Some of these have been successfully struck and small plants are to be seen in sections 2, 193, 194c and 195.

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