Agathis, commonly known as kauri or dammara, is a genus of evergreen coniferous trees, native to Australasia and Southeast Asia. It is one of three extant genera in the family Araucariaceae, alongside Wollemia and Araucaria (being more closely related to the former).[de Laubenfels, David J. 1988. Coniferales. P. 337–453 in Flora Malesiana, Series I, Volume 10. Dordrecht: Kluwer Academic.] Its leaves are much broader than most conifers. Kauri gum is commercially harvested from New Zealand kauri.
Description
Mature kauri trees have characteristically large trunks, with little or no branching below the crown. In contrast, young trees are normally conical in shape, forming a more rounded or irregularly shaped crown as they achieve maturity.
[Whitmore, T.C. 1977. A first look at Agathis. Tropical Forestry Papers No. 11. University of Oxford Commonwealth Forestry Institute.]
The bark is smooth and light grey to grey-brown, usually peeling into irregular flakes that become thicker on more mature trees. The branch structure is often horizontal or, when larger, ascending. The lowest branches often leave annular branch scars when they detach from the lower trunk.
The juvenile leaves in all species are larger than the adult, more or less acute, varying among the species from ovate to lanceolate. Adult leaves are opposite, elliptical to linear, very leathery and quite thick. Young leaves are often a coppery-red, contrasting markedly with the usually green or glaucous-green foliage of the previous season.
The male pollen cones appear usually only on larger trees after seed cones have appeared. The female seed cones usually develop on short lateral branchlets, maturing after two years. They are normally oval or globe shaped.
Seeds of some species are attacked by the caterpillars of Agathiphaga, some of the most primitive of all living moths.
Uses
Various species of kauri give diverse resins such as kauri gum. The timber is generally straight-grained and of fine quality with an exceptional strength-to-weight ratio and rot resistance, making it ideal for yacht hull construction. The wood is commonly used in the manufacture of guitars and ukuleles due to its low density and relatively low price of production. It is also used for some Go boards (goban). The uses of the New Zealand species (
A. australis) included shipbuilding, house construction, wood panelling, furniture making, mine braces, and railway sleepers. Due to the hard resin of the wood, it was the traditionally preferred material used by Māori for wooden weapons,
patu (fernroot beaters) and
barkcloth beaters.
Evolutionary history
Within
Araucariaceae, it is thought that
Agathis and
Wollemia share a common ancestor which lived between 90 and 55 million years ago, and the two genera form a sister clade to the older
Araucaria.[ Complete Chloroplast Genome of the Wollemi Pine (Wollemia nobilis): Structure and Evolution] The oldest fossils currently confidently assignable to
Agathis are those of
Agathis immortalis from the Salamanca Formation of Patagonia, which dates to the
Paleocene, approximately 64.67–63.49 million years ago.
Agathis-like leaves are also known from the slightly older Lefipán Formation of the same region, which date to the very end of the Cretaceous.
Some authors have suggested that
Agathis is known from earlier in the Cretaceous (
Aptian to
Cenomanian in North Africa.
Other fossils of the genus are known from the
Eocene of Patagonia, the Late Paleocene-
Miocene of southern Australia, and the
Oligocene-Miocene of New Zealand.
Species list
- Accepted species
|
|
| Queensland, Australia |
| North Island, New Zealand |
| western Malesia, Borneo |
| Philippines, Sulawesi, Maluku Islands |
| Peninsular Malaysia |
| Borneo |
| New Guinea |
| New Caledonia |
| Borneo |
| Fiji, Vanuatu, Solomon Islands |
| Queensland, Australia |
| New Caledonia |
| New Caledonia |
| Borneo |
| New Caledonia |
| Queensland, Australia; Papua New Guinea |
| Queensland and Papua New Guinea |
| Papua New Guinea |
| Vanuatu |
| Patagonia, South America Argentina |
|
- Formerly included
Moved to
Nageia
The placement of the fossil species
"Agathis" jurassica from the Late Jurassic of Australia in this genus is doubtful.
[ cited in ]
== Gallery ==
, the largest tree in New Zealand by volume]]
External links
