Orites Diversifolia

''Orites diversifolia (=diversifolius)'', commonly known as variable orites, is a member of the family Proteaceae and is endemic to Tasmania.Understorey Network. (2017). Orites diversifolius. nlineAvailable at: http://www.understorey-network.org.au/family-index.html?species=Orites%20diversifolius ccessed 7 Mar. 2017 The common name stems from the variable form of the leaves, which range from entire and linear to serrated and ovate. It is a common shrub in lowland rainforest, subalpine woodland and scrub.

Taxonomy

'' Orites'' is a genus of the family Proteaceae and is one of twelve Tasmanian genera. Within the genus there are nine species, of which seven are Australian endemics. The remaining two species are South American, located in Bolivia and the Chilean Andes respectively.George, A. and Hyland, B. (1995). Orites. In: Flora of Australia: Volume 16 Elaeagnaceae, Proteaceae 1, 1st ed. Melbourne: CSIRO Australia, pp.346-349. Four Australian endemics, ''Orites acicularis, Orites diversifolia, Orites milliganii'' and ''Orites revolutus'', are also endemic to Tasmania.Brown, M., Kirkpatrick, J. and Moscal, A. (1983). An Atlas of Tasmania's Endemic Flora. 1st ed. Hobart: The Tasmanian Conservation Trust Incorporated. ''Orites diversifolia'' was discovered by the Scottish botanist Robert Brown in 1804 and the name was published by the Linnean Society of London in 1810.Flora of Australia: Volume 16 Elaeagnaceae, Proteaceae 1. (1995). 1st ed. Melbourne: CSIRO Australia.Brown, R. (1810). On the Proteaceae of Jussieu. Transactions of the Linnean Society of London, 10(1), pp.15–226. The name was derived from the Greek word "oreites," which translates to “mountaineer,” as the species was discovered on Tasmanian mountains. The species name "diversifolia" was likely chosen due to the variable nature of the leaves.

Description

''Orites diversifolia'' is an erect, rigid, branching shrub to 3m tall which occasionally establishes as a small tree in good conditions. Branches are brown and hairy. The leaves are stiff, leathery and alternate along the stems. Both the upper and lower surfaces are glabrous, with the upper surface a shiny green and the lower surface pale and glaucous. Leaf shape is linear but variable, frequently with serrated edges. Leaf margins are recurved and appear almost flat. Size of the leaf varies significantly with habitat, with subalpine individuals having smaller leaves that are 3–5 cm long, while rainforest leaves are commonly around 10 cm long.

The inflorescences are axillary spikes on the upper end of branches which carry approximately twenty flowers on each spike. Flowers are small and very characteristic of the family Proteaceae. They are also sessile and paired in the axils of bracts.Curtis, W. (1967). The Student's Flora of Tasmania: Part 3 Angiospermae: Plumbaginaceae to Salicaceae. 1st ed. Hobart: St. David's Park Publishing, pp.603-604. Flowers are made up of four petaloid tepals (petals and sepals, the perianth, are indistinguishable) which are cream in colour and 4-5mm long. Tepals are linear, less than 1mm in width and are recurved. Each flower has four stamens which rise above the tepals and a superior ovary. Flowers of ''Orites diversifolia'' are also sweetly scented. The fruit is a dark brown and moderately woody follicle that splits on one side to release seed. The boat-shaped follicles are located on branch ends in small clusters and are 18-24mm long and 6-8mm wide. Follicles contain two or more seeds which are winged and flattened.

Habitat and distribution

''Orites diversifolia'' is endemic to Tasmania. It is found in lowland rainforest and mixed forest across western Tasmania and in subalpine woodlands and coniferous heath in the south-west to 1300m. ''Orites diversifolia'' is common on the subalpine slopes of Mount Wellington and spreads through much of Mount Field National Park and the Southwest National Park. It is also found in the south of Bruny Island and around Mt Darwin in the Franklin-Gordon Wild Rivers National Park.

Ecology

Cool, moist and shady sites are preferred by this species, however ''Orites diversifolia'' can tolerate higher light exposure in the subalpine zone by reducing leaf and overall size. It is both frost and snow tolerant. ''Orites diversifolia'' is present in multiple floristic communities which often contain dominant and co-dominant species such as '' Atherosperma moschatum'', '' Phyllocladus aspleniifolius, Nothofagus spp., Eucryphia spp. and Leptospermum sp''p.''Kitchener, A. and Harris, S. (2005). From Forest to Fjaeldmark: Descriptions of Tasmania's Vegetation. 1st ed. Hobart: Department of Primary Industries, Water and Environment, pp.168-181.

''Orites diversifolia'' flowers in spring between the months of October and November. Seed is shed from December to February as soon as follicles ripen and dehisce. The seeds of ''Orites diversifolia'' have one large terminal wing, suggesting their mode of dispersal is via wind.

Cytology

''Orites diversifolia'' has a diploid chromosome number of 2n=28, which is consistent with all other species in the tribe Oriteae (includes genus ''Orites'' and ''Neorites''), substantiating its taxonomic placement.Wiltshire, R. and Stace, H. (1997). The cytotaxonomy of four Tasmanian genera of Proteaceae. Telopea, 7(3), pp.181-185.

Evolution

The family Proteaceae are well represented in the fossil record due to the leaves having a high resistance to decay and subsequently many have been discovered in Tasmania.Jordan, G. (1995). Early-Middle Pleistocene leaves of extinct and extant Proteaceae from western Tasmania, Australia. Botanical Journal of the Linnean Society, 118(1), pp.19-35.Jordan, G., Carpenter, R. and Hill, R. (1998). The macrofossil record of Proteaceae in Tasmania: a review with new species. Australian Systematic Botany, 11(4), pp.465-501. It has been suggested that the current distribution of '' Orites'' came about through Gondwanan vicariance and fossil evidence dates the arrival in Australia to the early Oligocene.Carpenter, R. (2012). Proteaceae Leaf Fossils: Phylogeny, Diversity, Ecology and Austral Distributions. The Botanical Review, 78(3), pp.261-287. Despite this, vicariance can never be confirmed and evidence of long distance dispersal to contradict the theory may arise in the future. Macrofossils of an extinct close relative of ''Orites diversifolia'' from the Early-Middle Pleistocene known as ''Orites truncata'' G.J.Jord. as well as macrofossils of all other extant endemic Tasmanian '' Orites'' species were documented in Jordan 1995. This suggests that ''Orites diversifolia'' evolved sometime after this period.

References

External links

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Proteaceae