Diselma

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Diselma
Diselma archeri.jpg
Scientific classification OOjs UI icon edit-ltr.svg
Kingdom: Plantae
Clade: Tracheophytes
Clade: Gymnospermae
Division: Pinophyta
Class: Pinopsida
Order: Cupressales
Family: Cupressaceae
Subfamily: Callitroideae
Genus: Diselma
Hook.f.
Species:
D. archeri
Binomial name
Diselma archeri
Hook.f.
Synonyms

Fitzroya archeri (Hook.f.) Benth. & Hook.

Diselma archeri (dwarf pine or Cheshunt pine) [2] is a species of plant of the family Cupressaceae and the sole species in the genus Diselma. It is endemic to the alpine regions of Tasmania's southwest and Central Highlands, on the western coast ranges and Lake St. Clair. It is a monotypic genus restricted to high altitude rainforest and moist alpine heathland. Its distribution mirrors very closely that of other endemic Tasmanian conifers Microcachrys tetragona and Pherosphaera hookeriana .

Contents

Appearance and ecology

Scale-like leaves appear in a square in cross section and red coloration of juvenile cone formation. Photo: R. Wiltshire Diselma RW.jpg
Scale-like leaves appear in a square in cross section and red coloration of juvenile cone formation. Photo: R. Wiltshire
D. archeri cones D. archeri cones.png
D. archeri cones

Diselma archeri is a compact, prostrate shrub which commonly reaches 1–4 m in height but has been recorded to reach greater heights in subalpine rainforest zones. The foliage has a grey-green appearance with branchlets curving downward at their tips. Branches are short, ridged and very numerous. Branchlet foliage appears square in cross-section and scale-like leaves (2–3 mm) are overlapping and arranged in opposite decussate pairs which are pressed close to the stem. [3] The square leaf arrangement is similar to that of Microcachrys tetragona (Podocarpaceae) (creeping pine) and the two species can easily be confused. However, M. tetragona lives up to its name and grows low to the ground, spreading out with only occasional erect branches. Another species which can be confused with Diselma is Phaerosphaera hookeriana (previously known as Microstrobos niphophilus ) which is in the family Podocarpaceae. Both these species have a similar growth habit and distribution, however, the opposite pairs of leaves on D. archeri again make it distinguishable from the other species. [4] Bark is rough and scaly and often weathered revealing a reddish-brown inner bark. Being a gymnosperm no flowers are produced, instead seed development occurs on the surface of the scale-like leaves which are modified to form cones (see image). [5]

Diselma archeri is a dioecious shrub, where male and female cones are located on separate individuals. Both types of cones are very small (3–4 mm) and occur at the branch tips. The female cone is composed of two pairs of opposite cone scales and only the upper pair of scales is fertile. [6] At maturity up to four small winged seeds are produced which are wind dispersed. [7] D. archeri seedlings are uncommon as the species often re-sprouts from roots and trunks buried in peat soils. [2]

Taxonomy

Diselma : dis (meaning double) and selma (meaning upper) is a reference to either the two fertile scales in the female cone or the arrangement of the overlapping leaves in the opposite alternating pairs. archeri is named after botanical collector William Archer (1820-1874) who was also a Fellow of the Linnaean Society, an architect and Member of Parliament for Deloraine, Tasmania. [8] This species is commonly known as dwarf pine in reference to its prostrate growth pattern or Cheshunt pine which is in reference to a property belonging to William Archer, although the species would not have occurred there. [9]

Distribution map of Diselma archeri showing restriction to the South West and Central Plateau of Tasmania Diselma archeri distribution.png
Distribution map of Diselma archeri showing restriction to the South West and Central Plateau of Tasmania
A simplified phylogeny derived from molecular analysis showing the phylogenetic relationship of Diselma to closely related genera in the Cupressaceae. Diselma's closest relative appears to be the South American genus Fitzroya. Diselma phylogeny.png
A simplified phylogeny derived from molecular analysis showing the phylogenetic relationship of Diselma to closely related genera in the Cupressaceae. Diselma's closest relative appears to be the South American genus Fitzroya.

Distribution

Diselma archeri is endemic to Tasmania and is only found in high rainfall alpine and subalpine areas of the South West and Central Plateau of the state. Its altitudinal range varies from approximately 580-1400m above sea level. Like many Tasmanian conifers D. archeri is very fire sensitive and will only occur in fire free areas of alpine coniferous heath and montane rainforest. [11] This species can form a small tree (3-4m) in closed rainforest at high altitude and some ecologists consider Diselma to be one of the seven genera which can be used as rainforest indicators in Tasmania. [12] In more open coniferous heathland the Dwarf Pine grows more prostrate and only reaches approximately 1-2m in height.

Phylogeny

The closest relatives to Diselma appear to be the South American genus Fitzroya , another monotypic genus in the subfamily Callitroideae, the Southern Hemisphere clade of Cupressaceae. [10] Fossils of both Diselma and Fitzroya have been recorded in Tasmania. [13] This evidence indicates that Diselma archeri is most likely a paleoendemic and is the last remaining species in a genus that was once more extensive and has refuged to specific alpine zones due to changing climate. [14]

Related Research Articles

<span class="mw-page-title-main">Cupressaceae</span> Cypress family of conifers

Cupressaceae is a conifer family, the cypress, with worldwide distribution. The family includes 27–30 genera, which include the junipers and redwoods, with about 130–140 species in total. They are monoecious, subdioecious or (rarely) dioecious trees and shrubs up to 116 m (381 ft) tall. The bark of mature trees is commonly orange- to red-brown and of stringy texture, often flaking or peeling in vertical strips, but smooth, scaly or hard and square-cracked in some species.

<i>Lagarostrobos</i> Genus of conifers

Lagarostrobos franklinii is a species of conifer native to the wet southwestern corner of Tasmania, Australia. It is often known as the Huon pine or Macquarie pine, although it is actually a podocarp (Podocarpaceae), not a true pine (Pinaceae). It is the sole species in the genus Lagarostrobos; one other species L. colensoi formerly included has been transferred to a new genus Manoao. The genus was also formerly included in a broader circumscription of the genus Dacrydium.

<i>Prumnopitys</i> Genus of conifers

Prumnopitys is a genus of conifers belonging to the family Podocarpaceae. The nine recognized species of Prumnopitys are densely branched, dioecious evergreen trees up to 40 metres in height.

<i>Callitris</i> Genus of conifers

Callitris is a genus of coniferous trees in the Cupressaceae. There are 16 recognized species in the genus, of which 13 are native to Australia and the other three native to New Caledonia. Traditionally, the most widely used common name is cypress-pine, a name shared by some species of the closely related genus Actinostrobus.

<i>Libocedrus</i> Genus of conifers

Libocedrus is a genus of five species of coniferous trees in the cypress family Cupressaceae, native to New Zealand and New Caledonia. The genus is closely related to the South American genera Pilgerodendron and Austrocedrus, and the New Guinean genus Papuacedrus, both of which are included within Libocedrus by some botanists. These genera are rather similar to the Northern Hemisphere genera Calocedrus and Thuja: in earlier days, what is now Calocedrus was sometimes included in Libocedrus. They are much less closely related, as recently confirmed. The generic name means "teardrop cedar", apparently referring to drops of resin.

<i>Austrocedrus</i> Species of plant

Austrocedrus is a genus of conifer belonging to the cypress family (Cupressaceae). It has only one species, Austrocedrus chilensis, native to the Valdivian temperate rain forests and the adjacent drier steppe-forests of central-southern Chile and western Argentina from 33°S to 44°S latitude. It is known in its native area as ciprés de la cordillera or cordilleran cypress, and elsewhere by the scientific name as Austrocedrus, or sometimes as Chilean incense-cedar or Chilean cedar. The generic name means "southern cedar".

<i>Athrotaxis</i> Genus of conifers

Athrotaxis is a genus of two to three species of conifers in the cypress family, Cupressaceae. The genus is endemic to western Tasmania, where they grow in high-elevation temperate rainforests.

<i>Microcachrys</i> Genus of conifers

Microcachrys tetragona, the creeping pine or creeping strawberry pine, is a species of dioecious conifer belonging to the podocarp family (Podocarpaceae). It is the sole species of the genus Microcachrys. The plant is endemic to western Tasmania, where it is a low shrub growing to 1 m tall at high altitudes. Its leaves are scale-like, arranged in opposite decussate pairs, superficially resembling those of the unrelated Diselma archeri (Cupressaceae). It shares the common name Creeping pine with several other plants. Females produce tiny, red, edible berries in summer.

<i>Retrophyllum</i> Genus of conifers

Retrophyllum is a genus of conifers in the family Podocarpaceae. It contains five generally recognized extant species with a disjunct distribution in the Southern Hemisphere, found in Papuasia and also in South America. Retrophyllum are evergreen trees typically occurring in tropical rainforests and cloud forests.

<i>Phyllocladus aspleniifolius</i> Species of conifer

Phyllocladus aspleniifolius, commonly known as the celerytop pine, is an endemic gymnosperm of Tasmania, Australia. It is widespread and common in Tasmania, with the most abundance in the western highlands. Its ‘leaves’ appear similar to those of a celery plant, hence the common name.

<i>Athrotaxis cupressoides</i> Species of conifer

Athrotaxis cupressoides, is also known as pencil pine, despite being a species of the family Cupressaceae, and not a member of the pine family. Found either as an erect shrub or as a tree, this species is endemic to Tasmania, Australia. Trees can live for upwards of 1000 years, sustaining a very slow growth rate of approximately 12 mm in diameter per year.

<i>Callitris oblonga</i> Species of conifer

Callitris oblonga, also known as the South Esk pine, pygmy cypress pine, pigmy cypress pine, river pine, or Tasmanian cypress pine, is a species of conifer in the family Cupressaceae. It is endemic to Australia, where it is native to New South Wales and Tasmania, with one subspecies introduced in Victoria. It is considered vulnerable and faces a number of threats including land clearing, habitat degradation, and damage from or competition with invasive species.

<i>Eucalyptus coccifera</i> Species of eucalyptus

Eucalyptus coccifera, commonly known as the Tasmanian snow gum, is a small to medium-sized tree endemic to Tasmania. It has smooth, grey and cream-coloured bark, elliptic to lance-shaped adult leaves, flower buds in groups of between three and nine, usually white flowers and conical, hemispherical or cup-shaped fruit.

<i>Pterygopappus</i>

Pterygopappus is a genus of flowering plants in the tribe Gnaphalieae within the family Asteraceae. There is only one known species, Pterygopappus lawrencii, which is endemic to alpine Tasmania. It forms thick, light blue/green mats with densely packed leaves. It is most common in the mountains of the northeastern part of the island. It is a slow grower and prefers cool, moist environments.

Alpine vegetation refers to the zone of vegetation between the altitudinal limit for tree growth and the nival zone. Alpine zones in Tasmania can be difficult to classify owing to Tasmania's maritime climate limiting snow lie to short periods and the presence of a tree line that is not clearly defined.

<i>Richea gunnii</i> Species of flowering plant

Richea gunnii, the bog candleheath or Gunns richea, is an endemic Tasmanian angiosperm. It is a dicot of the family Ericaceae and is found in Central, Western and North-east Tasmania.

<span class="mw-page-title-main">Tasmanian coniferous shrubbery</span>

The vegetation in Tasmania's alpine environments is predominately woody and shrub-like. One vegetation type is coniferous shrubbery, characterised by the gymnosperm species Microcachrys tetragona, Pherosphaera hookeriana, Podocarpus lawrencei, and Diselma archeri. Distribution of these species is relevant with abiotic factors including edaphic conditions and fire frequency, and increasingly, the threat of climate change towards species survival exists. Conservation and management of coniferous shrubbery are necessary considering that the paleoendemic species, Microcachrys,Pherosphaera and Diselma, have persisted in western Tasmanian environments for millions of years.

<i>Pherosphaera hookeriana</i> Species of conifer

Pherosphaera hookeriana, or Mount Mawson pine, is a dwarf conifer endemic to Tasmania, at altitudes above 600 meters. There are roughly 30 known sites, with population numbers in the tens of thousands. The species occurs in a range of habitats typically in areas near water bodies, mostly on dolerite derived soils. The species is highly fire sensitive and an increase in fire events associated with climate change may lead to local extinction and fragmentation of habitat.

<i>Trochocarpa cunninghamii</i> Species of flowering plant

Trochocarpa cunninghamii is a flowering plant species of the family Ericaceae. It is commonly referred to as straggling purpleberry due to its round flattened mauve drupe fruits. This woody shrub is usually found in the understorey of rainforests and subalpine forests in the Central Plateau and western Tasmania, and is endemic to Tasmania.

<span class="mw-page-title-main">Tasmanian Central Highland forests</span> Terrestrial ecoregion in Tasmania, Australia

The Tasmanian Central Highland forests is a temperate broadleaf and mixed forests ecoregion in Australia. It covers Tasmania's Central Highlands region.

References

  1. Farjon, A. (2013). "Diselma archeri". IUCN Red List of Threatened Species . 2013: e.T42225A2962853. doi: 10.2305/IUCN.UK.2013-1.RLTS.T42225A2962853.en . Retrieved 19 November 2021.
  2. 1 2 "Diselma archeri (Cupressaceae)". utas.edu.au. University of Tasmania. Retrieved 28 September 2014.
  3. Kirkpatrick, J. 1997. Alpine Tasmania. An illustrated guide to the flora and vegetation. Oxford University Press" Melbourne. P. 18-19.
  4. "Key to Tasmanian Dicots".
  5. Raven, P.H., Evert, R.F., Eichorn, S.E. 2003. Biology of Plants. 6th Edition. W.H Freeman and Company
  6. Armin Jagel, Veit Dörken: Morphology and morphogenesis of the seed cones of the Cupressaceae - part III. Callitroideae. Bulletin of the Cupressus Conservation Project, Bd. 4(3), 2015, S. 91–103 (PDF)
  7. "Diselma archeri (Cheshunt pine) description".
  8. "Diselma archeri - Growing Native Plants".
  9. Wapstra, M., Wapstra, A., Wapstra, H. 2010. Tasmanian plant names unravelled. Fullers Bookshop Pty Ltd
  10. 1 2 Gadek, D.A., Alpers, D.L., Heslewood, M.M. and Quinn, C.J. 2000. Relationships within the Cupressaceae sensu lato: A combined morphological and molecular approach. American Journal of Botany 87(7): 1044–1057
  11. "Key to Tasmanian Dicots".
  12. Jarmen. S.J., Brown, M.J. 1983. A definition of cool temperate rainforest in Tasmania. Search14. P. 81-87
  13. Jordan, G.J., Barnes, R. and Hill, R.S. 1995. An early to Middle Pleistocene Flora of subalpine affinities in lowland Western Tasmania. Australian Journal of Botany. 43. 231-242
  14. Jordan, G.J., Barnes, R. and Hill, R.S. 1995. An early to Middle Pleistocene Flora of subalpine affinities in lowland Western Tasmania. Australian Journal of Botany. 43. 231-242