Diselma: Difference between revisions

| status = LR/lc LC
| status_system = IUCN2IUCN3.31

| classisparent_authority = [[Pinophyta|PinopsidaHook.f.]]

| ordospecies = [[Pinales]]archeri

| genussynonyms = '''''Diselma'''Fitzroya archeri'' [[(Hook.f.) [[George Bentham|Benth.]] & [[Hook.]]

'''''Diselma archeri''''' ('''Dwarfdwarf Pinepine''') or ('''Cheshunt pine''')<ref name="Diselma archeri Cupressaceae">{{cite web|title=Diselma archeri (Cupressaceae)|url=http://www.utas.edu.au/dicotkey/dicotkey/CONIFERS/sDiselma.htm|website=utas.edu.au|publisher=University of Tasmania|accessdateaccess-date=28 September 2014}}</ref> is a [[species]] of [[plant]] of the [[family (biology)|family]] [[Cupressaceae]] and the sole species in the [[genus]] '''''Diselma'''''. It is endemic to the alpine regions of [[Tasmania|Tasmania's]] [[Southwest National Park|southwest]] and [[Central Highlands (Tasmania)|Central Highlands]], on the western coast ranges and [[Lake St Clair, Tasmania|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 ''[[PhaerosphaeraPherosphaera hookeriana]]'' but differ in growth pattern.

== Appearance and Ecologyecology ==

[[File:Diselma RW.jpg|thumb|left| Scale-like leaves appear in a square in cross section and red coloration of juvenile cone formation. Photo: R. Wiltshire]] [[File:D. archeri cones.png|thumb|left|border|240x150px|D. archeri cones]]

''D.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 [[leaf|leaves]] (2–3&nbsp;mm) are overlapping and arranged in [[opposite decussate]] pairs which are pressed close to the stem.<ref>Kirkpatrick, J. 1997. Alpine Tasmania. An illustrated guide to the flora and vegetation. Oxford University Press" Melbourne. P. 18-19.</ref> The square leaf arrangement is similar to that of ''[[Microcachrys tetragona]]'' ([[Podocarpaceae]]) (Creepingcreeping Pinepine) 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 alsoin partthe of thefamily [[Podocarpaceae]] family. 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.<ref>{{Cite web|url=http://www.utas.edu.au/dicotkey/dicotkey/CONIFERS/sPhaerosphaera.htm|title = Key to Tasmanian Dicots}}</ref>

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).<ref>Raven, P.H., Evert, R.F., Eichorn, S.E. 2003. Biology of Plants. 6th Edition. W.H Freeman and Company</ref>

'''''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.<ref>{{Cite web|url=http://www.anbg.gov.au/gnp/gnp11/diselma-archeri.html|title = Diselma archeri - Growing Native Plants}}</ref>

This species is commonly known as '''Dwarfdwarf Pinepine''' in reference to its prostrate growth pattern or '''Cheshunt Pinepine''' which is in reference to a property belonging to William Archer, although the species would not have occurred there.<ref>Wapstra, M., Wapstra, A., Wapstra, H. 2010. Tasmanian plant names unravelled. Fullers Bookshop Pty Ltd</ref>

[[File:Diselma archeri distribution.png|thumb|left|none|280x190px|Distribution map of Diselma archeri showing restriction to the South West and Central Plateau of Tasmania]] [[File:Diselma phylogeny.png|thumb|right|220px|A simplified phylogeny derived from molecular analysis<ref name="Gadek, D.A. 2000">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</ref> 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 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.<ref>{{Cite web|url=http://www.utas.edu.au/dicotkey/dicotkey/CONIFERS/sDiselma.htm|title = Key to Tasmanian Dicots}}</ref> 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.<ref>Jarmen. S.J., Brown, M.J. 1983. A definition of cool temperate rainforest in Tasmania. Search14. P. 81-87</ref> In more open coniferous heathland the Dwarf Pine grows more prostrate and only reaches approximately 1-2m in height.

The closest relatives to ''Diselma'' is a [[monotipic]] genus and its closest relative appearsappear to be the South American genus ''[[Fitzroya]]'', andanother bothmonotypic ofgenus these species belong toin the subfamily [[Callitroideae]], the Southern Hemisphere clade of [[Cupressaceae]].<ref> name="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<"/ref> Macro fossilsFossils of both ''Diselma'' and ''Fitzroya'' have been recorded in Tasmania.<ref>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</ref> it can be assumed that ''D. archeri'' is the last remaining species of a once larger genus. 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 climatic episodesclimate.<ref>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</ref>

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{{reflistReflist}}

[[:Category:Cupressaceae]]

[[:Category:Monotypic conifer genera]]

[[:Category:Pinales of Australia]]

[[:Category:Least concern flora of Australia]]

[[:Category:FloraEndemic flora of Tasmania]]

[[:Category:EndemicTaxa named by floraJoseph ofDalton TasmaniaHooker]]