Diselma: Difference between revisions

| status_ref = <ref name="iucn status 19 November 2021">{{cite journaliucn | author = Farjon, A. |date=2013 |title = ''Diselma archeri'' | journal = [[The IUCN Red List of Threatened Species]] | volume = 2013 | page = e.T42225A2962853 | publisher = [[IUCN]] | date = 2013 | url = http://www.iucnredlist.org/details/42225/0 | doi = 10.2305/IUCN.UK.2013-1.RLTS.T42225A2962853.en | access-date =19 5 DecemberNovember 20172021}}</ref>

'''''Diselma archeri''''' ('''dwarf pine''' 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 ''[[Pherosphaera hookeriana]]''.

[[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]]

''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>

''Diselma archeri'' is a [[dioecious]] [[shrub]], where male and female cones are located on separate individuals. Both types of [[conifer cone|cones]] are very small (3–4&nbsp;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.<ref name="jagel, dörken">Armin Jagel, Veit Dörken: ''Morphology and morphogenesis of the seed cones of the Cupressaceae - part III. Callitroideae''. Bulletin of the Cupressus Conservation Project, Bd.&nbsp;4(3), 2015, S.&nbsp;91–103 ([http://www.cupressus.net/bulletin/10/BullCCP4_3.pdf PDF])</ref> At maturity up to four small winged seeds are produced which are wind dispersed.<ref>{{Cite web|url=http://www.conifers.org/cu/Diselma.php|title = Diselma archeri (Cheshunt pine) description}}</ref> ''D. archeri'' seedlings are uncommon as the species often re-sprouts from roots and trunks buried in [[peat]] soils.<ref name="Diselma archeri Cupressaceae"/>

'''''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>

[[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.