Athrotaxis laxifolia

Superregnum: Eukaryota
Regnum: Plantae
Divisio: Tracheophyta
Divisio: Pinophyta
Classis: Pinopsida
Ordo: Pinales

Familia: Cupressaceae
Subfamilia: Athrotaxidoideae
Genus: Athrotaxis
Nothospecies: Athrotaxis × laxifolia
Name

Athrotaxis × laxifolia Hook., Hooker's Icon. Pl. 6: t. 573. 1843.

Formula hybridae: Athrotaxis cupressoides male parent × Athrotaxis selaginoides female parent

Synonyms

Homotypic
Arthrotaxis laxifolia Hook., orth. var.
Arthrotaxis tetragona Hook., orth. var.
Heterotypic
Athrotaxis × doniana Henkel & W.Hochst., Syn. Nadelhölz.: 221. 1865.
Misapplied names
Athrotaxis tetragona auct. non Athrotaxis tetragona Hook. , Hooker's Icon. Pl. 6: t. 560. 1843.

Distribution
Native distribution areas:

Continental: Australasia
Regional: Australia
Tasmania

References: Brummitt, R.K. 2001. TDWG – World Geographical Scheme for Recording Plant Distributions, 2nd Edition
References
Primary references

Hooker, W.J. (ed.) 1843. Icones Plantarum; or figures, with brief descriptive characters and remarks, of new or rare plants, selected from the author's herbarium. Vol. VI [= Vol. II, new series.] Tt. DI–DC. Hippolyte Baillière, London. BHL Reference page. : t. 573.

Additional references

Isoda, K., Brodribb, T. & Shiraishi, S. 2000. Hybrid origin of Athrotaxis laxifolia (Taxodiaceae) confirmed by random amplified polymorphic DNA analysis. Australian Journal of Botany 48(6): 753–758. DOI: 10.1071/BT99032 Reference page.

Links

Athrotaxis x laxifolia in: Australian Plant Census (APC) 2017. IBIS database, Centre for Australian National Biodiversity Research, Council of Heads of Australasian Herbaria. Accessed: 2017 Feb. 21.
Govaerts, R. et al. 2017. Athrotaxis × laxifolia in World Checklist of Selected Plant Families. The Board of Trustees of the Royal Botanic Gardens, Kew. Published online. Accessed: 2017 Feb. 21. Reference page.
International Plant Names Index. 2017. Athrotaxis × laxifolia. Published online. Accessed: Feb. 21 2017.
Tropicos.org 2017. Athrotaxis × laxifolia. Missouri Botanical Garden. Published online. Accessed: 21 Feb. 2017.
Australian Plant Name Index (APNI) Athrotaxis × laxifolia Integrated Botanical Information System (IBIS). Australian National Botanic Gardens & Australian National Herbarium. Accessed: 2020 Jan 4.

Vernacular names
English: Loose-leaved Tasmanian cedar
中文: 疏密叶杉

Description

Athrotaxis laxifolia is an evergreen coniferous tree growing to 12–21 m tall with a conical, sparsely branched crown[2] and a trunk up to 1m diameter. It is commonly known as the Summit or Yellow-Twig athrotaxis.[2] The leaves are scale-like, 4–12 mm long and 2–3 mm broad, arranged spirally on the shoots. The seed cones are oblong-globose, 15–26 mm long and 14–20 mm diameter, with 14–18 spirally-arranged scales; they are mature about six months after pollination. The pollen cones are 3–5 mm long.[3] The bark of A. laxifolia is dark orange-brown, deeply fissured and flaky.[2] The species name laxifolia refers to the wider spacing of the leaves as compared with the other conifers in its genus, Athrotaxis cuppressoides and Athrotaxis selaginoides.[2]
Habitat & Distribution

Athrotaxis laxifolia is endemic to Tasmania, Australia, where it grows between 1,000–1,200 m altitude, in sub-alpine and alpine woodland.[3][1] One group of researchers have located nine different geographic locations for this species (5 hybrid populations and 4 single individuals).[4] The hybrid populations were found at Mount Reid, Tyndall Range, Crooked Lake, Brumbys Creek, and Tarn Shelf, while the individuals are located at Mount Kate, Pine Lake, Wylds Craig and Lake Dobson Road.[4]

Away from its native range, it is occasionally cultivated as an ornamental tree in northwestern Europe. Despite being the rarest of the three in the wild, it is the most frequently planted Athrotaxis in cultivation, though still only seen in major collections; trees in Ireland have reached 20 m tall.[5][6]
Threats & Conservation

Its status in the wild is little-known; it is the rarest of the three species of Athrotaxis. It is in many respects intermediate between Athrotaxis cupressoides and Athrotaxis selaginoides, and it is strongly suspected of being a natural hybrid between these two; however, genetic evidence for this is inconclusive.[3]

Later research has supported the theory of natural hybridization, as populations of A. laxifolia have been genetically studied and revealed to contain a range of genetic variance from pure A. cupressoides to pure A. selaginoides, and some genetically half-way between both.[4] Although listed as Endangered in the IUCN Red List of Threatened Species, the same research has suggested that this classification is unwarranted.[4] Even though A. laxifolia is rare in itself, given the multiple spontaneous hybridization events, it should be afforded the same status as it's parent species (A. cuppresoides and A. selaginoides) which is Vulnerable.[4]
References

Farjon, A. (2013). "Athrotaxis laxifolia". IUCN Red List of Threatened Species. 2013: e.T30532A2793806. doi:10.2305/IUCN.UK.2013-1.RLTS.T30532A2793806.en. Retrieved 17 November 2021.
"Athrotaxis laxifolia / Summit athrotaxis | Conifer Species". American Conifer Society. Retrieved 2022-02-19.
Farjon, A. (2005). Monograph of Cupressaceae and Sciadopitys. Royal Botanic Gardens, Kew. ISBN 1-84246-068-4
Worth, James R. P.; Larcombe, Matthew J.; Sakaguchi, Shota; Marthick, James R.; Bowman, David M. J. S.; Ito, Motomi; Jordan, Gregory J. (February 2016). "Transient hybridization, not homoploid hybrid speciation, between ancient and deeply divergent conifers". American Journal of Botany. 103 (2): 246–259. doi:10.3732/ajb.1500433. ISSN 0002-9122.
Mitchell, A. F. (1974). A Field Guide to the Trees of Britain and Northern Europe. Collins ISBN 0-00-212035-6
Tree Register of the British Isles