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Distribution map showing distributions of A. goroensis (green dots) and A. muelleri (red triangles), with estimated population size of each occurrence; a few smaller populations on the Goro Plateau, located near the sites shown, have been omitted (from Ruhsam et al. 2016).

 

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Conservation status 2017 per IUCN Guidelines Version 12

Araucaria goroensis

R.R. Mill et Ruhsam 2017

Common names

Goro araucaria (not stated in sources, but logical; it is the araucaria native to the Goro Plateau).

Taxonomic notes

Type: New Caledonia, Province Sud, Yaté commune, Goro Plateau above Rivière Kuébini (Mill et al. 2017). Belongs, with six other species, to the "large-leaved" clade of New Caledonian Araucaria. The species is rather unusual among conifers in that it was discovered through a molecular study of nuclear and plastid sequences in Araucaria muelleri (Ruhsam et al. 2016), although subsequent study confirmed that it also possesses distinctive morphological characters. The molecular analysis also showed that A. goroensis is most closely related to A. rulei (Mill et al. 2017).

Description

Monoecious trees to 30 m tall and 30 cm dbh, usually with a single, straight trunk, leafless except in uppermost part, even in saplings. Architecture follows the Rauh model, with an open, candelabra-shaped crown. Outer bark light grey, occasionally reddish grey, exfoliating in horizontal strips; inner bark dark red. Foliage-bearing twigs bunched at tips of branches in groups of 9–17, slightly incurving, narrowly cylindrical, broadest near the middle. Leaves present on first and second order branches, and uppermost part of trunk, but retained only on the terminal twigs. Leaves on young seedlings acicular, curved inwards towards tip, abaxially keeled, acute, longest in middle part of branchlet. Leaves on saplings divergent from axis, ovate lanceolate, subacute to acute with the extreme tip rounded, bright green and glossy, keeled abaxially. Adult leaves on terminal twigs broadly lanceolate to ovate, 26–33×11–16mm, not decurrent, widest just above their base (the widest point obscured by adjacent overlapping leaves), slightly divergent but appearing appressed especially in dried material, tapering to a slightly incurved, subacute apex, weakly convex. Stomatal rows 13-71, abaxial, at base of leaf; 0–11 short rows at apex; 90–140 rows on adaxial surface, typically in several alternating bands. Leaves subtending pollen cones similar to adult ones but slightly shorter, innermost ones relatively narrow and ligulate. The lowermost leaves subtending seed cones are slightly broader than the branchlet leaves immediately below, but otherwise similar; those of the inner spirals gradually become narrower and more like the cone bract tips. Pollen cones are terminal on ultimate foliage branches, erect when shedding pollen, cylindrical, green maturing to pinkish brown or brown, 11–21×2.7–4cm, straight or curved, slightly tapering towards apex. Microsporophylls attached to a stout rachis, imbricate; stalk linear, 3.5–6×1–1.2mm. Pollen sacs 12–14, in three unequal rows, linear, 2–4mm. Female cones (only immature seen) terminal on short branchlets, solitary, erect, green, ellipsoid, 10×7.5 cm, densely covered with recurved bract tips, bearing c. 250 bract scale complexes. Bracts flabellate, ending in a caudate, upward curved, acute and shortly pungent tip (Mill et al. 2017). See also the photographs provided by Mill et al. (2017).

Araucaria goroensis resembles A. muelleri, but the adult leaves are more strongly incurved and the lower surface is much more lustrous, with the stomatal rows confined to the base (and sometimes the extreme apex) instead of extending the length of the leaf, and by the denticulate (not erose or entire) margins of the microsporophylls, which are not proximally rugose and have a much longer, acute (not short and broadly rounded) tip. A. goroensis also resembles A. rulei, but has larger adult leaves (normally at least 25 mm long), the largest ones being near the middle of the branchlet, rather than in its lower third; it also has a less acute (often rounded) apex, and ovate (not broadly lanceolate or caudate) microsporophyll lamina, with its margins almost straight, not broadened into a shoulder-like basal area; it also has shorter, less caudate and less strongly-reflexed female cone bracts (Mill et al. 2017). A key to the seven species in the "large-leaved" clade of New Caledonian Araucaria is provided by Mill et al. (2017).

Distribution and Ecology

New Caledonia: Grande Terre, Province Sud; known only from Yaté commune, where it occurs at three main sites: the Goro Plateau, the Rivière des Lacs and the Mamié area. It grows at elevations of 150-550m on cuirasse, a lateritic iron crust oxisol derived from peridotite (an ultramafic rock type). Grows as an emergent in open forest and maquis vegetation (maquis minier). Dominants of the canopy layer include Dacrydium araucarioides and Gymnostoma deplancheanum (Casuarinaceae). Other associates include Dracophyllum ramosum and Styphelia pancheri (both Ericaceae), and Solmsia calophylla (Thymelaeaceae). For further ecological information see Enright et al. (2009, 2014), whose "A. muelleri" study sites were on the Goro Plateau and consequently concerned A. goroensis (Mill et al. 2017).

The proposed IUCN status is "endangered." The extent of occurrence is approximately 100 km2, with an area of occupancy considerably less than 500 km2. The primary threat seems to be, as for most New Caledonian conifers, continued nickel mining; a nickel processor has been built on the Goro Plateau. None of the areas of occurrence is in a protected area. Population sizes at each site are small to very small (5-50 individuals), except that about 200 individuals are known at Le Trou, and a mixed population of 500–1000 individuals of A. muelleri and A. goroensis occurs at Mamié (Mill et al. 2017).

Big tree

Oldest

Dendrochronology

Ethnobotany

Observations

See Mill et al. (2017) for a comprehensive discussion. Mamié seems the most rational place to seek it, since the population there is not only the largest known in this species, but the locale also hosts the two similar species A. muelleri and A. rulei, making it a logical location to compare the three in a field setting.

Remarks

The species was named for the Goro Plateau, the type locality (Mill et al. 2017).

Citations

Enright, N. J., B. Miller, and T. Jaffré. 2009. Ecology and population dynamics of the endemic New Caledonian conifer, Araucaria muelleri (Araucariaceae). Pp. 359-364 in M. D. Wilcox and R. L. Bielelski (eds.), Araucariaceae: Proceedings of the 2002 Araucariaceae Symposium, International Dendrology Society, Dunedin.

Enright, N. J., B. P. Miller, G. L. W. Perry, D. Goldblum, and T. Jaffré. 2014. Stress tolerator leaf traits determine population dynamics in the endangered New Caledonian conifer Araucaria muelleri. Austral. Ecol. 39(1):60–71.

Mill, R. R., M. Ruhsam, P. I. Thomas, M. F. Gardner, and P. M. Hollingsworth. 2017. Araucaria goroensis (Araucariaceae), a new monkey puzzle from New Caledonia, and nomenclatural notes on Araucaria muelleri. Edinburgh Journal of Botany. DOI: 10.1017/S0960428617000014.

Ruhsam, M., A. Clark, A. Finger, A. S. Wulff, R. R. Mill, P. I. Thomas, M. F. Gardner, M. Gaudeul, R. A. Ennos, and P. M. Hollingsworth. 2016. Hidden in plain view: cryptic diversity in the emblematic Araucaria of New Caledonia. American Journal of Botany 103(5):888–898.

See also

Association Endemia, a site devoted to New Caledonian species. Has excellent photos and a general description (in French).

Manauté, J., T. Jaffré, J. M. Veillon, M. L. and Kranitz. 2003. Revue des Araucariaceae de Nouvelle-Calédonie. Available http://horizon.documentation.ird.fr/exl-doc/pleins_textes/divers14-03/010032935.pdf, accessed 2017.04.16.

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Last Modified 2017-11-12