Agathis silbae
Santo kauri [English and Bislama], hoe [Petawa and Penour villages], khoe [Valpei village] (Corrigan et al. 2009).
No synonyms other than Agathis silbai, orthographic error. Type collection in 1986 from a cultivated tree on the coast near Tasmalum in south Santo; the species had previously (1979) been collected in the mountains of Santo, but misidentified as A. obtusa. Type is Askin 13156 (GH, K, NY, US). The nearest Agathis populations are all of A. macrophylla, but this species is most closely related to A. labillardieri of W New Guinea (Corrigan et al. 2009). Some authorities continue to maintain that it is synonymous with A. macrophylla.
Native peoples in the area recognize two varieties, the ho. laman (man kauri) with a long bole, large crown and reddish leaf, and the hoe haae (woman kauri) with shorter bole, smaller crown, and green leaf. The taxonomic significance of this distinction is unclear (Corrigan et al. 2009).
Monoecious evergreen trees to 200 cm dbh and 35(-60) m tall with a clear bole for usually <10 m and a broad crown of long, spreading and ascending branches. Bark smooth or scaly, exfoliating, gray weathering to white; inner bark red to pink, exuding a white resin that later turns pale yellow. Leaves subopposite, thick, coriaceous, with multiple subparallel nerves, glabrous, light green. Leaves on young trees or in shade lanceolate, 2-5 × 5-12 cm, apex acute to obtuse. Leaves on mature trees and in sun foliage similar but smaller, 2-4 × 4-8 cm. Pollen cones axillary, solitary on a 4-6 mm peduncle, oblong-cylindrical, red-brown, 15-18 × 37-55 mm. Seed cones solitary on thick penduncles 6-9 cm long, globose, 10-12 sm diameter, smooth, green, often resinous, ripening brown. Cone scales triangular, 3.5 cm long, 4-5 cm wide; seeds 12-15 × 7-8 cm, ovoid-oblong, with two unequal wings, one 20-25 × 13 17 mm; the other, opposite, a blunt triangle 4-6 mm wide. Flowering and fruiting unclear; may happen at various times of the year, possibly varying substantially from year to year (Corrigan et al. 2009, Farjon 2010).
Compared to A. macrophylla the seed cone peduncles are 6-9 cm long instead of 1-2 cm, the pollen cones are predominately 3 cm long instead of 4.5-5 cm, and the stems of seedlings are red-brown instead of green. Most diagnostically, the microsporophylls of the pollen cone have a "double prismatic" head not seen in any other species of Agathis. Seed cones are borne high in the canopy; seeds dispersed by wind (Corrigan et al. 2009).
Vanuatu: W coast of Santo Island, in four locations from Pic Santo to near the tip of the Cumberland Peninsula (Corrigan et al. 2009). Climate is tropical rainforest with precipitation ca. 4500 mm/year (Whitmore 1977, cited in Corrigan et al. 2009). Occurs at elevations of 450-760 m in "pockets" on the western side of ridges, on well-drained basaltic soils (Robinson 1969, cited in Corrigan et al. 2009; Farjon 2010). Functions as a keystone species due to its size and typical Agathis growth form at maturity, as a canopy emergent species (Corrigan et al. 2009).
Distribution data from Corrigan et al. (2009) modified to exclude areas at elevations below 450 m or above 760 m.
This species is listed as "VU D2" (vulnerable, known from fewer than five localities) by WCMC, which adds: "Logging is a major threat, but at present land disputes have halted logging activities temporarily."
Corrigan et al. (2009) report heights to 60 m and present photographs of trees ca. 200 cm dbh.
As of 2012, no age data have been reported. Comparably large trees in other tropical Agathis species live several centuries.
Traditionally, the resin has been used for lighting and to caulk canoes, and its soot for tattoos; the bark for medicines; and the root tips for "fattening babies" (Siwatibau et al. 1998 and Wheatley 1992, both cited in Corrigan et al. 2009). Some trees are cultivated in coastal villages. Santo kauri was commercially logged by a local operator between 1995 and 1997, and the wood is much in demand. Logging is the principal threat to the species, and Corrigan et al. (2009), who work with the Vanuatu Department of Forests, present detailed recommendations for its management.
Access is difficult, and the tree grows on private land (Corrigan et al. 2009). I suggest that any attempt to visit sites in the field be preceded by inquiries with the Vanuatu Department of Forests.
The species is named for John Silba, who financed the private expedition that discovered it in 1986 and co-authored the original description (Corrigan et al. 2009). The common name refers to its occurrence on the island of Santo (historically called Espiritu Santo).
The species was in the news in October, 2012 when New Zealand police raided the Auckland Botanic Garden and a private home, seizing plants and computers because of suspicion that a specimen of Agathis silbae had entered New Zealand in contravention of a law against non-native trees (Howie 2012, Rudman 2012).
Corrigan, H., S. Naupa, R. Likiafu, J. Tungon, C. Sam, L. Kalamor, L. Viji, L. Mele, and L. Thomson. 2009. A strategy for investigating, conserving, and managing the genetic resources of Santo kauri (Agathis silbae). Pp. 383-390 in R.L. Bieleski and M.D. Wilcox (eds.), Araucariaceae: Proceedings of the 2002 Araucariaceae Symposium, Araucaria-Agathis-Wollemia. Dunedin, New Zealand: International Dendrology Society.
Howie, C. 2012.10.14. 'Plant Nazis' hunt for outlawed trees. The New Zealand Herald www.nzherald.co.nz, accessed 2012.11.17.
de Laubenfels, D.J., and J. Silba. 1987. The Agathis of Espiritu Santo (Araucariaceae, New Hebrides). Phytologia 61(7):448-452.
Robinson, G.P. 1969. The Geology of North Santo. Vila (Sect. 3.2).
Rudman, B. 2012.10.17. Ministry barking up wrong tree in dawn raids. The New Zealand Herald www.nzherald.co.nz, accessed 2012.11.17.
Siwatibau, S., C. Bani, and J. Kaloptap. 1998. SPRIG Rapid Rural Appraisal Survey of selected tree species in Vanuatu. Report by Island Consulting to CSIRO Division of Forestry, SPRIG Project.
The species account at Threatened Conifers of the World.
Last Modified 2023-11-01
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