Virotia azurea H.C. Hopkins & Pillon, 2020

Hopkins, Helen C. F. & Pillon, Yohan, 2020, Virotia azurea (Proteaceae: Macadamieae), a striking new species endemic to New Caledonia and notes on V. francii and V. leptophylla, Candollea 75 (1), pp. 89-98 : 92-97

Virotia azurea H.C. Hopkins & Pillon , sp. nov. ( Fig. 1–3 ).

Holotypus: NEW CALEDONIA. Prov. Nord: Poindimié-Amoa, Wabuli , 20°57'26"S 165°14'24"E, 23 m, 6.II.2013, fl., Gâteblé et al. 87 ( P [ P01067947 ]!; iso-: NOU!) .

Virotia azurea H.C. Hopkins & Pillon is similar to V. leptophylla (Guillaumin) L.A.S. Johnson & B.G. Briggs but differs by its longer, oblanceolate leaves that often have a rather long, pointed apex and margins that are often bluntly toothed distally (beyond the widest point), and by the fruits that in lateral view are crescent-shape or elliptic and strongly beaked.

Slender, single- or multi-stemmed shrub or small tree 3 – 6 m high, following Corner’s model of architecture, sometimes with many iterations (D. Bruy, pers. comm.). Leaf-bearing stems circular in cross-section, 9 – 10.5 mm diam., with some minute hairs. Older stems with ± circular or kidney-shaped leaf-scars, the bark rough with numerous pale lenticels. Leaves in juvenile plants (seedlings, later stages of juvenile growth and regrowth shoots) not known. Leaves in adult plants spirally arranged, the distal ones clustered around the shoot apex, simple, shortly petiolate, erect to spreading; petioles 1.5– 3(– 7) cm long, fairly stout (3 mm diam.), terete; blades oblanceolate, 30–56 × 5.3–11.5 cm; base narrowly cuneate or sometimes decurrent, symmetric; apex acute, pointed with a rounded tip, or bluntly pointed to ± rounded; margins usually somewhat undulate and sinuate to bluntly toothed, occasionally ± flat and entire; both surfaces entirely glabrous or almost so (a few minute hairs at most on midrib and on lower surface, at × 40), dark shiny green above and lighter beneath; midrib on upper surface slightly indented to slightly raised towards the base, prominent, rounded and longitudinally ridged beneath; secondary and higher order venation minutely prominent on both surfaces in dry material; towards the base of the blade, secondary veins at a wide angle (c. 60– 70°) to the midrib, parallel to one another and linked by an intramarginal vein close to the margins; in the middle and distal part of the leaf, secondary veins gradually at a narrower angle to the midrib (c. 40–60° near the apex), either parallel or arcuate, branching and anastomosing further from the margins. Inflorescences: axes either inserted either singly in a leaf axil or 1–2 apparently arising from the axil of a leaf scar proximal to the current leaves (or rarely terminal, in Munzinger et al. 1462), erect or spreading; each a raceme of flower-pairs of total length 14–26 cm, including a common peduncle 7–9 cm long and bearing a few widely spaced bracts each to 3 mm long; flowering part cylindrical, 5.5– 8 cm diam., its central axis slender, 1 –2 mm diam., slightly ridged longitudinally, quite densely hairy when young, later sparsely to moderately hairy (at × 40), the hairs short, red-brown, adpressed. Flowers: in pairs, the axis of each pair arising in the axil of a small, minutely hairy bract 0.5 mm long. Peduncle of each flowerpair 1.5– 5 mm long, bearing 2 pedicels each (0 –) 1– 4 mm long, peduncle and pedicels together 3–9 mm long, slender, minutely hairy, slightly ridged longitudinally; bracts inserted close to the base of the pedicels (or sometimes below, on the peduncle), minute, triangular, 0.5 × 0.2 mm, hairy; hairs on peduncles, pedicels and bracts 0.1 mm, reddish, adpressed. Bud just prior to anthesis a straight slender tube (20–) 25–32 mm long, very narrow for most of its length, expanded into an ovoid at the tip, also slightly expanded at the base, blue; outer surface sparsely to moderately hairy (hairs minute, reddish, adpressed). Tepals post-anthesis splitting to or almost to the base (remaining united at the base for up to 3 mm), tips of lobes ovate, thickened, 2.5 × 1.5 mm, tepal lobes below the tip long and narrow, curling helically, blue to white (including light blue, mid-blue and white-violet), their inner surface glabrous. Stamens: free part of the filament very short, each one inserted towards the base of the ovate tip of a tepal; anthers 2 × 1 mm, the connective shortly prolonged at the apex. Disc an erect, hypogynous cup or collar, thin, glabrous, slightly undulate along the top margin to shallowly 4-lobed or the lobes sometimes splitting to the base, maximum height 0.4 mm. Gynoecium: ovary cylindrical-conical, 1.5–2.5 × 0.8 mm, glabrous or with a few minute hairs, blue or violet; style cylindrical, long and slender, 21–30 × 0.5 mm, glabrous, ± white, the distal 2.5 mm forming a slightly swollen pollen presenter, this glabrous and shiny black with longitudinal ridges when dry; stigma a short terminal slit. Fruit few per infructescence, each borne on a thickened pedicel/peduncle c. 8 mm long, somewhat laterally compressed, crescent shaped or ventral part ± elliptic in outline with a marked beak at the end of the dorsal margin, c. 7.3 cm long (including the beak 1.5 cm long) × 3.5 cm deep (between the mid-points of the ventral and dorsal margins); epicarp bright or dark shiny green, glabrous; seed (based on Gâteblé et al. 449) 1 per fruit, almond-shaped, c. 4 cm long × 1.7 cm wide, cotyledons pale blue to mauve or pale violet.

Etymology. – The epithet, azurea, describes the colour of the flowers. According to STEARN (1992: 241), azureus means sky-blue, a light, pure, lively blue. Fresh seeds have cotyledons that are also bluish, tinged with pale violet.

Distribution, habitat and phenology. – Virotia azurea is found in a restricted area of central Grande Terre that extends from Mt Aoupinié in the south to Povila in the north ( Fig. 4 ), growing in humid forest at altitudes between 20 and 600 m. Most collections are from non-ultramafic substrates; the type, Gatêblé et al. 87, is an exception as the field notes indicate the substrate as ultramafic. This reflects the geology of the area which is largely non-ultramafic but with pockets of ultramafic, especially serpentinite. One explanation for these small pockets or “filons” of ultramafic rock in otherwise non-ultramafic regions is that they may be due to diapirism (solid injection) along fault planes, in contrast to the large regions of ultramafics in the south and along the west coast of Grande Terre, in which over-thrust has been significant ( LILLIE & BROTHERS, 1970).

Mature flowers and large floral buds have been collected in February, April, June and October-November, and fruits in November-December and April.

Conservation status. – Most collections of the new species were made in the adjacent valleys and ridges of Amoa and Tchamba, where it can be locally abundant (see field notes of Bruy 1220). Other localities where it has been collected are Povila, plateau de Tango and Mount Aoupinié. Its habitat, rainforest, is relatively well-preserved in this part of New Caledonia. While Mount Aoupinié is a nature reserve, plateau de Tango has been heavily planted with the invasive tree Pinus caribaea Morelet. Dispersal of this large-fruited, large-seeded new species may be problematic because of hunting pressure on its putative dispersers (flying foxes and New Caledonian Imperial Pigeons). Virotia azurea was evaluated by the New Caledonia Red List Authority at a workshop held in Thio on October 24TH 2019. It qualifies as “Vulnerable” [VU B1ab(iii,v)+2ab(iii,v)] under the IUCN Red List Categories and Criteria ( IUCN 2012, 2017), based on an estimated AOO of 32 km ², an EOO of 578 km ² and its occurrence at six localities.

Notes. – Virotia azurea is similar to V. leptophylla but differs by its longer, oblanceolate leaves (30–56 cm long vs 7.5–22.5 cm in V. leptophylla ) that often have a rather long, pointed apex, and margins that are often bluntly toothed distally (beyond the widest point) (vs apex usually obtuse or rounded and retuse, and margins entire or sometimes minutely irregular), and by the fruits that in lateral view are crescent-shape or elliptic and strongly beaked (vs fruit ± circular in lateral view and slightly umbonate at most) ( Table 1). Although the leaf margins in both species can be sinuous-undulate, this character is more commonly seen in V. azurea .

Both species occur in forest at similar elevations in central Grande Terre, principally on non-ultramafic substrates. However, at present, few, if any, collections of V. leptophylla are known from the exact region where V. azurea has been collected. Virotia azurea is compared with other species of Virotia in Table 1.

Some material of Virotia azurea was previously identified as V. francii . These two species are not sympatric and morphologically, V. francii can be distinguished by its leaves, which typically have shorter blades, usually borne on longer petioles, and they have an intramarginal vein that extends along the entire length of the leaf (see below). Both V. leptophylla and V. francii usually have cream-white to pale yellow flowers, although rarely both have been reported to have some pink, lilac, violet or blue on the tepals (e.g. MacKee 12654 (P), V. leptophylla ).

Fig. 3B shows two bluish-mauve, naked cotyledons from a seed of V. azurea . Cotyledons pigmented with anthocyanin are also known to occur in V. neurophylla (Guillaumin) P.H. Weston & A.R. Mast (cotyledons of recently germinated seedlings deep purple-maroon on both inner and outer surfaces) and V. francii (cotyledons deep purple on the abaxial surface and plain green on the adaxial one) (P. Weston, pers. comm.).

The species that is most commonly sympatric with V. azurea , also occurring in the region from Povila and Haute Tchamba-Haute Amoa southwards to Mt Aoupinié, is V. rousselii (Vieill.) P.H. Weston & A.R. Mast. This is usually readily distinguished by the large, robust 3–5-lobed leaves that accompany the flowers and fruits. In rare instances where the leaves associated with reproductive structures are simple or only partially lobed, as in MacKee 13139 (P, K) the blades are broadly oblanceolate and broadly rounded at the apex, and the inflorescence is longer, broader and more robust than in V. azurea .

The long, oblanceolate leaves of V. azurea are rather similar to those of V. angustifolia (Virot) P.H. Weston & A.R. Mast , which is restricted to ultramafic substrates on and around the Massif de Tiébaghi in north-western Grande Terre. However, the leaf blades of V. angustifolia are long-attenuate at the base, typically lacking a petiole, and the margins are entire though they can be undulate. In addition, V. angustifolia commonly has rather short inflorescences, 6–17.5 cm long, and the flowers are bright pink, not blue or bluish.

In most herbarium specimens of Virotia azurea , the leaves are either detached from the stem or attached to only a short section of it, and the inflorescences appear either to arise in the axil of a fully developed leaf or, when described in field notes as borne on the stems or branches, presumably they arise in the axil of a leaf scar. However, in Munzinger et al. 1462, we have the apex of a stem with the leaves clustered around it ( Fig. 1B ) and the peduncle of a young inflorescence arising at the tip of this stem. The leaves could be loosely described as forming a “terminal cluster” but they do not terminate the growth of the stem and so are not truly terminal, whereas the inflorescence does appear to terminate the shoot. The peduncle has a series of small, triangular, adpressed bracts around the base and at intervals along its length.

Leaf manganese content was measured non-destructively on Virotia azurea ’s herbarium specimens with a handheld X-Ray Fluorescence (XRF) spectrometer ( JAFFRÉ et al., 2013; VAN DER ENT et al., 2019). We found significant variations with a high value of 4178 µg g-¹ for Gâteblé et al. 87, and lower values for other specimens: 819 µg g-¹ (MacKee 4651), 825 (MacKee 18031), 981 (Munzinger et al. 1462), and a value below the detection threshold for Veillon 4651. The accumulation of manganese is a typical characteristic of New Caledonian Proteaceae growing on ultramafic substrates ( JAFFRE, 1979), and these measurements are consistent with the dual ecology of this species, occurring on both serpentine and other metamorphic substrates.

Vieillard 3060 (“Wagap, in sylvis montium”, 1861–1867, st., K, P [2 sheets]) is a mixed collection consisting of flowers of Oxera Labill. (Lamiaceae) and leaves of Virotia (G. Gâteblé, pers. comm.). The flowers represent the type material of Oxera merytifolia Guillaumin (G. Gâteblé, pers. comm.; DE KOK & MABBERLEY, 1999). Based on their shape and venation, the leaves appear to belong to V. azurea although the petiole is longer than in other collections. Because the locality of Wagap is vague, this specimen has been omitted from the distribution map, and it is also omitted from the list of paratypes.

Paratypi. – NEW CALEDONIA. Prov. Nord: Amoa , 20°56'21"S 165°11'40"E, 330–340 m, 20.X.2018, fl., Bruy & Laudereau 1220 ( NOU) ; Povila , 20°57'21"S 165°17'29"E, 390–400 m, 20.IV.2019, fl., Bruy & Laudereau 1281 ( NOU) ; Tchamba , 21°00'26"S 165°14'36"E, 480 m, fr., Gatêblé et al. 449 ( NOU) ; crête entre Haute Amoa et Haute Tchamba , 600 m, 21.VI.1966, fl., MacKee 15159 ( NOU, P [2 sheets]) ; ibid. loco, Expl. Forestière Létocart, [21°00'54"S 165°14'11"E], 600 m, 22.XI.1967, fl. & y.fr., MacKee 18031 ( NOU, P [2 sheets]) ; Povila , [20°57'36"S 165°19'03"E], 400 m, 13.VI.1974, fl. buds, MacKee 28793 ( P) ; Mt Aoupinié , [21°11'S 165°16'E], 500 m, 2.XII.1993, buds & fr., MacKee [leg. Suprin] 46274 ( NOU, P) ; Haute Tchamba , 21°00'55"S 165°15'06"E, 10.XI.2002, fl., Munzinger et al.1462 ( P) ; Plateau de Tango , pentes du Pic 700 au NW de Palo, [20°59'S 165°01'E], 21.X.1981, old fl., Veillon 4651 ( NOU, P) .

Figures

Fig. 1. – Virotia azurea H.C. Hopkins & Pillon. A. Leaf; B. Apex of a shoot showing the arrangement of leaf bases and the base of an inflorescence axis (*); C. Inflorescence (conflorescence), the flowers post-anthesis; D. A flower-pair immediately prior to anthesis, their peduncle subtended by a minute bract and a small bract present at the base of each pedicel; E. A flower post anthesis, the tepals all helically curled; F. Base of a flower, two tepals removed to show the ovary and the cup-like disc around it; G. Apex of the style, slightly swollen and ridged, forming the pollen presenter; H. Distal part of a tepal, inner surface, with the anther attached; I. Immature fruit, note prominent beak. [A, C, E–H: Gâteblé et al. 87, P; B: Munzinger et al. 1462, P; D: MacKee 15159, P; I: MacKee 46274, P] [Drawing: Andrew Brown]

Fig. 2. – Virotia azurea H.C. Hopkins & Pillon. A. Inflorescence arising from a leaf axil; B. A flower-pair at anthesis plus flower buds; C. Pair of flowers (note helically curled tepals and nectar); D. Very young floral buds; E. Two purple ovaries (note disc at base) and white styles; F. Inflorescence; G. Under surface of foliage. [Photos: A, F–G: G. Gâteblé; B–E:C. Laudereau]

Fig. 3. – Virotia azurea H.C. Hopkins & Pillon. A. Fruit; B. Fruit cut open to reveal the bluish mauve cotyledons. [Photos: G. Gâteblé]

Fig. 4. – Distribution of Virotia azurea H.C. Hopkins & Pillon in New Caledonia. Areas with ultramafic substrate are shown in grey.