Solanum labyrinthinum D.McClelland, 2020

McClelland, Donald H. R., Nee, Michael & Knapp, Sandra, 2020, New names and status for Pacific spiny species of Solanum (Solanaceae, subgenus Leptostemonum Bitter; the Leptostemonum Clade), PhytoKeys 145, pp. 1-36 : 1

Solanum labyrinthinum D.McClelland sp. nov. Figure 1

Diagnosis.

Like S. dunalianum Gaudich. but with narrowly elliptic to lanceolate leaves, many-branched inflorescences arising from the middle of the internode, and smaller fruits.

Type.

Papua New Guinea. Milne Bay Province: Normanby Island, Waikaiuna [Bay], 5 m, 17 Apr 1956 (fl, fr), L.J. Brass 25460 (holotype: LAE [acc. # 47392]; isotypes: A, K [K000922591], L [L.4307630], S, US [acc. # 2408171]).

Description.

Erect shrub to ca. 2.5 m, the internodes to 6.5 cm long, apparently unarmed. Stems with a few scattered ferruginous sessile porrect-stellate trichomes when young, the rays 6-7, ca. 0.15 mm long, the midpoint more or less equal to the rays, the stems soon glabrescent; new growth sparsely pubescent with sessile stellate trichomes and minute glandular papillae; bark of older stems pale gray. Sympodial units difoliate, the leaves geminate or not, if geminate members of a pair more or less equal in size and shape. Leaves simple; blades 8.0-16.0 cm long, 1.4-3.7 cm wide, ca. 4.5-6.0 times as long as wide, narrowly elliptic to lanceolate, subcoriaceous, concolorous, unarmed; adaxial surfaces glabrous or with a few sessile porrect-stellate trichomes with 5-8 rays 0.15-0.2 mm long, the midpoints much shorter than the rays; abaxial surfaces glabrous; principal veins 7-10 pairs, the midrib raised both abaxially and adaxially, the lateral veins weakly brochidodromous, raised both abaxially and adaxially, drying yellowish or dark; base cuneate; margins entire or slightly wavy; apex acute to somewhat acuminate; petiole 0.9-1.8 cm long, 0.8-1.3 mm in diameter, channeled adaxially, glabrous when mature, unarmed. Inflorescence to 7.5 cm long, appearing lateral, extra-axillary, unbranched to forked to many-branched, with few to ca. 50 flowers, sparsely to moderately pubescent with sessile porrect-stellate trichomes when young, soon glabrous, unarmed; peduncle 0.1-0.6 cm long,, unarmed; pedicels 0.6-1.0 cm long, ca. 0.3 mm in diameter at the base, ca. 0.5 mm in diameter below the calyx, straight, gradually increasing in diameter from the base distally, articulated at the base; pedicel scars congested to spaced 0.9 mm apart, rigid, in two rows. Buds conical, the calyx enclosing the corolla when young, the corolla sparsely pubescent with scattered stellate trichomes and glandular papillae on exposed abaxial surfaces, strongly exserted from the calyx lobes before anthesis. Flowers 5-merous, all perfect. Calyx 1.4-1.7 mm long, with the tube to 0.8-1.2 mm long, in bud appearing nearly truncate with apiculate lobe tips to 0.5 mm long, splitting in the scarious sinuses at anthesis, the lobes 1.1-1.7 mm long, 1-1.4 mm wide, deltate, abaxially glabrous to sparsely pubescent with scattered porrect-stellate trichomes and minute glandular papillae, adaxially glabrous. Corolla ca. 1.2 cm in diameter, purple or deep violet, stellate, the interpetalar tissue not well-developed, the lobes 3.7-5.4 mm long, 1.6-2 mm wide, long-deltate, spreading at anthesis. abaxially densely stellate pubescent where exposed in bud, adaxially glabrous or with a few stellate trichomes near the tips. Stamens equal; filament tube minute; free portion of the filaments ca. 0.5 mm long, glabrous; anthers 3.5-4 mm long, 0.6-1 mm wide, tapering, connivent, yellow, poricidal at the tips, the pores directed distally. Ovary conical, glabrous; style 3.0-5.0 mm long, ca. 0.2 mm in diameter, exserted from or equal to the anther cone, filiform, straight, glabrous; stigma ca. 0.4 mm in diameter, bilobed, minutely papillate. Fruit a globose berry, 4.0-6.0 mm in diameter, red when mature, glabrous, the pericarp thin, shiny, opaque; fruiting pedicels 1.2-1.6 cm long, 0.4-1 mm in diameter at the base, 0.8-1.1 mm in diameter at the apex, erect; fruiting calyx not accrescent, the lobes 1.4-2.2 mm long, 1.0-1.5 mm wide, glabrous, appressed to the berry surface or slightly reflexed. Seeds 10-40 per berry, 1.8-2.5 mm long, 1.5-1.8 mm wide, flattened, suborbicular to reniform, notched at the point of attachment, yellow-ferruginous when dry, the surface minutely pitted (alveolate), the testal cells with straight walls. Chromosome number not known.

Distribution and ecology

(Figure 2 ). Solanum labyrinthinum is known from Normanby Island and adjacent East Cape on New Guinea; it has been collected along roads in rainforest from 5 to 185 m elevation.

Phenology.

Known to flower and fruit in Apr. Perhaps fertile year round like the other members of Solanum section Dunaliana .

Etymology.

The specific epithet was chosen to reflect the taxonomic labyrinth involving two other species of New Guinea Solanum that was unintentionally created by Symon (1985).

Preliminary conservation assessment

( IUCN 2019). EOO = 51 km2 [CR - Critically Endangered]; AOO = 12 km2 [EN - Endangered]. We assess Solanum labyrinthinum as EN (Endangered) using IUCN Criteria B1a,b, due to its restricted distribution, its primary forest habitat and lack of recent collections indicating population decline. Although it is found both on New Guinea and in the Solomon Islands, the destruction of lowland forest habitat in coastal areas suggests conservation concern.

Discussion.

Solanum labyrinthinum differs from other members of section Dunaliana (sensu McClelland 2012) in its almost completely glabrous narrowly elliptic or somewhat lanceolate leaves. Like Solanum torricellense Bitter of New Guinea, but unlike the other members of this group (section Dunaliana sensu McClelland 2012), the inflorescence of this species emerges from the middle of the internode. Solanum labyrinthinum differs from S. peekelii with which it has been confused (see below) in its narrow completely glabrous leaves at maturity with distinctive appressed stellate trichomes when young, its fewer principal leaf veins (7-10 versus 10-14) that often dry yellowish, its slightly smaller flowers (ca. 1.2 cm in diameter versus to 1.5 cm in diameter) and fruits, and in its distribution. The stems of S. labyrinthinum are often purplish tinged, and the flowers are darker purple than those of S. peekelii .

Symon (1985) applied the name S. peekelii to the plants we here recognise as S. labyrinthinum , then applied the name S. torricellense to plants matching the description of S. peekelii and provided a new name for plants matching the type of S. torricellense , thus creating a taxonomic labyrinth (see below under typification of S. peekelii for details, and Solanaceae Source (www.solanaceaesource.org) for descriptions of the other taxa involved).

Additional specimens examined.

Papua New Guinea. Milne Bay Province: Awaiama, Sep 1895 (fr), Fitzgerald 16 (MEL); Normanby Island, Sewa Bay, 600 ft, 20 Apr 1956 (fl), J. Womersley & L. Brass NGF-8678 (A [2 sheets], BM [2 sheets], BO, BRI, CANB, K, L, LAE, NSW, SING).

Figures

Figure 1. Solanum labyrinthinum D. McClelland (isotype Brass 25460, US [acc. 2408171]). Reproduced with permission.

Figure 2. Distribution of Solanum labyrinthinum and S. peekelii.