Solanum miyakojimense T.Yamaz. & Takushi, J. Jap. Bot. 66: 46. 1991.

Aubriot, Xavier & Knapp, Sandra, 2022, A revision of the " spiny solanums " of Tropical Asia (Solanum, the Leptostemonum Clade, Solanaceae), PhytoKeys 198, pp. 1-270 : 1

27. Solanum miyakojimense T.Yamaz. & Takushi, J. Jap. Bot. 66: 46. 1991.

Figs 2B , 43

Type.

Japan. Ryuku Islands: Cultivated in Nago, Okinawa Island [originally collected in Miyako Island [Miyakojima], Agarihetona], 20 Dec 1989, A. Takushi [6400] s.n. (holotype: TI [TI00085080]; isotypes: TI [TI00085081, TI00085082]) .

Description.

Woody herb or subshrub, the branches to 1 m long, spreading and prostrate, armed or unarmed. Stems terete, unarmed or sparsely prickly and moderately to densely eglandular pubescent, the prickles, if present, 0.1-0.35 cm long, straight or very slightly curved, somewhat broad-based, the pubescence of sessile or short-stalked porrect-stellate trichomes, the stalks if present ca. 0.1 mm, the rays 5-8, 0.2-0.4 mm long, the midpoints absent or ca. 0.1 mm long, occasionally to 0.5 mm long; new growth densely (moderately in cultivation) pubescent with sessile or short-stalked porrect-stellate trichomes like those of the stems; bark of older stems pale tan-brown. Sympodial units difoliate, the leaves geminate or not geminate. Leaves simple or very shallowly lobed, the blades 1.2-4 cm long, 0.9-3 cm wide, 1.1-1.3 times longer than wide, broadly ovate to nearly orbicular, widest in the lower half, somewhat thick and fleshy, concolorous or slightly discolorous, unarmed or sparsely armed with a few straight prickles to 0.2 cm long; adaxial surfaces densely pubescent with the lamina still somewhat visible, the pubescence of sessile and short-stalked porrect-stellate trichomes, the stalks 0.1-0.3(0.5) cm long, the rays 5-8, ca. 0.5 mm long, the midpoints absent or 0.3-0.5 mm long, the prickles few or absent; abaxial surfaces densely pubescent with the lamina completely obscured, the pubescence of sessile and short-stalked porrect-stellate trichomes, the stalks usually longer than those of the adaxial surface trichomes, 0.2-0.5 mm long, the rays 6-10, 0.5-0.6 mm long, the midpoints ca. 0.5 mm long; principal veins 2-3 pairs, only visible on the adaxial surfaces; base acute; margins entire or very shallowly lobed, the lobes rounded at the tips, the sinuses reaching less than 1/3 of the way to the midrib, rounded; apex obtuse and rounded; petioles 0.3-0.9 cm long, densely stellate-pubescent like the stems and leaves. Inflorescences internodal, 0.1-0.3(-1.5) cm long, occasionally longer but always with a flower emerging from the very base, unbranched and usually looking like a tiny spur on the stem, the 1-2(4) flowers often seeming to emerge directly from stem, 1-2 flowers open at any one time,; densely stellate-pubescent with sessile and short-stalked porrect-stellate trichomes, the stalks if present ca. 0.1 mm, the rays 5-8, 0.2-0.4 mm long, the midpoints absent or ca. 0.1 mm long, occasionally to 0.5 mm long; peduncle absent to 1.5 mm long; pedicels ca. 0.9 cm long, ca. 0.8 mm in diameter at the base, ca. 1 mm in diameter at the apex, abruptly narrowing to calyx base, densely to moderately pubescent with sessile and short-stalked porrect-stellate trichomes like the stems, articulated at the base; pedicel scars tightly packed at tip of minute inflorescence, with the lowermost one near the stem. Buds ellipsoid, the corolla ca. halfway included in the calyx tube until just before anthesis. Flowers 5-merous, apparently all perfect. Calyx tube 2.5-3.5 mm long, cup-shaped, the lobes mere enations on the rim to 1 mm long, broadly deltate, tearing during development, densely to moderately pubescent with sessile and short-stalked porrect-stellate trichomes, the stalks if present ca. 0.1 mm, the rays 5-8, 0.2-0.4 mm long, the midpoints absent or ca. 0.1 mm long, occasionally to 0.5 mm long, the sinuses scarious, the tips rounded. Corolla 1-1.2 cm in diameter, white, stellate, lobed ca. 3/4 of the way to the base, the lobes 4.5-5 mm long, ca. 1.5 mm wide, spreading at anthesis, glabrous adaxially, densely pubescent where exposed in bud with tangled sessile and short-stalked porrect-stellate trichomes, the stalks ca. 0.1 mm long, the rays 6-8, ca. 0.2 mm long, the midpoints absent. Stamens equal; filament tube minute; free portion of the filaments 0.25-0.3 mm long, glabrous; anthers 4-4.5 mm long, ca. 1.5 mm wide, strongly tapering, yellow, poricidal at the tips, the pores directed distally. Ovary conical, glabrous; style 5.5-6 mm long, slightly curved, white, sparsely pubescent in the lower half with weak sessile porrect-stellate trichomes; stigma minutely bilobed, the surfaces minutely pubescent. Fruit a globose to somewhat elongate berry, 1-1.5 cm in diameter, orange (with "green longitudinal bands" fide Takushi s.n.) when mature, the pericarp glabrous, shiny, thin and somewhat translucent; fruiting pedicels 1.2-1.5 cm long, ca. 1.5 mm in diameter at the base, ca. 2.5 mm in diameter at the apex, thickened and woody, curved downwards, glabrescent to sparsely stellate-pubescent; fruiting calyx slightly accrescent, woody, the tube 3-3.5 mm long, the lobes 2-2.5 mm long, splitting irregularly with incrassate margins, appressed to the base of the fruit. Seeds 20-60 per berry, 2-2.5 mm long, ca. 2 mm wide, flattened reniform, straw-yellow, the surfaces minutely pitted, the testal cells sinuate in outline. Chromosome number: not known.

Distribution

(Fig. 44 ). Solanum miyakojimense occurs from the southernmost Ryuku Islands of Miyako and Irabu (Okinawa prefecture) to the island of Ponso no Tao (Lan Yu or Orchid Island) off the southeastern coast of Taiwan to the islands of the Batanes group in the Philippines.

Ecology and habitat.

Solanum miyakojimense occurs in rocky coastal areas, often on coral bluffs ( Hsu et al. 2007) near sea level; often occurring in sea spray.

Common names and uses.

None recorded.

Preliminary conservation status

( IUCN 2019). Endangered (EN [B1a,biii,iv]). EOO (641 km2, VU); AOO (40 km2, EN). Solanum miyakojimense is known from only a few wild collections scattered along the chain of islands across a large geographical distance, and although this makes the extent of occurrence larger than an endangered status might warrant, we consider the threats to habitats and the widely distant populations warrant this preliminary assessment.

Discussion.

In describing S. miyakojimense Yamazaki and Takushi (1991) suggested it was endemic to the Ryuku Islands; we have since found it to be more widely distributed, but still only along the island arc that runs south from Miyakojima Island to the Batanes Islands in the Philippines. Solanum miyakojimense is superficially similar to both S. procumbens and S. violaceum . It differs from S. procumbens , which occurs from China east to Thailand and the islands of Timor and Flores (Indonesia), in its seaside habitat; it can also be distinguished in its straight or only slightly curved stem prickles (versus strongly hooked), tiny inflorescences with only a few flowers with no or a very tiny peduncle (versus a longer thin peduncle), smaller flowers with broadly triangular corolla lobes (versus flowers with long-triangular corolla lobes), shorter pedicels in fruit and seeds with sinuate (versus pentagonal) cell walls. Berries of S. procumbens are bright red and globose at maturity, while those of S. miyakojimense are orange or orange-red and usually somewhat ellipsoid ( Hsu et al. 2007).

The inflorescences of S. miyakojimense are shorter and fewer-flowered than those of the widespread S. violaceum , and the fruiting pedicels are conspicuously curved (not markedly spreading and straight as in S. violaceum ) at fruit maturity. In S. miyakojimense the flowers are usually borne at the very base of the rhachis where it joins with the stem such that there is no clear peduncle; S. violaceum has a clearly pedunculate inflorescence. The leaves of S. violaceum are more markedly discolorous than those of S. miyakojimense . Solanum violaceum is a relatively robust shrub that can reach 2 m tall, while S. miyakojimense is a prostrate plant. Solanum violaceum is found in the northwestern part of the main island of Taiwan but has not been collected on Lan Yu (Orchid) island off the southeast coast. The only collections of S. violaceum from the Philippines are from cultivated plants.

Specimens examined.

See Suppl. materials 1-3.

Figures

Figure 2. Vegetative characters for tropical Asian spiny solanums A large and densely hairy repand leaf of S. lasiocarpum (Meeboonya et al. RM 287, Thailand) B small, pubescent, very shallowly lobed leaf of S. miyakojimense (field photograph, unvouchered, Taiwan) C entire, pubescent leaf of S. robinsonii (Nuraliev 3031, Vietnam) D glabrescent and deeply dissected leaf of S. virginianum (Sampath Kumar et al. 126968, India) E conical straight prickles on a pubescent young stem of S. hovei (field photograph, unvouchered, India) F strongly hooked prickles on a glabrous young stem and on the abaxial leaf surface of S. trilobatum (Meeboonya et al. RM 242, Thailand) G needle-like purple prickles on the adaxial leaf surface of S. cyanocarphium (field photograph, unvouchered, Vietnam) H pubescent young stem of S. barbisetum armed with prickles and bristles (Suksathan et al. PS 3832, Thailand). Photograph credits: A, B, D-F X. Aubriot C, G M. Nuraliev H D. Pedersen.

Figure 43. Solanum miyakojimense T. Yamaz. & Takushi A herbarium specimen (holotype) collected in Japan in 1989 (Takushi [6400] s. n., TI 00085080) B habit (Hsu 16234, Taiwan) C detail view of the prickles and the pubescence of a stem (Hsu 16234, Taiwan) D detail view of a flower (Hsu 16234, Taiwan) E detail view of a fruit with seeds inside (Hsu 16234, Taiwan). Photograph credits: A TI B-E M. - I. Weng.

Figure 44. Distribution of S. miyakojimense.