Solanum involucratum Blume, Bijdr. Fl. Ned. Ind. 13: 701. 1826.

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

20. Solanum involucratum Blume, Bijdr. Fl. Ned. Ind. 13: 701. 1826.

Figs 2G , 3C , 4C , 35

Solanum ferox L. var. involucratum (Blume) Miq., Fl. Ned. Ind. 2: 647. 1857. Type. Based on Solanum involucratum Blume.

Type.

Indonesia. Java: Sin. loc., C.L. Blume s.n. (lectotype, designated here: L [L0003633]) .

Description.

Shrub to 2 m tall, strongly armed. Stems erect, terete, densely prickly and pubescent; prickles to 8 mm long, to 3 mm at the base, straight, awl-shaped to deltate, pale yellow, glabrous; trichomes porrect-stellate, mixture of subsessile and stalked, the stalks to 0.75 mm long, the rays 4-6, 0.4-1.5 mm long, the midpoints shorter than the rays or up to 2.25 mm long, sometimes purple-tinged on living plants; new growth densely pubescent with mixture of subsessile and long-stalked stellate trichomes; bark of older stems brownish, glabrescent. Sympodial units difoliate, the leaves not geminate. Leaves simple, shallowly to deeply lobed, the blades 12-30 cm long, 9.5-19 cm wide, ca. 1-1.5 times longer than wide, broadly elliptic to ovate, chartaceous, discolorous, armed with ca. 20-80 prickles per leaf side, prickles to 20 mm long, to 6 mm wide at the base, straight, awl-shaped, conical, pale yellow, on dried material, sometimes purple-tinged on living plants, glabrous; adaxial surface moderately pubescent, with sessile porrect-stellate trichomes, the rays 3-6, 0.1-0.25 mm long, the midpoints to 1.75 mm; abaxial surface densely stellate-pubescent with trichomes like those of the adaxial surface but stalked, the stalks to 0.4 mm; major veins 5-6 pairs drying light green; base attenuate; margins shallowly to deeply lobed, the lobes 5-6 on each side, 1-1.2 cm long, 3-5 cm wide, broadly deltate, apically acute, the sinuses less than halfway to the midrib; apex acute; petiole 3.5-17.5 cm long, 1/3-4/5 of the leaf blade length, prickly with 5-17 prickles like those of the blade, densely stellate-pubescent with porrect trichomes like those of the stem. Inflorescences apparently lateral, 3-8 cm long, unbranched, with 3-10 flowers, 1 to many flowers open at any one time, densely stellate pubescent with stellate-porrect trichomes like those of the stems but often tinted with purple, unarmed; peduncle 1-4 mm long, unarmed; pedicels 3-10 mm long, 1-2 mm in diameter at the base, ca. 1.5 mm in diameter at the apex, spreading, unarmed or sparsely prickly with a few prickles, densely stellate-pubescent with purple porrect-trichomes like the inflorescence axes, articulated at the base; pedicel scars spaced 0.5-1 mm apart. Buds ovoid, included in the calyx lobes until just before anthesis. Flowers 5-merous, apparently all perfect. Calyx with the tube 3.5-4 mm long, cup-shaped and slightly inflated at the base and appearing saccate, the lobes 4-6 mm long, 4-4.5 mm wide, deltate to broadly deltate, apically acute, armed with numerous prickles and densely stellate pubescent with purple-tinted porrect-trichomes like those of the pedicels. Corolla 1-1.2 cm in diameter, white, stellate, lobed ca. 1/2-2/3 of the way to the base, interpetalar tissue present, the lobes 4-6 mm long, 2-3 mm wide, deltate, spreading at anthesis, glabrous adaxially, densely stellate-pubescent abaxially on parts exposed in bud with trichomes like those of the calyx but white. Stamens equal; anthers 5-6 mm long, 1.5-2 mm wide, connivent, tapering, glabrous, poricidal at the tips, the pores directed distally, not elongating to slits with drying; filament tube ca. 0.5 mm long, glabrous; free portion of the filaments ca. 0.25 mm long, glabrous. Ovary conical, densely covered with long simple hairs; style ca. 6 mm long, slender, curved at the apex, glabrous; stigma capitate, the surfaces minutely papillose. Fruit a globose berry, 3-10 per infructescence, 1-2 cm in diameter, orange when mature, the pericarp thick, very densely stellate-pubescent with porrect-trichomes like those of the adaxial surface of the leaves; fruiting pedicels 0.8-2 cm long, ca. 1 mm in diameter at the base, 2.5-2.8 mm in diameter at the apex, woody, erect to spreading, armed with 3-25 prickles; fruiting calyx lobes expanding to 2 cm long, completely enclosing the fruit at maturity, armed with ca. 10-20 prickles per lobe, the lobes white with purplish venation and trichomes. Seeds>100 per berry, 2-3 mm long, 1.5-2 mm wide, flattened-reniform, dull yellow, the surface minutely pitted, the testal cells sinuate in outline. Chromosome number: not known.

Distribution

(Fig. 36 ). Solanum involucratum is widely distributed in Indochina and Malay Archipelago (Indonesia, Malaysia, and Christmas Island).

Ecology and habitat.

Solanum involucratum is a plant of tropical evergreen or deciduous rainforest, it grows on limestone or on clay soil, also in secondary forests; from 50 to 1,400 m elevation.

Common names and uses.

Laos. hma:k sè:n, khüa khünx, hma:k khüa hlè:z, khüa hna:m ( Hul and Dy Phon 2014). Thailand. Prachinburi: sa-uk [Thai] (Kerr 19844); Prachuap Khiri Khan: ma uk muak [Thai] (Kerr 10780); Vietnam. ca duoc nui [Vietnamese] (Fleury 29910); cà du’o’c nui, cây cà rai, cà ung, co chu [Munong] ( Hul and Dy Phon 2014).

Preliminary conservation status

( IUCN 2019). Least Concern (LC). EOO (1,868,808 km2, LC); AOO (216 km2, EN). Solanum involucratum is found over a very broad range in the archipelago, the AOO measurement certainly reflects collecting bias.

Discussion.

Solanum involucratum is a distinctive species, with pubescent berries entirely enclosed within a spiny accrescent calyx. In flower the corolla lobes are shorter than the calyx, so the flowers appear to be entirely within the calyx at anthesis. In flower the calyx tube appears to be somewhat inflated, but it is appressed against the berry in fruit. The bristly, prickly accrescent calyx in fruit is similar to that of S. barbisetum , S. cyanocarphium and S. praetermissum , but all of those species have glabrous fruits, while those of S. involucratum are densely pubescent with stiff, stellate trichomes. The inflorescences of S. cyanocarphium are few-flowered like those of S. involucratum , but not robust. Inflorescences of S. barbisetum and S. praetermissum are elongate and multi-flowered.

On the island of Sulawesi S. involucratum is sympatric with the very similar S. sulawesi. It differs from that species in its accrescent calyx in fruit, larger mature berries and more densely pubescent stems and leaves. Both S. involucratum and S. lasiocarpum have leaves with petioles that are longer relative to leaf size than S. sulawesi , but these three species can be difficult to distinguish.

Solanum involucratum was considered by Miquel (1857) to be a variety of S. lasiocarpum (as S. ferox var. involucratum ). The two species are not closely related; S. involucratum is a member of a clade comprising S. procumbens , S. expedunculatum Symon and S. leptacanthum Merr. & L.M.Perry (the latter two species from New Guinea), itself apparently related, but with poor support, to S. barbisetum and S. praetermissum ( Aubriot et al. 2016a). Solanum lasiocarpum on the other hand has been shown in numerous studies to be a member of the otherwise American Lasiocarpa clade (e.g., Bruneau et al. 1995; Bohs 2004; Stern et al. 2011).

Heiser (1996, 2001) followed Miquel (1857) in using the name S. ferox L., nom utique rej. (see Knapp 2011) for S. involucratum , recognising it at the varietal level, while Whalen et al. (1981) regarded it as ambiguous. Care should be taken with specimens annotated as S. ferox in collections, they could be either S. lasiocarpum (more common in our experience, see discussion under that species) or S. involucratum .

Hul and Dy Phon (2014) incorrectly cited a specimen at L as "holo - L!" for S. involucratum . This is not a holotype (see McNeill 2014) and we have selected as lectotype a specimen at L (L0003633) that matches the protologue and appears to have been original material; this is probably the same sheet referred to as holotype by Hul and Dy Phon (2014).

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 3. Diversity of inflorescences and flowers in tropical Asian spiny solanums A lax, spreading inflorescences and stellate flowers of Solanum violaceum (Sampath Kumar et al. 126945, India) B condensed, recurved inflorescences and stellate flowers of S. multiflorum (Sampath Kumar et al. 126950, India) C inflorescences and large stellate flowers of S. involucratum (field photograph, unvouchered, Vietnam) D inflorescences and stellate flowers of S. pubescens with unequal stamens, one long and recurved (Sampath Kumar et al. 126956, India) E large rotate flower of S. insanum with abundant interpetalar corolla tissues (Sampath Kumar et al. 126918, India) F many flowered inflorescence and infructescence of S. pseudosaponaceum (field photograph, unvouchered, Philippines) G many flowered inflorescences of S. torvum; flowers with well-developed interpetalar corolla tissues (Suksathan et al. PS 3815, Thailand) H small stellate flowers of S. viarum (Sampath Kumar et al. 126944, India). Photograph credits: A, B, D, E, H X. Aubriot C M. Nuraliev F D. Tandang G D. Pedersen.

Figure 4. Diversity of fruits and seeds in tropical Asian spiny solanums A large oval fruit of Solanum insanum (Sampath Kumar et al. 126918, India) B condensed infructescence and small rounded fruits of Solanum hovei (field photograph, unvouchered, India) C large rounded hairy fruit of S. involucratum with strongly accrescent and spiny calyx (field photograph, unvouchered, Vietnam) D small rounded fruit of Solanum pubescens with elongated calyx lobes (Sampath Kumar et al. 126956, India) E rounded fruit of Solanum cyanocarphium with strongly accrescent and spiny calyx (field photograph, unvouchered, Vietnam) F small rounded fruit of S. trilobatum in transverse cut (Meeboonya et al. RM 242, Thailand) G rounded fruit and accrescent calyx of S. praetermissum in transverse cut (field photograph, unvouchered, Vietnam) H oval fruit of Solanum virginianum in transverse cut (field photograph, unvouchered, India). Photograph credits: A, B, D, F, H X. Aubriot C, E, G M. Nuraliev.

Figure 35. Solanum involucratum Blume A herbarium specimen collected in Thailand in 1930 (Kerr 19844, BM 000886046) B Habit and leaves (field photograph, unvouchered, Vietnam) C detail of the trichomes and prickles on the adaxial surface of a blade (field photograph, unvouchered, Vietnam) D detail view of an inflorescence and a flower (field photograph, unvouchered, Vietnam) E detail view of an accrescent fruiting calyx (field photograph, unvouchered, Vietnam). Photograph credits: A CC-BY, © copyright The Trustees of the Natural History Museum, London B-E M. Nuraliev.

Figure 36. Distribution of S. involucratum.