Solanum subgenus Leptostemonum Bitter, the Leptostemonum Clade

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

Solanum subgenus Leptostemonum Bitter, the Leptostemonum Clade

Description.

Herbs, vines, scandent or prostrate shrubs, shrubs or small trees; armed or apparently (to almost completely) unarmed; young stems stellate-pubescent, the trichomes multangulate or more often porrect-stellate with the rays all in a single place, occasionally lepidote, sometimes glabrescent; prickles absent, sparse or dense, straight or curved; bark of older stems grey or brown, sometimes glabrescent. Sympodial units plurifoliate or difoliate, the leaves geminate or not. Leaves entire to deeply pinnately lobed, usually stellate-pubescent on both surfaces, sometimes glabrescent or the trichomes very sparse; pubescence of porrect, multangulate or lepidote stellate trichomes, these sessile or variously stalked, with or without midpoints, the midpoints if present very short and bump-like to elongate. Inflorescences lateral and internodal or opposite the leaves, unbranched to many times branched, usually pedunculate, not bracteate, variously stellate-pubescent; petioles articulated near the base. Flowers actinomorphic or zygomorphic, bisexual (hermaphroditic) or unisexual and the plants andromonoecious; calyx 5-parted (rarely 4-parted or more than 5-parted in cultivated forms of S. melongena ), usually stellate-pubescent, sometimes glabrescent; corolla 5-parted (rarely 4-parted or more than 5-parted in cultivated forms of S. melongena ), rotate-stellate to deeply stellate, white, lilac or deep purple, some species polymorphic for flower colour, interpetalar tissue absent to copious; stamens 5 (rarely 4 or more than 5 in cultivated forms of S. melongena ), the filaments equal or unequal, usually glabrous; anthers equal or unequal, yellow or cream, blunt to strongly tapered, tightly connivent or spreading, dehiscing by terminal pores, the pores usually not lengthening to slits with age; ovary bicarpellate (fasciated in cultivars of S. melongena ), globose to conical, glabrous or stellate-pubescent; style straight or curved, in andromonoecious species shorter than the anthers and held within the anther cone; stigma minutely to large-capitate or clavate, sometimes bilobed. Fruit a berry, usually globose or nearly globose (but variously shaped in S. mammosum and S. melongena ), the pericarp dry, fleshy or leathery, glabrous or stellate-pubescent, the surfaces shiny or matte; fruiting calyx lobes not enlarging or often accrescent, sometimes completely enclosing the berry. Seeds flattened-reniform, the testal cells sinuate or polygonal in outline. Chromosome number: n = 12, 24, 36 (see Scaldaferro et al. 2012).

Distribution.

Members of the Leptostemonum Clade are found worldwide, in all habitats but the group is most diverse in the tropics (see Whalen 1984; Bohs 2005; Gagnon et al. 2022). They are often weedy plants of disturbed areas.

Discussion.

The Leptostemonum Clade is the largest monophyletic group in the genus Solanum . The clade is characterised by the possession of stellate trichomes (sometimes modified), prickles (sometimes absent) and long-attenuate, tapering anthers with distally directed pores that do not elongate to laterally dehiscing slits (as do those of other groups of Solanum , see Knapp et al. 2019a). Here we have chosen to treat the species occurring in tropical Asia as a group to fill a significant gap in the understanding of the species level taxonomy of spiny solanums. As for other geographically based groupings in spiny solanums, Asian members of the Leptostemonum Clade do not form a monophyletic assemblage (e.g., Aubriot et al. 2016a; Vorontsova and Knapp 2016); when the species treated have been included in phylogenetic studies, their hypothetical evolutionary relationships are provided in species discussion sections. For further discussion and previous assignments of the taxa treated here to species groups see sections on Taxonomy and Phylogeny above and Table 1 .

We have cited types but not reproduced synonymy and complete descriptions of the introduced species here; these can be found in the cited monographic works and on Solanaceae Source. Several of these names are lectotypified here because they were incorrectly cited as having holotypes in previous works. We have cited all synonyms based on specimens from tropical Asia. Many of these introduced taxa are expanding in range with increased disturbance and environmental damage, so the distribution given in Table 2 is what we know now; we expect some of these to be found elsewhere in the future.

Artificial key to tropical Asian spiny solanum species (including non-native adventive taxa)

Artificial key to all species

1	Young stems and/or upper leaf surfaces with simple (unbranched) trichomes only	2
-	Young stems and/or upper leaf surfaces glabrous or with stellate, multangulate or lepidote trichomes	6
2	Trees to 10 m tall; corollas> 4 cm in diameter with copious interpetalar tissue; anthers 14-16 mm long, slightly curved; mature berries hard, green and subtended by a swollen calyx. Cultivated as street trees	Solanum wrightii
-	Shrubs or subshrubs; corollas <4 cm in diameter, without copious interpetalar tissue; anthers 5.5-12 mm long, straight; mature berries yellow or orange, the calyx not markedly swollen. Weeds of disturbed areas	3
3	Flowers pale to medium purple; anthers 8-12.5 mm long; berry globose or variously lobed and extended into a nipple. Introduced and weedy	Solanum mammosum
-	Flowers white or greenish white; anthers 5-7.5 mm long; berry globose	4
4	No stellate trichomes on any part of the plant; berry bright orange; seeds winged. Introduced and weedy	Solanum capsicoides
-	Stellate trichomes present on lower leaf surfaces; berry yellow; seeds not winged	5
5	Calyx lobes 5-6.5 mm long, long-acuminate; stems sparsely glandular; ovary stipitate-glandular. Introduced and weedy	Solanum aculeatissimum
-	Calyx lobes 0.8-2 mm long, deltate; stems densely and evenly glandular; ovary puberulent. Introduced and weedy	Solanum viarum
6	Leaf trichomes lepidote (the ray bases fused into a shield-like structure); rhizomatous shrubs. Introduced and weedy, India	Solanum elaeagnifolium
-	Leaf trichomes stellate or multangulate, occasionally almost completely absent; plants without rhizomes	7
7	Mature leaves glabrous or very sparsely pubescent above (the pubescence confined to the leaf base or along the midrib)	8
-	Mature leaves variously pubescent above, not appearing glabrous, the pubescence easily visible	19
8	Stems armed with strongly curved downwards (hooked) prickles	9
-	Stems armed with straight prickles or unarmed	11
9	Erect shrubs to trees; sympodial units plurifoliate; berries 1.8-3 cm in diameter	Solanum arundo
-	Scandent herbs to shrubs to trees; sympodial units difoliate, the leaves geminate; berries 0.3-1.2 cm in diameter	10
10	Leaves 7-11 cm long (rarely smaller); corolla 0.5-1 cm in diameter; berries 0.3-0.5 cm in diameter; seeds 6-9 per berry. Indonesia	Solanum graciliflorum
-	Leaves 2.5-6.5 cm long; corolla 2-3 cm in diameter; berries 0.7-1.2 cm in diameter; seeds 16-47 per berry. India and Indochina	Solanum trilobatum
11	Leaves deeply lobed, densely prickly with bright yellow or straw-colored prickles; flowers fragrant. India to China	Solanum virginianum
-	Leaves entire or shallowly lobed, if prickly only sparsely so, the prickles various, but not bright yellow or straw-colored	12
12	Androecium zygomorphic, with one anther markedly longer than the rest. Southern India and Sri Lanka	Solanum vagum
-	Androecium actinomorphic, all anthers the same length	13
13	Stem prickles (if present) downwardly pointing (retrorse); leaves narrowly elliptic to lanceolate. Philippines, Indonesia (?Taiwan, Lanyu Island)	Solanum retrorsum
-	Stem prickles (if present) not strongly retrorse; leaves orbicular to elliptic	14
14	Scandent to erect shrub; leaves orbicular, as long as wide. Western India	Solanum cordatum
-	Erect herbs or shrubs; leaves ovate to elliptic, 1.5-3 times longer than wide	15
15	Inflorescence unbranched; berries usually large (usually>1 cm in diameter), often flattened and/or ridged. Cultivated plants, perhaps escaped from gardens	16
-	Inflorescence forked to many times branched; berries <1 cm in diameter (not known in S. kachinense )	17
16	Berries 4-6 cm in diameter; flowers heterostylous and the plants strongly andromonoecious; corolla subrotate with abundant interpetalar tissue	Solanum macrocarpon
-	Berries 1.5-2.5 cm in diameter; flowers all perfect, only occasionally with a few distal staminate; corolla stellate	Solanum aethiopicum
17	Pubescence of multangulate trichomes, these scurfy and deciduous; inflorescence many times branched and erect. India, Sri Lanka	Solanum giganteum
-	Pubescence of porrect-stellate trichomes, these merely sparse, not deciduous; inflorescence forked or several times branched, not markedly erect	18
18	Leaves drying black or dark brown; leaf base oblique and appearing more or less truncate; major veins 6-8 pairs; corolla 1.5-1.8 cm in diameter. Myanmar	Solanum kachinense
-	Leaves drying olive green; leaf base acute to cuneate; major veins 5-6 pairs; corolla 2-2.4 cm in diameter. Taiwan	Solanum peikuoense
19	Trichomes of upper leaf surfaces multangulate (the rays not in a flat plane)	20
-	Trichomes of upper leaf surfaces porrect-stellate with the rays in a single flat plane	21
20	Inflorescences many times branched; trichomes scurfy and deciduous; upper leaf surfaces glabrate in older plants. India, Sri Lanka	Solanum giganteum
-	Inflorescences unbranched; trichomes not scurfy and deciduous; upper leaf surfaces densely pubescent. Indonesia (Java)	Solanum comitis
21	Inflorescences forked to many times branched	22
-	Inflorescences unbranched (simple)	50
22	Stem prickles absent (reproductive growth), the stems unarmed	23
-	Stem prickles present (reproductive growth), the stems weakly to strongly armed	26
23	Inflorescences stellate-pubescent and densely glandular pubescent, the glandular hairs unbranched; rest of plant eglandular. Introduced and naturalised, widespread	Solanum torvum
-	Inflorescences variously stellate-pubescent, not glandular (unless rest of plant densely glandular pubescent)	24
24	Leaves shiny above; berries 1-1.3 cm in diameter. Taiwan	Solanum peikuoense
-	Leaves not markedly shiny above; berries less than 1 cm in diameter	25
25	Androecium zygomorphic, with one anther markedly longer than the rest; corolla 2-3 cm in diameter; berries 0.8-1 cm in diameter. Southern India and Sri Lanka	Solanum vagum
-	Androecium actinomorphic, all anthers the same length; corolla 1-1.4 cm in diameter; berries 0.6-0.8 cm in diameter. Philippines, Indonesia (?Taiwan, Lanyu Island)	Solanum retrorsum
26	Stem prickles strongly curved downwards (hooked)	27
-	Stem prickles straight	36
27	Leaves 1-2 times as long as wide (ovate to elliptic ovate)	28
-	Leaves more than 2 times as long as wide (elliptic to narrowly elliptic)	32
28	Berries> 2 cm in diameter; prickles of leaves straight, usually>10 mm long. Kathiawar peninsula, Gujarat, India	Solanum arundo
-	Berries <2 cm in diameter; prickles of leaves various, never 10 mm long and straight	29
29	Erect shrubs; berries orange when mature; fruiting pedicels strongly spreading. Widespread in the region	Solanum violaceum
-	Scandent shrubs; berries red or red-orange when mature; pedicels erect or pendant, not strongly spreading	30
30	Corolla 2-3 cm in diameter; anthers 7-9 mm long; plants of forests and forest edges. India and Indochina to Philippines	Solanum trilobatum
-	Corolla 0.9-2.4 cm in diameter; anthers 3-7 mm long; plants of dry, desert habitats. Western India	31
31	Stem pubescence of multangulate trichomes; petioles winged from decurrent leaf bases	Solanum cordatum
-	Stem pubescence of porrect-stellate trichomes; petioles not winged	Solanum forskalii
32	Leaf margins entire, the leaves not lobed; berries 3-5 cm long, ovoid. Indonesia and Philippines	Solanum schefferi
-	Leaf margins variously lobed; berries not as above	33
33	Corolla 0.5-1 cm in diameter; anthers unequal in size. Indonesia	Solanum graciliflorum
-	Corolla> 1 cm in diameter; anthers all equal in size	34
34	Inflorescence stellate-pubescent and densely and uniformly glandular with small, unbranched glandular trichomes; rest of plant eglandular. Widespread and naturalised	Solanum torvum
-	Inflorescence variously pubescent, never with glandular trichomes, unless rest of plant glandular	35
35	Inflorescence several times branched; calyx lobes long-acuminate with a distinct acumen; fruiting pedicels erect to slightly spreading; seeds> 20 per berry. Southern China and Indochina to Philippines	Solanum pseudosaponaceum
-	Inflorescence forked (once branched); calyx lobes deltate, apically acute; fruiting pedicels strongly spreading; seeds <20 per berry. Widespread in the region	Solanum violaceum
36	Stem and leaf trichomes multangulate, often deciduous through rubbing off. India, Sri Lanka	Solanum giganteum
-	Stem and leaf trichomes porrect-stellate (all rays in a single plane), not deciduous	37
37	Stem prickles strongly retrorse and downward pointing. Philippines, Indonesia (?Taiwan, Lanyu Island)	Solanum retrorsum
-	Stem prickles not strongly retrorse	38
38	Pubescence of upper leaf surfaces sparse, scattered and mostly along veins, if present on lamina very sparse	39
-	Pubescence of upper leaf surfaces moderate to dense, easily visible to the naked eye	40
39	Leaves deeply lobed, the blades 3-11 cm long, 2-4 cm wide, densely prickly; corolla 2.5-3 cm in diameter; prostrate shrubs. India to China	Solanum virginianum
-	Leaves shallowly lobed, the blades 11-22 cm long, 5.2-11.5 cm wide, sparsely prickly; corolla 1.5-1.8 m in diameter; erect shrubs. Myanmar	Solanum kachinense
40	Leaves 1-2 times longer than wide (ovate to broadly elliptic)	41
-	Leaves> 2 times longer than wide (elliptic to narrowly elliptic)	43
41	Inflorescences many times branched; sympodial units plurifoliate. Vietnam	Solanum harmandii
-	Inflorescences forked (once branched); sympodial units difoliate	42
42	Scandent shrubs of deserts; leaf bases cordate to rounded; corolla 1.3-2.4 cm in diameter, divided nearly to the base; seeds dark brown, almost black. Western India	Solanum forskalii
-	Erect shrubs of many habitats; leaf bases truncate, often oblique; corolla 1.3-3 cm in diameter, divided half to two-thirds of the way to the base; seeds yellow to orange-brown. Widespread in the region	Solanum violaceum
43	Leaves entire, the margins not lobed. Indonesia (Sulawesi)	Solanum dunalianum
-	Leaves lobed, the margins shallowly to deeply dissected	44
44	Fruiting pedicels curved and strongly deflexed. Western Ghats, India	Solanum multiflorum
-	Fruiting pedicels erect or spreading, not curved or deflexed	45
45	Leaves ovate; fruiting pedicels strongly spreading. Widespread in the region	Solanum violaceum
-	Leaves elliptic to narrowly elliptic; fruiting pedicels erect or spreading from weight of fruit	46
46	Inflorescence densely and minutely glandular-pubescent, the glandular trichomes simple. Naturalised, widespread throughout, except western India	Solanum torvum
-	Inflorescence variously pubescent, no inflorescence trichomes glandular	47
47	Corolla 2-5 cm in diameter; leaf pubescence golden or reddish gold	48
-	Corolla 1-2 cm in diameter; leaf pubescence not markedly rusty-golden, usually tan	49
48	Corolla 2-2.6 cm in diameter; style 6-9 mm long, mature berries yellow to orange yellow; leaf pubescence rusty-golden colour. Indonesia, Philippines	Solanum torvoideum
-	Corolla to 5 cm in diameter; style 10-13.5 mm long; mature berries greenish yellow; leaf pubescence reddish brown. Introduced, China, India, Malaysia, Sri Lanka	Solanum chrysotrichum
49	Calyx lobes strongly keeled; corolla white; berries 0.8-1.5 cm in diameter. Indonesia (except Borneo)	Solanum poka
-	Calyx lobes not keeled; corolla purple; berries 0.7-1 cm in diameter. China and Indochina, to Philippines and Taiwan	Solanum pseudosaponaceum
50	Leaves entire (occasionally the margins somewhat sinuate, but never distinctly lobed)	51
-	Leaves variously lobed	60
51	Stem prickles strongly curved	52
-	Stem prickles straight or absent	53
52	Corolla 2-3 cm in diameter; berries to 5 cm long, ovoid; climbing vines of rainforests. Indonesia, Philippines	Solanum schefferi
-	Corolla 0.9-1.6 cm in diameter; berries to 0.8 cm long, globose; scandent shrubs of dry habitats. Western India	Solanum cordatum
53	Flowers strongly zygomorphic, with one or two anthers much longer than the rest and strongly curved	54
-	Flowers actinomorphic or only weakly zygomorphic, all anthers of equal length or only slightly differing in size, never in shape	56
54	Corolla 3.5-5 cm in diameter; long anthers 2, 12-15 mm long; fruiting pedicels strongly deflexed; berries dry and held inside the accrescent calyx. Western Ghats, India	Solanum wightii
-	Corolla <3 cm in diameter; long anther 1, <10 mm long; fruiting pedicels not deflexed; berries soft and fleshy, the fruiting calyx not accrescent	55
55	Flowers white; leaves lanceolate to elliptic, strongly discolorous, eglandular. Southern India and Sri Lanka	Solanum vagum
-	Flowers purple; leaves ovate to broadly triangular, concolorous, densely glandular, sticky to the touch. Eastern India, Sri Lanka	Solanum pubescens
56	Trichomes of upper leaf surfaces multangulate, all rays pointing upwards; sympodial units difoliate, the leaves geminate; anthers all of equal size. Indonesia (Java)	Solanum comitis
-	Trichomes of upper leaf surfaces porrect-stellate, the rays in a single plane; sympodial units plurifoliate, the leaves not geminate; anthers often slightly unequal	57
57	Scandent shrubs; flowers often 4-merous. China, Indochina, Indonesia	Solanum procumbens
-	Erect spindly shrubs; flowers 5-merous	58
58	Leaf bases attenuate; corolla deeply stellate, divided nearly to the base. Hainan Island, China, southern Vietnam	Solanum nienkui
-	Leaf bases cuneate; corolla stellate, divided ca. halfway to the base	59
59	Leaves strongly discolorous, 2-3 times longer than wide; trichomes of stems and leaves with bulbous midpoints. Vietnam	Solanum robinsonii
-	Leaves only slightly discolorous, less than 2 times longer than wide; trichomes of stems and leaves without bulbous midpoints. Thailand	Solanum putii
60	Stem prickles absent or extremely sparse (ca. 1-2 per 10 cm or more of stem)	61
-	Stem prickles always present, occasionally very dense	64
61	Berries smaller than 1 cm in diameter, several per inflorescence	62
-	Berries larger than 1 cm in diameter, usually only one or two per inflorescence	63
62	Leaves ovate to suborbicular; corolla 0.8-1 cm in diameter; plants of seashore dunes. Vietnam	Solanum camranhense
-	Leaves elliptic to narrowly elliptic; corolla 1-1.4 cm in diameter; plants of forests. Philippines, Indonesia (?Taiwan, Lanyu Island)	Solanum retrorsum
63	Corolla 0.8-1 cm in diameter, white; berries bright red, often somewhat flattened or ribbed. Cultivated (scarlet eggplant)	Solanum aethiopicum
-	Corolla 2.5-5 cm in diameter, purple or occasionally white; berries white, yellow or purple, variously shaped. Cultivated (brinjal eggplant)	Solanum melongena
64	Stem prickles strongly curved (hooked)	65
-	Stem prickles straight	77
65	Leaves decurrent onto the stem, rhombic or broadly ellipsoid	66
-	Leaves distinctly petiolate, variously shaped	67
66	Mature berries densely pubescent; stems strongly winged from decurrent leaf bases; flowers greenish white. Introduced, India, Réunion (France)	Solanum robustum
-	Mature berries glabrous and shiny; stems not winged from the leaf bases; flowers white. Introduced, widespread in the region but scattered	Solanum jamaicense
67	Erect shrubs	68
-	Prostrate or scrambling shrubs (can be as tall as 2 m)	70
68	Inflorescence densely glandular-pubescent (in addition to stellate-pubescent), the glandular trichomes simple and minute; rest of plant eglandular. Naturalised throughout the region	Solanum torvum
-	Inflorescence stellate-pubescent, not glandular-pubescent, unless rest of plant with glandular trichomes	69
69	Berries 2.5-3.5 cm in diameter, densely pubescent at maturity, the trichomes with elongate midpoints; leaves repand; fruiting pedicels bending from weight of fruit, not markedly deflexed. Cultivated throughout the region	Solanum lasiocarpum
-	Berries 1-1.2 cm in diameter, glabrous; leaves not repand; fruiting pedicels strongly deflexed. Yunnan, China (Myanmar?)	Solanum deflexicarpum
70	Leaves elliptic to narrowly elliptic	71
-	Leaves ovate to broadly ovate or suborbicular	73
71	Calyx accrescent in fruit, covering half or more of the berry, densely prickly; anthers of equal size. Indochina, Indonesia, Malaysia, Philippines	Solanum cyanocarphium
-	Calyx not accrescent in fruit, if enlarged not covering half or more of the berry, not markedly prickly; anthers of slightly different sizes	72
72	Leaves 7-11 cm long (rarely smaller); corolla 0.5-1 cm in diameter; berries 0.3-0.5 cm in diameter; seeds 6-9 per berry. Indonesia	Solanum graciliflorum
-	Leaves 2-6.5 cm long; corolla 1-1.5 cm in diameter; berries 0.6-1 cm in diameter; seeds to 25 per berry. China, Indochina, Indonesia, Timor Leste	Solanum procumbens
73	Flowers zygomorphic, with two anthers longer than the rest; berries dry, held inside an accrescent calyx on straight, strongly deflexed pedicels. India	Solanum wightii
-	Flowers actinomorphic; berries fleshy, the fruiting calyx not accrescent; fruiting pedicels not as above	74
74	Peduncle absent to 0.15 mm long, the flowers borne at the very base of the inflorescence; fruiting pedicels strongly recurved, woody; ripe berries orange. Ryuku Islands (Japan) to Philippines	Solanum miyakojimense
-	Peduncle to 2 cm long, always present; fruiting pedicels erect or pendant; mature berries red	75
75	Corolla 0.8-1 cm in diameter; plants of dunes along seashore. Vietnam	Solanum camranhense
-	Corolla> 1 cm in diameter; habitat not as above	76
76	New growth densely stellate-pubescent, the trichomes with 6-10 rays; sympodial units difoliate, the leaves not geminate. Western India	Solanum forskalii
-	New growth sparsely stellate-pubescent, the trichomes with 2-5 rays; sympodial units difoliate, the leaves geminate. Widespread, India to Philippines	Solanum trilobatum
77	Mature berries densely pubescent, the trichomes with long midpoints; leaves usually large and somewhat repand	78
-	Mature berries glabrous or with only a few stellate trichomes at the apex; leaves various, not repand	80
78	Leaf bases attenuate; leaves widest near the middle; upper leaf surface glabrate and densely prickly. Indonesia (Sulawesi)	Solanum sulawesi
-	Leaf bases truncate; leaves widest in the lower third; upper leaf surfaces pubescent, prickly or not	79
79	Berries completely enclosed in an accrescent, prickly calyx; corolla 1-1.2 cm in diameter; anthers 5-6 mm long. Indochina, Malay Archipelago, Christmas Island	Solanum involucratum
-	Berries not enclosed in an accrescent calyx; corolla 2.5-3.5 cm in diameter; anthers 6-8.5 mm long. Cultivated throughout the region	Solanum lasiocarpum
80	Inflorescences with distal staminate flowers and a single to a few basal hermaphroditic flowers, the plants strongly andromonoecious; berries usually> 2 cm in diameter	81
-	Inflorescences with all flowers hermaphroditic (perfect), if staminate flowers occur these are few and at the very tip of the inflorescence of otherwise hermaphroditic flowers; berries usually <1 cm in diameter	83
81	Prostrate shrubs with densely prickly stems and leaves; leaves glabrescent; flowers fragrant. India to Malay Archipelago	Solanum virginianum
-	Herbs or shrubs, moderately to sparsely prickly; leaves not glabrescent; flowers not fragrant	82
82	Inflorescences usually with only a single hermaphroditic flower at the base; staminate flowers 1-2; berries usually large, variously shaped. Cultivated (see description, can be very difficult to distinguish from S. insanum )	Solanum melongena
-	Inflorescences with more than one hermaphroditic flower at the base; staminate flowers> 2; berries 1.5-3 cm in diameter, globose. Weedy throughout	Solanum insanum
83	Calyx accrescent in fruit, covering more than half of the berry, densely prickly	84
-	Calyx not accrescent in fruit, if enlarged not covering more than half of the berry, moderately to sparsely prickly	87
84	Leaves deeply divided to pinnatifid; corollas 2-3 cm in diameter; accrescent calyx peeling back at fruit maturity to reveal the red berry. Introduced and adventive, China and India	Solanum sisymbriifolium
-	Leaves shallowly lobed or entire, not pinnatifid or bipinnatifid; corollas usually less than 2 cm in diameter; accrescent calyx remaining around the berry at maturity. Native plants	85
85	Scrambling vine or shrub; leaves elliptic to narrowly elliptic; leaf bases attenuate; berries red when mature. Indochina, Indonesia, Malaysia, Philippines	Solanum cyanocarphium
-	Erect shrubs; leaves broadly elliptic to ovate; leaf bases truncate; berries whitish green when mature	86
86	Young growth densely prickly and bristly, the bristles long-stalked and some topped with stellate rays; inflorescences 3-10 cm long; corolla 1.8-2.2 cm in diameter. Indonesia, China to Indochina	Solanum barbisetum
-	Young growth sparsely prickly, not bristly; inflorescences 1.5-3 cm long; corolla 0.7-1.5 cm in diameter. India to China and Indochina	Solanum praetermissum
87	Flowers with the anthers slightly unequal, often 4-merous; sympodial units plurifoliate, the leaves not geminate. China, Indochina, Indonesia, Timor Leste	Solanum procumbens
-	Flowers with anthers of equal size, 5-merous; sympodial units difoliate, the leaves geminate or not	88
88	Fruiting pedicels strongly reflexed; trichomes of stems and leaves with elongate midpoints to 2 mm long. Western Ghats, southern India	Solanum multiflorum
-	Fruiting pedicels erect or spreading; trichomes of stems and leaves with midpoints not markedly longer than the rays	89
89	Calyx lobes long-acuminate, strongly keeled; seeds> 100 per berry. Indonesia (except Borneo)	Solanum poka
-	Calyx lobes deltate, not strongly keeled; seeds 10-20 per berry	90
90	Leaf bases cuneate to attenuate; upper leaf surfaces moderately to sparsely stellate-pubescent; fruiting pedicels strongly deflexed. Western Ghats, southern India	Solanum hovei
-	Leaf bases acute or truncate; upper leaf surfaces densely stellate-pubescent; fruiting pedicels spreading. Widespread throughout	Solanum violaceum

Synoptic character list for tropical Asian spiny solanums

This synoptical character list can be used as a multi-entry key for identification. We have only listed diagnostic characters here, for example, entire and pinnatifid leaves are listed but not lobed leaves in general. For distributional information please see Table 2 . The list is intended to be used as a tool via a process of elimination; any character can be selected and in combination with other characters, a smaller selection of species can be obtained, for which the descriptions will be useful for coming to a final identification.

Plants found in cultivation (agricultural settings or home gardens): aethiopicum, macrocarpon, mammosum, melongena

Scrambling or prostrate plants: cordatum, cyanocarphium, forskalii, miyakojimense, procumbens, schefferi, trilobatum, wightii

Plants unarmed (no obvious prickles anywhere on plant): aethiopicum, camranhense, comitis, cordatum, deflexicarpum, dunalianum, giganteum, lasiocarpum, macrocarpon, melongena, miyakojimense, nienkui, peikuoense, pubescens, putii, retrorsum, robinsonii, torvoideum, torvum, vagum, violaceum, wrightii

Plants drying black on herbarium specimens: giganteum, kachinense, poka, pseudosaponaceum

Plants andromonoecious (with basal hermaphroditic and distal staminate flowers): arundo, barbisetum, insanum, lasiocarpum, macrocarpon, melongena, schefferi, virginianum, wightii

Small trees, taller than 3 m: arundo, chrysotrichum, (comitis?), dunalianum, giganteum, peikuoense, pseudosaponaceum, torvoideum, wrightii

Simple trichomes (never stellate) on stems: aculeatissimum, capsicoides, mammosum, viarum

Stems white from dense pubescence of multangulate stellate trichomes: arundo, forskalii, giganteum

Stems with strongly hooked prickles: cordatum, cyanocarphium, graciliflorum, jamaicense, procumbens, schefferi, trilobatum

Stem prickles straight and strongly retrorse: retrorsum

Rays of stellate trichomes fused at the base (lepidote or almost lepidote): elaeagnifolium, robinsonii

Trichomes and/or prickles purple or purplish black in live plants (sometimes also visible on herbarium specimens): barbisetum, cyanocarphium, hovei, involucratum, lasiocarpum, praetermissum (insanum and melongena prickles purple only)

Leaves on reproductive branches <1.5 times longer than wide: camranhense, cordatum, forskalii, involucratum, lasiocarpum, miyakojimense, praetermissum, pubescens, sulawesi, trilobatum, virginianum, wightii

Leaves on reproductive branches entire (without lobes): camranhense, comitis, cordatum, dunalianum, elaeagnifolium, forskalii, giganteum, miyakojimense, nienkui, poka, praetermissum, procumbens, pseudosaponaceum, pubescens, putii, retrorsum, robinsonii, schefferi, torvum, vagum

Leaves on reproductive branches with secondary lobing (some lobing to pinnatisect): arundo, multiflorum, sisymbriifolium, violaceum, virginianum

Leaves glabrous or glabrescent adaxially: aethiopicum, arundo, cordatum, giganteum, graciliflorum, kachinense, macrocarpon, melongena (rarely), peikuoense, retrorsum, trilobatum, vagum, virginianum

Leaves with bright yellow, straight prickles> 1 cm long: aculeatissimum, arundo, capsicoides, sulawesi, virginianum

Leaves with only simple trichomes adaxially: aculeatissimum, capsicoides, mammosum, viarum, wrightii

Pubescence of adaxial leaf surfaces of multangulate trichomes with all rays pointing upwards: comitis

Pubescence of white mealy multangulate trichomes that are easily rubbed off: giganteum, vagum

Leaf bases decurrent onto the stem: macrocarpon, robustum

Leaf bases cordate/truncate: camranhense, cordatum, forskalii, melongena, pubescens, wightii

Inflorescence many times branched: dunalianum, giganteum, graciliflorum, harmandii, kachinense, multiflorum, peikuoense, pseudosaponaceum, schefferi, torvoideum

Inflorescence glandular pubescent: aculeatissimum, pubescens, torvum, viarum

Peduncles absent or very short (<5 mm): cordatum, miyakojimense, sulawesi, torvoideum, violaceum, wightii

Calyx lobes foliaceous: macrocarpon, melongena, robustum

Calyx lobes with a distinct acumen: camranhense, peikuoense, poka, robinsonii, torvoideum, vagum, virginianum

Corolla stellate-rotate or pentagonal (with abundant interpetalar tissue): comitis, insanum, macrocarpon, melongena, virginianum, wightii

Corolla deeply stellate (lobed nearly to the base): barbisetum, graciliflorum, kachinense, retrorsum, schefferi, vagum

Anthers unequal (even slightly so): nienkui, procumbens, pubescens, putii, robinsonii, vagum, wightii

Anthers with several markedly different in size and shape, strongly curved: pubescens, vagum, wightii

Calyx strongly accrescent in fruit, more than half covering the berry: barbisetum, cyanocarphium, involucratum, macrocarpon, praetermissum, wightii

Immature berries marbled green and white: aculeatissimum, arundo, insanum, jamaicense, miyakojimense, viarum, virginianum

Mature berry> 3 cm in diameter: aethiopicum, arundo, lasiocarpum, macrocarpon, mammosum, melongena, schefferi, wrightii

Mature berries not strictly globose: hovei, macrocarpon, mammosum, melongena, miyakojimense, schefferi

Mature berries red or orange, thin-skinned and fleshy (usually juicy): camranhense, cordatum, deflexicarpum, dunalianum, forskalii, giganteum, hovei, involucratum, jamaicense, lasiocarpum, miyakojimense, multiflorum, nienkui, peikuoense, procumbens, pseudosaponaceum, pubescens, retrorsum, robinsonii, sisymbriifolium, trilobatum, vagum, violaceum

Mature berries bright yellow when ripe: aculeatissimum, arundo, insanum, violaceum, virginianum

Mature berries greenish yellow or yellowish green when ripe: chrysotrichum, insanum, melongena, poka, torvoideum, torvum, torvoideum, wightii (just before dehiscence)

Mature berries white or greenish white when ripe: barbisetum, praetermissum

Mature berries black or purple when ripe: melongena, peikuoense, torvoideum

Mature berries leathery: aculeatissimum, arundo, capsicoides, chrysotrichum, elaeagnifolium, insanum, macrocarpon, mammosum, melongena, viarum, virginianum, wrightii

Mature berry dry, pseudo-capsular or the pericarp shattering: elaeagnifolium, wightii

Mature berries densely and uniformly pubescent: involucratum, lasiocarpum, robustum, sulawesi

Inner flesh of berry spongy and not at all juicy: capsicoides, mammosum, melongena

Seeds> 100 per berry: cyanocarphium, insanum, involucratum, lasiocarpum, poka, pseudosaponaceum, schefferi, sulawesi, torvoideum, virginianum, wrightii

Seeds 10 or fewer per berry: camranhense, cordatum, forskalii, graciliflorum, hovei, multiflorum, nienkui, procumbens, retrorsum, robinsonii, vagum, violaceum

Seeds dark brown or blackish brown: cordatum, forskalii

Seeds with a distinct wing: capsicoides

Species descriptions