Solanum hirtulum A.Rich., Tent. Fl. Abyss. 2: 101. 1850

Saerkinen, Tiina, Poczai, Peter, Barboza, Gloria E., Weerden, Gerard M. van der, Baden, Maria & Knapp, Sandra, 2018, A revision of the Old World Black Nightshades (Morelloid clade of Solanum L., Solanaceae), PhytoKeys 106, pp. 1-223 : 1

5. Solanum hirtulum A.Rich., Tent. Fl. Abyss. 2: 101. 1850 Figures 16 , 17

Solanum monactinanthum Dammer, Bot. Jahrb. Syst. 48: 236. 1912.

Solanum monactinanthum Type. Ethiopia. "Galla-Hochland: Arussi-Galla, Jidah", 2600 m, Jul 1900, H. Ellenbeck 1452 (holotype: B, destroyed; no duplicates found).

Solanum hirtulum Steud. ex Dunal, Prodr. [A. P. de Candolle] 13(1): 44. 1852, nom. illeg. (isonym), not S. hirtulum A.Rich. (1850).

Solanum monactinanthum Type. Based on same type as Solanum hirtulum A.Rich.

Type.

Ethiopia. Amhara: “Enschadcap” [ Inch'et Kab Bota in Simien Mountains ], 29 Jan 1838, G.H.W. Schimper 977 (lectotype, designated by Lester 1997, pg. 286: P [P00343990]; isolectotypes: BM [BM000907529, BM000907530], BR [BR0000008799999, BR0000008421876], E [E00193283] G [G00343567, G00301657, G00343597], G-DC [G00137892], GH [GH00219333], GOET [GOET003536], HOH [HOH009832], K [K000922317], L [L0403968], LE, M [M0105600, M0105601, MO [MO-2289035, acc. # 2918258], MPU [MPU011268, MPU011269, MPU011270, P [P00343991, P00343992], PAL, REG [REG000397], S [acc. # S-G-5693], STU [STU000030, STU000031], TCD [TCD0000844], TUB [TUB003992, TUB003993], U [U0113936], W [1889-0288845, 0000606], WU [WU0033427], ZT [ZT- 00010272, ZT- 00010273]) .

Description.

Annual to short-lived, mostly prostrate perennial herbs to 5-20(-150) cm high, branches ascending from woody tap-root. Stems decumbent to ascending, terete or very slightly winged from decurrent leaf bases, green or straw coloured, older stems not appearing spinescent, yellowish-brown, not markedly hollow; new growth moderately pubescent with simple, antrorse, uniseriate, eglandular trichomes, these 5-7-celled, 0.5-0.8 mm long, white. Sympodial units difoliate, the leaves not geminate. Leaves simple, 1.5-5.0(-6.0) cm long, 0.7-1.8 cm wide, narrowly elliptic to lanceolate, narrowing gradually to the base, concolorous, without smell; adaxial surface sparsely and evenly pubescent with simple, uniseriate trichomes like those on stem; abaxial surface with a few evenly scattered trichomes like those of the adaxial surface; major veins 5-7 pairs; base long-attenuate, decurrent on the petiole; margins entire to sinuate; apex acute to acuminate, the tip slightly rounded; petioles absent, the laminar tissue extending to the junction of leaf and stem. Inflorescences 0.5-2.2 cm long, opposite the leaves, simple, sub-umbelliform to shortly racemose, with 1-5 flowers clustered in the distal portion, sparsely pubescent with antrorse simple uniseriate trichomes like those of the stems; peduncle 0.4-1.8 cm long, straight; pedicels 0.7-1.6 cm long, ca. 0.5 mm in diameter at the base and apex, stout and spreading, articulated at the base; pedicel scars clustered at the tip of the inflorescence rhachis and overlapping, occasionally the basal scar 1-2.5 mm distant. Buds ellipsoid, the corolla halfway exserted from the calyx tube before anthesis. Flowers 5-merous, all perfect. Calyx tube 2.0-3.0 mm long, conical, the lobes 0.8-1.2 mm long, 0.8-1.2 mm wide, linear-oblong, tips rounded, densely pubescent with trichomes like those of the stems and pedicels. Corolla 12-18(-20) mm in diameter, deep purple to pale violet, stellate, lobed 3/4 of the way to the base, the lobes 4.5-8 mm long, 2-3 mm wide, spreading to reflexed, densely papillate abaxially, the papillae denser along margins and tips. Stamens equal; filament tube ca. 0.5 mm long; free portion of the filaments ca. 0.5-1.0 mm long, adaxially densely pubescent with tangled simple uniseriate trichomes; anthers 2.3-2.8 mm long, 0.6-0.9 mm wide, ellipsoid, yellow, poricidal at the tips, the pores lengthening to slits with age and drying. Ovary rounded, glabrous; style 4.5-5.5 mm long, densely pubescent with simple trichomes in the basal 1/3, exserted ca. 1 mm beyond anther cone; stigma large-capitate, the surfaces minutely papillose. Fruit a globose berry, 5-6 mm in diameter (immature?), mature berry colour not known, the pericarp thin and matte or somewhat shiny; fruiting pedicels 0.7-1.6 cm long, 0.5 cm in diameter at the base and 1.0-1.2 mm at the apex, stout with slight curving at the base, reflexed, dropping with mature fruits, not persistent; fruiting calyx not accrescent, the tube ca. 1 mm long, the lobes 1-1.5 mm long, appressed to the berry. Seeds (10-)20-35 per berry, ca. 1.8-2.0 mm long, ca. 1.5 mm wide, not markedly flattened, tear-drop shaped with a subapical hilum, pale yellow, the surfaces minutely pitted, the testal cells pentagonal to rectangular in outline. Stone cells 2 per berry, ca. 0.6 mm in diameter. Chromosome number: not known.

Distribution

(Figure 18 ). Endemic to the high mountains of Ethiopia on the western side of the Rift Valley.

Ecology.

Grows in open grassy areas, arable land, along river banks, in forest and along roadsides; between 2,200 and 3,500 m elevation.

Common names.

None recorded.

Uses. None recorded.

Preliminary conservation status

( IUCN 2016). Solanum hirtulum is a country-restricted endemic with AOO of 48 km2 (EN) and EOO of 49,487 km2 (LC). The species is known from a small number of records, and it could be that the lack of collections reflects small population sizes and/or local rarity. From the EOO measure, it would be assessed as LC (Least Concern), but since it is a single-country endemic, it merits some attention and we assign the species as NT (Near Threatened; Table 7 ). The high mountains where it grows are at threat from grazing and human disturbance, but S. hirtulum , like other members of this group, is a species of open, disturbed areas. The Simien Mountains have protected status as both a World Heritage Site and as a National Park in Ethiopia.

Discussion.

Solanum hirtulum is a distinctive prostrate, creeping herb with narrow lanceolate attenuate leaves with strigose, somewhat antrorse pubescence. The flowers are larger than others in the group in Africa and appear to always be purple or “blue”; this, however, must be taken with caution given the high degree of flower colour polymorphism in other species. The inflorescences are usually few-flowered with tightly spaced flowers at the very tip. Solanum hirtulum is similar to S. memphiticum in having black berries with a somewhat accrescent calyx, but the flowers of S. memphiticum are always smaller, usually white and more delicate (see description of S. memphiticum ). The leaf bases in S. hirtulum are strongly attenuate and decurrent on to the stem.

Solanum hirtulum is a plant of Afromontane vegetation (sensu White 1981, 1983, 1993). Linder ( Linder et al. 2005; Linder 2014) showed that this vegetation type (as “Tropic-montane”) was not necessarily a distinct unit across Africa, but instead was locally distinct based on high turnover in particular mountain blocks. Most clades from these forest types were Miocene in age ( Linder 2014). For Ethiopia, Friis et al. (2010) further characterised this vegetation as "moist evergreen Afromontane forest", with additional complexity added by the grasslands that are characteristic of the seral stages of forest regrowth in these areas. This forest type is only intact in limited areas ( Friis et al. 2010); these are the forests where wild coffee grows and are areas of high endemism in the Ethiopian flora ( Vivero et al. 2006). It is likely that S. hirtulum also occurs at the lower levels of Afroalpine vegetation (sensu Friis et al. 2010), in grasslands at forest edges. The type of S. hirtulum was collected from the Simien Mountains, the most important hotspot of endemism for Afroalpine and Afromontane species ( Vivero et al. 2006).

The type number of S. hirtulum (Schimper 977) is also that for a plant collected in 1837 in Saudi Arabia (the type of Seddera intermedia Hochst., Convolvulaceae , see http://apps.kew.org/herbcat/getImage.do?imageBarcode=K000852498). He clearly reused numbers for his Ethiopian plants.

Solanum monactinanthum is here placed in synonymy based on the description and following Edmonds (2006a), no duplicates of the type (Ellenbeck 1452) that was destroyed in Berlin have been found.

Specimens examined.

Ethiopia. sin. loc., 26 Oct 1862, Schimper 631 (BM, E, K, P, W); Addis Ababa: Addis Ababa, 30 Sep 1937, Piovano 511 (FT); Addis Ababa, 19 Oct 1937, Senni 1837 (FT); Amhara: Semien, Debarek Semien Gonder Region, 11 Jul 1909, Chiovenda 889 (FT); 10 km SE of Debre Markos along rd to Addis Ababa, between Debre Markos and Addis Ababa, 25 Oct 2004, Friis et al. 11912 (K); Bichena Awraja, c. 36 km NW of Debre Work ( Gojjam region ), 30 Oct 1981, Mesfin Tadese & Kagnew 1659 (K); in campis Debra Eski, 19 Oct 1850, Schimper 74 (P); Semien, Derasghie, 25 Dec 1952, Scott 292 (K); Dejen to Debra Marcos, 48 km NW of Dejen, 24 May 1980, Thulin 3914 (K, MO); mule track between Debarak and Geech, 16 Sep 1969, de Wilde & Gilbert 5 (EA, MO); Oromia: Semien Shewa region , Holetta, 4 May 1953, Mooney 4752 (K); Addis Alem, 20 Sep 1926, Omer Cooper s.n. (K); Tigray: Adua, Prope Adoam, Abyssinia, 1852, Schimper s.n. (P) .

Figures

Figure 16. Solanum hirtulum A. Rich A Habit B Detail of adaxial leaf surface C Eglandular hair D Inflorescence E Flower F Infructescence G Seed (A-G Friis et al. 11912). Scale bar: 3 cm (A), 4 mm (B), 0.6 mm (C), 7 mm (D), 5 mm (E), 1 cm (F) and 2 mm (G). Drawing by L. Smith.

Figure 17. Solanum hirtulum A. Rich A Habit B Detail of flower and fruits C Detail of flower and fruits (Schimper 977, A, C isolectotype STU 000030, B isolectotype MPU 011270).

Figure 18. Distribution of Solanum hirtulum A. Rich.