Solanum angustum [Domin ]

Solanum angustum

Citation author:

Domin

Citation:

Biblioth. Bot. 89: 1142. 1929.

Type:

Australia. Queensland: Cook District, Walsh River, north of Chillagoe, February 1910, K. Domin s.n. (holotype, PR 530924 [photo ADW]).

Last edited by:

Bohs, L.

Written by:

M.F. Agra

Habit:

Sprawling, herbaceous resprouter, c. 0.3 m tall. Juvenile stage unknown. Stems grey or yellow, very densely stellate-pubescent, the stellae 0.3-0.5 mm in diameter, the stalks 0-0.1 mm long, the lateral rays 6-8, porrect, the midpoints 0.5-1 times as long as lateral rays, eglandular; finger hairs absent; very short, gland-tipped hairs absent; prickles straight, acicular, 3-6 mm long, 10-15 times longer than wide, with 5-30 prickles per dm.

Sympodial structure:

Sympodial units unknown.

Leaves:

Leaves simple, the blades 1.5-4 x 0.4-1.4 cm, 3-7.5 times as long as wide, elliptical or ovate, chartaceous, green and sparsely to moderately stellate-pubescent adaxially, the hairs distributed throughout, spaced 0.3-0.9 mm apart, 0.25-0.4 mm across, sessile, the lateral rays 6-8, porrect, the midpoints 0.5-1 times as long as lateral rays, eglandular; finger hairs absent; very short, gland-tipped hairs absent; prickles absent or present on midvein only, 0-3, straight, acicular, 3-6 mm long; green or yellowish and sparsely to densely stellate-pubescent abaxially, the hairs spaced 0.1-0.7 mm apart, 0.3-0.6 mm in diameter, the stalks 0-0.1 mm long, the lateral rays 7-8, porrect, the midpoints 0.5-1 times as long as lateral rays, eglandular; finger hairs absent; very short, gland-tipped hairs absent; prickles absent; base cuneate, the oblique part 0-1 mm long; margin entire or shallowly lobed throughout, the lobes 2-3 on each side, obtuse, the lobing index 1-1.3; apex obtuse; petioles 0.3-2.2 cm long, 17-55% length of lamina, very densely stellate-pubescent, prickles absent.

Inflorescences:

Inflorescence leaf-opposed, unbranched, solitary or pseudo-racemose, with 1-4 flowers, the axes very densely stellate-pubescent, armed; peduncle 0-1.5 cm; pedicels ca. 7 mm long in flower, ca. 0.8 mm thick, 15-20 mm long in fruit, 0.9-1.2 mm thick at mid-point, articulated at the base.

Flowers:

Flowers 5-merous, the calyx tube 2.5-3 mm long, the lobes 2-2.5 mm long, deltate, densely stellate-pubescent, the hairs transparent, 0.3-0.4 mm in diameter, sessile, the lateral rays 7-8, the midpoints 0.5-1 times as long as lateral rays, eglandular; finger hairs absent; very short, gland-tipped hairs absent; prickles present, 2-10 per flower, 1-4 mm long; fruiting calyx with lobes more than half length of mature fruit, armed with prickles 1-4 mm long. Corolla ca. 10 mm long, shallowly lobed or stellate, chartaceous. Stamens unknown. Ovary, style, and stigma unknown.

Fruits:

Fruits 1 per inflorescence, 1.6-2 cm in diameter, globose, green.

Seeds:

Seeds 2.5-3 mm long, pale yellow.

Chromosome number:

stage missing = ploidy missing = chrom_num missing = voucher missing =

Distribution:

Solanum angustum is endemic to Queensland and known only from the type and two other collections. The label of the only recent collection indicated that the species was growing in “low eucalypt woodland with shallow clay soil”.

Phenology:

Very poorly known. Fruits have been collected in April.

Phylogeny:

Solanum angustum is a typical member of Solanum subgenus Leptostemonum. It is placed into the S. ellipticum group (Group 27) by Bean (2004) on morphological grounds; its phylogenetic position has not been investigated using molecular data.

Commentary:

The affinities of this species are not known with any certainty, and it is only tentatively placed in the S. ellipticum group.

Symon (1981) considered S. angustum to be a synonym of S. parvifolium and stated: “The type specimen consists of three leafy portions, one with a fruit attached and a second detached fruit present. From the photograph, the plant is obviously closely related to S. parvifolium R. Br. and to a lesser extent S. ferocissimum Lindl. The type locality of S. angustum is at the northern extremity of the distribution of S. parvifolium. The berry of S. angustum was described as 1.5 cm diam., which is larger than usual for S. parvifolium. However, the seeds of S. angustum, which have been examined, are very similar to those of the two related species. I therefore prefer to consider S. angustum Domin as an extreme form of S. parvifolium until further specimens are collected.”

Conservation status: S. angustum has been collected just four times, in 1908, 1910, 1939 and 1992. A recent visit to the 1992 collection site failed to find the species. It has not been seen since 1992, despite deliberate searches during the summer months, especially in the Chillagoe-Walsh River area. Although there are no known extant populations, a presumption of extinction is premature. There would appear to be much available habitat within the extent of occurrence, although the required habitat for the species is still not known.

Applying the IUCN guidelines (IUCN, 2001), and using the 1992 location as an existing location, a category of “Endangered” is recommended (EN C2a(ii); D).

References:

Symon, D.E. 1981. A revision of Solanum in Australia.
J. Adelaide Bot. Gard. 4: 1-367.

IUCN Species Survival Commision 2001. IUCN Red List Categories and Criteria: Version 3.1.
Gland, Switzerland and Cambridge, UK: IUCN.

Bean, A.R. 2004. The taxonomy and ecology of Solanum subg. Leptostemonum (Dunal) Bitter (Solanaceae) in Queensland and far north-eastern New South Wales.
Austrobaileya 6 (4): 639-816.

Solanaceae Source

A global taxonomic resource for the nightshade family

Solanaceae

Solanum angustum Domin

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