Solanum phrixothrix Gouvea & S. Knapp, sp. nov.
Creators: name: Knapp, Sandra
name: Gouvêa, Yuri F.
name: Giacomin, Leandro L.
Publisher: name: Zenodo
Year: 2025
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Magnoliopsida
Solanales
Solanaceae
Solanum
Solanum phrixothrix

description: 4.Solanum phrixothrixGouvêa & S. Knapp sp. nov.
Fig. 9
Diagnosis.
Solanum phrixothrix differs from all other members of the S. hexandrum group in its rotate, white corollas. It is similar to S. aciculare and S. sublentum in its cordate non-decurrent leaf bases, but differs from both in its eglandular pubescence. The eglandular bristle-like trichomes completely lacking lateral rays distinguish it from S. aciculare and its densely bristly stems distinguish it from S. sublentum. It differs from S. hexandrum, S. hydroides and S. stagnale in its cordate non-decurrent leaf bases and from S. stagnale, it is acicular, rather than broad-based and usually curved prickles.
Type.
Brazil. Espirito Santo: Mun. Linhares, bairro Bebedouro, mata de tabuleiro, estrada ES-245, sentido a Regência, mata de cabruca (Cacau), UTM: 394627, 7851005 [19°25'57.1"S, 40°00'13.5"W], 12 Jun 2017, D. A. Folli 7560 (holotype: BHCB [BHCB 221244]; isotype: CVRD [acc. # 15743]).
Description.
Shrubs to ca. 2 m tall, erect to somewhat spreading, strongly armed and bristly. Stems terete, conspicuously fistulose (at least the younger ones), densely bristly and prickly; the bristle-like trichomes simple, 3.4–19.2 mm long, with a long multiseriate stalk and a shorter uniseriate mid-point at the tip, the stalks 2.5–16 mm long, the mid-points 0.9–3.2 mm long, 1–2 - celled, underlying pubescence of sparse, very tiny papillate trichomes, these drying golden yellow; the prickles 0.5–1.2 cm long, the base ca. 1 mm in diameter, straight to retrorse, somewhat laterally compressed, yellowish-golden at base, becoming yellowish-brown towards the tip; the epidermis densely dotted with crystal sand (inclusions of calcium oxalate); new growth densely bristly and prickly, with simple bristle-like trichomes and prickles like those of the stems; bark of older stems not known. Sympodial units plurifoliate, the leaves not geminate. Leaves lobed, the blades 21–30 cm long, 20–24 cm wide, ca. 1–1.25 times as long as wide, broadly ovate to broadly elliptic, usually widest in the basal half, membranous, concolorous, sparsely to moderately prickly on the mid-rib and major veins of both surfaces with prickles like those of the stems, but usually smaller; adaxial surface densely to moderately pubescent to hirsute with simple bristle-like trichomes similar to those of the stems, but smaller, 0.8–6.5 mm long, the stalks 0.2–4.5 mm long, the mid-points 0.7–2 mm long; abaxial surfaces more sparsely pubescent with trichomes like those of the adaxial surface, these restricted to the mid-rib, major and minor veins and usually smaller and thinner-walled; principal veins 5–7 pairs; base cordate to angular-cordate often with a prominent pair of basiscopic lobes, not decurrent on to the petiole, symmetrical; margins 4–6 - lobed, leaves of young plants or new growth also with secondary lobing, the sinuses 1 / 3–1 / 5 of the distance to the mid-rib; apex acute to obtuse; petiole 4.8–9.5 cm long, densely bristly, moderately to densely prickly with trichomes and prickles like those of the stems. Inflorescences opposite the leaves or internodal, 12–15 cm long, unbranched, with 19–25 flowers; axes densely to moderately bristly and prickly with trichomes and prickles like those of the stems, but the prickles sometimes thinner; peduncle 2.7–3.6 cm long; pedicels 1–2 cm long, 0.6–0.9 mm in diameter at the base, same diameter at the apex (excluding trichomes), erect to directed downwards, moderately to densely bristly with bristle-like trichomes like those of the stems, prickly or not, articulated at the base; pedicel scars more or less evenly spaced 1–5 mm apart on mature inflorescences, more closely packed distally. Buds ellipsoid to narrowly ellipsoid, the calyx lobes soon splitting, exceeding the length of the corolla until just before anthesis. Flowers 5 - merous, heterostylous, the proximal flowers long-styled (co-sexual) and distal ones short-styled (functionally staminate), the plants andromonoecious. Calyx with the tube 4.3–7.5 mm long, 4–8 mm in diameter, shallowly cup-shaped to obconical, the lobes 4.5–11.3 mm long, triangular to somewhat lanceolate, sometimes varying in size in a single flower, densely bristly with trichomes like those of the stems, prickly or not. Corolla 3–3.6 cm in diameter, white, rotate, shallowly campanulate or tubular, lobed less than 1 / 8 of the way to the base, interpetalar tissue indistinguishable from the rest of the lobe or nearly so, copious and reaching nearly to the tips, the lobes 3.8–5 mm long, 16.5–25 mm wide, rounded to retuse, glabrous with pubescence restricted to the lobe apices on both surfaces, the trichomes minute, simple. Stamens equal; filament tube 1.5–1.7 mm long, glabrous; free portion of the filaments 1.4–1.8 mm long, glabrous; anthers 6.5–10 mm long, 2.2–3 mm wide, broadly lanceolate and tapering, connivent, glabrous, yellow, abaxially swollen in the lower half (gibbous) and somewhat papillate, poricidal at the tips, the pores directed distally, not elongating to slits with age. Ovary cup-shaped, moderately to densely pubescent, the trichomes simple, glandular, very tiny papillate and sessile to 0.6 mm long, 1–5 - celled, thin-walled, the longer ones less abundant, pubescence sometimes restricted to the ovary apex; style 8.8–12 mm long in long-styled flowers, 1.2–3.6 mm long in short-styled flowers, straight, sparsely to moderately puberulent with very tiny papillate trichomes; stigma clavate, the surface minutely papillose. Fruit and seeds not known. Chromosome number not known.
Distribution
(Fig. 10). Solanum phrixothrix is endemic to the south-eastern region of Brazil and known only from two collections; one with a specific locality from Espírito Santo State and another made by A. St. - Hilaire that is likely to be from Minas Gerais State (see Dwyer (1955)).
Ecology and habitat.
The only known collection with locality and vegetation type information of S. phrixothrix is from wet evergreen forests of the lower Rio Doce drainage, at approximately 13 m elevation. This collection is from a “ cabruca ” (cacao plantation). These cacao plantations retain the upper strata of the forest for shade, but the understorey is significantly damaged by shrub and herb removal, along with significant cacao leaf litter.
Common names and uses.
None recorded.
Etymology.
The species epithet is derived from the Greek, meaning with bristling (or horrid) hairs.
Preliminary conservation status
(IUCN 2020). Solanum phrixothrix is known from only two collections, gathered 200 years apart and so must have a preliminary assessment of Data Deficient. That said, however, it is imperative that more populations be sought to better assess its range and population density. It is likely to be of conservation concern, as the single collection with an accurate locality (Folli 7506) is from a highly disturbed anthropogenic site (cacao plantation), not within a protected area. It is near the Floresta Nacional de Goytacazes in Espiríto Santo State and should be sought there. Other protected areas close to this collection, such as Reserva Biológica de Sooretama and Reserva Natural Vale are well-inventoried and we have seen no specimens of S. phrixothrix from them in any of the many herbaria we consulted.
Discussion.
Solanum phrixothrix is a distinctive, densely bristly plant that has only been collected twice, once by Auguste St. Hilaire in the early 19 th century and more recently in 2017 (Folli 7506) along the Rio Doce in Espiríto Santo State. It differs from other taxa in the group in its rotate to rotate-pentagonal corollas (Fig. 9 E, F) and densely bristly stems with no stellate trichomes present (Fig. 9 B). The long inflorescences and somewhat delicate pedicels are similar to those of S. aciculare, but that species has copious glandular stellate to multangulate pubescence and stellate corollas (Fig. 2 F, G, I). It is surprising that this species has escaped notice for so long, but members of the S. hexandrum group often occur in very small populations at the bases of rocky outcrops and may easily overlooked despite their large size and fearsome appearance.
Solanum phrixothrix shares dense bristly stems with S. aciculare but can be easily distinguished from that species by its lack of copiously glandular pubescence of long-stalked stellate trichomes. Solanum phrixothrix appears to lack long-stalked stellate trichomes on any part. White flowers are also found in S. hydroides (Fig. 7 D) and S. sublentum (Fig. 13 H), as well as occasionally in S. aciculare (Fig. 2 F). Corollas in these three species are always stellate with variously deltate to triangular lobes, whereas those of S. phrixothrix are rotate and somewhat campanulate with the lobes reduced to tiny apiculae.
description: Published as part of Knapp, Sandra, Gouvêa, Yuri F. & Giacomin, Leandro L., 2025, A revision of the endemic Brazilian Solanum hexandrum group (Leptostemonum, Solanum, Solanaceae), pp. 199-259 in PhytoKeys 253 on pages 199-259, DOI: 10.3897/phytokeys.253.138216