Research Article |
Corresponding author: Leandro Lacerda Giacomin ( giacomin.leandro@gmail.com ) Academic editor: Eric Tepe
© 2020 Yuri Fernandes Gouvêa, Luiza Fonseca Amorim de Paula, João Renato Stehmann, Leandro Lacerda Giacomin.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Gouvêa YF, de Paula LFA, Stehmann JR, Giacomin LL (2020) Solanum hydroides (Solanaceae): a prickly novelty from the land of the sugar loaves, central Brazilian Atlantic Forest. PhytoKeys 139: 63-76. https://doi.org/10.3897/phytokeys.139.46635
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Solanum hydroides Gouvêa & Giacomin, sp. nov., is described from central Brazilian Atlantic Forest. It is known from only three localities in Espírito Santo and Minas Gerais states, where granitic/gneissic outcrops (inselbergs or sugar loaves) are ubiquitous. The new species, here described, belongs to Solanum subgenus Leptostemonum (or the Leptostemonum clade; i.e. the spiny solanums) and is morphologically related to S. hexandrum Vell. and S. sublentum Hiern, with which it shares the shrubby habit, decurrent leaf bases and well-developed calyces that become accrescent, covering glabrous fruits. Solanum hydroides is unique in its combination of comparatively more delicate habit, indumentum of exclusively stellate eglandular trichomes, accrescent but never inflated fruiting calyces that only partially cover the fruits and comparatively shortly lobed and strictly white corollas. The species is threatened with extinction and assessed as Vulnerable (VU), based on the IUCN criteria.
Solanum hydroides Gouvêa & Giacomin, sp. nov., é aqui descrita para região central da Floresta Atlântica brasileira. Ela é conhecida apenas para três localidades, nos estados do Espírito Santo e Minas Gerais, em uma região onde afloramentos graníticos/gnáissicos (inselbergues ou pães de açúcar) são onipresentes. A nova espécie pertence a Solanum subgen. Leptostemonum (ou Solanum clado Leptostemonum, i.e. espécies espinhentas com tricomas estrelados) e é morfologicamente semelhante a S. hexandrum Vell. e S. sublentum Hiern, com quem compartilha o hábito arbustivo, a base das lâminas foliares decurrentes e cálices bem desenvolvidos, acrescentes em seus frutos glabros. Solanum hydroides é, contudo, a única espécie que apresenta a seguinte combinação de caracteres: hábito delicado, indumento composto apenas por tricomas estrelados egandulares, cálices frutíferos acrescentes, mas nunca inflados, que cobrem parcialmente os frutos e corolas com lóbulos curtos e estritamente brancas. A espécie é considerada como ameaçada de extinção, na categoria Vulnerável (VU), segundo os critérios da IUCN.
Leptostemonum clade, Brazil, inselbergs, new species, eglandular trichomes
Clado Leptostemonum, Brasil, inselbergs, espécie nova, tricomas eglandulares
Solanum L. (Solanaceae) is one of the largest genera of flowering plants with about 1,400 species, mostly distributed in the Neotropics (
The Atlantic Forest domain is considered one of the 36 hotspots of global biodiversity, defined as a region of the world with a large number of endemics and highly endangered, with its original coverage extremely reduced (
The Central Atlantic Forest is delimited to the south by the Doce River and to the north by the São Francisco (
During a floristic inventory of one inselberg located in the Brazil´s South-Eastern region (
Observations are all based on examination of herbarium specimens from BHCB, CEPEC, HUEFS, MBML, RB and UEC (acronyms follow Index Herbariorum; http://sweetgum.nybg.org/science/ih/), as well as in-field observations by LFAP and YFG. Type specimens of related taxa were consulted in BR, G and M or through high resolution images available on the Global Plants website (https://plants.jstor.org) and original descriptions of related species were checked when necessary. Measurements of reproductive characters comprise the dimensions of both fresh and dried materials. The terms used to describe the morphological character states are based on
Differs from S. sublentum Hiern in its indumentum of strictly stellate eglandular trichomes and in its accrescent, but not inflated, cupuliform fruiting calyx; also differs from S. hexandrum Vell. in its more delicate habit, smaller flowers with white shallowly stellate corollas and in having accrescent, but not inflated, fruiting calyces that partially cover the mature fruits.
BRAZIL. Minas Gerais: Mun. Teófilo Otoni, afloramento rochoso lado esquerdo da MG-418, cerca de 30 km norte de Teófilo Otoni, 17°51'22"S, 41°15'39"W, 560 m elev., 27 Jan 2014 (fl, fr), L.F.A. de Paula, L. Azevedo, R. Fernandes & J. R. Stehmann 669 (holotype: BHCB [BHCB053358]; isotype: RB, to be distributed).
Shrubs 1–1.5 m tall, erect, armed. Branches directed upwards and spreading. Young stems moderately pubescent to tomentose and sparsely to moderately prickly; pubescence of ochraceo-ferruginous to purple-tinged porrect short- to long-stalked stellate trichomes, with multiseriate 0.5–1.5 mm long stalks, the rays 4-8, 0.5–1 mm long, the midpoints 1– to 2–celled, always shorter than the rays; prickles 4–6 mm long, 2–6 mm wide at the base, broad-based and recurved. Bark of older stems glabrescent, drying olivaceous to brown. Sympodial units plurifoliate, the leaves not geminate. Leaves simple, nearly entire to shallowly lobed, the blades 2.8–12.1(21.8) cm long, 2.2–7.5(10.1) cm wide, elliptic to ovate, membranous, slightly discolorous when dry; adaxial surface brown to dark green when dry, densely to moderately stellate-pubescent and prickly, the trichomes like those of the stem but with (1–)4–6 rays, the prickles along the midrib and major veins, to 5.5 mm long and 1 mm wide at the base, straight and laterally compressed; abaxial surface whitish-green when dry, more densely stellate-pubescent than the adaxial surface, the trichomes like those of the adaxial surface, the prickles like those of the adaxial surface but to 6.5 mm long and 2 mm wide at the base; base attenuate to truncate or rounded, less often with 1 or 2 basiscopic lobes, decurrent onto the petiole, sometimes asymmetrical; margins shallowly lobed, the lobes (0)3–5 on each side, 1–12(14.8) mm long, 3.2–11(23) mm wide at base with usually acute, sometimes rounded or obtuse apices, the sinuses 3.2–8.5 mm deep; apex acute to acuminate; primary veins 4–6 pairs, more prominent beneath, prickly on both surfaces; petioles 0.6–3.3 cm long, densely to moderately pubescent with porrect-stellate trichomes like those of the leaves, usually armed with 1–5 prickles. Inflorescence a monochasial cyme (drepanium) to 6 cm long, internodal, unbranched, with 4–10 flowers, up to 2 flowers open at a time, the axes glabrescent to densely tomentose, with trichomes like those of the stem but sometimes with the midpoint as long as the rays, usually unarmed; peduncles 0.4–2.3 (-3.8) cm long pedicels 3–17 mm long, 0.5–0.8 mm in diameter at base and up to 1.5 mm at the apex, straight to slightly curved, articulated at base, unarmed, with trichomes like those of the inflorescence axes; pedicel scars evenly spaced 1–7 mm apart. Buds ovoid to ellipsoid, with the corolla enclosed by the calyx until just before anthesis. Flowers 5-merous, heterostylous with long-styled flowers (hermaphroditic) at the base of inflorescence, short-styled (functionally male) flowers more distally and the plants andromonoecious. Calyx tube 2.6–4.3(6) mm long, 6.5–8 mm in diameter at anthesis, widely obconic to cupuliform, the lobes 3–7 mm long, 3–5.5 mm wide, triangular to deltate, with acute apices, glabrous adaxially, densely pubescent to hirsute abaxially with bristly purple-tinged, hyaline or ochraceo-ferruginous porrect to multiangulate long-stalked stellate trichomes, the stalks of the fully developed trichomes multiseriate, 1.1–3.8 mm long, rays 4-8 to 1.5 mm, the midpoints 1–2 celled, shorter than or the same length as the rays, associated with minute, nearly sessile, uniseriate, simple glandular trichomes along the epidermis and sometimes at the basal portion of the stellate trichomes stalks, armed or unarmed, the prickles acicular, 2.8-4 mm long, ca. 0.5 mm wide in flower to 1.1 mm in fruit. Corolla 2.4–3 cm in diameter, 7.1–12.2 mm long, white, shallowly stellate, interpetalar tissue nearly absent, lobed ca. halfway to the base, the fused part (tube) 7.1–12.2 mm long, the lobes 5.9–8.8 mm long, 9.9–12.2 mm wide, acute to apiculate apices, pubescent abaxially on the petal midvein and/or apices with sparse delicate short-stalked porrect-stellate trichomes with stalks to 0.9 mm long. Stamens equal; filament tube to 1 mm long; free portion of the filaments 0.7–1 mm long, glabrous; anthers 6.5–8 mm long, 2.5–3 mm wide, lanceolate, yellow, glabrous, connivent or divergent at the apices, sagittate and slighty gibbous at the base, swollen and papillose abaxially, the pores directed upwards or slightly extrorse, not lengthening to slits. Ovary somewhat conical, glabrous; style 8–10 mm long in long-styled flowers, ca. 3 mm long in short-styled flowers, straight, glabrous; stigma clavate to bilobed, the surface papillose and irregular, the style poorly developed in short-styled flowers. Fruit a globose berry, 0.9–1.8 cm in diameter, green to whitish-green at maturity, drying dark brown, glabrous, matte; fruiting pedicels 1–1.5 cm long, usually unarmed; fruiting calyx partially accrescent, the tube enclosing ½–¾ of the fruit at maturity, the lobes 5.8–8 mm long, 7–9.6 mm wide, with trichomes often with the base of the stalks markedly expanded and bristly, the stalks to 4.8 mm long. Seeds ca. 250 per berry, 2.2–2.6 mm long, 1.6–2 mm wide, pyriform to reniform, not markedly flattened, the surface irregularly pitted, the testal cells pentagonal in outline. Chromosome number not known.
Solanum hydroides Gouvêa & Giacomin. (A, G–I field pictures from specimens L.F.A. de Paula et al. 669, BHCB; B–E Y.F. Gouvêa & G.V.A. Santos 325, BHCB). A Habit (bottom right corner: young plant with larger leaves) B flowering branch C inflorescence and a flower in lateral view (note that calyx does not have a plicate aspect at the base of the calyx tube) D long-styled flower, front view E mature fruit (note the calyx does not completely cover the berry) F scanning electron micrograph of seed G trichomes; upper: the usual morphology of the stellate trichomes of S. hydroides adaxial leaf surface; lower: examples of stellate trichomes with reduced number of rays (note the multiseriate stalks) H stem indumentum; I adaxial leaf surface indumentum. Scale bars: 30 cm (A); 7.5 cm (B); 1.3 cm (C–D); 1 cm (E); 0.8 mm (F–I). Photographs: A by L.F.A de Paula B–E, G–I by Y.F. Gouvêa.
Endemic to South-eastern Brazil, with records in three localities in north-eastern Minas Gerais (Mun. Teófilo Otoni) and northern (Mun. Nova Venécia) and central (Mun. Santa Teresa) Espírito Santo States (Fig.
Solanum hydroides inhabits the edge of seasonal semi-deciduous tropical rainforests associated with granitic or gneissic rock outcrops (inselbergs) and somewhat disturbed sites at their base, like roadsides and clearings; from 300 to 600 m elevation. It also occasionally grows in epilithic vegetation patches lying on the flatter parts of inselbergs.
Flowering specimens were collected in January, April, May, August, September and December, suggesting that S. hydroides blooms year-round. Fruiting specimens have been found only in January.
Solanum hydroides is named for the resemblance of the long-stalked stellate trichomes of its calyces to the marine serpulid worm Hydroides Gunnerus, 1768 (illustrative images can be found at the Encyclopedia of Life; e.g. https://eol.org/search?utf8=%E2%9C%93&q=Hydroides).
Vulnerable (VU). EOO = 7,766 km2 (VU - vulnerable); AOO = 28 km2 (EN - endangered). Solanum hydroides is known from only three disjunct localities and is represented by only one collection in one of them (i.e. Serra do Toma Vento, Mun. Santa Teresa, Espírito Santo State). All other specimens were found in vegetation remnants associated with two inselbergs, located in the municipality of Nova Venécia, Espírito Santo state and in Minas Gerais State’s municipality of Teófilo Otoni. Both, however, are in the central Brazilian Atlantic Forest, where botanical knowledge gaps are known to exist (
Solanum hydroides shares a set of morphological features with species of a small and still unnamed group, recently proposed on the basis of morphological (
The comparatively smaller leaves and thinner stems, petioles and inflorescence axis give a more delicate overall aspect of S. hydroides, differentiating it from all other species of the group, but S. sublentum. Solanum hydroides can, however, be readily distinguished from S. sublentum by the indumentum of stellate eglandular trichomes (Figs
Distinctive characters of species morphologically related to Solanum hydroides Gouvêa & Giacomin. [A, C, E, G: S. hexandrum Vell. (L.L. Giacomin et al. 875, BHCB); B, D, F, H: S. sublentum Hiern. (J.R. Stehmann et al. 6372, BHCB)]. A–B Habit (note difference in robustness) C long-styled flower, front view D inflorescence and flower in back view (note the inflated and plicate aspect of the calyx tube) E inflorescence with fruits in different stages of development (note that the inflated fruiting calyx completely covers the fruit in all stages of development) F long-styled flower G fruits (note the plicate aspect of the fruiting calyx) H–I indumentum of the adaxial leaf surface. Scale bars: 15 cm (A); 10 cm (B); 3 cm (C); 2 cm (D, G); 1.4 cm (E); 1 mm (F); 1.2 mm (H). Photographs: A, C, E by L.L. Giacomin B, D, F by J.R. Stehmann G–H by Y.F. Gouvêa.
Although being a markedly less robust species (compare Figs
Leaf measurements are also useful for distinguishing S. hydroides from S. hexandrum. The leaves of S. hydroides are generally smaller (7.5–13.6 cm long and 5-8.7 cm wide) than those of S. hexandrum (17–45 cm long and 10.5–32 cm wide). Nevertheless, like many species belonging to the Leptostemonum clade (sensu
The trichome morphology in S. hydroides is not particularly variable within individual plants and amongst plants of the same population; however, there is a significant variation in the number of trichome rays between some populations. Trichomes of specimens from the southernmost known population (in Santa Teresa municipality, Espirito Santo State) are mostly six- to eight-rayed and usually more densely distributed throughout the plant, while those of plants from the other populations (Teófilo Otoni and Nova Venécia municipalities of Minas Gerais State) are mostly four-rayed (Figs
The exploitation of natural resources in Brazil is far from being sustainable (
BRAZIL. Espírito Santo: Mun. Nova Venecia, APA da Pedra do Elefante, Serra de Baixo, Pedra do Elefante, inselbergue, 18°46'S, 40°27'W, 653 m elev., 10 May 2008 (fl), A.P. Fontana et al. 5259 (MBML, RB); Serra de Baixo, Pedra da Torre, inselbergue, 18°46'58"S, 40°26'47"W, 420–500 m elev., 18 Feb 2008 (fr), C.N. Fraga et al. 1899 (CEPEC, MBML, RB, UPCB); estrada não pavimentada de acesso à Pedra do Elefante, 18°46'40"S, 40°26'37"W, 352 m elev., 1 Apr 2019 (fl, fr), Y.F. Gouvêa & G.V.A. Santos 325 (BHCB); 18°46'42"S, 40°26'50"W, 301 m elev., 1 Apr 2019 (fl, fr), Y.F. Gouvêa & G.V.A. Santos 328 (BHCB); morro lado direito na estrada para Pedra do Elefante, afloramento rochoso, inselbergue, 18°46'12"S, 40°26'51"W, 300–600 m elev., 14 Jan 2009 (fl), L. Kollmann et al. 11385 (CEPEC, MBML, RB, UPCB); Mun. Santa Teresa, Serra do Toma Vento, em inselberg, 19°54'29"S, 40°47'44"W, 747 m elev., 26 Aug 2014 (fl), T.M. Machado et al. 673 (BHCB). Minas Gerais: Mun. Teófilo Otoni, afloramento rochoso lado esquerdo da MG-418, cerca de 30 km norte de Teófilo Otoni, 17°51'33"S, 41°15'46"W, 546 m elev., 8 Jan 2011 (fl, fr), L.F.A. de Paula 148 et al. (BHCB); 16 Apr 2011 (fl), L.F.A. de Paula & M. Augsten 247 (BHCB); 17°51'42.1"S, 41°15'54.4"W, 533 m elev., 9 Sep 2011 (fl), L.F.A. de Paula et al. 388 (BHCB); 17°51'45.9"S, 41°16'00.5"W, 450 m elev., 27 Dec 2011 (fl), L.F.A. de Paula et al. 581 (BHCB).
We gratefully thank the curators of the visited herbaria and NYBG for allowing the use of the SEM facility. We are also grateful to Nara F. Mota for facilitating the acquisition of the SEM images, Pedro L. Viana for suggesting the name of the species and to S. Knapp for fruitful insights. Financial support was given to YFG by CNPQ (440610/2015-0), to JRS by FAPEMIG (APQ-04156-15, APQ-03792-16) and CNPq (440610/2015-0, 306086/2017-4) and to LLG by CNPq (427198/2016-0) and FAPESPA/CAPES (Proc. AUXPE 88881.159124/2017-01).
Searchable XLS file of all specimens examined of Solanum hydroides Gouvêa & Giacomin
Data type: species data
Searchable XLS file of all records used to map distributions of Solanum hexandrum Vell. and Solanum sublentum Hiern
Data type: species data