Solanum adamantium Gouvea

Gouvêa, Yuri & Stehmann, João, 2019, Solanum adamantium (Solanaceae), a New Narrowly Endemic Species from a Diamondiferous Region of the Espinhaço Range in Minas Gerais State, Brazil, Systematic Botany 44 (4), pp. 923-929 : 923-928

Solanum adamantium Gouvea ˆ, sp. nov. T

YPE: BRAZIL. Minas Gerais: Mun . Gr~ ao Mogol , próximo à Praia do Vau, trecho final da trilha que leva do fim da rua Hilário Marinho à Praia do Vau, crescendo em solo arenoso à margem da trilha, 16°35, 13̎S, 42°53, 32̎W, 667 m, Jan 2018 (fl, fr), Y.F Gouvˆea & I.F. Gouvea ˆ254 (holotype: BHCB! [ BHCB189841 ]; isotypes: RB, HUEFS).

This new species differs from S. thomasiifolium in its branched inflorescences (vs. unbranched inflorescences in S. thomasiifolium ), in its adaxial leaf surface indumentum composed exclusively of stellate-glandular trichomes (vs. adaxial leaf surface indumentum composed of both simple- and stellate-glandular trichomes in S. thomasiifolium ) and in its corolla completely lacking interpetalar tissue (vs. corollas with

conspicuous interpetalar tissue in S. thomasiifolium ); also differs from S. buddleiifolium in its branched inflorescences (vs. unbranched inflorescences in S. buddleiifolium ), in its erect fruiting pedicels that hold the fruits upward (vs. pendent fruits in S. buddleiifolium ).

Shrubs to slender treelets up to 4 m, erect, unbranched to few-branched when young, older plants moderately- to much-

branched. Young stems terete, pale green to greenish pale yellow, densely tomentose with hyaline to ochraceous stellateglandular trichomes, the epidermis not to barely visible, the trichomes sessile to short-stalked with multiseriate stalks up to 0.65 mm long, 2–4 cells wide, the rays 7–15, porrect to multiradiate, usually eglandular and 1-celled, 2–3-celled when glandular, sometimes with an early deciduous capitate glandular distal cell, the midpoint 3–4-celled, equal or shorter than the rays, the distal cell always glandular, usually persistent; stems moderately to densely armed with flattened prickles up to 1 cm long and to 3.3 mm wide at base, straight, golden to ferruginous; bark of older stems dark grey. Sympodial units plurifoliate, the leaves not geminate. Leaves simple, lobed, 5–19.5 cm long, 2–13 cm wide, the blade lanceolate, chartaceous, slightly discolorous, green to light green adaxially, lighter green abaxially; adaxial surface densely tomentose with hyaline to ochraceous stellate-glandular trichomes, always visible, the trichomes sessile to short-stalked with multiseriate stalks up to 0.5 mm long, 3–8 cells wide, the rays 5–20, antrorse to multiangulate, the eglandular rays usually longer and 1-celled, the glandular rays usually shorter and 2–3-celled, these often deciduous, the midpoints 3-celled, slightly shorter to slightly longer than the rays; the abaxial surface densely tomentose (a little denser than the adaxial) with the epidermis usually barely visible, the trichomes like those of the adaxial surface; sparsely armed along the midrib and the primary veins of both surfaces with straight, laterally compressed prickles reaching up to 6.2 mm long and to 0.9 mm wide at the base; primary veins 6–8 pairs; base slightly cordate to rounded or obtuse, strongly asymmetric to symmetric, not decurrent onto the petiole; margins irregularly lobed to nearly serrate, usually with secondary lobes, the lobes up to 2 cm long and to 3.5 cm wide at base, acute or less often rounded at the apex; apex acute, rarely narrowly rounded; petiole 0.7–5(–7.4) cm, densely tomentose with trichomes like those of the stem, sparsely to moderately armed. Inflorescence a branched cyme, erect, furcate, less often trifurcate (unbranched inflorescence may be occasionally produced among the branched ones on the same shoot), terminal, becoming internodal (lateral) by the subsequent sympodial unit’ s development, the axis densely tomentose with trichomes like those of the stem, unarmed to densely armed, the prickles straight; the peduncles (0.7) 1–3.7 cm long; the rachis (1.2) 1.7–9.4 cm long; with 8–60 flowers (4–30 per rachis), up to 6 flowers open at the same time (3 per rachis); pedicel insertion points 0–1.8 cm apart, becoming more closely spaced towards the inflorescence’ s apex; pedicels 4–8.4 mm long in open flowers, straight, articulated at base, unarmed or sparsely armed with minute prickles, densely tomentose with trichomes like those of the stem, the epidermis usually purple. Flowers 5-merous, the plants andromonoecious, producing hermaphroditic flowers (longstyled) and functionally male short-styled flowers, which vary in proportion (number of long- vs short-styled flowers) between inflorescences, with the proximal flowers usually longstyled and the distal ones short-styled. Calyx obconic, green to purple, unarmed, densely tomentose with the epidermis usually visible, the trichomes like those of the stems; the calyx tube 0.6–1.9 mm long, 1.9–2.5 mm in diameter at the widest point, the lobes 0.8–2 mm long, 0.7–1.5 mm wide at the base, triangular, the apices acuminate and usually slightly attenuate. Corolla (0.8) 1.5–2.2 cm in diameter, lilac to whitish lilac with the midvein purple, deeply stellate, slightly to markedly zygomorphic, with the three upper lobes closer to each other

than to the two lower ones, lobed 2/3 to 3/4 of its length, the sinuses deeper between the 3 upper and 2 lower lobes, interpetalar tissue absent, the tube 2–4.7 mm long, the lobes (3.1) 6–8 mm long, (1.8) 2.5–4 mm wide, narrowly triangular to nearly oblong or lanceolate, the apex acuminate to acute, densely to moderately tomentose abaxially with trichomes like those of the stems, glabrescent adaxially with some scattered trichomes near the apex and/or on the midvein. Stamens equal or slightly unequal, with 1–3 stamens slightly longer than the others; free portion of the filaments 1–2 mm long, glabrous; anthers (4.1)7.5– 6.5 mm long, 1–1.5 mm wide, 0.8–1.1 mm thick at the widest point, lanceolate, narrowed towards the apex, sagittate at base, connivent, poricidal at the tips, the pores about the same diameter as the anther apices, not lengthening with age, the epidermis smooth. Ovary cupuliform, 2-locular, densely pubescent with simple glandular trichomes mixed with some poorly developed, usually 1–3-rayed, stellate trichomes, these glandular or not; style 6.5–10 mm long in long-styled flowers, 1.2–2.3 mm long in short-styled flowers, cylindrical, sparsely to moderately puberulent with the same trichomes as those of the ovary; stigma clavate, up to 0.4 mm long in long-styled flowers, papillose, green when fresh. Fruit a globose berry, 7.2–9 mm long and 7.6–9.8 mm wide when mature, the pericarp smooth, marbled dark green and green when immature, reddish orange at maturity, moderately and evenly puberulent with short simple glandular trichomes all over the mature fruit surface; fruiting pedicels 5–7.3 mm long, unarmed or sparsely and minutely armed; fruiting calyx not accrescent, the tube 0.9–1.2 mm long and 3.9–5 mm in diameter at the widest point, the lobes 1.8–4 mm long, 1.2–2.1 mm wide at base. Seeds ca. 4–12 per berry, ca. 2.7–3.2 mm long, 3.4–4.3 mm wide, 0.9–1.5 mm thick, reniform, beige. Chromosome number: Not known. Figure 1 .

Distribution —This new species is endemic to the Gr~ ao Mogol range, part of the northern portion of the Minas Gerais State’ s Espinhaço range ( Fig. 2 ). Solanum adamantium occurs at elevations ranging from 650 to ca. 1000 m.

Ecology and Habitat — Solanum adamantium grows on and among rocks in high elevation quartzite/sandstone rocky fields (i.e. campo rupestre vegetation), and in nutrient-poor sandy soils associated with them, which also extend towards and along the lower lands of the Itacambiruçu river valley (See Pirani et al. 2003 for more details on the geography and the floristic composition of Gr~ ao Mogol’ s region). The campos rupestres are characterized, besides the strictly edaphic component, by extreme environmental conditions (i.e. hydric restriction, high solar radiation, wide daily temperature range, high elevation, and continuous exposure to winds; Giulietti et al. 1997; Rapini et al. 2008) to which this kind of vegetation is subjected. These conditions seem to have led to morphological convergences among the unrelated species inhabiting it (e.g. reduced and/or imbricate leaves usually restricted to the branch tips; see Giulietti et al. 1987), which are also observed in S. adamantium , S. buddleiifolium , and S. thomasiifolium . Like many ‘spiny’ Solanum species, however, S. adamantium can grow in, and colonize, somewhat disturbed and unstable sites, which is where several specimens were observed by the first author during fieldwork. Its flowers have morphologically adapted anthers for buzz pollination (i.e. anthers dehiscing by apical pores; Fig. 1E ) by vibrating bees, as in most Solanum species. The marked zygomorphy displayed by the corollas of older individuals of S. adamantium ( Fig. 1E ) is relatively rare in Solanum ( Knapp 2002; Bohs et al. 2007), especially among

Brazilian species. This unusual corolla shape (i.e. bilateral symmetry) may reflect a more specific plant-pollinator interaction (see Fenster et al. 2004), but it requires further study. The reddish orange colour of the S. adamantium fruits ( Fig. 1F ), together with the absence of scent and the permanent attachment suggest that its primary dispersal agents are birds (ornithochory; Van der Pijl 1972), which requires further investigation to be confirmed.

Phenology —Flowering specimens were found from December to October, indicating that S. adamantium may bloom and fruit year-round.

Etymology —The epithet adamantium is derived from the Latin “adamas,” meaning diamond; a reference to the history of the Minas Gerais State and the region of Gr~ ao Mogol (where the world’ s first extraction of diamonds from rocks was recorded; Karfunkel et al. 1994; Chaves et al. 2009), which are marked by the presence of this mineral.

Preliminary Conservation Status —We propose that if a formal conservation assessment were prepared and submitted to the IUCN, that this species would be classified as Endangered (EN) given its Extent of occurrence (EOO) of 24.5 km 2, and area of occupancy (AOO) of 24 km 2 ( IUCN 2017). The extremely narrow EOO of S. adamantium suggests that it might merit the status of CR. However, this is tempered by the incipient nature of our knowledge about this species (especially regarding the extent of its range), its ability to grow in somewhat disturbed sites, as well as the existence of the Parque Estadual de Gr~ ao Mogol.

Notes — Solanum adamantium shares ecological and morphological features with S. buddleiifolium and S. thomasiifolium , which in Stern et al. (2011) were resolved as sisters in one of the two lineages composing the poorly known Thomasiifolium clade. Both S. adamantium and S. buddleiifolium have narrower distributions, growing exclusively on rocks and in sandy soils of the elevated quartzite/sandstone rocky fields lying along the Espinhaço range. Solanum thomasiifolium , on the other hand, is more widely distributed, and also occurs (in a disjunct manner in relation to its Espinhaço range’ s populations) in the open vegetation of the sandy coastal lowlands (i.e. restinga; Araújo 1992). Despite sharing similar habitat preferences, these species were not found in sympatry thus far.

The morphological characters common to these three species seem to be related to the colonization of such extreme habitats (see Ecology and Habitat): small leaves restricted to the branch apices, short internodes, older stems with a nonphotosynthetic lignified bark up to the most proximal leaf, and densely indumented stems and leaves (see Figs. 1 , 3 ). These characteristics become more conspicuous with the plant’ s age, making species identification easier ( Figs. 1B , 3B ). Despite their overall similarity in the earlier stages of development, when in the reproductive phase, S. adamantium can be readily distinguished from S. buddleiifolium and S. thomasiifolium by having distinctive branched inflorescences rather than unbranched inflorescences (compare Figs. 1C, F , 3E, F ).

Solanum adamantium mostly resembles S. thomasiifolium , with which it shares glandular indumentum ( Figs. 1G , 3H ), somewhat cordate leaf bases, an erect inflorescence axis (even when fruiting), and erect fruiting pedicels holding the fruits upwards ( Figs. 1F , 3F ). However, in S. adamantium the leaves are not imbricate ( Fig. 1B ); the leaf blades are lanceolate, and covered exclusively by stellate-glandular trichomes ( Figs. 1B, G ); the corollas completely lack interpetalar tissue and are markedly zygomorphic ( Fig. 1E ); and the fruiting calyces

are inconspicuously accrescent. In S. thomasiifolium the leaves are imbricate with relatively short petioles, which give it a sessile appearance (mainly in older plants; Fig. 3F ); the leaf blades are cordate and covered in simple- and stellateglandular trichomes and simple-eglandular ones (the latter less conspicuous; Fig. 3H ); the corollas possess developed interpetalar tissue and are actinomorphic or slightly zygomorphic ( Fig. 3D ); and the fruiting calyces are conspicuously accrescent (up to ¾ of the fruit length).

Throughout the development of S. adamantium , the produced leaves gradually develop to a smaller size, making older specimens more similar to S. buddleiifolium in overall appearance ( Fig. 1B ). But S. adamantium can be recognized, in addition to the characters mentioned in the diagnosis, by its strongly glandular indumentum ( Fig. 1G ), while in S. buddleiifolium the indumentum is eglandular ( Fig. 3G ), or rarely with some glandular-stellate trichomes mixed with the eglandular-stellate trichomes, which are the vast majority.

Additional Specimens Examined— Brazil. — MINAS GERAIS: Mun. Gr~ ao Mogol, Córrego da Escurinha, campo arenoso, 16°35’S, 42°57’W, 750 m elev., 29 May 1988 (fl), A. Bidá et al. proj. C. F. C. R. 12102 ( RB!, SPF!); campo rupestre com abundancia ˆde arenito próximo de Grao~ Mogol, 12 April 1981 (fl), A. Furlan et al. proj. C. F. C. R. 750 ( RB!, SPF!); ca. 7 km à direçao~ sul da cidade, na estrada para Francisco Sá, campo rupestre/cerrado, afloramento de arenito e areia branca, 16°37’S, 42°56’W, 700–850 m elev., 15 October 1988 (fr), R. M. Harley et al. 25034 ( BM!); rua Hilário Marinho, campo rupestre cercado (loteamento) próximo ao fim da rua, crescendo em substrato acumulado sobre/entre rochas em campo rupestre onde houve supress~ ao da vegetaç~ ao, 16°34, 32̎ S, 42°53, 29̎ W, 785 m elev., January 2018 (fl, fr), Y. F. Gouvˆea & I. F. Gouvea ˆ255 ( BHCB!); interspread with wet rocky campo, ca. 8 km West of Gr~ ao Mogol, 950 m elev., 16 February 1969 (fl, fr), H. S. Irwin et al. 23368 ( HUEFS!, MO); Serra do Jambreiro, próximo ao Rio Itacambiruçu, 900 m elev., 10 May 1979 (fl, fr), H. C. de Lima et al. 995 ( BHCB!, JPB!, RB!); Trilha da Tropa, 16°33, 04̎ S, 42°54, 00̎ W, 990 m elev., 6 July 2007 (fl, fr), F. Marino et al. 288 ( BHCB!); escarpas à direita do Riacho Ribeir~ ao, 960 m elev., 21 May 1987 (fl), R. Mello-Silva & J. R. Pirani proj. C. F. C. R. 10772 ( BHCB!, HUEFS!); Vale do Rio Itacambiruçu, 4 September 1985 (fl, fr), R. Mello Silva et al. proj. C. F. C. R. 8342 ( BHCB!, SPF!); Jambreiro, margem direita da BR-251 (Gr~ ao Mogol – Montes Claros), área de extraç~ ao de quartzito, 687 m elev., 5 July 2011 (fl, fr), N. F. O Mota & C. N. Fraga 2275 ( BHCB!); Vale do rio Itacambiruçu, solo arenoso fino com rochas, ca. 16°36’S, 42°55’W, ca. 650 m elev., 12 December 1989 (fl, fr), J. R. Pirani et al. proj. C. F. C. R. 12563 ( BHCB!, SPF!); Estrada Grao~ Mogol – Cristália, ca. 6 km de Grao~ Mogol, campos rupestres com elementos de caatinga, 16°35, 47̎ S, 42°54, 05̎ W, ca. 650 m elev., 11 July 2001 (fl, fr), V. C. Souza et al.25675 ( ESA, RB!).

Figures

FIG. 1. Type collection of Solanum adamantium (Y.F. Gouvˆea & I.F. Gouvˆea 254, BHCB). A. Plant habit; note the difference in leaf size between the older shoots (left arrow) and a resprout shoot (right arrow). Inset left side: detail of a young plant. B. Branches; note the difference in leaf size and shape between young (left) and older (right) plants. Inset upper left corner:old stem;bottom right corner:young stem.C.Inflorescence; note that it is branched. D.Flowering calyx. E. Short-styled flower, frontal view; note the zygomorphic shape of its corolla. F. Infructescence with mature fruits. G. Infructescence with immature fruits. H. Indumentum of the adaxial leaf surface (upper right corner: detail of the trichome type composing its indumentum; arrow = glandular midpoint). Scale bars: H = 1 mm (inset upper right corner = 200 µm). Photographs by Y. F. Gouvˆea.

FIG. 2. Distribution of Solanum adamantium.

FIG.3. Distinctive characters of the species morphologically related to S.adamantium [A, C, E, G:S. buddleiifolium (Y.F.Gouvˆea and I.F.Gouvˆea 258, BHCB); B, D, F, H: S. thomasiifolium (Y.F. Gouvˆea 287, BHCB)]. A. Habit and habitat. B. Habit of an old plant and its habitat. Inset upper left corner: young plant; note the overall differences between young and old plants. C. Short-styled flower. D. Short- and long-styled flowers. E. Infructescence with immature fruits (upper left corner: infructescence with a nearly mature fruit); note the pendent fruits. F. Infructescence with both mature (red) and immature fruits; note the erect fruits.G.Indumentum of the adaxial surface (upper right corner:detail of the eglandular-stellate trichomes composing the indumentum).H.Indumentum of the adaxial surface (upper right corner: detail of the trichomes type composing the indumentum; left arrow: simple eglandular trichome; middle arrow:glandularstellate trichome; right arrow: simple-glandular trichome). Scale bars: G, H = 1 mm (insets upper right corner = 350 µm). Photographs by Y.F. Gouvˆea.