Euphorbia sobolifera O.L.M.Silva & P.J.Braun

Silva, Otávio Luis Marques da, Braun, Pierre, Riina, Ricarda & Cordeiro, Inês, 2021, Three new species of Euphorbia subgenus Chamaesyce (Euphorbiaceae) endemic to Brazil, European Journal of Taxonomy 733, pp. 72-86 : 78-79

Euphorbia sobolifera O.L.M.Silva & P.J.Braun sp. nov.

urn:lsid:ipni.org:names:77214815-1

Figs 2 , 4

Diagnosis

Euphorbia sobolifera O.L.M.Silva & P.J.Braun sp. nov. is similar to E. appariciana Rizzini , but differs in being dioecious, decumbent and having soboliferous growth, with stems reaching up to 2 m long.

Type

BRAZIL • Bahia, Serra do Tombador ; 11°3′4.5″ S, 40°39′22.8″ W; 911 m a.s.l.; 11 Aug. 2019; B.G. Brito 11; holotype: SP; isotypes: HUEFS, SPF, RB .

Etymology

The epithet refers to the soboliferous growth form of the species: when a stem becomes decumbent and reaches the soil, it starts branching and eventually roots. This allows E. sobolifera sp. nov. to form dense colonies in the rocky outcrops where it grows ( Fig. 4B ).

Description

Decumbent dioecious shrubs, branches reaching up to 2 m long; underground system much branched; latex white. Stems slightly 6-costate, whorled branched, green to slightly reddish at the apex, glabrous, soboliferous. Leaves opposite, deciduous, subsessile (petioles reaching up to 1 mm long); stipules lateral and glanduliform, globose, inconspicuous (up to 1 mm long); leaf blade membranaceous, glabrous on both surfaces, concolorous, elliptic, narrow-elliptic or oblong, (0.5–)1–1.5(–2) × 0.1–0.5 cm, base attenuate, margin entire, apex cuspidate, venation hyphodromous. Cyathia solitary and sessile (pistillate) or glomerulate and subsessile (staminate), terminal; peduncle up to 1 mm long, glabrous; cyathophylls opposite, sessile, wide-elliptic to triangular, 1.0–1.5 × 0.5–0.8 mm, with 2(3) pairs of lateral colleters at the base, chartaceous, glabrous on both surfaces, persistent, base truncate, margin entire, apex cuspidate, venation hyphodromous; involucre campanulate, 1.5–2.5 × 1.5–2.5 mm, actinomorphic, glabrous on the outer surface; involucral lobes triangular, pale to greenish, margin fimbriate, with simple trichomes; cyathial glands 5(6), yellow, transversely elliptic, punctate, glabrous, 0.5–1.0 × 1.5–2.0(–2.5) mm; short crenulate white appendages. Staminate cyathia: staminate flowers 20–30, arranged in 5 cincinni with 4–6 flowers each; bracteoles lanceolate, ciliate; pedicels up to 1.0 mm long, filaments up to 0.5 mm long, anthers ca 1 mm wide, dorsifixed, extrorse, transversely dehiscent; pistillate flowers reduced to a pistillode, ca 0.5 mm long, with three inconspicuous styles that never exceed the involucre rim of the cyathia. Pistillate cyathia: staminate flowers atrophied and not exceeding involucre rim of the cyathia; pistillate flowers ca 2 mm long; pedicel up to 0.5 mm long; ovary globose, ca 0.5 × 0.5 mm, glabrous; styles 3, up to 1 mm long when fully developed, free at the base, bifid for half their length and revolute at the apex. Capsules 3-lobed, subglobose, 2–3 × 3–4 mm (immature), glabrous, green; pedicel shortly accrescent, reaching up to 2 mm long (immature fruit); columella and seeds not seen.

Distribution, ecology and phenology

Euphorbia sobolifera sp. nov. grows in open vegetation on sandstone outcrops ( Fig. 4A ) in the Serra do Tombador, near the Jacobina Municipality, in the northern portion of the Chapada Diamantina complex in Bahia State, within the Caatinga domain ( Fig. 2 ). The species was collected during the dry season (August) with immature fruits, but individuals cultivated in the S„o Paulo Botanical Garden have been producing cyathia throughout the year, although we could not make them produce viable fruits.

Provisional conservation status

Euphorbia sobolifera sp. nov. is only known from a single locality ( Fig. 2 ), with AOO <10 km ² and EOO <100 km ², and its habitat is subjected to continuing decline in area, extent and quality. We suggest that it should be classified as Critically Endangered (CR; B2ab[iii]).

Figures

Fig. 2. Geographical distribution ofEuphorbia blepharadena O.L.M.Silva & Cordeiro sp. nov. (triangle), E. longipedunculata O.L.M.Silva & Riina sp. nov. (star) and E. sobolifera O.L.M.Silva & P.J.Braun sp. nov. (square).

Fig. 4. Euphorbia sobolifera O.L.M.Silva & P.J.Braun sp. nov. A. Habitat. B. Habit. C. Portion of a branch producing soboles. D. Apical portion of branches with reduced opposite leaves. E. Detail of a node with opposite leaves. F. Cyathium showing one of the cyathophylls bearing colleters on its margin (arrows). G. Detail of a cyathium showing an involucre lobe (arrow). H. Grouped staminate cyathia. I. Solitary pistillate cyathium. J. Detail of a pistillate cyathium showing the pistillate flower. K. Immature fruit. L. Staminate cyathium opened, showing staminate cymules, bracteoles and a central pistillode. M. Pistillate cyathium opened, showing poorly developed staminate flowers and bracteoles. Photos: A–B: P.J. Braun in the field; C–K: O.L.M. Silva; L–M: Illustrations of plants cultivated at the Instituto de Botânica by Klei Souza.