Borreria savannicola E.B. Souza, Nepom. & L.M. Miguel, 2022

Souza, Elnatan Bezerra De, Nepomuceno, Álvaro, Da Costa Ribeiro, Maria Luiza R. & Miguel, Laila Mabel, 2022, Borreria savannicola (Spermacoceae, Rubiaceae), a new species from savanna patches within the Caatinga, Ceará State, Brazil, Phytotaxa 576 (3), pp. 279-288 : 281-286

Borreria savannicola E.B. Souza, Nepom. & L.M. Miguel sp. nov.

Type:— BRAZIL. CEARÁ: Granja , 03°11’11’’S 40°44’35’’W, 50 m, 21 June 2018, fl., fr., E. B. Souza 5313, F. F. Araújo, E. K. S. Brandão & I. V. Nepomuceno (Holotype: EAC!, isotypes CTES!, HUEFS!, HUVA!). ( Figs. 1–5 ) .

Borreria savannicola strongly resembles Borreria scabiosoides Cham. & Schltdl. , but it differs in the erect habit (vs. decumbent), linear and papillose leaves (vs. narrowly elliptic to elliptic and without papillae), terminal glomerule with 4–6(–10) involucral bracts (vs. terminal glomerule with 4 involucral bracts), capsule 5–6 mm long, obovoid (vs. capsule 2–5 mm long, ellipsoid).

Herb to subshrub, erect, (20–)30–40(–100) cm tall; stem simple or with lateral branches, quadrangular to subquadrangular, glabrous, green–yellowish when dry. Leaves pseudo-verticillate, sessile, leaf blades (1.5–)3–5(–10.5) × (0.1–)0.2–0.5(–0.6) cm, linear, acute at apex, attenuate at base, chartaceous, densely papillose above, glabrous below, rarely with papillae on the main nerve abaxially, margins revolute, sometimes with 3 pairs of inconspicuous secondary veins; stipular sheaths (2–) 3–4 mm long, glabrous, with (3–)5–6(–10) fimbriae; fimbriae 1–2.5 mm long, glabrous and collector–tipped. Floral branches trichotomous, mostly with the central axis developed. Inflorescence terminal, sometimes 1 axillary, glomerules hemispherical; involucral bracts 4–6(–10), (1.5–)2–5(–7) × (0.1–)0.2–0.4(–0.5) cm, linear, abaxially puberulous or glabrous on the basal portion, the external pair as long as to three times larger than glomerule diameter. Flower subsessile, pedicel c. 1 mm long; hypanthium 2.5–3 mm long, pubescent in the upper portion; calyx 4–lobed, lobes (1–) 2–3.5 mm long, narrowly triangular, pilose on the margin; corolla 5–6 mm long, infundibuliform, white, external surface glabrous with papillae on the apex of the lobes, sparsely pilose inside the lobes, internal surface with a ring of moniliform hairs in the middle of the tube and scarce hairs on the lobes; stamens exserted, filaments 1.2–1.5 mm long, anthers 1–1.5 mm long, white; pollen grains 8–10 zonocolporate, oblatespheroidal, medium, P= 26.2–28.6 µm, E= 26.3–30.2 µm, short colpi (5–8 µm length) as ectoaperture, endocigulum as endoaperure, exine 1.3–1.5 µm high, tectate–perforate, uniformly spinulate; style 5–6 mm long, stigma bilobed with papillae, nectariferous disk bipartite. Capsule (5–)6 × 1.5–2 mm, obovoid, pubescent on the upper portion, with longitudinal dehiscence splitting into two dehiscent valves. Seeds (1.5–)2.5–3 × 0.5–0.7(–1) mm, ellipsoid, brown, ventral surface with a longitudinal groove covered by a strophiole; exotesta reticulate-foveate. Figures 2 to 4.

Representative specimens examined (paratypes): — BRAZIL. Ceará: Granja, Parada do km 35, 03°09’49’’S, 40°46’32’’W, 40 m, 15 June 2022, fl., fr., E. B . Souza 6443, L. H . X. Portela, J. G . Freitas, R. L. S . Medeiros & A. P . Sousa ( HUVA); margem da CE-362, 03°11’12’’S, 40°44’48’’W, 67 m, 26 June 2019, fl., E. B . Souza 5683 ( CTES, EAC, HUVA); Papagaios, 03°11’11’’S, 40°44’39’’W, 58 m, 26 June 2019, fl. Fr. , E. B . Souza 5709 ( CTES, EAC, HUVA); 03°10’44’’S, 40°45’17’’W, 42 m, 21 June 2018, fl., fr., E. B . Souza 5328, 5341, F. F . Araújo, E. K. S . Brandão & I. V . Nepomuceno ( CTES, EAC, HUEFS, HUVA); idem, 21 May 2015, fl., E. B . Souza 3435, 3468 ( EAC, HUVA); idem, 23 April 2015, fl., E. B . Souza et al. 3404, 3426 ( EAC, HUVA) .

Phenology: —Specimens with flowers were collected in April, May, and June, and specimens with fruits in June.

Distribution and habitat: —This species is known only from the municipality of Granja, Ceará. The geographic distribution of the species is associated with savanna enclaves amidst seasonally dry tropical forests in the Caatinga domain ( Nepomuceno et al. 2021), in the proximity of carnauba palms ( Copernicia prunifera (Mill.) H.E.Moore ), in areas with clay-covered soils, subject to periodic flooding ( Figure 1 ).

Etymology:—The epithet is a reference to the habitat where the new species is found since its occurrence was associated with savanna enclaves in the middle of the Caatinga of northwestern Ceará ( Nepomuceno et al. 2021).

Preliminary conservation status:—The species is known only from the type locality, being represented by only one population, which is not within any protected areas. According to the criteria used by the IUCN (2022), the calculated area of occurrence is 1.401 km ² and the estimated occupancy area is 16.000 km ². Therefore, due to the species occurrence area being fragmented in relation to vegetation, mainly due to human interference and changing climatic conditions, and the number of mature individuals being below 250 in the entire population, in addition to the low rate of mature individuals found, we classified the species as Critically Endangered (CR) ( Figure 1 ).

Remarks: — Borreria savannicola has an affinity with B. scabiosoides , being confused with it mainly by the morphological characteristics of the leaves, inflorescences, and flowers, besides the same habitat preference.

Among the other species of the genus, B. savannicola shares with B. scabiosoides the infundibuliform and white corolla, the bilobed stigma, the ellipsoid seed with a reticulate-foveate exotesta, and even the 8–10 zonocolporate, oblate–spheroidal pollen grains, with tectate–perforate, uniformly spinulate exine. Nevertheless, the new species differs mainly in erect habit, linear leaves, terminal glomerule with up to 10 involucral bracts, and obovoid capsule. These species also coincide in their habitat preference, growing in open areas that are permanently or periodically flooded. B. scabiosoides is widely distributed in the Americas, from Cuba to Bolivia and Brazil ( Cabral et al. 2011, Miguel & Cabral 2013).

Borreria savannicola is anatomically distinct from B. scabiosoides by the presence of lamellar collenchyma in the stem ( Figure 5B ). On the other hand, the latter was characterized by angular collenchyma in the stem ( Figure 5E )., a pattern also observed in B. latifolia and B. orientalis analyzed by Zini et al. (2016). Another striking aspect of Borreria savannicola are the papillae on the adaxial surface of the leaves, a feature that was observed in Galianthe palustris (Cham. & Schltdl.) Cabaña Fader & E.L. Cabral [= B. palustris ] ( Zini et al. 2016). Borreria savannicola papillae have thick and ornamented cuticle and, according to Dickson (2000), such characteristics can help to reduce the temperature, reflecting the radiation. Besides the papillae, idioblasts containing raphides and tannin were observed, these substances having two important functions in plants that grow in regions with high insolation levels, such as in the Caatinga biome: 1. protects from intense lighting, acting as a sunscreen, and 2. are unpalatable, creating a barrier to herbivory ( Rôças et al. 1997; Barros & Soares 2013). Other anatomical features that separate the two species can be seen in Table 1 .

Figures

FIGURE 1. Geographic location and AOO and EOO of Borreria savannicola.

FIGURE 2. Borreria savannicola. A. Vegetation of the locality. B. Stipule. C. Branch with glomerule and stipule. D.–E. Detail of the glomerule and insect landing on the glomerule. F. Glomerule with fruits, view from below. G. Glomerule with fruits, view from above. Photos: E.B. Souza.

FIGURE 3. Borreria savannicola. A. Floral branch. B. Stipular sheath. C. Flower. D. Opened corolla. E. Hypanthium, calyx, style, and stigma. F. Capsule. G. Seed in ventral view. H. Seed in dorsal view. Illustration: L. Simón.

FIGURE 4. Microphotography of Borreria savannicola. A–C. Flower: A. Open bud. B. Open corolla. C. Detail of the stigma. D– E. Fruit: D. Capsule. E. Dehiscence valve in ventral view. F–H. Seed: F. Dorsal view. G. Ventral view. H. Detail of the exotestal. I– M. Pollengrain: I. Equatorialview. J. Polarview. K. Insideofpollengrain,detailofendoaperture. L. Exinebetweenectoaperture. M. Exine in polar view. Scale bars in each image.

FIGURE 5. Anatomical features. Stem: A–C. Borreria savannicola. A. Showing stomata. B. Lamellar collenchyma. C. Vascular system respectively. D–F. Borreria scabiosoides. D. Stipular colleter showing raphides. E. Stem with angular collenchyma. F. Vascular system with cambium. Leaf blade: G–J. Borreria savannicola. G. Shows the midrib. H. Papillae. I. Phenolic idioblasts. J. Stomata. L–O. Borreria scabiosoides. L. Showing the midrib. M. The stomata and substomatic chambers. N. The spongy parenchyma with braciform cells. Arrow = raphides, LC = lamellar collenchyma, AC = angular collenchyma, PH = phloem and XY = xylem, Bar = 100µm in A, B, D and E, 200 µm in C, F and O and 400 µm in G, H and I.