Hohenbergia densa B.P. Cavalcante, 2021

Cavalcante, Brayan Paiva & Silva, Maciel Florêncio Da, 2021, Hohenbergia densa (Bromeliaceae), a new species from Rio Grande do Norte, Brazil, Phytotaxa 520 (2), pp. 203-208 : 204-207

Hohenbergia densa B.P. Cavalcante , spec. nov. ( Figs. 1–3 )

Hohenbergia densa is closely related to H. flava , but differs by its smaller size when flowering (ca. 70 cm vs. ca. 130 cm), narrow rosette (ca. 60 cm vs. 90 cm diam.), primary bracts exceeding the basal branches (vs. shorter than the basal branches), smaller inflorescence (ca. 40 cm vs. 70–110 cm long), stipes of the primary branches longer (up to 5 cm vs. less than 2 cm), short-stipitate secondary branches (vs. absent or nearly none), larger spikes (ca. 7 cm vs. 3–5 cm) and flowers (ca. 2.2 cm vs. 1.5 cm), floral bracts shorter than the sepals (vs. distinctly exceeding the sepals) and dark-purple petals (vs. yellow petals).

Type:— BRAZIL. Rio Grande do Norte. Espírito Santo. Arredores da Mata do pilão, Caatinga aberta próximo das trilhas que levam para gameleira, 6°23’40.0”S 35°17’19.0”W, 36 m. s.m. elev., 09 Feb. 2021, B. P . Cavalcante 102 (Holotype UFRN26874 !) .

Plants 60–90 cm tall when flowering, terrestrial, heliophyte or rarely growing at the forest edges, reproducing by basal shoots, grouped in clumps of a few rosettes 50–70 cm in diam., with a great capacity to impound water. Leaves 30–45 cm long, more than 15 in number, yellowish, lustrous and inconspicuously white-lepidote abaxially; sheath 10–13 cm × ca. 13 cm, elliptic, coriaceous, margins entire, dark-brown on both surfaces, lepidote; blade 20–35 × 6–9 cm, lanceolate, slightly arcuate, inconspicuously lepidote abaxially only, with spinescence margins, with an acuminate and erect pungent apex, apical mucro ca. 1 cm long, dark brown; spines black, rigid, ca. 0.7 cm long. Peduncle 20–45 long, ca. 1 cm in diam., light-red, erect, not completely concealed by the peduncle bracts, densely white-lanate; peduncle bracts 5–9 cm long, light brown, densely white-lanate, lanceolate, margins entire, apex pungent, chartaceous, not imbricate, surpassing the internodes. Inflorescence (fertile portion), twice-branched, 20–40 cm long, 19–25 cm wide at the base, erect, sub-cylindrical, with erect to patent branches, light-red, covered by a dense white-lanate indument; primary bracts 12–16 cm long, lanceolate, margins entire, light-brown, strongly nerved, exceeding the basal branches; primary branches 8–12 cm long, elongate with short and erect to patent stipe; stipe of the primary branches 2–5 cm long, light-red, erect, covered by a white-lanate indument; secondary branches (spikes) 6–7 cm × ca. 2 cm, elongate, stipe short; stipes 0.5–1.5 cm long, light-red, erect, covered by a white-lanate indument; floral bracts ca. 1.4 × 1.3 cm, green with a pink apex, triangular with a prominent mucronate apex, nerved, shorter than the sepals; flowers diurnal (4 am–15 pm) and with a sweet fragrance, 1.9–2.1 cm long, flattened adaxially, corolla sub-tubular; sepals 10–12 × 11–13 mm, green, ovate-triangular, asymmetrical, with an one sided extended margin (marginal wing), apex acute, densely white-lanate indument in the apex; petals 17–19 × 7–8 mm long, dark-purple, spathulate, apex broadly rounded then obtuse to acute, sub-erect, bearing 2 appendages; appendages ca. 2 mm long, lacerate, situated in the basal third of the petals; stamens 14–15 mm long, white, included in the corolla, exceeding the gynoecium; ovary 2–3 mm long, ovoid-triangular; ovules numerous, with a prominent chalazal appendage; style 13–14 mm long, white, erect; stigma conduplicate-spiral; fruit ca. 1.7 cm long, blue when ripe; seeds ca. 2 mm long, ellipsoid and dark-brown.

Examined material: — Brazil, Rio Grande do Norte : São Tomé, próximo à rodovia RN – 203, Caatinga aberta. 5°59’43.0”S 36°02’27.0”W, 9 February 2021, B. P . Cavalcante 103 ( UFRN26875 ! Paratype). Rio Grande do Norte: entre Rio de Fogo e Zumbi, Praia de Zumbi , Mata de tabuleiros (ou restinga). 20 Aug. 1998, C . Martinelli 15075 & T . Barbará, J. A . Medeiros Neto ( RB 341729). Rio Grande do Norte: Espírito Santo, Próximo a rodovia, estrada que leva a Mata do Pilão. Fev. 2021, B. P . Cavalcante 101 ( UFRN26873 !). Rio Grande do Norte , Monte das Gameleiras próximo ao portal de entrada da sede municipal. 21 Dec. 2015, Tomaz 96, ( UFRN18232 !). Rio Grande do Norte, Monte das Gameleiras, embasamento do embasamento cristalino. 30 Dec. 2016, G. S . Garcia 452 ( UFRN22954 !). Rio Grande do Norte, Natal, Parque da Cidade Dom Nivaldo Monte. 29 Jun. 2015, A. A . Roque 1659 ( UFRN20243 !) .

Etymology:— The specific epithet “densa” refers to the aspect of the plant, that commonly is seen as a short and robust plant, with a denser inflorescence and primary branches than other Caatinga-endemic species.

Distribution and habitat: — Hohenbergia densa was found in fully sun exposed sandy soils or close to the forest edges, in Caatinga forest or in transitional areas between Caatinga and Atlantic forest. Plants of this species can be seen in Caatinga of almost all southern part of Rio Grande do Norte state, associate with others bromeliads, like Wittmackia patentissima Mez (1891: 278) and Encholirium spectabile Schultes & Schultes (1830: 1233) . It is commonly seen growing in sympatry with E. spectabile , and they share many ecological traits (except the rupiculous habit of E. spectabile ) in the dry vegetation of Rio Grande do Norte.

Phenology:— Hohenbergia densa has been found flowering in the rainy season, between November and February.

Conservation status: — The species is only known for the Caatinga vegetation of the Rio Grande do Norte state. The region suffers constantly by fires, both caused by dry weather as well as human activity (burning for cattle forage of these areas is common). Nevertheless, the species occurs in a vast area, and by plotting its knowing occurrences in Geocat software (geocat.kew.org), the estimated extent of occurrence (EOO) is 25,636.338 km ², and the area of occupancy (AOO) is 52.000 km ², evaluating this species as Near Threatened (NT C2ab (ii)).

Observations: — Hohenbergia densa is the smallest member of the H. catingae group, sharing many traits with H. flava , and with H. catingae , such as the funnelform rosette with lanceolate leaf blade, the reddish inflorescence, the elongate spikes and the sharp mucronate floral bract apex, plus the occurrence in dry environments. Hohenbergia densa can be easily recognized ( Tab. 1) and distinguished from close relatives by its, narrow rosette (ca. 70 cm diam. vs. 80–110 cm in H. flava and 90–150 cm in H. catingae ), the smaller inflorescence (20–40 × 19–25 cm vs. 70–110 × 12–28 cm in H. flava and 80–100 × 35–50 cm in H. catingae ) and by the dark-purpled petals (vs. yellow in H. flava and light-lilac in H. catingae ). Another species that can be confused with H. densa is H. horrida Harms (1935: 525) , but H. densa can be distinguished from it by its smaller size (60–90 × 50–70 cm vs. 70–100 × 80–100 cm in H. horrida ), wider leaf blade (8 cm vs. ca. 4 cm), smaller (30 × 22 cm vs. 70 × 44 cm) reddish inflorescence (vs. whitish), and erect petals at anthesis (vs. reflexed) ( Tab. 1).

Furthermore, Hohenbergia densa can be mistaken for H. ridleyi , that can be seen growing close to the occurrence area of this species, but only inside the forest and presenting a lax-pyramidal inflorescence with lilac and reflexed petals. However, Hohenbergia densa has shorter leaves (30–45 vs. 70–120 cm long), acuminate and erect leaf apex (vs. cuspidate and reflexed), smaller inflorescence (20–40 × 19–25 cm vs. 100–130 × 40–70 cm) with the primary bracts exceeding the branches (vs. shorter than the branches), elongate spikes (vs. short and slightly globose) and by the erect petals (vs. reflexed) that conceal the gynoecium and androecium (vs. exposed them) ( Tab. 1).

Figures

FIGURE 1. Geographic distribution of Hohenbergia densa (red circles) and the type of vegetations that the new species inhabits.

FIGURE 2. Hohenbergia densa; A. Flowering plant; B. Detail of the inflorescence, showing the short stipitate branches with the primary bracts exceeding them; C. Primary bracts partly covering the basal branches; D. Primary branch; E. Primary branch with flowers at anthesis.

FIGURE 3. Hohenbergia densa. A. Habit; B. Primary branch; C. Flower. D. Longitudinal section of a flower showing the relative height of the anthers and gynoecium. E. Sepal. F. Petal with the ligules and an anther. G. Lateral view of an anther. Drawing by Brayan Paiva Cavalcante.