Senna hatschbachii, Souto, Flávio Sousa, Queiroz, Rubens Teixeira De & Agra, Maria De Fátima, 2025

Souto, Flávio Sousa, Queiroz, Rubens Teixeira De & Agra, Maria De Fátima, 2025, Senna hatschbachii (Leguminosae, Caesalpinioideae): a newly discovered endangered species from the Brazilian Atlantic Forest, Phytotaxa 702 (1), pp. 61-71 : 63-66

Senna hatschbachii F.S. Souto & Agra, sp. nov. ( Fig. 1 )

Diagnostic characters: Senna hatschbachii is morphologically similar to Senna multijuga var. lindleyana , but can be distinguished by having linear stipules (≤ 0.1 mm wide), a subulate extrafloral nectary, and leaves with 6–13 pairs of leaflets. In contrast, Senna multijuga var. lindleyana features setiform stipules 0.2–0.4 mm wide, ovoid to narrow ovoid extrafloral nectaries, and leaves with 15–46 pairs of leaflets.

Type: — BRAZIL. Paraná: Primeiro de Maio, Fazenda Santa Rosa, 15 March 2002 (fl), O. C. Pavão s.n. (holotype: MBM 270076 ; isotypes: ESA 080344 , FUEL! 31714, FURB! 10031). Holotype image available at: https://specieslink.net/rec/40/270076

Shrub, ca. 5–15 m tall; branches cylindrical, striated, lenticelate, brown, glabrescent to viscid-tomentulose. Stipules 5.6–7 × ca. 0.1 mm, linear, glabrescent, caducous. Leaves 13.6–20.2 cm long, alternate-spirals; petiole 1.5–3.3 cm long, cylindrical, adaxially sulcate, glabrescent to viscid-tomentulose; rachis 6.2–15.4 cm long, cylindrical, adaxially sulcate, glabrescent to viscid-tomentulose; interleaflet segments 6.9–13.2 mm long; one extrafloral nectary between the first pair of leaflets, 1.5–2.4 mm long, subulate, sessile to sub-sessile, blackish, glabrous; leaflets 6–13 pairs, 17.4–32.7 × 6.5–11.6 mm, oblong to oblong-obovate, apex obtuse to emarginate, mucronulate, base oblique, margins slightly revolute, chartaceous, discolorous, adaxial face dark green, abaxial face light green, pallid, glabrous on the adaxial face, glabrescent on the abaxial face, primary vein impressed above, secondary veins brochidodromous, 7–9 pairs, visible but not prominent on the adaxial face, prominent on the abaxial face, tertiary veins not prominent on either face. Inflorescence in terminal panicles due to non-expansion of the distal leaves, 8.5–14 cm long, peduncle 1.1–2.6 cm, glabrescent to viscid-tomentulose; flower bud oblong, rounded at the apex; bracts 1.1–1.8 × 0.2–0.3 mm, elliptic, cymbiform, apex acuminate, foliaceous, tomentulose, precociously caducous, observed only on young buds. Flowers 2.8–3.4 cm long, pedicel 1.6–2.1 cm long, glabrescent to viscid-tomentulose; calyx with five sepals, heteromorphic, the two external sepals small 1.5–2.3 × 1.2–2 mm, the three internal sepals large, 3.5–4.7 × 2.4–2.8 mm, oblong to obovate, apices rounded, yellowish-green, internally glabrous, external sepals externally tomentulose, internal sepals glabrous; corolla with five petals, strongly asymmetrical, three adaxial petals 9.5–12.8 × 4.5–6.8 mm, obovate, unguiculate, two abaxial petals, one obovate, 12.2–13 × 7.2–8.4 mm, unguiculate, and one oblong, slightly curved at apex, 8.5–19 × 9.8–12 mm, sessile, yellow, glabrous; fertile stamens 7, filaments and anthers glabrous, anthers oblong, yellow, three abaxial stamens with filaments of unequal sizes, 2.5–4.8 mm long, and anthers 5.3–5.5 mm long, distally confluent and fused into a tubular tip, 1.4–1.5 mm long, recurved; the four median stamens 1.2–1.5 mm long with anthers 3.7–4.4 mm, tip 0.4–0.5 mm long, three staminodes 2 mm long; ovary 10–13 mm long, stipitate, tomentulose; style 1.3–1.5 mm long, arched, glabrous; stigmatic cavity elliptic. Legume 6.9 × 1.3–1.5 cm, oblong, flat-compressed, brown to blackish, glabrous, stipitate, stipe 5–5.6 mm long. Seeds not observed.

Additional specimens examined (Paratypes): — BRASIL. Paraná: Ibiporã, Fazenda Doralice, 09 Mar 2001 (fl.), O. C. Pavão et al. s.n. ( FUEL! 30716, HUEFS 142124 ) ; Leópolis, margem do Rio Tangará , 21 May 1999 (fr.), O. M. Gonçalves et al. s.n. ( FUEL! 33247, RB 375151 ) ; ibid., Rio Tangará , 13 Mar 2011 (fl.), J. A. Ferreira et al. s.n. ( INPA 227985 , SP 366058 ) ; Londrina, Parque Estadual Mata dos Godoy , Capoeira na margem direita do Rio dos Apertados, 02 Apr 1996 (fl., fr.), F. Chagas-Silva & L. H. Soares-Silva 1913 ( RB 370616 ) ; Ortigueira, Fazenda Banhado, 16 Mar 1999 (fl.), E. M. Francisco et al. s.n. ( BHCB 50485 , SP 338871 ) ; São Sebastião da Amoreira, Sítio Atanabio, Rio Três Barras , Mata ciliar, 22 May 1998 (fr.), E. M. Francisco et al. s.n. ( MG 202723 , VIC 34510 ) ; Sertaneja, Rio Tangará , 11 May 1998 (fr.), O. M. Gonçalves et al. s.n. ( CEN 69729 , MBM 241698 ) ; Sertanópolis, Sítio Dois Irmãos, 27 March 2001 (fl.), O. C. Pavão et al. s.n. ( FUEL! 33830, RB 393318 ) .

Distribution and habitat: — Senna hatschbachii is endemic to the Brazilian Atlantic Forest. Its distribution is restricted to Semideciduous Seasonal Forest sites in northern Paraná State ( Fig. 2 ), typically along forest borders, roadsides, and near the edges of riparian forests. Despite its proximity to São Paulo State, no specimens of S. hatschbachii were encountered in São Paulo State.

Phenology: —Flowering specimens have been observed in March and April, with fruiting specimens in April and May.

Etymology: —The epithet “ hatschbachii ” is a tribute to the botanist Gerdt Guenther Hatschbach (1923–2013) who dedicated a large part of his life to scientific research and founded the Municipal Botanical Museum of Curitiba, Paraná State, to which he donated more than 18,000 exsiccates from his private collection.

Preliminary conservation status: — Senna hatschbachii is assessed as Endangered (EN) under IUCN Red List criteria B1ab(iii)+2ab(iii) ( IUCN 2022). Its extent of occurrence (EOO) is estimated to be 3732 km 2, and its area of occupancy (AOO) to be 32 km 2, both statistics meeting thresholds for an Endangered (EN) classification. The species is known only from eight Atlantic Forest biome collections made in northern Paraná State, Brazil.

The Atlantic Forest is considered one of 34 global biodiversity hotspots, but it is now fragmented along the Brazilian coast and retains only about 29% of its original forest coverage ( Myers et al. 2000, RAD 2024). The Paraná State ranked third in Brazil in terms of Atlantic Forest deforestation in 2022, with 2883 hectares lost to illegal logging and other anthropic activities ( SOS Mata Atlântica 2022). However, in 2023, deforestation of the Atlantic Forest in Paraná State decreased by approximately 70% compared to 2022 ( RAD 2024).

Among the known sites of occurrence of Senna hatschbachii , only one is located within a legally protected area: the Mata dos Godoy State Park, which encompasses 690 hectares ( IAP 2002). Given the species’ limited distribution, habitat fragmentation, and ongoing deforestation, S. hatschbachii is considered Endangered (EN) based on IUCN criteria.

Vernacular names: —“pau-de-pito” (O.C. Pavão et al. s.n., RB 393318) and “pau-cigarra” (O.M. Gonçalves et al., CEN 69729).

Taxonomic comments: — Senna hatschbachii exhibits morphological features that align it with Senna sect. Peiranisia ser. Interglandulosae , including leaves with an extrafloral nectary positioned on the leaf rachis between the first pair of leaflets; flowers characterized by strongly asymmetrical corollas; poricidal anthers on three abaxial stamens that converge distally into a tubular tip; and flat-compressed legumes. The species closely resembles Senna multijuga var. lindleyana and has been misidentified as such in herbarium collections. S hatschbachii can be distinguished, however, by having linear stipules (≤ 0.1 mm wide), a subulate extrafloral nectary between the first pair of leaflets, and leaves with 6–13 pairs of leaflets. Senna multijuga var. lindleyana , on the other hand, has setiform stipules (0.2–0.4 mm wide), an ovoid to narrow-ovoid extrafloral nectary located between the first pair of leaflets (and occasionally between subsequent pairs), and leaves with 15–46 pairs of leaflets. A list of comparative morphological traits of these taxa is presented in Table 2.

Identification Key: —We provide a key for identifying tree taxa of Senna ser. Interglandulosae in Brazil based on morphological characteristics. This key may aid in identifying previously unidentified or misidentified specimens in Brazilian herbaria and support taxonomic studies of Senna .

Figures

FIGURE 1. Senna hatschbachii F.S.Souto & Agra. A. Flowering branch. B. Detail of the branch stipules. C. Leaf. D. Detail of an extrafloral nectary on the leaf rachis. E. Flower. F. Fruit. Illustration prepared by Rubens Santos.

FIGURE 2. Known distribution of Senna hatschbachii F.S.Souto & Agra in the Atlantic Forest, in northern Paraná State, Brazil.