Pterogyne Tul., Ann. Sci. Nat., Bot., ser . 2, 20: 140. 1843.

Bruneau, Anne, de Queiroz, Luciano Paganucci, Ringelberg, Jens J., Borges, Leonardo M., Bortoluzzi, Roseli Lopes da Costa, Brown, Gillian K., Cardoso, Domingos B. O. S., Clark, Ruth P., Conceicao, Adilva de Souza, Cota, Matheus Martins Teixeira, Demeulenaere, Else, de Stefano, Rodrigo Duno, Ebinger, John E., Ferm, Julia, Fonseca-Cortes, Andres, Gagnon, Edeline, Grether, Rosaura, Guerra, Ethiene, Haston, Elspeth, Herendeen, Patrick S., Hernandez, Hector M., Hopkins, Helen C. F., Huamantupa-Chuquimaco, Isau, Hughes, Colin E., Ickert-Bond, Stefanie M., Iganci, Joao, Koenen, Erik J. M., Lewis, Gwilym P., de Lima, Haroldo Cavalcante, de Lima, Alexandre Gibau, Luckow, Melissa, Marazzi, Brigitte, Maslin, Bruce R., Morales, Matias, Morim, Marli Pires, Murphy, Daniel J., O'Donnell, Shawn A., Oliveira, Filipe Gomes, Oliveira, Ana Carla da Silva, Rando, Juliana Gastaldello, Ribeiro, Petala Gomes, Ribeiro, Carolina Lima, Santos, Felipe da Silva, Seigler, David S., da Silva, Guilherme Sousa, Simon, Marcelo F., Soares, Marcos Vinicius Batista & Terra, Vanessa, 2024, Advances in Legume Systematics 14. Classification of Caesalpinioideae. Part 2: Higher-level classification, PhytoKeys 240, pp. 1-552 : 1

Pterogyne Tul., Ann. Sci. Nat., Bot., ser. 2, 20: 140. 1843.

Figs 19 , 20

Type.

Pterogyne nitens Tul.

Description.

Medium to tall trees, mostly 4-8 m but sometimes to 20 m, unarmed (Fig. 19A ); bark light grey; short shoots absent. Stipules very small and falling well before leaf expansion (Fig. 19B ). Leaves imparipinnate, petiole and leaf rachis dorsally flattened and sulcate, the rachis extending beyond the distal leaflet, 7-13-foliolate, leaflets alternate, mostly elliptical, pinnately veined, secondary veins brochidrodromous; stipels setiform, small, caducous (Fig. 19B ); extrafloral nectaries absent. Inflorescence bracteate, amentiform, densely multi-flowered, short racemes, these isolated or grouped in short axillary clusters (Fig. 19C, D ). Flowers small (ca. 3-5 mm diam), actinomorphic, bisexual or unisexual (staminate), pedicellate, greenish-yellow (Fig. 19E ); hypanthium absent; sepals 5, free; petals 5, free, imbricate, reflexed; stamens 10, free; pollen grains in monads, 3-colporate, exine psilate ( Soares et al. 2020); intrastaminal disk short with an undulate rim; ovary shortly stipitate, pubescent, narrowly winged along the adaxial margin at the distal half, the style laterally attached near the apex of the ovary, staminate flowers lacking a gynoecium or provided with a pistilode composed by an ovary but lacking a style. Fruit a wind-dispersed one-seeded samara, flat compressed, straw coloured, stipitate; seed-chamber strongly veined with a small beak (style remnant) laterally displaced near the apex; wing paleaceous (Fig. 19F ). Seed oblong, flat compressed, with a punctiform terminal hilum (Fig. 19G ).

Chromosome number.

2 n = 20 ( Bandel 1974; Melloni 2010).

Included species and geographic distribution.

Monospecific ( P. nitens ), distributed across north-eastern, eastern and central Brazil, northern Argentina and Paraguay and south-eastern Bolivia (Fig. 20 ).

Ecology.

Pterogyne nitens is a tree of the South American tropical and subtropical seasonally dry forests of north-eastern Brazil (Caatinga), central Brazil (Cerrado) and chaquean forests (northern Argentina, Paraguay and southern Bolivia), also occurring in eastern Brazilian semi-deciduous forests of the Mata Atlântica. It occurs mostly as a pioneer tree colonizing degraded areas. It flowers in a very short period and the flowers are visited by a wide range of small insects ( Pfeiffer 2018).

Etymology.

From pteros (Greek: πτέρυξ = wing) and gynos - (Greek: γυνή = woman, gynoecium) referring to the ovary provided with a narrow wing along one margin.

Human uses.

Pterogyne nitens is planted as an urban tree (Fig. 19A ). Its silica rich wood is rated as moderately durable in terms of decay resistance and easy to work both by hand and machine tools. It can be used for flooring, furniture, cabinetry, interior trim and turned objects ( Lewis 2005b; Meier 2021). It is a fast growing tree occurring in soils of low natural fertility, and has been recommended for planting in riparian forest with periodic flooding, and resetting and restoration of degraded areas ( Mauro et al. 2008). Preparations from the stem bark have been used by local Paraguayan populations in the therapy of ascariasis ( Crivos et al. 2007). Several guanidine alkaloids with cytotoxic activity have been isolated from leaves and fruits ( Regasini et al. 2009). Leaves are reported as toxic to livestock.

Notes.

The phylogenetic position of the genus is still uncertain and conflicting among different analyses (see Fig. 18 and discussion above).

The compact catkin-like racemes with rather small flowers and the samara fruits are similar to those found in the African-Asiatic genus Pterolobium R. Br. ex Wight & Arn. of tribe Caesalpinieae ( Gagnon et al. 2016; see Caesalpinieae tribe, page 103), but Pterogyne is an unarmed tree with imparipinnate leaves and alternate leaflets, the ovary has a uniquely winged margin along the distal half and the style attachment is displaced to a subterminal position, while Pterolobium has branches armed with prickles, the leaves are bipinnate with opposite leaflets, the ovary is unwinged and the style is attached at the apex. The samara wing of Pterogyne is clearly derived from the expansion of the marginal wing of the ovary below the style. The style remains as a beak on the fruit and is laterally displaced above the seed-chamber ( Polhill and Vidal 1981).

Taxonomic references.

Lewis (2005b); Polhill and Vidal (1981); Queiroz (2009); Tulasne (1843).

Figures

Figure 18. Contrasting phylogenetic positions for Pterogyne as supported by different analyses A sister to all Caesalpinioideae, except Ceratonieae and Gleditsiae (ca. 1500 nuclear genes; Zhao et al. 2021) B sister to Cassieae (SUSY nuclear gene and combined trnL intron + morphological data; Manzanilla and Brunau 2012, Herendeen et al. 2003 a, respectively) C sister to Caesalpinieae (trnL intron and coding plastid genes; Bruneau et al. 2001; Zhang et al. 2020) D sister to the remaining Caesalpinioideae (plastid non-coding loci; Zhang et al. 2020).

Figure 19. Pterogyne nitens Tul., the only species of tribe Pterogyneae A cultivated tree in Brasilia (Brazil) B flowering branch showing the foliage and inflorescences; note the alternate leaflets; the insets show an expanding leaf (left) highlighting the tiny caducous stipules (arrow) and a stipel at the leaflet attachment (right) C inflorescences with a visiting Syrphidae fly (Diptera) D part of the spicate raceme with some flowers removed E close-up of flowers F samaras, the inset showing the subterminal style remnant at the top of the seed chamber (arrows) G samara seed chamber opened to show the seed. Photo credits A-G RT Queiroz https: // rubens-plantasdobrasil. blogspot. com /.

Figure 20. Distribution of Pterogyne based on quality-controlled digitised herbarium records. See Suppl. material 1 for the source of occurrence data.