Pithecellobium Mart., Flora 20 (Beibl. 2): 114. 1837.

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

Pithecellobium Mart., Flora 20 (Beibl. 2): 114. 1837.

Figs 217 , 218

Spiroloba Raf., Sylva Tellur.: 119. 1838. Type not designated.

Type.

Pithecellobium unguis-cati (L.) Benth. [≡ Mimosa unguis-cati L.]

Description.

Shrubs and trees, 1-15 m. Stipules spinescent, sometimes absent on some flowering branches, minute or obsolete in P. keyense Britton. Leaves bipinnate, the rachis occasionally winged, extrafloral nectaries cupular, either sessile or shortly stipitate, between each pair of pinna, and also at tip of all pinnae; pinnae 1-2 (11) pairs; leaflets 4-16 (23) pairs per pinna, variously obovate, elliptic, oblong, obovate and suborbicular, venation pinnate and usually also reticulate. Inflorescence units either capitula or relatively short dense spikes, either axillary to the leaves, on efoliate brachyblasts, or paniculately pseudoracemose. Flowers sessile, homomorphic, 5-merous; calyx hemispherical, campanulate or sub-cylindrical, shortly toothed; corolla tubular or trumpet-shaped, rarely turbinate, lobes erect or reflexed; stamens 16-76, the tube as long or longer than corolla; intrastaminal disc with small callosities, rarely developed into lobes; pollen in 16-grained polyads, isodiametric; ovary either oblong or ellipsoid, either sessile or long-stipitate. Fruits oblong or linear pods, reflexed or coiled and sometimes also twisted, the shallowly undulate or evenly curved sutures broad but not prominent, valves fleshy leathery or woody, red or fuscous, biconvex over seeds, the cavity continuous, incipiently septate or compartmentalised into locules; passively or elastically dehiscent either through both sutures or through the ventral suture only. Seeds following dehiscence, dangling on and invested by a red, pink, or whitish, spongy, biconvex arilliform funicle, the testa typically hard, lustrous brown or black, pleurogram present or absent.

Chromosome number.

2 n = 26 (Yeh et al. 1986; Tapia-Pastrana and Gómez-Acevedo 2005).

Included species and geographic distribution.

Twenty species, 18 recognised by Barneby and Grimes (1997), and two additional ones by Duno et al. (2013) and García-Lara et al. (2015). USA (Florida Keys and southern California and Arizona), Mexico, Central America and northern South America south as far as Ecuador, Peru, and Brazil, and the Antilles (Bahamas, Cuba, Hispaniola, Jamaica and throughout the lesser Antilles) (Fig. 218 ). One species ( P. dulce ) cultivated and widely introduced in early Spanish colonial times, now naturalised across the tropics.

Ecology.

Largely confined to seasonally dry and arid vegetation including coastal dunes, thickets, thorn-scrub, and spiny chaparral, savanna margins, brush-savanna, pine woodland, pine-palmetto savanna, and deciduous or semi-deciduous forests. Several species are adapted to shallow rocky coastal limestone soils sometimes derived from coral reefs, e.g., in Belize and the Bahamas. The conspicuous spongy arils clasping the seeds (Fig. 217I, J ) serve as elaiosomes, attractive to birds, ants and humans and thereby contributing to dispersal of the seeds.

Etymology.

Greek = pithecos, monkey + ellobion, earring; in allusion to the pendulous, contorted fruit, the spelling and meaning often modified from Pithecolobium , as though from pithecos + lobos, fruit, and later to Pithecollobium .

Human uses.

Pithecellobium dulce has edible seed-arils ( Barneby and Grimes 1996). It is also commonly cultivated as an ornamental, hedge plant, and shade tree in Central and South America, and sporadically across the tropics (e.g, in north-west India) ( Barneby and Grimes 1996). Recently, the wood has been used for handicrafts (Duno de Stefano 2008). It is also used for forage and living fences in Mexico ( Grether 2007).

Notes.

Pithecellobium was long considered the main “dustbin” genus of the old sense tribe Ingeae. The genus has gradually changed its circumscription from the late nineteenth century to its current much reduced form, defined for the first time by Britton and Rose (1928), a circumscription followed by Barneby and Grimes (1997), who presented a detailed taxonomic account of the genus recognising 18 species.

Pithecellobium can be distinguished from all other genera of former tribe Ingeae by the presence of a seed funicle modified into a usually conspicuous spongy white, pink or crimson aril that cups the lower half of the seed (Fig. 217I, J ).

One species, P. x bahamense Northrop is hypothesised by Barneby and Grimes (1997) to be of putative hybrid origin between P. keyense Britton and P. histrix (A. Richard) Benth.

Taxonomic references.

Barneby and Grimes (1997) with illustrations; Bentham (1844, 1875); Britton and Rose (1928); Tamayo-Cen et al. (2022).

Figures

Figure 217. Morphology of selected species of the Pithecellobium clade A Ebenopsis ebano (Berland.) Barneby & J. W. Grimes, fruit B, C Havardia albicans (Kunth) Britton & Rose B leaves C inflorescence D Gretheria campylacantha (L. Rico & M. Sousa) Duno & Torke, fruit E Ricoa leptophylla (DC.) Duno & Torke, inflorescence and young flowers F Painteria elachistophylla (A. Gray ex S. Watson) Britton & Rose, fruit G Pithecellobium dulce (Roxb.) Benth. habit H Pithecellobium unguis-cati (L.) Benth. inflorescence I Pithecellobium lanceolatum (Humb. & Bonpl. ex Willd.) Benth. pod and seeds J Pithecellobium winzerlingii Britton & Rose pod and seed K Sphinga acatlensis (Benth.) Barneby & J. W. Grimes flowers L Sphinga platyloba (Bertero ex DC.) Barneby & J. W. Grimes flowers. Photo credits A, E, F, H R Duno de Stefano B, C, J GA Romero Gonzalez D, I, K CE Hughes G D Pedersen L C Ramirez.

Figure 218. Distribution of Pithecellobium based on quality-controlled digitised herbarium records. See Suppl. material 1 for the source of occurrence data.