Pityrocarpa (Benth.) Britton & Rose, N. Amer. Fl. 23(3): 190. 1928.

Borges, Leonardo M., Inglis, Peter W., Simon, Marcelo F., Ribeiro, Petala Gomes & de Queiroz, Luciano P., 2022, Misleading fruits: The non-monophyly of Pseudopiptadenia and Pityrocarpa supports generic re-circumscriptions and a new genus within mimosoid legumes, PhytoKeys 205, pp. 239-259 : 239

1. Pityrocarpa (Benth.) Britton & Rose, N. Amer. Fl. 23(3): 190. 1928.

Monoschisma Brenan, Kew Bull. 10(2): 179. 1955, nom. inval., non Monoschisma Duby, Mém. Soc. Phys. Genève 19: 294. 1868. Type. Monoschisma leptostachyum (Benth.) Brenan, syn. nov.

Pseudopiptadenia Rauschert, Taxon 31(3): 559. 1982. Type. Pseudopiptadenia leptostachya (Benth.) Rauschert, syn. nov.

Basionym.

Piptadenia sect. Pityrocarpa Benth., J. Bot. (Hooker) 4: 339. 1842.

Type.

Pityrocarpa moniliformis (Benth.) Luckow & R.W. Jobson [≡ Piptadenia moniliformis Benth., designated by Britton and Rose 1928].

Description.

Unarmed trees or shrubs. Leaves bipinnate; petiole with an extrafloral nectary between or shortly below the first pair of pinnae; pinnae 1-4 (5) pairs, exceptionally to 10 pairs in Pi. leptostachya ; leaflets 1-10 pairs per pinna, rarely to 20 pairs ( Pi. brenanii and Pi. leptostachya ), mostly rhomboid sometimes also asymmetrically elliptical or lanceolate. Inflorescences spikes, solitary in the axils of coeval leaves, commonly pendulous. Flowers pentamerous; petals free (except possibly Pi. leucoxylon ), glabrous; stamens 10, anther gland present; ovary shortly stipitate and included within or exserted from the corolla. Fruit a follicle, dehiscing along the lower suture, flat compressed, mostly moniliform, the margins deeply and regularly constricted, rarely sinuous margins and shallowly constricted ( Pi. brenanii and occasionally in Pi. leucoxylon ); valves stiffly coriaceous. Seeds mostly flat compressed with a coriaceous testa and a narrow marginal wing, lacking a pleurogram or, less frequently, ovoid or discoid with a hard, whitish testa, wingless and with a ‘U’ -shaped pleurogram ( Pi. leucoxylon , Pi. moniliformis and Pi. obliqua ); embryo with a rudimentary plumule (except Pi. brenanii ). Seedlings with bifoliolate eophylls.

Distribution.

Pityrocarpa is distributed in tropical America, from Mexico to southern Brazil and Paraguay. Most species occur in the Brazilian Atlantic rainforests ( Pi. inaequalis , Pi. leptostachya , Pi. schumanniana ), in the northern Amazonian rainforests ( Pi. leucoxylon ), in seasonally dry tropical forests and woodlands in the north-eastern Brazilian Caatinga ( Pi. brenanii , Pi. moniliformis , Pi. obliqua subsp. brasiliensis ), western Mexico ( Pi. obliqua subsp. obliqua ) or in Venezuelan savannas and Paraguayan Chaco ( Pi. moniliformis ).

Notes.

As circumscribed here, Pityrocarpa includes seven species, all with a moniliform fruit, with the margins deeply constricted between the seeds (Fig. 4 ). This trait is shared by species formerly included in Pityrocarpa (sensu Jobson and Luckow 2007) and some species previously placed in the genus Pseudopiptadenia (sensu Lewis and Lima 1991). These two genera had been separated based on seed morphology, Pityrocarpa characterised by ovoid or discoid seeds with a hard, whitish seed coat and a ‘U’ -shaped pleurogram, while Pseudopiptadenia included species with flat compressed and narrowly winged seeds with a coriaceous testa lacking a pleurogram. Pityrocarpa brenanii and Pi. leucoxylon have fruits with only shallowly sinuous margins, more similar to species of the genus Marlimorimia .

Besides sharing these fruit traits, Pityrocarpa species also have leaves with few pinnae (1 to 4 [5] pairs, rarely up to 10 pairs in Pi. leptostachya ) and relatively large rhomboid leaflets compared to species of Marlimorimia . One exception are the leaves of Pi. brenanii , which are similar to those of M. bahiana . All species of Pityrocarpa present an extrafloral nectary between or shortly below the first pair of pinnae, in contrast to species of Marlimorimia that have the nectary below mid-petiole, frequently close to the pulvinus.

Floral traits, although previously disregarded as being generically diagnostic in the group, provide further evidence for the distinction between Pityrocarpa and Marlimorimia . The solitary inflorescence spikes in the axils of coevally developing leaves in Pityrocarpa contrast with the more complex synflorescences of Marlimorimia (Fig. 3 ; see notes under Marlimorimia ). All species of Pityrocarpa have free and glabrous petals, except for Pi. leucoxylon , in which the petals are connate for a little over 1 mm ( Barneby and Grimes 1984).

Lima (1985) and Lewis and Lima (1991) provided additional information on embryos and seedlings that are potentially useful for distinguishing Pityrocarpa from Marlimorimia . Embryos of Pityrocarpa species have a rudimentary plumule, while in Marlimorimia , the plumule is developed and multifid. This seems to be correlated with seedling morphology as the studied species of Pityrocarpa have bifoliolate eophylls and those of Marlimorimia species have pinnate or bipinnate eophylls ( Lewis and Lima 1991). Pityrocarpa brenanii , however, has embryo morphology more similar to that reported for species of Marlimorimia ( Lewis and Lima 1991).

Figures

Figure 3. Inflorescences of Parapiptadenia, Pityrocarpa and Marlimorimia A Parapiptadenia pterosperma (Benth.) Brenan showing reddish inflorescences in the axils of coeval leaves B Pa. rigida (Benth.) Brenan showing yellowish inflorescences and fruits with valves plicate above the seeds C Pityrocarpa brenanii showing whitish, solitary spikes in the axils of coeval leaves D Pi. moniliformis showing yellowish, solitary spikes in the axil of a coeval leaf E Marlimorimia bahiana (G. P. Lewis & M. P. Lima) L. P. Queiroz & L. M. Borges, showing whitish spikes clustered in efoliate terminal pseudoracemes F Marlimorimia sp. showing yellowish spikes clustered in efoliate terminal pseudoracemes (Photos: A PG Ribeiro; B RT de Queiroz C-E LP Queiroz; F G Siqueira).

Figure 4. Fruits of Pityrocarpa species A Pi. brenanii (from Lewis et al. 1899, NY) B Pi. inaequalis (from Moreira et al. 3, F) C Pi. leptostachya (from Baez et al. 1174, NY) D Pi. leucoxylon (from de Bruijn 1750, NY) E Pi. moniliformis (from Nunes 597, HUEFS) F Pi. obliqua subsp. brasiliensis (from Mori 11837, NY) G Pi. schumanniana (from Lima 2994, RB).