Parasenegalia Seigler & Ebinger, Novon 25(2): 181. 2017.
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https://dx.doi.org/10.3897/phytokeys.240.101716 |
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https://treatment.plazi.org/id/10CCA150-5034-5634-8B94-C3EEA5FD67EE |
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scientific name |
Parasenegalia Seigler & Ebinger, Novon 25(2): 181. 2017. |
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Parasenegalia Seigler & Ebinger, Novon 25(2): 181. 2017. View in CoL
Figs 192 View Figure 192 , 193 View Figure 193
Type.
Parasenegalia skleroxyla (Tussac) Seigler & Ebinger [≡ Acacia skleroxyla Tussac]
Description.
Unarmed trees (some to 25 m), shrubs (often lianescent) or lianas; bark (known for only few species) grey to brown, smooth to shallowly flat-ridged or shallowly fissured; brachyblasts absent. Stipules small, often falling tardily, rarely absent ( P. lundellii Seigler & Ebinger), not spinescent. Leaves bipinnate, not sensitive; extrafloral nectaries present on petiole (variably positioned) and rachis (below uppermost 1-7 pairs or sometimes all pairs of pinnae), sessile or occasionally stipitate; pinnae normally 3-16 (-20) pairs [except 1-2 pairs in P. miersii (Benth.) Seigler & Ebinger]; paraphyllidia present or absent; leaflets opposite, normally 6-46 (65) pairs per pinna (except 1 or rarely 2 pairs in P. miersii ). Inflorescences comprising pedunculate, loosely flowered spikes (1-4 in leaf axils) or densely flowered heads (1-4 in leaf axils or arranged in large, axillary and/or terminal racemes or panicles); peduncles lacking a multi-bracteate involucre. Flowers hermaphrodite, uniform, 5-merous, with a basal nectariferous disk, sessile, white to cream (sometimes aging yellowish); perianth connate, valvate, not scarious; stamens numerous (40-140), free; anther gland normally present; pollen comprising 16-grained polyads, the grains porate and lacking pseudocolpi, exine surface psilate with circular depressions or rugulate-perforate, exine lacking columellae; ovary sessile to subsessile (except stipitate with stipe to 1.6 mm long in P. vogeliana ). Fruits dehiscent along both sutures (sometimes tardily so), flattened, valves chartaceous or coriaceous. Seeds sometimes with a narrow marginal wing, exarillate; pleurogram U-shaped (open at hilar end) or sometimes circular, rarely absent (e.g., P. miersii ) (Fig. 192I, J View Figure 192 ).
Chromosome number.
2 n = 26 (known only for P. visco ), fide Goldblatt and Johnson (1979 -), as Acacia .
Included species and geographic distribution.
Eleven species, widely but discontinuously distributed in the Neotropics from the Caribbean (three endemic species) through Central America (one species in Belize and Guatemala) to South America (two species in Argentina, Bolivia, Chile and Peru, and five endemic to Brazil) (Fig. 193 View Figure 193 ).
Ecology.
Commonly found in evergreen or semi-evergreen tropical, often riparian, forests or disturbed second growth forests and thickets, 0-800 m. (except P. visco from northern Argentina, Bolivia, northern Chile and Peru, which grows in seasonally wet montane regions between 1000-3000 m), as well as seasonally dry deciduous or semi-deciduous forests, savannas and desert scrub.
Etymology.
The genus name Parasenegalia is from the Greek para (= beside, near) + Senegalia , in reference to the close relationship to that genus.
Human uses.
The wood of P. muricata (L.) Seigler & Ebinger is sometimes used for construction and P. visco is commonly cultivated in Peru where it is economically important as a source of cabinet wood ( Rico-Arce 2007).
Notes.
Prior to the recognition of Parasenegalia , most species now assigned to this genus had been included in a broadly circumscribed Senegalia (e.g., Seigler et al. 2006a; Barros and Morim 2014) and before that, regarded as Acacia (s.l.). Bentham (1875) included two of the species, P. muricata (= A. nudiflora Rich. ex Willd.) and P. skleroxyla in his treatment of Acacia under the Nudiflorae group of subseries Americanae Spiciflorae ; this group also included species now assigned to Mariosousa and Senegalia . For a short period, some species of Parasenegalia were referred to the informal ' Parasenegalia skleroxyla ' group of Acacia subg. Aculeiferum (fide Seigler et al. 2017; Miller et al. 2017).
When Parasenegalia was first recognised it included seven species that were comprehensively described and illustrated (see Seigler and Ebinger in Seigler et al. 2017). Seigler and Ebinger (2018) subsequently recognised an additional four species and provided an identification key to all 11 species as well as a key to the four genera of the Senegalia grade, together with Acaciella .
Parasenegalia and Pseudosenegalia were simultaneously described by Seigler et al. (2017) as New World segregates of Senegalia , differing from that genus notably by their lack of prickles. In a companion paper, Miller et al. (2017) found Parasenegalia to be strongly supported as monophyletic so long as P. visco was excluded from the group. These authors suggested that future studies may show that this species may warrant recognition as a distinct, monotypic genus. Indeed, as noted above, in a recent sparsely sampled phylogenetic study where Parasenegalia was represented by P. visco and P. vogeliana (= Albizia leonardii ) ( Terra et al. 2022), these two species did not form a monophyletic group, supporting doubts about the monophyly of Parasenegalia (Fig. 188 View Figure 188 ). Apart from its distinctive habitat (see above), P. visco differs from other members of Parasenegalia in having larger flower heads (16-23 mm diam. vs 5-14 mm) and leaflets with dark bluish purple midveins; these leaflets are at the lower end of the size range for the genus in being 3-7 × 0.8-2.1 mm. Notwithstanding these morphological differences, P. visco was included in Parasenegalia on account of its leaflet size (3-7 × 0.8-2.1 mm) and its possession of anther glands (fide Miller et al. 2017).
The principal morphological characters that distinguish Parasenegalia from Pseudosenegalia are noted below under the latter genus. Note that pollen data are only available for three species of Parasenegalia , namely, P. miersii , P. santosii (G.P. Lewis) Seigler & Ebinger and P. visco ( Caccavari and Dome 2000; Duarte et al. 2021).
Taxonomic references.
Barros and Morim (2014); Bentham (1875); Miller et al. (2017); Nielsen (1992); Seigler and Ebinger (2018); Seigler et al. (2006a, 2017); Terra et al. (2022).
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