Afrocalliandra E.R. Souza & L.P. Queiroz, Taxon 62(6): 1213. 2013.
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https://dx.doi.org/10.3897/phytokeys.240.101716 |
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https://treatment.plazi.org/id/159ED588-1EA8-3D05-208B-8EF147B11C28 |
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scientific name |
Afrocalliandra E.R. Souza & L.P. Queiroz, Taxon 62(6): 1213. 2013. |
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Afrocalliandra E.R. Souza & L.P. Queiroz, Taxon 62(6): 1213. 2013. View in CoL
Figs 197 View Figure 197 , 198 View Figure 198 , 199 View Figure 199 , 201 View Figure 201
Type.
Afrocalliandra redacta (J.H. Ross) E.R. Souza & L.P. Queiroz [≡ Acacia redacta J.H. Ross]
Description.
Shrubs to 2.5 m, densely branched (Fig. 197D View Figure 197 ), the branches provided with brachyblasts from which leaves and inflorescences emerge, armed with tapering branches becoming spinescent at the tips ( A. gilbertii ) or with spinescent stipules ( A. redacta ). Stipules either leafy or modified into long, paired, straight or slightly curved, rigid spines (Fig. 199B View Figure 199 ), persistent. Leaves bipinnate; petioles without extrafloral nectaries; pinnae 1 pair; leaflets 3-9 pairs per pinna, small. Inflorescences capitate, pedunculate, homomorphic, few-flowered (Fig. 198C View Figure 198 ). Flowers sessile or subsessile; calyx cup-shaped, 5-merous; corolla 5-merous; stamens 10-34, long exserted from the corolla, with their bases fused forming a conspicuous tube, this slightly exserted above the corolla, creamy white or pink, the anthers eglandular; pollen in (7) 8 (10)-grained acalymmate polyads, bilateral, flattened-ovoid, with the basal grain acutely narrowed, with a rather inconspicuous sticky appendage; stigma capitate ( A. gilbertii ). Fruits narrowly oblanceolate, erect, flattened, slightly curved, with thickened margins, the valves thick coriaceous (Fig. 199B View Figure 199 ), dehiscing elastically along both margins, recurving from apex downwards, 2-4 seeds per fruit. Seeds rounded, ca. 5 × 3 mm, compressed, flattened, pointed towards the hilar end, areolate.
Chromosome number.
Unknown.
Included species and geographic distribution.
Two species distributed allopatrically in distant arid areas of Africa. Afrocalliandra redacta is endemic to a restricted area of the Northern Cape Province, across the mountains of the Richtersveld, South Africa, and A. gilbertii is found in the Mandera District, Kenya and in adjacent Somalia (Fig. 201 View Figure 201 ).
Ecology.
Both species of Afrocalliandra occur in arid zones, in areas surrounded by open, shrubby vegetation. Afrocalliandra redacta has been reported to grow on rocky slopes of schistoid granite, at 700 m elevation, whereas A. gilbertii has been found on sandstone ridges at 450-500 m.
Etymology.
African Calliandra , from Greek, calli - (= beautiful) and - andrus (= male), pertaining to the highly attractive stamens.
Human uses.
Unknown.
Notes.
Based on a nuclear and plastid DNA sequence phylogeny, Souza et al. (2013) transferred to Afrocalliandra the two African species originally placed in Calliandra . Although the morphology of the African species is similar to some Calliandra species inhabiting arid areas of the New World, they differ by some fundamental features, such as the (7) 8 (10)-celled, acalymmate polyads, and the presence of axillary branches or stipules modified into thorns, although both types of armature also occur sporadically within Calliandra [spinescent stipules in C. pauciflora and C. haematomma (Bertero ex DC.) Benth., and spinescent shoots in C. spinosa ].
Contrasting with the current view to maintain Calliandra and Afrocalliandra as separate genera, Thulin (2023) recently proposed a return to the circumscription of Calliandra as an amphi-Atlantic genus that includes the two African species, here regarded as Afrocalliandra . As emphasised by Thulin (2023), Calliandra and Afrocalliandra are two closely related monophyletic sister taxa that are morphologically not easily separable. Thulin (2023) noted that the two Afrocalliandra species may be distinguished morphologically from all of the Neotropical Calliandra only by a single microscopic character: the acalymmate polyads, a plesiomorphic character state among mimosoids. However, the calymmate condition in Calliandra is rarely found in other Mimoseae and clearly distinguishes this genus from Afrocalliandra . An associated structure present in all Calliandra species, as well as in Afrocalliandra , is the sticky appendage attached to the basal polyad cell. This appendage, which is destroyed in acetolysed material, seems to be rudimentary in Afrocalliandra ( Thulin et al. 1981, fig. 3G), whereas in the observed Calliandra species it is extremely large and evident (see fig. 2 in Hernández 1986). In addition to the differential polyad characters, all available phylogenies show that the Calliandra and Afrocalliandra clades are supported by long branches reflecting ancient cladogenesis (Suppl. material 2), even longer than the morphologically dissimilar Acaciella . Consequently, considering the important differences in polyad structure, the separation of the two genera by long branches in the existing phylogenies, and their geographic separation in Africa and America, we have opted here to keep the two genera separate.
Taxonomic references.
Souza et al. (2013); Thulin (1993, 2023); Thulin et al. (1981).
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.