Dichrostachys Wight & Arn., Prod. Fl. Ind. Orient.: 271. 1834.

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

Dichrostachys Wight & Arn., Prod. Fl. Ind. Orient.: 271. 1834.

Figs 144 , 145 , 146 , 158

Cailliea Guill. & Perr., Fl. Seneg. Tent.: 239. 1832, nom. rej. vs. Dichrostachys Wight & Arn. Type: Cailliea dichrostachys Guill. & Perr., nom. illeg. [≡ Mimosa nutans Pers. (= Dichrostachys cinerea subsp. africana Brenan & Brummitt)]

Type.

Dichrostachys cinerea (L.) Wight & Arnott [≡ Mimosa cinerea L.]

Description.

Shrubs or small trees to 7 m (Fig. 144K ), branching from base, unarmed or the branches modified into thorns, branches plagiotropic, young stems terete, rarely angled with corky ridges; older stems terete, brachyblasts present, clothed in distichous fused stipule bases. Stipules monomorphic, ovate-triangular, striate, stramineous, persistent. Leaves bipinnate; extrafloral nectaries usually between the proximal pair of pinnae but sometimes at mid-petiole and sometimes additional glands between more distal pinnae, usually cylindrical, raised; pinnae 1-15 (20) pairs; leaflets 1-40 pairs per pinna, linear to ovate, venation brochidodromous to fused eucamptodromous, obscure to abaxially raised, pubescent to glabrous. Inflorescences pedunculate condensed spikes (Fig. 145K, L ), the peduncle often bearing a few lanceolate bracts, 1-3 in leaf axils of new growth or more frequently on the brachyblasts, not forming paniculiform secondary inflorescences; bracteoles subtending each flower carinate, 1-nerved; spikes composed of sterile flowers proximally, rarely sterile flowers absent ( D. kirkii f. puccioniana ), fertile flowers distally, and often a few functionally staminate flowers in between. Flowers sessile, pseudopedicels absent; sepals and petals valvate in bud; sterile flowers smaller than the hermaphrodite ones with 10, showy, filamentous or flattened and ribbon-like staminodia, bright rose-pink fading white; functionally staminate flowers similar to bisexual ones but either lacking or having only a rudimentary ovary; hermaphroditic flowers with a 5-lobed calyx, petals 5, free or sometimes centrally or basally connate, usually linear or lanceolate, 1-nerved; stamens 10, the filaments either exserted or included at anthesis, anthers with a spherical, long-stipitate, apical gland or gland absent (Madagascar); pollen in 16-grained, acalymmate polyads shed as single grains or calymmate polyads of 8-16 grains, exine verrucate to reticulate; ovary oblong to ovate, sessile, densely strigose with silky white hairs, style exserted at anthesis, white, stigma punctate. Fruits sessile, dorsiventrally compressed, elastically dehiscent from the apex (Fig. 146P ) and coiling after dehiscence, or indehiscent (Fig. 146O ); pericarp coriaceous in elastically dehiscent species, woody in the indehiscent ones, the sutural ribs well defined but not greatly enlarged and overtopping the valves, the interior of the fruit usually invaginated between the seeds. Seeds obliquely oriented, ovate to rhomboidal, pleurogram either U-shaped or forming nearly a complete oval on the face of the seed.

Chromosome number.

2 n = 28 (36, 54, 56, 78) in D. cinerea ( Atchison 1951) which forms a poorly understood polyploid series ( Brenan and Brummitt 1965).

Included species and geographic distribution.

ca. 13-14 species, D. cinerea with many varieties. One species native and widespread in Africa, India, and Australia, and widely introduced and weedy elsewhere; one species restricted to the Horn of Africa; one endemic to Socotra; one endemic to Australia; 10 species in Madagascar (Fig. 158 ).

Ecology.

Many diverse habitats, from open savannas and seasonally dry forests to arid tropical scrub. Mostly deciduous. Dichrostachys cinerea is a problematic weed in many parts of the tropics, where it can form pure stands and outcompete native vegetation.

Etymology.

From Greek, di - (= two), chroma (= colour) and - stachys (= spike), in reference to the bi-coloured spicate inflorescence found in the genus (Fig. 145K, L ).

Human uses.

Wood used for fuel and for small tools, leaves and fruits are important sources of livestock forage. Dichrostachys cinerea has been used in soil reclamation projects and as an ornamental ( Pedroso and Kaltschmitt 2012).

Notes.

As currently circumscribed, Dichrostachys is non-monophyletic (Fig. 143 ; Hughes et al. 2003; Luckow et al. 2005; Ringelberg et al. 2022). This non-monophyly will be dealt with via erection of a new genus, Famoha ined. (Luckow in prep.) in a forthcoming monograph that includes a species-level taxonomic account of the four closely related genera: Dichrostachys , Gagnebina , Alantislodendron , and the upcoming new genus.

Taxonomic references.

Brenan and Brummitt (1965); Thulin (1989).

Figures

Figure 143. Generic relationships in the Dichrostachys clade (tribe Mimoseae). Note that the non-monophyly of Dichrostachys and Alantsilodendron has been simplified in this figure (see Suppl. material 2). For description of phylogeny and support values, see Fig. 6 caption (page 63).

Figure 144. Habit and growth forms of genera of the Dichrostachys clade A herbaceous to weakly woody thicket of shrubby Neptunia plena (L.) Benth. in seasonally inundated ruderal habitat, Bolivia (Saerkinen 2159) B, C medium-sized to large trees of Lemurodendron capuronii Villiers & P. Guinet, north-western Madagascar (Koenen 429) D small tree of Leucaena matudae (Zarate) C. E. Hughes in seasonally dry tropical forest, Guerrero, Mexico (Hughes 2153) E shrub of Kanaloa kahoolawensis Lorence & K. R. Wood cultivated, National Tropical Botanical Garden, Kaua'i, Hawaii F small treelet of Desmanthus fruticosus Rose, Baja California, Mexico (Hughes 1532) G prostrate woody suffrutex of Desmanthus acuminatus Benth., Potosi, Bolivia (Hughes 2314) H shrub of Mimozyganthus carinatus (Griseb.) Burkart, Santa Cruz, Bolivia (Hughes 2476) I shrub of Prosopidastrum globosum (Gillies ex Hook. & Arn.) Burkart, Mendoza, Argentina J shrublet of Calliandropsis nervosa (Britton & Rose) H. M. Hern. & P. Guinet, Puebla, Mexico (Hughes 1784) K small treelet of Dichrostachys cinerea (L.) Wight & Arn., Kruger National Park, South Africa L small treelet of Alantsilodendron pilosum Villiers, S. Madagascar (Luckow 4162) M treelet of Gagnebina pterocarpa (Lam.) Baill., Madagascar N shrub of Dichrostachys venosa Villiers, in dry spiny forest, southern Madagascar. Photo credits A, D-H, J CE Hughes B, C E Koenen I Estepa Patagonica K B Dupont L M Luckow M C Commenge naturetropicale N D Du Puy.

Figure 145. Inflorescences and flowers of genera of the Dichrostachys clade A Lemurodendron capuronii Villiers & P. Guinet (Koenen 435) B inflorescence of Neptunia plena (L.) Benth., basal flowers sterile with showy yellow petaloid staminodia (Wood 26650) C inflorescence of Leucaena esculenta (Sesse & Mocino ex DC.) Benth. (Hughes 1326) D inflorescences and tergeminate leaves of Kanaloa kahoolawensis Lorence & K. R. Wood E fascicles of capitate inflorescences in axils of coevally developing leaves, Schleinitzia fosbergii Nevling & Niezgoda F inflorescences of Desmanthus bicornutus S. Watson showing basal sterile flowers with exserted white showy staminodia (Hughes 1526) G capitate inflorescences of Prosopidastrum globosum (Gillies ex Hook. & Arn.) Burkart H semi-spherical capitate inflorescences of Calliandropsis nervosa (Britton & Rose) H. M. Hern. & P. Guinet (Hughes 1784) I inflorescence of Alantsilodendron ramosum Villiers J spicate inflorescences of Gagnebina pterocarpa (Lam.) Baill., the basal flowers sterile with showy white staminodia K spicate inflorescence of Dichrostachys cinerea (L.) Wight & Arn., basal flowers sterile with showy pink staminodia L compact spikes of Dichrostachys akataensis Villiers the basal flowers sterile with showy pale pink staminodia. Photo credits A E Koenen B, C, F, H, J, K CE Hughes D A Palomino E Lauren Gutierrez G D Cabral, Flora Mondocina I, L D Du Puy.

Figure 146. Fruits of genera of the Dichrostachys clade A leaves and pod of Lemurodendron capuronii Villiers & P. Guinet, north-eastern Madagascar (Koenen 429) B Neptunia plena (L.) Benth. fruits dehiscing along the dorsal suture (Wood 26650) C ripe pods of Leucaena cruziana Britton & Rose, Oaxaca, Mexico (Hughes 1300) D cluster of unripe pods on a single inflorescence of Leucaena leucocephala (Lam.) de Wit subsp. glabrata (Rose) S. Zarate, Honduras (Hughes 1557) E ripe pods of Desmanthus leptophyllus Kunth dehiscing along both sutures (Hughes 3098) F unripe fruit of Mezcala balsensis (J. L. Contr.) C. E. Hughes & J. L. Contr., held erect, Guerrero, Mexico G ripe fruits of Mezcala balsensis dehiscing from the apex along both sutures H, I unripe and ripe fruits of Kanaloa kahoolawensis Lorence & K. R. Wood, cultivated at the Olinda rare plant propagation facility, Maui, Hawaii, USA J ripe fruits of Schleinitzia insularum (Guilemin) Burkart, the valves tardily splitting along both sutures but indehiscent K winged fruits of Gagnebina pterocarpa (Lam.) Baill., Madagascar L unripe, lomentiform fruits of Prosopidastrum globosum (Gillies ex Hook. & Arn.) Burkart which break up into one- or few-seeded fragments when ripe M ripe fruits of Mimozyganthus carinatus (Griseb.) Burkart, S Bolivia (Hughes 2476) N ripe fruits, elastically dehisced from the apex, Calliandropsis nervosa (Britton & Rose) H. M. Hern. & P. Guinet, Puebla, Mexico (Hughes 1784) O unripe coiled fruits of Dichrostachys cinerea (L.) Wight & Arn. P ripe fruits dehiscing elastically from the apex, Dichrostachys venosa Villiers, southern Madagascar Q ripe fruits of Alantsilodendron pilosum Villiers, Madagascar. Photo credits A E Koenen B-E, M, N C Hughes F, G J Luis Contreras H, I A Palomino J G McCormack, Cook Islands Biodiversity K, P, Q D Du Puy L I Specogno, Flora Mendocina O Atamari (CC-BY-SA- 3.0).

Figure 158. Distribution of Dichrostachys based on quality-controlled digitised herbarium records. See Suppl. material 1 for the source of occurrence data.