Advances in Legume Systematics 14. Classification of Caesalpinioideae. Part 2: Higher-level classification Author Bruneau, Anne https://orcid.org/0000-0001-5547-0796 Institut de recherche en biologie vegetale and Departement de Sciences biologiques, Universite de Montreal, 4101 Sherbrooke E., Montreal (QC) H 1 X 2 B 2, Canada anne.bruneau@umontreal.ca Author de Queiroz, Luciano Paganucci https://orcid.org/0000-0001-7436-0939 Universidade Estadual de Feira de Santana, Departamento de Ciencias Biologicas, Av. Transnordestina s / n, Campus, Novo Horizonte. 44036 - 900, Feira de Santana, BA, Brazil Author Ringelberg, Jens J. https://orcid.org/0000-0003-0567-5210 Department of Systematic and Evolutionary Botany, University of Zurich, Zollikerstrasse 107, 8008 Zurich, Switzerland & School of Geosciences, University of Edinburgh, Old College, South Bridge, Edinburgh EH 8 9 YL, UK Author Borges, Leonardo M. https://orcid.org/0000-0001-9269-7316 Universidade Federal de Sao Carlos, Departamento de Botanica, Rodovia Washington Luis, Km 235, 13565 - 905, Sao Carlos, SP, Brazil Author Bortoluzzi, Roseli Lopes da Costa https://orcid.org/0000-0002-7445-7244 Programa de Pos-graduacao em Producao Vegetal, Universidade do Estado de Santa Catarina, Centro de Ciencias Agroveterinarias, Avenida Luiz de Camoes 2090, 88520 - 000, Lages, Santa Catarina, Brazil Author Brown, Gillian K. https://orcid.org/0000-0002-7940-5435 Queensland Herbarium and Biodiversity Science, Department of Environment and Science, Toowong, Queensland, 4066, Australia Author Cardoso, Domingos B. O. S. https://orcid.org/0000-0001-7072-2656 Instituto de Pesquisas Jardim Botanico do Rio de Janeiro, Pacheco Leao 915, 22460 - 030, Rio de Janeiro, RJ, Brazil & Programa de Pos-Graduacao em Biodiversidade e Evolucao (PPGBioEvo), Instituto de Biologia, Universidade Federal de Bahia (UFBA), Rua Barao de Jeremoabo, s. n., Ondina, 40170 - 115, Salvador, BA, Brazil Author Clark, Ruth P. https://orcid.org/0000-0001-9974-2933 Accelerated Taxonomy Department, Royal Botanic Gardens, Kew, Richmond, TW 9 3 AE, UK Author Conceicao, Adilva de Souza https://orcid.org/0000-0002-8800-422X Programa de Pos-graduacao em Diversidade Vegetal, Universidade do Estado da Bahia, Herbario HUNEB, Campus VIII, Rua do Gangorra 503, 48608 - 240, Paulo Afonso, Bahia, Brazil Author Cota, Matheus Martins Teixeira https://orcid.org/0000-0003-0654-7501 Universidade Estadual de Feira de Santana, Departamento de Ciencias Biologicas, Av. Transnordestina s / n, Campus, Novo Horizonte. 44036 - 900, Feira de Santana, BA, Brazil Author Demeulenaere, Else https://orcid.org/0000-0002-1815-3051 Center for Island Sustainability and Sea Grant, University of Guam, UOG Station, Mangilao, 96923, Guam Author de Stefano, Rodrigo Duno https://orcid.org/0000-0003-1707-4121 Centro de Investigacion Cientifica de Yucatan, A. C. (CICY), Calle 43 No. 130 x 32 y 34, Chuburna de Hidalgo; CP 97205, Merida, Yucatan, Mexico Author Ebinger, John E. Eastern Illinois University, Charleston, IL 61920, USA Author Ferm, Julia https://orcid.org/0000-0002-8762-3942 Department of Ecology, Environment and Plant Sciences, 10691, Stockholm University, Stockholm, Sweden Author Fonseca-Cortes, Andres https://orcid.org/0000-0001-7207-9940 Universidade Estadual de Feira de Santana, Departamento de Ciencias Biologicas, Av. Transnordestina s / n, Campus, Novo Horizonte. 44036 - 900, Feira de Santana, BA, Brazil Author Gagnon, Edeline https://orcid.org/0000-0003-3212-9688 Department of Integrative Biology, University of Guelph, 50 Stone Road, Guelph (ON) N 1 G 2 W 1, Canada & Chair of Phytopathology, Technical University Munich, 85354 Freising, Germany & Royal Botanic Garden Edinburgh, 20 A Inverleith Row, Edinburgh, EH 3 5 LR, UK Author Grether, Rosaura https://orcid.org/0000-0003-2673-665X Departamento de Biologia, Universidad Autonoma Metropolitana-Iztapalapa, Apdo. Postal 55 - 535, 09340 Ciudad de Mexico, Mexico Author Guerra, Ethiene https://orcid.org/0000-0002-9495-1717 Universidade Federal do Rio Grande do Sul, Programa de Pos-Graduacao em Botanica, Av. Bento Goncalves 9500, Bloco IV - Predio 43433, Porto Alegre, RS, 91501 - 970, Brazil Author Haston, Elspeth https://orcid.org/0000-0001-9144-2848 Royal Botanic Garden Edinburgh, 20 A Inverleith Row, Edinburgh, EH 3 5 LR, UK Author Herendeen, Patrick S. https://orcid.org/0000-0003-2657-8671 Chicago Botanic Garden, 1000 Lake Cook Road, Glencoe, IL 60022, USA Author Hernandez, Hector M. https://orcid.org/0000-0002-1741-5515 Departamento de Botanica, Instituto de Biologia, Universidad Nacional Autonoma de Mexico, Cd. Universitaria, 04510 Ciudad de Mexico, Mexico Author Hopkins, Helen C. F. https://orcid.org/0000-0003-4984-8224 Accelerated Taxonomy Department, Royal Botanic Gardens, Kew, Richmond, TW 9 3 AE, UK Author Huamantupa-Chuquimaco, Isau https://orcid.org/0000-0002-4153-5875 Herbario Alwyn Gentry (HAG), Universidad Nacional Amazonica de Madre de Dios (UNAMAD), AV. Jorge Chavez N ° 1160, Madre de Dios, Peru Author Hughes, Colin E. https://orcid.org/0000-0002-9701-0699 Department of Systematic and Evolutionary Botany, University of Zurich, Zollikerstrasse 107, 8008 Zurich, Switzerland Author Ickert-Bond, Stefanie M. https://orcid.org/0000-0001-8198-8898 Department of Biology & Wildlife & Herbarium (ALA) at the University of Alaska Museum of the North, University of Alaska Fairbanks, P. O. Box 756960, Fairbanks AK 99775 - 6960, USA Author Iganci, Joao https://orcid.org/0000-0002-5740-3666 Universidade Federal do Rio Grande do Sul, Programa de Pos-Graduacao em Botanica, Av. Bento Goncalves 9500, Bloco IV - Predio 43433, Porto Alegre, RS, 91501 - 970, Brazil & Programa de Pos-Graduacao em Fisiologia Vegetal, Universidade Federal de Pelotas, Instituto de Biologia, Campus Universitario Capao do Leao, Passeio Andre Dreyfus, Departamento de Botanica, Predio 21, Pelotas, Rio Grande do Sul, 96010 - 900, Brazil Author Koenen, Erik J. M. https://orcid.org/0000-0002-4825-4339 Evolutionary Biology & Ecology, Universite Libre de Bruxelles, Faculte des Sciences, Campus du Solbosch - CP 160 / 12, Avenue F. D. Roosevelt, 50, 1050 Bruxelles, Belgium Author Lewis, Gwilym P. https://orcid.org/0000-0003-2599-4577 Accelerated Taxonomy Department, Royal Botanic Gardens, Kew, Richmond, TW 9 3 AE, UK Author de Lima, Haroldo Cavalcante https://orcid.org/0000-0003-2154-670X Instituto de Pesquisas Jardim Botanico do Rio de Janeiro, Pacheco Leao 915, 22460 - 030, Rio de Janeiro, RJ, Brazil & Instituto Nacional da Mata Atlantica / INMA-MCTI, Av. Jose Ruschi, 4, Centro, 29650 - 000, Santa Teresa, Espirito Santo, Brazil Author de Lima, Alexandre Gibau https://orcid.org/0000-0002-9168-2507 Instituto de Pesquisas Jardim Botanico do Rio de Janeiro, Pacheco Leao 915, 22460 - 030, Rio de Janeiro, RJ, Brazil & Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden Author Luckow, Melissa https://orcid.org/0009-0007-2543-0516 School of Integrative Plant Science, Plant Biology Section, Cornell University, 215 Garden Avenue, Roberts Hall 260, Ithaca, NY 14853, USA Author Marazzi, Brigitte https://orcid.org/0000-0003-3252-5816 Natural History Museum of Canton Ticino, Viale C. Cattaneo 4, 6900 Lugano, Switzerland Author Maslin, Bruce R. https://orcid.org/0000-0002-3039-0973 Western Australian Herbarium, Department of Biodiversity, Conservation and Attractions, Locked Bag 104, Bentley Delivery Centre, Western Australia, 6983, Australia & Singapore Herbarium, 1 Cluny Road, Singapore, Singapore Author Morales, Matias https://orcid.org/0000-0001-5540-9725 Instituto de Recursos Biologicos, CIRN-CNIA, INTA. N. Repetto & Los Reseros s. n., Hurlingham, Buenos Aires, Argentina & Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET), Godoy Cruz 2290 (C 1425 FQB), Ciudad Autonoma de Buenos Aires, Argentina Author Morim, Marli Pires https://orcid.org/0000-0003-0872-8429 Instituto de Pesquisas Jardim Botanico do Rio de Janeiro, Pacheco Leao 915, 22460 - 030, Rio de Janeiro, RJ, Brazil Author Murphy, Daniel J. https://orcid.org/0000-0002-8358-363X Royal Botanic Gardens Victoria, Melbourne, Victoria, 3004, Australia Author O'Donnell, Shawn A. https://orcid.org/0000-0003-0731-7425 Geography and Environmental Sciences, Northumbria University, Ellison Place, Newcastle upon Tyne, NE 1 8 ST, UK Author Oliveira, Filipe Gomes https://orcid.org/0000-0003-0244-3262 Universidade Estadual de Feira de Santana, Departamento de Ciencias Biologicas, Av. Transnordestina s / n, Campus, Novo Horizonte. 44036 - 900, Feira de Santana, BA, Brazil Author Oliveira, Ana Carla da Silva https://orcid.org/0000-0001-7042-5360 Universidade Estadual de Feira de Santana, Departamento de Ciencias Biologicas, Av. Transnordestina s / n, Campus, Novo Horizonte. 44036 - 900, Feira de Santana, BA, Brazil Author Rando, Juliana Gastaldello https://orcid.org/0000-0002-3714-8231 Programa de Pos-graduacao em Ciencias Ambientais, Universidade Federal do Oeste da Bahia, Rua Professor Jose Seabra Lemos 316, 47800 - 021, Barreiras, Bahia, Brazil Author Ribeiro, Petala Gomes https://orcid.org/0000-0002-0070-9971 Universidade Estadual de Feira de Santana, Departamento de Ciencias Biologicas, Av. Transnordestina s / n, Campus, Novo Horizonte. 44036 - 900, Feira de Santana, BA, Brazil Author Ribeiro, Carolina Lima https://orcid.org/0000-0001-9508-2894 Universidade Estadual de Feira de Santana, Departamento de Ciencias Biologicas, Av. Transnordestina s / n, Campus, Novo Horizonte. 44036 - 900, Feira de Santana, BA, Brazil Author Santos, Felipe da Silva https://orcid.org/0000-0002-1068-0578 Universidade Estadual de Feira de Santana, Departamento de Ciencias Biologicas, Av. Transnordestina s / n, Campus, Novo Horizonte. 44036 - 900, Feira de Santana, BA, Brazil Author Seigler, David S. https://orcid.org/0009-0003-5177-5893 Department of Plant Biology, University of Illinois, Urbana, IL 61801, USA Author da Silva, Guilherme Sousa https://orcid.org/0000-0002-4250-0017 Instituto de Biologia, Universidade Estadual de Campinas, Campinas, 13083 - 876, Sao Paulo / SP, Brazil Author Simon, Marcelo F. https://orcid.org/0000-0002-5732-1716 Empresa Brasileira de Pesquisa Agropecuaria (Embrapa) Recursos Geneticos e Biotecnologia, Parque Estacao Biologica, Caixa Postal 02372, 70770 - 917, Brasilia / DF, Brazil Author Soares, Marcos Vinicius Batista https://orcid.org/0000-0003-2660-1771 Universidade Federal do Rio Grande do Sul, Programa de Pos-Graduacao em Botanica, Av. Bento Goncalves 9500, Bloco IV - Predio 43433, Porto Alegre, RS, 91501 - 970, Brazil Author Terra, Vanessa https://orcid.org/0000-0001-5669-1304 Instituto de Biologia, Universidade Federal de Santa Maria, 97105 - 900, Santa Maria / RS, Brazil text PhytoKeys 2024 2024-04-03 240 1 552 http://dx.doi.org/10.3897/phytokeys.240.101716 journal article http://dx.doi.org/10.3897/phytokeys.240.101716 1314-2003-240-1 B699D9DE2B435B1093DE3C38C703D430 Acacia Mill., Gard. Dict. Abr., ed. 4, [25]. 1754 nom. cons. Figs 237 , 238 , 239 , 240 Acacia sect. Phyllodineae DC., Prodr. [A.P. de Candolle] 2: 448. 1825. Type not designated. Racosperma Mart., Hort. Reg. Monac.: 188. 1829, nom. inval. (name not accepted by author) Phyllodoce Link, Handbuch 2: 132. 1829, non Phyllodoce Salisb., Parad. Lond. ad t. 36. 1806 ( Ericaceae ). Type not designated. Racosperma Mart., Index Seminum [ Muenchen (Monacensis)]: 4. 1835. Lectotype (designated by Pedley 1986 ): Racosperma penninerve (Sieber ex DC.) Pedley [≡ Acacia penninervis Sieber ex DC.] Cuparilla Raf., Sylva Tellur.: 120. 1838. Lectotype (designated by Pedley 1986 ): Cuparilla myrtifolia (Sm.) Raf. [≡ Mimosa myrtifolia Sm. (≡ Acacia myrtifolia (Sm.) Willd.)] Drepaphyla Raf., Sylva Tellur.: 120. 1838. Lectotype (designated by Pedley 1986 ): Drepaphyla lanigera (Cunn.) Raf. [≡ Acacia lanigera A. Cunn.] Hectandra Raf., Sylva Tellur.: 120. 1838. Lectotype (designated by Pedley 1986 ): Hectandra suaveolens (Sm.) Raf. [≡ Mimosa suaveolens Sm. (≡ Acacia suaveolens (Sm.) Willd.)] Zigmaloba Raf., Sylva Tellur.: 120. 1838. Type: Zigmaloba sulcata (R. Br.) Raf. [≡ Acacia sulcata R. Br.] Chithonanthus Lehm., Pl. Preiss. 2: 368. 1848. Type: Chithonanthus restiaceus (Benth.) Lehm. [≡ Acacia restiacea Benth.] Tetracheilos Lehm., Pl. Preiss. 2: 368. 1848. Type: Tetracheilos tetragonocarpa Meisn., nom. illeg. Acacia sect. Phyllodoce (Link) Kuntze, in T.E. von Post & C.E.O. Kuntze, Lex. Gen. Phan.: 2. 1903. Type not designated. Phytomorula Kofoid, Univ. Calif. Publ. Bot. 6: 38. 1914. Type: Phytomorula regularis Kofoid. [described as an alga but shown to be pollen of Acacia sp., vide Copeland 1937 ]. Type . Acacia penninervis Sieber ex DC. Description. Trees, shrubs or subshrubs, never lianas; prickles absent. Stipules normally present and caducous, rarely spinose. Leaves bipinnate or modified to polymorphic phyllodes, rarely reduced to scales or absent; extrafloral nectaries normally present. Inflorescences globose or oblongoid capitula or spikes, axillary or aggregated in racemes or infrequently panicles, pedunculate or sometimes sessile. Flowers bisexual or staminate and bisexual within a single inflorescence, 5-merous or sometimes 4-merous, uniform, white to golden, rarely mauve-pink or red; sepals free to united, very rarely absent; corolla connate, valvate; stamens numerous, normally free, rarely basally united; pollen in polyads normally 8, 12 or 16 grains, the grains extraporate or sometimes porate, surface with pseudocolpi, exine granular (i.e., lacking columellae that occur in Vachellia Wight & Arn.); ovary solitary or very rarely 2-5 (e.g., A. celastrifolia Benth.). Fruits variable, dehiscent, rarely indehiscent. Seeds normally with a pleurogram and without endosperm; funicle arillate or sometimes exarillate. Chromosome number. Mostly 2 n = 26 with ca. 100 species examined ( Hamant et al. 1975 ; Goldblatt and Johnson 1979 -; Rice et al. 2015 ), but there are a few notable exceptions and examples of polyploidy. In several members of the 'Mulga' group (i.e., Acacia aneura F. Muell. ex Benth. and close relatives ( Miller et al. 2002 ; Maslin and Reid 2012 ), which predominate in the arid zone, tetraploids (2 n = 52), triploids (2 n = 39) and pentaploids (2 n = 65) were reported by Andrew et al. (2003) . Acacia brachystachya Benth., a close relative of the 'Mulga' group, is tetraploid ( Hamant et al. 1975 ). There are a few other arid zone species not closely related to the 'Mulga' group that are polyploids ( Hamant et al. 1975 ; Moran et al. 1992 ; Maslin and Thomson 1992 ). Two extra-Australian tetraploid species are A. koa A. Gray (Hawaii) and A. heterophylla (Lam.) Willd. (Reunion Island), whereas their close relative, the widespread, eastern Australian species, A. melanoxylon R. Br., is diploid ( Brown et al. 2012 ). Natural triploids and tetraploids have also been recorded in populations of the Australian bipinnate-leaved species, Acacia dealbata Link. ( Blakesley et al. 2002 ; Nghiem et al. 2018 ). Included species and geographic distribution. 1082 species, the majority in Australia. These species are distributed throughout the continent with the major centre of species-richness located in south-west Western Australia, and secondary centres of richness in eastern Australia south of the Tropic of Capricorn associated with the Great Dividing Range, and in northern and north-eastern Australia. Although species of Acacia are a conspicuous component of the central Australian arid zone, this is a relatively species-poor region ( Hnatiuk and Maslin 1988 ). Only 17 species occur naturally outside Australia (of which seven species plus one subspecies also occur within Australia), where they extend to South East and East Asia (north to Taiwan), the Pacific Ocean (east to Hawaii) and Indian Oceans (i.e., Mascarene islands); see Pedley (1975) , Brown et al. (2012) , WorldWideWattle (2022) (Fig. 240 ). Species of Acacia are widely distributed globally as weeds, ornamentals or cultivated for economic, social or environmental purposes. Ecology. Species of Acacia within Australia grow in a wide range of habitats, from coastal to subalpine, tropical to arid ecological vegetation classes. They are particularly conspicuous and common in many semi-arid and sub-tropical shrublands and woodlands, and while they dominate much of the arid zone the species numbers are, relatively speaking, not especially high. The diverse shrublands of Western Australia and Eucalyptus woodlands of eastern Australia associated with the Great Dividing Range, located between the arid and temperate zones, are especially species-rich, but Acacia is often not a dominant element of the vegetation ( Hnatiuk and Maslin 1988 ). Etymology. It is normally regarded that the name Acacia is derived from the Greek, ake (= a point), in reference to the spiny stipules that characterised the first (African) species described as Acacia ; these species now belong to the genus Vachellia . Human uses. Acacias have had extensive utilisation for economic, social and environmental purposes. A discussion of these uses is presented by McDonald et al. (2001) and a listing of them is given in the "Info Gallery/Utilisation" at WorldWideWattle (2022) . Commercially, the most important use of Acacia is for wood products where the species A. auriculiformis A. Cunn. ex Benth., A. crassicarpa A. Cunn. ex Benth., A. mangium Willd. and A. x mangiiformis Maslin & L.A.J. Thomson are especially important in tropical forestry plantation industries, particularly in south-east Asia and India ( Griffin et al. 2011 ; Maslin et al. 2019b ). Acacia mearnsii De Wild., which was initially grown for tannin production, is now highly regarded by the pulp and paper industries in several countries, most notably, Brazil, India and South Africa ( Griffin et al. 2011 ). Within Australia the wood of A. melanoxylon (Blackwood) provides a niche market for fine furniture ( Beadle and Brown 2007 ). The potential of Acacia species as a new woody crop plant to assist with salinity control in the agricultural regions of southern Australia (within the 250-650 mm rainfall zone) was assessed by Maslin and McDonald (2004) . As noted by Griffin et al. (2011) , a suite of multi-purpose Acacia species have been introduced in dry zone regions of Africa and elsewhere to assist with meeting the demand for food, fodder, fuelwood, poles, and site amelioration ( Doran and Turnbull 1997 ). Acacia saligna (Labill.) H. Wendl. is the most widely planted of the non-timber species, with around 600,000 ha established worldwide; it is used as an animal fodder, in landscape amelioration projects, and for a range of other purposes ( Midgley and Turnbull 2003 ; Maslin 2011 ). Acacia colei Maslin & L.A.J. Thomson has been used as a human food and has been incorporated into local farming systems in Sub-Saharan Africa ( Rinaudo and Cunningham 2008 ). The potential of this and other species of Acacia as a human food within Australia was assessed by Maslin et al. (1998) . Several species of Acacia have displayed significant invasiveness in places where they have been introduced. Examples include A. cyclops A. Cunn. ex G. Don, A. baileyana F. Muell., A. dealbata Link, A. mangium , A. melanoxylon , A. pycnantha Benth. and A. saligna . Factors promoting the spread of such species as weeds include the production of large quantities of tough, long-lived seeds, prolific seedling recruitment following fire or other environmental disturbances, and the absence of natural invertebrate predators and fungal pathogens. Richardson et al. (2011) provides a good introduction and review of this subject. Indigenous Australians have long used species of Acacia as a source of food and medicine, tools and weapons, and various other purposes (e.g., Aboriginal Communities of the Northern Territory 1993 ; Latz 1995 ; Searle 2004 ; WorldWideWattle 2022 ). As discussed at WorldWideWattle (2022) , Acacia has great symbolic significance to Australians where it is the National Flora Emblem, is incorporated into the Australian Coat of Arms, and more. Notes. In recent years there have been substantial changes to both the classification and nomenclature of Acacia . The reasons for this are twofold. Firstly, molecular and other evidence have shown that the former broadly circumscribed, pantropical genus Acacia is polyphyletic and should be treated as comprising at least seven genera (see below). Secondly, the name Acacia is now conserved with a new type, namely, the Australian species Acacia penninervis Sieber ex DC. which replaces the Afro-Asian species, Acacia nilotica (L.) Willd. ex Delile. This retypification has meant that about half of the non-Australian species formerly called Acacia are now Vachellia and the name Racosperma Mart. [preferred by Pedley (1986) for most Australian species] is now a synonym of Acacia . There is an extensive literature regarding these two interrelated matters, but useful summaries are presented in Murphy (2008) , Miller and Seigler (2012) , Maslin (2015) and WorldWideWattle (2022) . Summaries of issues concerning the retypification for the name Acacia are provided in McNeill and Turland (2010) , Moore et al. (2010) and Thiele et al. (2011) . Some of the more important phylogenetic studies that have demonstrated the non-monophyly of Acacia s.l. include Miller and Bayer (2000 , 2001 ), Luckow et al. (2003) , Murphy et al. (2003) , Kyalangalilwa et al. (2013) , Miller et al. (2017) and Koenen et al. (2020a) . The current correct names for all species of the former broadly defined genus Acacia are available at WorldWideWattle (2022) . For several years prior to the fragmentation of Acacia s.l. the genus was commonly viewed as comprising three subgenera as defined by Vassal (1972) , namely, Acacia subg. Acacia (now Vachellia ), Acacia subg. Aculeiferum Vassal (now Senegalia Raf.) and Acacia subg. Heterophyllum Vassal (= subg. Acacia Phyllodineae (DC.) Ser., now Acacia ). Vassal's classification was based primarily on characters of seedling ontogeny and seed morphology from 127 species (representing less than 10% of those recognised for the genus at that time), supplemented by data on other characters, including pollen of Guinet (1969) . These subgenera broadly corresponded to groupings of six series of Acacia that Bentham (1875) had previously recognised and which had been used to accommodate species of the genus. Discussions of Vassal's classification in relation to Bentham's is provided in Maslin (2001) and Murphy (2008) for Australian species and by Ross (1979) for African species. Although Vassal's subgenera (but not his lower-order categories) were adopted by some authors (e.g., Nielsen 1992 ), Pedley (1986) elevated them to genera: Acacia (= Acacia subg. Acacia sensu Vassal, now Vachellia ), Racosperma (= Acacia subg. Heterophyllum ≡ subg. Phyllodineae , now Acacia ) and Senegalia (= subg. Senegalia Aculeiferum ). However, Pedley's (1986) classification was not widely adopted at that time and it was not until later that genetic evidence clearly showed that Acacia s.l. was polyphyletic (e.g., Luckow et al. 2003 ; Miller and Seigler 2012 ) and that multiple genera for Acacia s.l. were accepted and the fragmentation of the genus began. This resulted in seven currently recognised genera: Acacia s.s., Acaciella Britton & Rose (15 species, New World), Mariosousa Seigler & Ebinger (14 species, New World), Parasenegalia Seigler & Ebinger (11 species, New World), Pseudosenegalia Seigler & Ebinger (two species, New World), Senegalia Raf. (219 species, pantropical) and Vachellia (164 species, pantropical). Although all genetic studies have shown Acacia s.s. to be monophyletic, the morphological and other characters that separate this genus from the six genera excised from Acacia s.l. have been poorly studied. Nevertheless, 95% of Acacia s.s. species possess phyllodes which readily distinguishes them from the bipinnate-leaved species of the other six genera (but there are also 73 bipinnate-leaved species in Acacia s.s.; WorldWideWattle 2022 ). Other attributes that help characterise Acacia s.s. include their extraporate pollen grains which possess pseudocolpi on their exine surface (a character otherwise not found elsewhere in Mimoseae , Guinet 1981a ), the sequence of their seedling leaf development ( Vassal 1972 ) and some biochemical and biological characters summarised by Pedley (1986) . However, with the possible exception of the pollen, these attributes have not been comprehensively surveyed across Acacia s.l. The infrageneric classification adopted for Acacia today is that of Pedley (1978) in which the species are arranged in seven sections, Acacia sect. Acacia (= sect. Acacia Phyllodineae DC.), Acacia sect. Alatae (Benth.) Pedley, Acacia sect. Botrycephalae (Benth.) Taub., Acacia sect. Juliflorae (Benth.) C. Moore & Betche, Acacia sect. Lycopodiifoliae Pedley, Acacia sect. Plurinerves (Benth.) C. Moore & Betche, and Acacia sect. Pulchellae (Benth.) Taub. Although this is a convenient scheme for grouping species of this large genus, it is artificial and does not define monophyletic groups ( Murphy 2008 ). Molecular phylogenetic studies have provided useful insights into evolutionary questions and informal names have been proposed for some of the major clades, but these studies have been hampered by lack of resolution for some relationships and incomplete sampling of species to date (e.g., Murphy et al. 2010 ; Mishler et al. 2014 ). Taxonomic references. Andrew et al. (2003) ; Bentham (1875) ; Guinet (1969 , 1981a ); Hnatiuk and Maslin (1988) ; Maslin (2001 , 2011 , 2015 ); Maslin and McDonald (2004) ; Maslin and Reid (2012) ; Maslin and Thomson (1992) ; Maslin et al. (2019b) ; McDonald et al. (2001) ; Miller and Bayer (2000 , 2001 ); Miller and Seigler (2012) ; Miller et al. (2002) ; Mishler et al. (2014) ; Moran et al. (1992) ; Moore et al. (2010) ; Murphy (2008) ; Murphy et al. (2003 , 2010 ); Pedley (1975 , 1978 , 1986 ); Ross (1979) ; Thiele et al. (2011) ; Vassal (1972) .