Variation in armature of Prosopis, Strombocarpa, Neltuma and XerocladiaANeltumadenudans (nodal spines on a zig-zag stem) BN.humilis (paired striate spine-tipped branches) CProsopiscineraria (scattered internodal prickles) DNeltumasericantha (spine-tipped stems) EStrombocarpaburkartii (stipular spines) FNeltumaargentina (single nodal axillary spine) GN.kuntzei (spinescent shoots) HStrombocarpaferox (stipular spines) IS.strombulifera (stipular spines) JNeltumaelata (variation in paired nodal spines on one specimen) KN.alba (paired nodal spines) LN.velutina (paired nodal spines) MProsopisfarcta (scattered internodal prickles) NNeltumaruscifolia (single nodal axillary spine) OXerocladiaviridiramis (recurved, deflexed stipular spines) (5 cm scale bar). All specimens at K A drawn from Seijo 1489 BTweedie s.n. CWillcox 299 D MERL 8792 EAcosta & Rosas 748 FGuaglianone et al. 1762 GNee & Coimbra 35556 HAtahuachi et al. MA1147 IHunziker 2036 JLegname & Cuezzo 10396 (large and small spines from same specimen) KHughes & Forrest 2312 LHarding & Balsinhas 140 MGuest et al. 17463 NWood & Mamani 14063 OKolberg & Tholkes HK2493. Drawn by Andrew Brown, July 2021.

Variation in armature across Prosopis s.l. and allies A stipular spines of StrombocarpastrombuliferaB internodal prickles on shoots and branches of Indopiptadeniaoudhensis which it shares with its sister group, Prosopis s.s. illustrated in C; C internodal prickles of ProsopisfarctaD stipular spines of Xerocladiaviridiramis which it shares with its sister group, the genus Strombocarpa illustrated in A; E axillary nodal spines of NeltumajulifloraF spinescent straight cylindrical shoots of the subaphyllous Neltumakuntzei. Photos courtesy of Guillermo Debandi (A) (see https//www.inaturalist.org/taxa/78750-Prosopis-strombulifera/browse_photos), Dr. Omesh Bajpai and Dr. Lal Babu Chaudhary (B), Zeynel Cebeci (C) (see https//commons.wikimedia.org/wiki/FileProsopis_farcta_-_Syrian_mesquite_01), N. Dreber (D) (see http//www.southernafricanplants.com/), Colin Hughes (E, F).

Fruits of Prosopis, Strombocarpa, Xerocladia and IndopiptadeniaAProsopiscinerariaBAnonychiumafricanumCStrombocarpapalmeriDProsopisfarctaEStrombocarpaferoxFS.strombuliferaGS.pubescensHS.abbreviata (2 examples) IS.tamarugoJS.torquataKS.burkartiiLXerocladiaviridiramisMIndopiptadeniaoudhensisA-G, M (5 cm scale bar) H-L (1 cm scale bar with asterisk). All specimens at K A drawn from Gazanfar SG4332 BDembele & Sanogo ML-146 and longitudinal section of fruit from Barter 1193 CHughes et al. 1552 Dvan der Maesen 1627 EAtahuachi et al. MA1147 FHunziker 2036 GAcocks 1788 HTweedie s.n. (from 2 type specimens) IAronson 7742 JVuilleumier 1019 KAcosta & Rosas 748 LKolberg & Tholkes HK2493 MBajpai & Babu 264498. Drawn by Andrew Brown, July 2021.

Variation in fruits across Prosopis s.l. and allies A indehiscent pods of Anonychiumafricanum with thick pulpy mesocarp collected as fodder for livestock B plano-compressed pods of Indopiptadeniaoudhensis lacking a thickened mesocarp and dehiscent along both sutures C indehiscent fruits of Prosopisfarcta with a thick pulpy mesocarp D tightly coiled indehiscent screwbean fruits of StrombocarpastrombuliferaE indehiscent pods of Strombocarpaferox with a thick pulpy mesocarp F indehiscent fruits of StrombocarpapalmeriG small reniform to flabellate, flattened, indehiscent, 1 (–2)-seeded, winged fruits of Xerocladiaviridiramis which are unique within mimosoid legumes H indehiscent fruits of Neltumaarticulata with a thick mesocarp and a hard bony segmented endocarp which remains closed I. Unripe indehiscent pods of Neltumakuntzei with a thick pulpy mesocarp, these turning dark blackish-brown when ripe, reminiscent in colour to fruits of Anonychium. Photos courtesy of Marco Schmidt (A) (see Dressler et al. 2014), Dr. Omesh Bajpai and Dr. Lal Babu Chaudhary (B), Zeynel Cebeci (C) (https//en.wikipedia.org/wiki/Prosopis_farcta), Dick Culbert (D) (see https//eol.org/pages/640506, Colin Hughes (E, F, H, I), and Herta Kolberg (G) (see Plants of Namibia https//herbaria.plants.ox.ac.uk/bol/namibia).

The distributions of Indopiptadenia, Prosopis s.s., Anonychium, Xerocladia, Neltuma and Strombocarpa, based on 6,469 quality-controlled species occurrences from GBIF (www.gbif.org), DryFlor (www.dryflor.info), SEINet (www.swbiodiversity.org/seinet) and several other data sources (Ringelberg et al., in prep.). Map created using R packages ggplot2 (Wickham 2016), sf (Pebesma 2018) and rnaturalearth (South 2017). The eight occurrence records, mapped in Bahia Brazil, are of Neltumaruscifolia which is considered potentially native to that region (Burkart 1976 Oliveira & Queiroz 2020), while records of N.juliflora from Bahia, which is introduced and naturalised in that region, have been eliminated.

A Phylogeny of the Caesalpinioideae showing the placement of the Prosopis grade (boxed in red) within the subfamily, based on analyses of DNA sequences of 997 nuclear genes (Ringelberg et al. 2022) B the part of the phylogeny that includes all elements of Prosopis s.l. Genera recognised in the new generic system presented here are in bold. Pie charts show the fraction of gene trees supporting that bipartition in blue, the fraction of gene trees supporting the most likely alternative configuration in green, the fraction of gene trees supporting additional conflicting configurations in red and the fraction of uninformative gene trees in grey. Numbers above pie charts are Extended Quadripartition Internode Certainty (Zhou et al. 2020) scores. Branch lengths are expressed in coalescent units and terminal branches were assigned an arbitrary uniform length for visual clarity, see Ringelberg et al. (2022); the root is not drawn to scale C, D the two most likely alternative tree topologies which would allow for a monophyletic Prosopis s.l., either without (C) or with (D) Xerocladia and Indopiptadenia. In C and D numbers above pie charts = number of gene trees supporting the species tree, numbers below pie charts = number of gene trees conflicting with the species tree C lack of gene tree support (just 69 gene trees) for the alternative species tree topology where sections Algarobia + Monilicarpa (≡ Neltuma) are sister to section Strombocarpa (≡ Strombocarpa) vs. 573 genes supporting a sister group relationship between Strombocarpa and Xerocladia (as shown in D) D lack of gene trees (zero gene trees) supporting a monophyletic Prosopis s.l.