Entada Adans., Fam. Pl. 2: 318. 1763, emended S.A. O'Donnell & G.P. Lewis.

O'Donnell, Shawn A., Ringelberg, Jens J. & Lewis, Gwilym P., 2022, Re-circumscription of the mimosoid genus Entada including new combinations for all species of the phylogenetically nested Elephantorrhiza (Leguminosae, Caesalpinioideae, mimosoid clade), PhytoKeys 205, pp. 99-145 : 99

Entada Adans., Fam. Pl. 2: 318. 1763, emended S.A. O'Donnell & G.P. Lewis.

Gigalobium P. Browne, Civ. Nat. Hist. Jamaica: 362. 1756.

Perima Raf., Sylva Tellur.: 118. 1838.

Strepsilobus Raf., Sylva Tellur.: 117. 1838.

Elephantorrhiza Benth., J. Bot. (Hooker) 4: 344. 1841. Synon. nov.

Pusaetha L. ex Kuntze, Revis. Gen. Pl. 1: 204. 1891.

Entadopsis Britton, N. Amer. Fl. 23: 191. 1928.

Type species.

Entada rheedei Spreng.

Description.

Lianas, scandent shrubs, small trees or geoxylic suffrutices, unarmed or with spinescent stipules in E. spinescens . Leaves: bipinnate; primary and secondary axes either eglandular or, in some Madagascan species, with extrafloral nectaries (see Note below) and at least in E. phaseoloides , with unusual ‘pit’ nectaries on stems at nodes adjacent to petiole; rachis in lianescent taxa terminating in a bifurcating tendril (modified terminal pinnae pair); pinnae 1-many pairs per leaf; leaflets 1-many pairs per pinna; lamina often asymmetric and apically mucronate or emarginate. Inflorescence: spiciform racemes or spikes, axillary to supra-axillary, solitary or clustered, sometimes into terminal panicles. Flowers: 5-merous, sessile to shortly pedicellate, staminate or bisexual, cream-coloured, yellow, green, red or purple; calyx gamosepalous, campanulate, the fused sepals distinctly toothed or not; petals 5, free to basally connate, adnate basally with the stamens and a perigynous disc forming a stemonozone; stamens 10, fertile, free or basally united, anthers usually with a caducous spheroidal apical gland, sessile to stipitate; pollen tricolporate, columellate, dispersed as monads; style tapering to a tubular to rarely cupuliform stigma, ovary glabrous and multi-ovulate. Fruit: a craspedium, torulose or not, compressed to flattened, straight to curved to rarely spirally twisted, sometimes gigantic (up to 2 m long in taxa with sea-drifted seeds); epicarp woody to thinly coriaceous; endocarp woody to parchment-like; splitting along transverse septa into one-seeded segments upon ripening or valvately dehiscent, the entire valve breaking away from the replum and the epicarp also separating from the endocarp. Seeds: globular to elliptic, usually laterally compressed, longest axis up to 6 cm in large-fruited taxa, dark brown, smooth, with or without areole, pleurogram (when present) usually open. Fig. 2 .

As delimited here, a genus of 40 species (traditionally ± 30 species), widespread, primarily tropical, but reaching subtropical latitudes in southern Africa and eastern Asia (Fig. 3 ); 29 species in Africa (including Madagascar), nine species in Asia, four species in the Americas; two species ( E. rheedei and E. gigas ) occur in two of these regions. Frequently found in riparian and littoral vegetation, though also in savannah, open woodland, thickets or dense humid to more open and dry forest, often on sandy substrates.

Note on extrafloral nectaries

While much of the literature on Entada (e.g. Brenan 1966; Lewis and Elias 1981; Nielsen 1981, 1992; Villiers 2002; Wu and Nielsen 2010; Braga et al. 2016) noted the absence of petiolar and leaf rachis nectaries that are otherwise common across the mimosoid clade, examination of herbarium specimens from Madagascar uncovered several species that do appear to possess putative extrafloral nectaries. Six species of Entada are native to Madagascar ( Villiers 2002): E. chrysostachys (Benth.) Drake; E. leptostachya Harms; E. louvelii (R. Vig.) Brenan; E. pervillei (Vatke) R. Vig.; E. rheedei Spreng.; and E. tuberosa R. Vig. Of these, E. louvelii , E. pervillei and E. tuberosa are endemic to the Island. Villiers (2002) noted that E. tuberosa "is easily recognisable by the white, glandular mucro at the tip of the leaf rachis and the axes of the pinnae (generally present)" ( Villiers 2002, p. 169). Close examination of specimens at K reveals structures that are here interpreted as extrafloral nectaries on five of the six Madagascan Entada species ( E. chrysostachys is the only species on which these structures were not observed) (Fig. 4 ). These nectaries are visible as annular structures on shoots immediately beneath the base of stipules, in similar positions to those documented for E. phaseoloides ( Blüthgen and Reifenrath 2003; Marazzi et al. 2019) (Fig. 5 ), in all five potentially extrafloral nectary-bearing species. In addition, multiple vouchers of E. pervillei contain material with small basin-like structures at the distal end of adaxially grooved rachises that are also interpreted here as nectaries (Fig. 4C, D ). Finally, structures comparable to those described by Villiers (2002) for E. tuberosa and confirmed on several K vouchers ascribed to this species (e.g. Fig. 4F ), were also observed on specimens identified as E. rheedei (Fig. 4E ). Examination of living material, chemical analyses of any exudates that might issue from all the above-mentioned structures and observations of animal visitation are needed to verify the interpretation offered here that these structures are indeed nectaries. The presence of these structures begs the question about how widespread they might be across the genus. A detailed study of extrafloral nectaries across the full geographical range of Entada should be carried out, this using a high-powered microscope and backed up by fieldwork.

We present no infrageneric classification at this point, pending a more densely sampled species-level molecular phylogeny and more detailed taxonomic revision which are foci of proposed future work. Instead, species are here simply alphabetically ordered. Species descriptions, species delimitation and synonymy are based on regional floristic treatments in Brenan (1959, 1966, 1970), Ross (1974, 1975a, 1975b), Nielsen (1992), Barneby (1996), Cowan (1998), Villiers (2002), Tateishi et al. (2008), Wakita et al. (2008), Ohashi et al. (2010), Wu and Nielsen (2010), Grobler (2012) and Braga et al. (2016), as well as Lungu’s (1995) global synopsis and, for the ex- Elephantorrhiza species, rely almost entirely upon Ross (1974, 1975a) with occasional additions from Brenan (1970) and Grobler (2012). Where opinions in literature differ, we defer to Brenan (1959, 1966, 1970), Ross (1974, 1975a), Nielsen (1992) and Villiers (2002) with any exceptions noted in the corresponding species descriptions. In addition to basionyms, we include synonyms only when these are names published in the genus Entada . For example, under Entada abyssinica , we do not present the synonyms published in the genera Pusaetha , Gigalobium or Entadopsis . We include type details for all accepted species, but not for synonyms.

Figures

Figure 2. Genus-wide variation in morphological characters. A-D habit A large woody liana, E. rheedei (photo: B Wursten, Hyde et al. (2021)) B small tree, E. abyssinica (photo: G Baumann, Dressler et al. (2014 a)) C shrub, E. burkei (photo: M Schmidt, Dressler et al. (2014 a, b )) D geoxylic suffrutex, E. dolichorrhachis (photo: M Bingham, Bingham et al. (2021)) E, F leaves E bipinnate leaf with few pinnae, few large leaflets and ending in a bifurcating tendril, E. rheedei (photo: AP Balan, Balan and Predeep (2021)) F bipinnate leaf with many pinnae, many small leaflets and no tendril, E. rangei (photo: A Dreyer, Dressler et al. (2014 a)) G-I inflorescences G terminal panicle of up-turned spikes, E. polyphylla (photo: R Vasquez Martinez, CC BY-NC-SA 3.0, MBG (2021)) H axillary fascicles of spiciform racemes, E. goetzei (photo: G Baumann, Dressler et al. (2014 a)) I short spiciform raceme of dark red flowers, E. wahlbergii (photo: R Mangelsdorff, Dressler et al. (2014 a)) J-M fruits J immature, weakly falcate, segmented craspedium up to 2 m long, E. rheedei (photo: photographer unknown, Centre for Australian National Biodiversity Research (CANBR), 2000) K immature, segmented, laxly spiralled craspedium up to 120 cm long, E. gigas (photo: R Aguilar CC BY-NC-SA 2.0, Aguilar (2021)) L ripe segmented craspedia breaking up into one-seeded segments with exfoliating epicarp, E. africana (photo: B Eichhorn, Dressler et al. (2014 a)) M ripe unsegmented craspedium, the entire valve breaking away from the persistent replum, E. burkei (photo: M Kriek CC BY-SA 4.0, Ueda (2021) observation 85675968) N, O seeds N one-seeded endocarp segment and small ovoid, flattened seed with elliptic pleurogram, E. africana (photo: B Eichhorn, Dressler et al. (2014 a)) O ripe one-seeded fruit segments with large circular, laterally compressed seeds lacking a pleurogram, E. gigas (photo: J Stevens, Dressler et al. (2014 a)). Scale bars: 1 cm (N, O).

Figure 3. Global distribution of 4415 digitised, quality-controlled herbarium records of Entada (including those for ex- Elephantorrhiza species) in GBIF (www. GBIF. org), DryFlor (www. dryflor. info) and SEINet (swbiodiversity. org / seinet) from Ringelberg et al. (in prep.). Map created using R packages ggplot 2 (Wickham 2016), sf (Pebesma 2018) and rnaturalearth (South 2017). Map: J Ringelberg.

Figure 4. Putative extrafloral nectaries on herbarium specimens of five of the six native Madagascan species of Entada A E. leptostachya, Du Puy et al. M 235 B E. louvelii, Reserves Naturelles RN 1447 C E. pervillei, Service Forestier 10525 _ SF D E. pervillei, Service Forestier 11481 _ SF E E. rheedei, Gautier LG 3153 F E. tuberosa, Jongkind et al. 3264. Scale bars: 2 mm (A-F). Photos: S O'Donnell.

Figure 5. Extrafloral nectaries at nodes on stems of cultivated Entada phaseoloides grown in California from seed. A, B Pit nectary at node on stem adjacent to petiole, indicated by arrow C-E Argentine ants (Linepithema humile) visiting nectaries F dipteran nectary visitor. Scale bars: 5 mm (A-F). Photos: S O'Donnell.