Two new species of Poecilanthe (Leguminosae: Papilionoideae: Brongniartieae) from Bolivia and Brazil

Additional keywords: Fabaceae, Neotropics, taxonomy.

The Neotropical, predominantly Brazilian (Meireles 2010) genus Poecilanthe Benth. was first described by Bentham (1860, p. 80) who recognised the following three species: P. grandiflora Benth. (now known to occur in caatinga and Mata Atlântica vegetation in the Brazilian states of Alagoas, Bahia, Ceará, Maranhão, Minas Gerais, Paraíba and Pernambuco), P. subcordata Benth. (found in cerrado (savanna) in the Brazilian states of Bahia, Minas Gerais, and Piauí) and P. parviflora Benth. (in Mata Atlântica and gallery forest, in Argentina, Uruguay, on the Paraguay–Brazil border, and in the Brazilian states of Paraná, Rio Grande do Sul, Santa Catarina and São Paulo). All three species are retained within the current circumscription of Poecilanthe (Meireles 2007; Meireles and de Azevedo Tozzi 2007; Meireles et al. 2014).

Since Bentham’s publication (Bentham 1860), another eight species have been transferred into the genus or have been described as new species within it. Heringer (1952) transferred Pterocarpus falcatus Vell. into Poecilanthe, making the combination Poecilanthe falcata (Vell.) Heringer (a species growing in sandy soils of Espirito Santo and Rio de Janeiro states). Poecilanthe ulei (Harms) Arroyo & Rudd was moved into the genus by Rudd (1973) after its tentative placement in Machaerium Pers. by Harms (1908). The species occurs in Alagoas and Bahia in caatinga or open arboreal steppe (‘estepe arborea aberta’) vegetation. Lewis (1989) added Poecilanthe itapuana G.P.Lewis, described from ‘restinga’ vegetation (in the Mata Atlântica biome) on the stabilised white sand dunes near Salvador, Bahia, Brazil. The most recently described, and very distinctive, new species to have been added to the genus is Poecilanthe fluminensis Meireles & H.C.Lima (Meireles and de Lima 2013), which is endemic to montane and lowland forest in the Brazilian state of Rio de Janeiro. The remaining four species that were at one time considered to belong to Poecilanthe are now placed in either the reinstated monospecific genus Amphiodon Huber, or the recently described genus Limadendron Meireles & A.M.G.Azevedo (Meireles and Azevedo Tozzi 2014, 2015; Meireles et al. 2014). Poecilanthe effusa (Huber) Ducke (1932) has been reinstated as Amphiodon effusus Huber (1909, pp. 398–400), and Poecilanthe ovalifolia Kleinhoonte (1925) is now treated as a synonym of it (Meireles and Azevedo Tozzi 2014). Poecilanthe amazonica (Ducke) Ducke (1932) and P. hostmannii (Benth.) Amsh. (Amshoff 1939), both having originally been described in the genus Cyclolobium Benth., are now recognised as Limadendron amazonicum (Ducke) Meireles & A.M.G.Azevedo and L. hostmannii (Benth.) Meireles & A.M.G.Azevedo respectively (Meireles and Azevedo Tozzi 2015).

Poecilanthe belongs to the papilionoid legume tribe Brongniartieae Hutch. (Ross and Crisp 2005), which has undergone significant expansion since Kalin Arroyo (1981) circumscribed it, to comprise the two amphitropical American genera, Brongniartia Kunth and Harpalyce DC. It expanded to five after Crisp and Weston (1987) formally included the Australian genera Hovea R.Br., Lamprolobium Benth., Plagiocarpus Benth. and Templetonia R.Br. This repositioning of the ‘Templetonia group’ of genera has been supported by a series of phylogenetic studies (Crisp and Weston 1987; Crisp et al. 2000; Kajita et al. 2001; Thompson et al. 2001; Wojciechowski et al. 2004; Cardoso et al. 2012, 2013), and is confirmed by several morphological traits that are shared by the American and Australian genera. Ross (2001) added to the number of genera in the Brongniartieae by segregating the monospecific genera Cristonia J.H.Ross and Thinicola J.H.Ross from Templetonia. Various studies also supported the transfer of the neotropical genera Cyclolobium and Poecilanthe to the Brongniartieae (Hu et al. 2000, 2002; Wojciechowski et al. 2004; de Queiroz et al. 2010; Cardoso et al. 2012, 2013; Meireles et al. 2014). The recently described Brazilian monospecific genus Tabaroa L.P.Queiroz, G.P.Lewis & M.F.Wojc. was also unequivocally placed in the Brongniartieae (de Queiroz et al. 2010). The first, and to date only, African genus to be associated with the tribe is Haplormosia Harms, which is resolved as sister to the American–Australian Brongniartieae clade (Cardoso et al. 2017) and is the long-anticipated African ‘missing link’ between the neotropical and Australian genera. Meireles and co-workers reinstated the genus Amphiodon (Meireles and Azevedo Tozzi 2014; Meireles et al. 2014) and segregated the new genus Limadendron from Poecilanthe (Meireles and Azevedo Tozzi 2015; Meireles et al. 2014). The most recent addition to the tribe is the Cuban-endemic, monospecific genus Behaimia Griseb. (de Queiroz et al. 2017), which was formerly placed in the tribe Millettieae (Geesink 1984; Lewis 1988; Schrire 2005). As a result of all these taxonomic realignments, the tribe Brongniartieae now comprises 15 genera.

The species described here as Poecilanthe goiasana G.P.Lewis was first noticed in a gift of legume duplicate herbarium specimens from IBGE to K. The combination of trifoliolate leaves with large elliptic to widely elliptic leaflets, together with its large flowers, and the geographical location of the collection suggested a novelty. To date, no second collection of the species has been made and the fruits remain unknown.

Specimens of the small tree described here as Poecilanthe boliviana G.P.Lewis were first collected by one of us (JRIW) in flower in November 2007, again in flower in November 2010, and in fruit in March 2011. The specimens did not match the only known species of the genus recorded for Bolivia, nor any previously published species in the genus. The species is presently known from a very restricted area in the Department of Santa Cruz. Analysis of the foliage, flowers and fruits left no doubt that the collections together represent another species new to science.

A preliminary maximum-parsimony analysis of a nuclear DNA ITS dataset of a sample of taxa from tribe Brongniartieae by M. F. Wojciechowski (pers. comm., 2009) included specimens of the two new species described here. It placed a representative of the first new species, Mendonça et al. 2881 (K), as sister to Poecilanthe falcata, and the two together as sister to a clade that included a representative of the second new species, Wood et al. 23849 (K), as sister to P. parviflora. Meireles et al. (2014) also recognised two distinct clades in the genus and placed P. grandiflora and P. ulei with P. falcata. Although including fewer species in their studies, Cardoso et al. (2017) and de Queiroz et al. (2017) presented the same relationship between these two clades of Poecilanthe, but neither study included specimens of the two new species proposed here.

Type: Brazil, Goiás, Município de Niquelândia, estrada entre Niquelândia e a Companhia de Níquel Tocantins, 14°22′14″S, 48°23′15″W, 20 Oct. 1996 (fl.), R.C.Mendonça, R. Marquete, A.M.S.F.Vaz, M.L.Fonseca & G.Gomes 2881 (holo: IBGE 40976!; iso: HUEFS 29488 n.v., K!, RB 398799!).

In leaflet number per leaf and leaflet size, P. goiasana most resembles P. ulei, but the elliptic to broadly elliptic leaflets of P. goiasana differ from the generally ovate to broadly lanceolate leaflets of P. ulei. In addition, the flowers of P. goiasana are 3–3.3 cm long and the corolla white, whereas the flowers of P. ulei are <1.1 cm long and the corollas purplish. Poecilanthe goiasana differs from P. grandiflora and P. falcata in having fewer leaflets per leaf (3 v. 6–9) and white (v. purplish) corollas, as well as an elongate raceme (v. a pyramidal raceme or panicle). Flowers of P. falcata can attain a length of 3 cm, i.e. almost the maximum length of the flowers of P. goiasana.

Heliophytic, saxicolous shrub (only known from regrowth material) up to 60 cm tall; bark smooth. Leaves compound, petiole 9 cm long, densely tomentose, leaf rachis 8 cm long, densely tomentose, three subsessile alternate leaflets, these 10.5–14 × 9–13 cm, elliptic (longer than broad) to widely elliptic (broader than long), apex rounded to obtuse to acute, base shallowly cordate, upper surface of leaflets moderately pubescent, lower surface sparsely pubescent, venation brochidodromous, with 6–7(–9) pairs of secondary veins, main vein prominent on the lower surface of leaflets, main vein and secondaries densely pubescent with spreading hairs on both surfaces of the leaflets, tertiary veins reticulate. Inflorescence racemose, leaf-opposed, 17 cm long (including a 1-cm-long peduncle). Flowers 3–3.3 cm long, pedicellate, pedicel 10–12 mm long, a persistent, lanceolate, 3-mm-long bract at the pedicel base, a persistent 2-mm-long bracteole inserted on the pedicel 2 mm below the 10–12 × 7-mm calyx tube, calyx teeth 5–7 mm long, the lowest tooth slightly longer than the other 4, the upper 2 teeth partially fused, their free tips 2–2.5 mm long, the calyx rusty-tomentose externally; corolla white, standard petal ~30 × 20 mm (including an 8-mm-long thickened claw), wing petals 25–30 × 7–10 mm (including an 8–12-mm claw), keel petals loosely fused (and easily separated), 17–20 × 3–5 mm (including an 8-mm-long claw); staminal sheath apparently diadelphous, 9 + 1 (although because of the lack of available material to dissect, and floral insect damage, it is possible that the sheath is monadelphous, or variable), anthers alternately long and short, the longer anthers ~2 mm long, dehiscing by longitudinal slits, ovary 7 mm long, style 8 mm long, stigma capitate, terminal. Fruits unknown. (Fig. 1.)

Apparently endemic to the state of Goiás, Brazil.

Growing in undulating terrain of ‘campo sujo’ (a form of open, herbaceous and shrubby cerrado (savanna) vegetation) in lateritic soil at 720-m elevation; the area recently burnt at the time of collection.

The single known collection of the species was collected in flower in October.

Because the species is known from only a single gathering, it is considered Data Deficient (DD) in respect to its conservation status, following IUCN Red List categories and criteria (IUCN 2012).

The species epithet alludes to this being the only Poecilanthe known to occur in the Brazilian state of Goiás at the time of publication.

Six of the seven previously recognised species of Poecilanthe have compound leaves; only the recently described P. fluminensis (Meireles and de Lima 2013) is simple-leaved. Within the compound-leaved Poecilanthe, Meireles et al. (2014) recognised two well supported clades. One clade comprises P. falcata, P. grandiflora and P. ulei and is characterised by flowers with a monadelphous androecium and unpaired axillary racemes; the other clade contains the species P. itapuana, P. parviflora and P. subcordata, all having paired axillary racemes and an androecium varying from monadelphous to diadelphous within the same plant. Morphologically, P. goiasana apparently bridges these two clades in having an unpaired raceme but diadelphous androecium. A different fruit type also separates the two clades; however, fruits are not known for the new species. We predict that, if found, the fruits will be woody and dehiscent, and release their seeds explosively by twisting of the two valves (as in P. falcata, P. grandiflora and P. ulei). Preliminary molecular data placed P. goiasana as sister to P. falcata (M. F. Wojciechowski, pers. comm., 2009). If additional collections of the new species become available, variation in foliage, flower size and possibly colour might also become apparent, and some reconsideration of morphological similarities will be necessary.

Currently only known from the type collection.

Fig. 1.  Poecilanthe goiasana. A. Leaf. B. Detail of indumentum on leaflet upper surface. C. Detail of indumentum on leaflet lower surface. D. Inflorescence. E. Calyx opened out, outer surface. F. Standard petal. G. Wing petal. H. Keel petals. J. Staminal sheath opened out, showing dimorphic anthers. K. Gynoecium. Scale bars: 10 mm (A, D), 1 mm (B, C) and 5 mm (E–K). All from Mendonça et al. 2881 (K). Drawn by Margaret Tebbs.

Type: Bolivia, Santa Cruz, Chiquitos, approx. 42 a 43 km de Taperas a San Juan, 17°46′07″S, 60°02′47″W, 24 Nov. 2010 (fl.), J.R.I.Wood & D.Soto 26966 (holo: USZ!, iso: K [3 sheets]!, LPB!, UB!).

Poecilanthe boliviana is morphologically similar in appearance to P. parviflora. Both species are medium-sized trees with pinnate leaves, with the terminal leaflet largest, but P. boliviana differs by the cordate leaflet bases (v. cuneate or rounded in P. parviflora), the young leaflets moderately to densely pubescent on both surfaces (v. almost entirely glabrous, except for a few scattered hairs on the pulvinus, the base of the main vein and on the leaflet margin), its slightly larger flowers with longer petal claws (2–2.5 v. 1.5 mm long), the standard petal wider than long and laterally elliptic (v. equally as long as wide and broadly ovate, wider at its base than in the middle), the standard blade apex emarginate (v. obtuse to shallowly retuse), the upper two calyx teeth fused for their entire length or almost so to their retuse apex (v. the two upper lobes with free tips 0.5–1 mm long), the ovary pubescent to hirsute along both sutures (v. densely pubescent along the upper suture, and the lower suture glabrous or almost so), and by its different fruit shape, broader near the apex than the base, slightly falcate and scimitar-shaped (v. subelliptic, broader near the middle and with an abruptly narrowed short base.

Deciduous tree, 5–15 m tall; bark dark grey to coffee-coloured-greyish, breaking off in small woody plates, inner bark yellow; young stems pubescent. Leaves imparipinnate, 5-foliolate, the terminal leaflet largest, petiole 1.4–1.7 cm long, pubescent, rachis 2.3–4 cm long, pubescent, leaflets alternate to subopposite, terminal leaflet 3.3–6.2 × 2.0–4.7 cm, basal leaflets 2.2–3.8 × 1.4–3.4 cm, all leaflets with a 2–3-mm-long pulvinule, leaflet lamina lanceolate to ovate to broadly ovate, apex obtuse to acute to retuse, base deeply to shallowly cordate to rounded, young leaflets densely appressed pubescent on both surfaces, hairs white, or basally brown and apically white, the main vein and secondaries clearly demarcated by a concentration of brown hairs, mature leaflets lustrous on upper surface, less so below, moderately pubescent to glabrescent on upper surface, except for the persistently pubescent main and secondary veins, pubescence denser on lower surface, leaflet margin slightly thickened and ciliate, leaflet venation brochidodromous, the main vein prominent on lower surface, tertiary and quaternary veins reticulate and clearly visible on the lower surface. Inflorescence a subsessile, solitary, lateral, or less often axillary, raceme, or the racemes occasionally in pairs, each ~10–15-flowered, most flowering occurring on the woody growth of the previous year, and below the current-season young flush foliage, racemes 2–3 cm long, much shorter than the leaves, peduncle and rachis pubescent, peduncle 1–1.5 mm long. Flowers 5.5–8 mm long, pedicellate, the pedicels 0.75–1.5 mm long, pubescent; a densely pubescent, persistent, ovate, 1-mm-long bract at the pedicel base, persistent densely pubescent bracteoles at the calyx base, calyx appressed pubescent externally, the acuminate 2.5–3 mm long, slightly inrolled teeth subequalling the 2.2–3-mm tube, the upper two teeth fused their entire length, or almost so to their retuse apex (the calyx thus appearing 4-lobed), the three lower narrowly triangular teeth acute; corolla white, the standard petal with a central-basal yellowish-green blotch on the inner face, this surmounted by a corona of purplish insect guide lines, the keel with a pale-purplish tip, standard petal 7–8.5 (including a 2–2.5-mm-broad thickened claw) × 8–9 mm, the petal blade wider than long, laterally elliptic, the apex emarginate, wing petals 8 (including a 2-mm-long claw) × 2–3 mm, keel petals 6.5–8 (including a 2–2.5-mm claw) × 2–3 mm, their blades partially fused for half their length from the apex; stamens diadelphous (9 + 1) or the vexillary stamen united with the other 9 for half its length from the base (pseudo-monadelphous), staminal sheath 5–5.5 mm long, free portion of the filaments 1–2 mm long, both staminal sheath types present on the same specimen, anthers alternately longer (1 mm) and lanceolate, or shorter (0.3 mm) and ovate, the vexillary stamen with a shorter anther; ovary pubescent to hirsute along both margins, 3–3.5 mm long, 2–4-ovuled, style 1.5 mm long, stigma capitate, terminal. Fruits woody, dehiscent, broader near the apex and narrower at the base, 3.3–4.2 × 1.4–1.6 cm, the upper suture slightly ridged, glabrous, stipitate, the stipe 1.5–2 mm long, 1- or 2-seeded, mature seeds unknown. (Fig. 2, 3.)

Poecilanthe boliviana is known from a single population beside the road from Taperas to San Juan in Chiquitos Province, in the Department of Santa Cruz, Bolivia.

The species is a component of a seasonally dry forest, in the area where the Cerrado–Chaqueño vegetation is in transition to Chiquitano Dry Forest at ~335-m altitude. It grows in an area of plain, with somewhat compacted sandy clay soil, which is water-retentive during the rainy season.

Collected in flower in November and in fruit in March.

Poecilanthe boliviana is common in forest over an area of ~1 km². No individuals were seen outside this area despite searching and, as currently known, it is a rare species. Because this is an accessible area on a flat plain, it is at risk of clearance for cattle ranching. On the basis of its rarity and the risk of deforestation, the species might be tentatively classified as Critically Endangered (CR) following IUCN guidelines (IUCN 2012). However, it must be emphasised that the whole area is botanically unexplored apart from passages along the road by one of us (JRIW) and perhaps by one or two other passing botanists. There is every hope, therefore, that additional populations will be found when the region is more thoroughly explored.

The species epithet refers to the taxon being a narrowly restricted endemic in Bolivia. Its sister species P. parviflora has a much wider distribution in South America, including a single collection from Bolivia (see Notes).

A fruiting collection, Vargas et al. 3450 (K), from 18°12′747″S, 59°27′036″W, growing at 200-m elevation in the Valle de Tucavaca, 20 km north-east of Santiago de Chiquitos, was cited under P. parviflora in the Catálago de las Plantas Vasculares de Bolivia (Jørgensen et al. 2014) and is the only collection of Poecilanthe included in the Catalogue. We confirm that identification. The habitat of Vargas et al. 3450 is given as ‘bosque de llanura de inundación a los márgenes del Río Tucavaca’, a vegetation type distinct from that of the new species, P. boliviana. As the two species are morphologically similar and molecularly shown to be sister taxa, more collections from the field and a detailed analysis of the relationship between the two in Bolivia are desirable.

BOLIVIA. Departamento Santa Cruz, Provincia Chiquitos, 41 km de Taperas en el camino a San Juan, 17°46′04″S, 60°03′56″W, 10 Nov. 2007 (fl.), J.R.I.Wood et al. 23849 (K, LPB, USZ, UB); ibid., 42 km de Taperas hacia San Juan, 17°46′40″S, 60°03′55″W, 5 Mar. 2011 (fr.), J.R.I.Wood & D.Soto 27146 (K [2 sheets], LPB, USZ).

Fig. 2.  Poecilanthe boliviana. A. Flowering branch. B. Fruiting branch. C. Axillary resting bud. D. Indumentum on leaflet lower surface. E. Flower bud. F. Calyx opened out, outer surface. G. Standard petal. H. Wing petal. J. Keel petals. K. Staminal sheath unopened. L. Staminal sheath opened out, showing dimorphic anthers. M. Two anther types. N. Gynoecium. Scale bars: 10 mm (A, B), 1 mm (C–L, N) and 0.5 mm (M). A and C–N from Wood 26966 (iso; K), B from Wood & Soto 27146 (K). Drawn by Margaret Tebbs.

Fig. 3.  Poecilanthe boliviana. A. Young tree. B. Bark of older tree. C. Foliage and inflorescences. All photographs by J. R. I. Wood.

The authors declare that they have no conflicts of interest.

J. R. I. Wood thanks the Darwin Initiative Project (16-004) for financial support for field work in Bolivia and to field workers, especially Daniel Soto, who accompanied him when assessing the population of Poecilanthe boliviana.