Boliviadendron E.R. Souza & C.E. Hughes, 2022
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publication ID |
https://dx.doi.org/10.3897/phytokeys.205.82256 |
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persistent identifier |
https://treatment.plazi.org/id/6F760332-0B1A-5B60-BEBC-B51613BF5AE7 |
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treatment provided by |
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scientific name |
Boliviadendron E.R. Souza & C.E. Hughes |
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gen. nov. |
Boliviadendron E.R. Souza & C.E. Hughes gen. nov.
Fig. 2 View Figure 2
Type.
Boliviadendron bolivianum (C.E. Hughes & Atahuachi) E.R. Souza & C.E. Hughes.
Diagnosis.
Boliviadendron is similar in almost all respects to the genus Leucochloron and is segregated first and foremost because these two lineages are phylogenetically not closely related (Fig. 1 View Figure 1 ; Koenen et al. 2020). Boliviadendron differs from Leucochloron in its more evidently asymmetrical leaflet bases, by having just 1-2 (-3) primary veins visible vs. the evident reticulate secondary and tertiary venation on the lower leaflet surface in Leucochloron , by the consistent purple-black blotches on the upper surface of the leaflets (sometimes the whole surface suffused purplish-black, but never glossy) vs. the strongly discolorous leaflets of Leucochloron where the upper surface dries dark brown and is often glossy and finally, by the shorter, white indumentum vs. the more generally ferruginous and longer indumentum of Leucochloron species.
Description.
(modified from Hughes and Atahuachi 2006, publ. 2007). Small, unarmed multi-stemmed tree to 5-6 (-10) m tall and 20-35 cm dbh with an irregular spreading crown (Fig. 2A View Figure 2 ). Outer bark smooth, mid grey-brown, with horizontal lines of lenticels when young (Fig. 2B View Figure 2 ), becoming thick and corky and vertically fissured with age; inner bark reddish, then cream, gritty. Woody shoots glabrate, lenticellate, dull grey, lenticels round pustulate, the outer bark papery, slightly striate and sometimes slightly exfoliating. Young shoots, leaf stalks and peduncles minutely and sparsely to densely puberulent with whitish or dull golden 0.1- 0.2 mm hairs. Resting buds perulate, ovoid to 1.5 mm long and densely pilosulous (as for shoots), but these generally lacking. Stipules linear-triangular, 3 × 1.7-2 mm, caducous. Leaves bipinnate with 4-5 (-6) pairs of pinnae, leaf stalks canaliculate with two parallel longitudinal ridges, 7-11 cm long, ending in a 2 mm long mucro and including a 2.5-3.6 cm long petiole charged with a 1-1.3 mm diameter circular or weakly ellipsoid sessile or subsessile, thick-rimmed, cupular nectary at or slightly above mid-petiole position; similar smaller nectaries variably present between distal 1-2 pairs of pinnae or sometimes between all pinnae pairs. Longer interpinnal segments 1.3-1.7 cm long, the rachis of longer pinnae 6-8 cm with 15-20 pairs of leaflets per pinna. Leaflets slightly decrescent proximally and distally, larger leaflets 7-10 × 2.1-3.0 (-3.2) mm, not strongly discolorous, nearly glabrous or very sparsely puberulent above, sparsely puberulent below, on small, ridged, transversely elliptic, asymmetric 3 × 0.6 mm pulvinules, the first anterior or first pair of leaflets reduced to 1.2-1.5 mm long paraphyllidia. Leaflets linear-oblong, obliquely truncate at base, obtuse at apex, the tip sometimes acute, venation indistinct, palmate-pinnate brochidodromous, with 1-2 (-weakly 3) primary veins at base, the main primary vein distinctly asymmetric, dividing the blade 1:2-2.5, giving rise on each side to 3-4 sinuous secondary veins, albeit these often indistinct or obscured by the indumentum, venation very faintly immersed or invisible above, the 1-2 (-3) primary veins clearly visible and weakly prominulous below. Flowers sessile, homomorphic and arranged in lax globose capitula (Fig. 2C View Figure 2 ) on 2.5-3 cm-long slender peduncles, moriform in bud, 12-13 mm in diameter (excluding the filaments), the receptacle 1.3 mm in diameter, each capitulum with 20-25 flowers, whitish-green in bud due to dense silky puberulent indumentum on calyx and corolla. The capitula immersed in new foliage, solitary or in fascicles of 2-3 in axils of coeval leaves. Bracts sessile, short spatulate, 0.2-0.4 mm long, puberulent. Calyx narrowly campanulate, 2.5 mm long, the triangular lobes 0.3-0.4 mm long. Corolla tubular, slightly funnel-shaped, 5-6 mm long, the free lobes 1 mm, slightly reflexed. Androecium of ca. 40 stamens to 10 mm long, fused basally into a 3-4 mm long tube that is not or hardly exserted beyond the corolla. Ovary 0.8 mm long, sessile, the style 2.5 mm, held below anthers of the stamens. Pods (Fig. 2D View Figure 2 ) 1 per capitulum, sessile, (6-) 7-10 × 1.7-2 (-2.7) cm, (3-) 4-6 (-8)-seeded, flat plano-compressed, linear-oblong or oblong, obtuse at each end, sometimes with a short apiculum at apex, the valves straight or with slightly undulate margins, stiff papery, pale whitish- or yellow-green when unripe, turning dull orange-brown when ripe, obscurely venulose, sparsely and minutely puberulent overall, internally dull stramineous, framed by plain sutures <1 mm wide, tardily dehiscent along both sutures, opening narrowly to release seeds, the valves remaining attached after dehiscence. Seeds horizontal at middle of pod, flat disciform, broadly suborbicular, 11-13 mm in diameter, <1 mm thick, the testa thin, lustrous, translucent castaneous, slightly wrinkled when dry, pleurogram lacking, surrounded by a narrow 0.4-0.6 mm dark marginal nerve or minute wing.
Geographic distribution.
The monospecific genus Boliviadendron occupies a narrowly restricted distribution endemic to Bolivia and has been recorded from just a small number of localities on the eastern flanks of the Andes at mid-elevations in interior Andean valleys in the Departments of La Paz, Cochabamba and Santa Cruz (Fig. 3 View Figure 3 ).
Habitat.
Locally common in fence-lines and remnant patches of subhumid or seasonally dry Yungas forest and secondary thickets of Baccharis dracunculifolia DC., Dasyphyllum brasiliense (Spreng.) Cabrera (both Asteraceae), Dodonaea viscosa Jacq. ( Sapindaceae) and Tecoma stans Juss. ( Bignoniaceae). Other associated species include Apurimacia michelii Harms., Coursetia brachyrhachis Harms., Erythrina falcata Benth., Mimosa boliviana Benth., M. woodii Atahuachi & C.E. Hughes, Parapiptadenia excelsa (Griseb.) Burkart (all Leguminosae), Schinopsis haenkeana Engl. ( Anacardiaceae), Cordyline dracaenoides Kunth ( Asparagaceae), Kageneckia lanceolata Ruiz & Pav. ( Rosaceae) and Cleistocactus laniceps (K. Schum.) Rol.-Goss ( Cactaceae). Boliviadendron is known only from the slopes of interior valleys of Bolivia between 2150 and 2770 m alt., around the transition from seasonally-dry tropical inter-Andean valley forests to more moist mid-elevation montane Ceja de Monte Yungeña vegetation. Most collections (apart from two outlying localities in Dept. Santa Cruz) come from two nearby tributaries of the upper Río Cotacajes, in Prov. Ayopaya, Cochabamba and Prov. Inquisivi, La Paz, Bolivia, an area with several other narrowly-endemic plants, including Justicia pluriformis Wash. & J.R.I. Wood ( Acanthaceae), Philibertia fontellae (Murillo) Goyder ( Apocynaceae), Solanum stellativelutinum Bitter and S. tunariense Kuntze ( Solanaceae) and Mimosa woodii ( Leguminosae). Boliviadendron (as Leucochloron bolivianum ) was assigned an IUCN threat category of Endangered (EN) B1ab(iii,iv) in 2011 ( Atahuachi 2012) on account of its very limited extent of occurrence and threats from habitat destruction caused by agricultural expansion and fire which are continuing today.
Etymology.
Boliviadendron is one of just two mimosoid legume genera known to be endemic to Bolivia (the other being Pseudosenegalia Seigler & Ebinger with two species) and that Bolivian endemism is highlighted here by the double-barrelled reference to that country in the name Boliviadendron bolivianum .
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