Bahiana occidentalis K. Wurdack, 2023

Wurdack, Kenneth J., 2023, A new, disjunct species of Bahiana (Euphorbiaceae, Acalyphoideae): Phytogeographic connections between the seasonally dry tropical forests of Peru and Brazil, and a review of spinescence in the family, PhytoKeys 219, pp. 121-144 : 121

Bahiana occidentalis K. Wurdack sp. nov.

Figs 3 , 5

Diagnosis.

Differs from Bahiana pyriformis in leaves smaller (3.5-6[8.1] × 2.1-3.9[4.6] versus 6-12 × 3-6 cm), staminate cymules 1-flowered (versus usually 3-flowered), fruits smaller and subglobose (ca. 9 × 14 mm versus 18-28 × 17-23 mm and usually obovoid to pyriform), fruit pedicels longer (10-18 versus up to 5 mm), and seeds smaller (6.9-7.3 long × 6.4-6.5 wide × 6.8-7.4 thick versus 10-15 long × 8-11 wide × 8-13 thick mm).

Type.

Peru. Tumbes: Zarumilla Province, Matapalo, zona "El Caucho-Campo Verde", Parcela 2 × 500 m ( evaluación florística) paralela a parcela “V” de evaluación forestal permanente, desde 420 m hasta 500 m, 03°50'29"S, 080°15'30"W (-3.8413800, -80.2583300), 500 m, 11 Feb 1993 (fr), C. Díaz S. et al. 6288 (holotype: MO sheet 7004543; isotypes: K, NY, US, USM; 13 reported duplicates).

Description.

Small trees, 4-10 m, trunk to 12 cm dbh, probably dioecious (collections unisexual); bark of branches smooth, lenticellate; lateral leafy branchlets 1-6 cm long, 1-2 mm wide, terete, sometimes as brachyblasts with numerous compressed nodes, or with zones of compressed nodes (long shoot/short shoot transitions on same axis), sparsely pubescent when young. Indumentum simple, pale, to 0.5 mm long. Stipules free, persistent, paired; when young appressed to stem, triangular 1.5-2.5 × 1 mm, with prominent midrib and narrow membranous margins extending ca. 0.1 mm, sparsely short puberulent; with age spinose, stiff, accrescent to 5-6 mm long, base with shield-like attachment zone to stem, projecting 45-90° from stem, glabrescent; resting buds with multiple series of spines and scales; bud scales 1.5 × 1 mm, triangular, navicular. Leaves alternate, simple, petiolate. Petioles 3-7(11) mm long, 0.5-0.7 mm tall × 0.7-1 mm wide (mid-length cross section), slightly dorsiventrally flattened (rarely terete), adaxially moderately pubescent and abaxially distinctly less pubescent to nearly glabrous. Leaf blades elliptic, 3.5-6(8.1) × 2.1-3.9(4.6) cm, length:width ratio 1.45-2.91:1 (mean = 2.00, SD = 0.313, n = 55, 5 leaves each from 11 collections); base obtuse to acute; apex obtuse to acute, tip minutely retuse and tipped by a globose gland as on marginal teeth; chartaceous, margins subentire proximally (near base obscurely crenate with little evidence of teeth) to distinctly toothed (crenate) distally, tooth depth varying 0.2-0.5 mm, 7-15 well-defined teeth per side, tooth tip bearing persistent sub-globose glandular knob to 0.2 mm diam. that terminates principal (tertiary) vein; laminar glands (cicatricose-crateriform glands sensu Cervantes et al. 2009) abaxial, scattered, 5-20 glands per leaf, elliptic, 0.1-0.2 × 0.1-0.25 mm, associated with tertiary or quaternary veins; other laminar or petiolar glands absent; trichomes abaxially usually only associated with major veins (rarely uniformly pubescent, A. Gentry et al. 37824), sparsely present along midvein but more densely as acarodomatial tufts in axils of primary/secondary vein junctions; acarodomatia with narrow flaps of vein tissues extending to 0.1 mm from vein junctions, not coincident with laminar glands; adaxial surface micropustulate (likely an artifact of drying around subsurface crystals), pustules mostly tracing vein fabric. Venation pinnate, agrophic veins absent, major secondaries bronchidodromous, 5-7 secondary veins per side, intersecondaries absent, tertiary and quaternary veins mixed percurrent. Staminate inflorescences axillary and appearing terminal, 6-11 mm long in young bud, racemose, simple, ca. 20+ cymules in 3 anticlockwise spirals, cymules each containing 1 bud, subtended by a bract and 2 lateral bractlets; bract 1.5 × 1 mm, navicular, tip acuminate; bractlets navicular, 1.7 × 0.4 mm, glabrous internally and hirsute externally. Staminate flowers: sepals 5?, densely hirsute externally, glabrous internally; receptacle glandular, hirsute; stamens 12-15, filaments free; anthers dorsifixed, introrse, pollen sacs unequal with dorsal pair longer than ventral, connective with protrusion; petals and disc segments absent. Pistillate infructescences axillary, with 1-2 nodes, dichotomously branched, 1-2 fruits per inflorescence; proximal internode (peduncle) 10-40 mm long; ultimate branches (pedicels) 10-18 mm long, 0.5-0.6 mm diam., articulated and often bent at middle but not detaching there, proximal segment (relative to articulation) 3-9 mm long, distal segment 4-8 mm long, slightly thicker and usually darker colored; nodes subtended by navicular bract to 2 mm long. Pistillate flowers (details inferred from fruits) sepals 5, 1.5 × 1-1.5 mm, triangular, slightly unequal in size, interior glabrous, disk annular, thin, densely hirsute; locules 3, styles 3, undivided, thin, to 2.5 mm long, not connate into a column, glabrous. Fruits schizocarps, subglobose, trilobed, ca. 9 (long) × 14 (wide) mm, splitting septicidally and loculicidally into 3 equal 2-valved mericarps; valve segments ca. 13 × 5 mm; sepals and styles persistent; sparsely pubescent, pericarp dry; endocarp woody, 0.8-1 mm thick (equatorial at dorsal dehiscence suture); epicarp ca. 0.2 mm thick, separating when dry, inner surface vascularized, colliculate internally and externally; septa of mericarps thin, nearly complete except for distal funicular gap, shallow basal triangle 4 × 1 mm; columella 5-6 mm long, 1.2-1.3 mm wide (middle), trigonous, tip retaining arms to 1-1.5 mm long, persistent. Seeds 1 per chamber, ellipsoid, laterally slightly compressed, 6.9-7.3 (long) × 6.4-6.5 (wide) × 6.8-7.4 (thick) mm, minutely apiculate for 0.2-0.4 mm; testa ca. 0.2 mm thick, dry, smooth, obscurely brown-marbled; ecarunculate, raphe ventral; hilum near top, triangular, ca. 1.5-2 × 1.5-2 mm; embryo axile spathulate, straight, stalk 1.2 × 0.6 mm, cotyledons ovate, 4.5 (long) × 4 (wide) × 0.1 (thick) mm, with midrib and higher order veins evident, nearly filling seed profile; endosperm firm, oily; central cavity absent.

Etymology.

The specific epithet Bahiana occidentalis refers to western, and indicates the distribution of the new species in western South America, in contrast to B. pyriformis , which grows on the eastern side of the continent.

Distribution and ecology.

The populations of Bahiana occidentalis in Tumbes and San Martín are separated by more than 520 km and represent two (equatorial and eastern, respectively) of the three SDTF subunits defined for Peru ( Linares-Palomino 2006). The new species is expected also to occur in adjacent Ecuador, which contains extensions of the Tumbesian SDTF, and perhaps also in the Marañón inter-Andean STDF that is in between the two populations, although it is isolated from them and mostly at a higher elevation. It occurs in lowland SDTF (500-720 m in Tumbes, 350 m in San Martín). Seasonal rains typically fall (Dec-) Jan to Apr (85% of annual precipitation; Cueva-Ortiz et al. 2020), after critically dry Sep to Nov. Flowering appears to coincide with the start of the rainy season (young staminate inflorescences present until mid-Nov) and mature fruit by Feb. The collections, although not diagnostic due to having only very young inflorescences or fruits, appear unisexual, which probably indicates dioecy as has been documented for B. pyriformis ( Carrión et al. 2022). The Tumbesian SDTF appears to have few other endemic Euphorbiaceae (e.g., Acalypha delicata Cardiel, Croton tumbesinus Riina) ( Cardiel 2006; Linares-Palomino et al. 2010; Feio et al. 2018).

Conservation status.

Following the criteria and categories of IUCN (2012), B. occidentalis is given a preliminary status of Vulnerable (VU) under geographic range criteria B2 area of occupancy <2000 km2 (B2a, known to exist at no more than 10 locations; B2b, continuing decline projected). The Tumbes population is within the Reserva Nacional de Tumbes, a protected area of relatively pristine forest and will ensure long term conservation of the taxon. However, the eastern SDTFs in San Martín are fragmented due to farming, including in the area around the Gentry collection locality (fide Google Earth imagery). Bahiana pyriformis is presently known from a single, small population in a mostly deforested region that is not protected and still at risk.

Additional specimens examined.

Peru. San Martín: 31 km S of Tarapoto, dry forested slopes overlooking Río Huallaga, Transect 1, 06°35'S, 076°25'W (-6.5833333, -76.4166667), 350 m, 18 Jul 1982, A.H. Gentry et al. 37732 (MO sheet 3029763) ; ibid. loc., Transect 3, 20 Jul 1982 (stam infl), A.H. Gentry et al. 37824 (MO sheet 3211186) . Tumbes: Zarumilla, Matapalo. Entre P.C. "El caucho" y P.C. “Campoverde”, Bosque Nacional de Tumbes, Reserva de Biósfera del Noroeste, Arbol #326, 03°50'29"S, 080°15'33"W (-3.8413889, -80.2591667), 720 m, 21 Jul 1992, C. Díaz S. et al. 5009 (MO sheet 5564626) ; ibid. loc., Arbol #359, 22 Jul 1992, C. Díaz S. et al. 5072 (MO sheet 6060058). Parcela “V” de evaluación permanente, No. 393, 03°50'29"S, 080°15'33"W (-3.8413800, -80.2591600), 720 m, 27 Oct 1992, C. Díaz S. et al. 5176 (MO sheet 6060054) ; ibid. loc., No. 427, 27 Oct 1992, C. Díaz S. et al. 5201 (MO sheet 6060056) ; ibid. loc., No. 641, 27 Oct 1992 (stam infl), C. Díaz S. et al. 5390 (MO sheet 5707417) ; ibid. loc., No. 658, 31 Oct 1992 (stam infl), C. Díaz S. et al. 5432 (MO sheet 5707423) ; ibid. loc., No. 666, 31 Oct 1992 (stam infl), C. Díaz S. et al. 5438 (MO sheet 5707422) ; ibid. loc., No. 679, 31 Oct 1992 (stam infl), C. Díaz S. et al. 5472 (MO sheet 5707421) ; ibid. loc., No. 719, 2 Nov 1992 (stam infl), C. Díaz S. et al. 5486 (MO sheet 5707420) ; ibid. loc., No. 720, 2 Nov 1992, C. Díaz S. et al. 5487 (MO sheet 5707415) ; ibid. loc., No. 732, 2 Nov 1992, C. Díaz S. et al. 5489 (MO sheet 5707416) ; ibid. loc., No. 735, 2 Nov 1992, C. Díaz S. et al. 5491 (MO sheet 5707419) ; ibid. loc., No. 721, 2 Nov 1992, C. Díaz S. et al. 5520 (MO sheet 5707428) ; ibid. loc., No. 725, 2 Nov 1992, C. Díaz S. et al. 5521 (MO sheet 6060063) ; ibid. loc., No. 729, 2 Nov 1992 (stam infl), C. Díaz S. et al. 5522 (MO sheet 6060062) ; ibid. loc., No. 743, 2 Nov 1992, C. Díaz S. et al. 5537 (MO sheet 5707424) ; ibid. loc., No. 326, 10 Nov 1992, C. Díaz S. et al. 5957 (MO sheet 6060061) ; ibid. loc., No. 359, 10 Nov 1992, C. Díaz S. et al. 5979 (MO sheet 6060060). Parcela de evaluación florística (2 mt. × 500 m) paralela a la parcela “V”, orientación Este-Oeste , 03°50'29"S, 080°15'33"W (-3.8413800, -80.2591600), 500 m, 12 Nov 1992, C. Díaz S. et al. 6007 (MO sheet 6060059) ; ibid. loc., 12 Nov 1992, C. Díaz S. et al. 6127 (MO sheet 6060052) ; ibid. loc., 12 Nov 1992 (stam infl), C. Díaz S. et al. 6148 (MO sheet 5707407) ; ibid. loc., 12 Nov 1992, (stam infl), C. Díaz S. et al. 6149 (MO sheet 6060065) ; ibid. loc., 12 Nov 1992, C. Díaz S. et al. 6151 (MO sheet 6060064). Entre P.C. "El caucho" y P.C. “Campoverde,” Bosque Nacional de Tumbes, Reserva de Biósfera del Noroeste, Arbol 326, 03°50'29"S, 080°15'33"W (-3.8413800, -80.2591600), 720 m, 21 Jul 1992, C. Díaz S. et al. 5009 (MO sheet 5564626); Arbol #359, 22 Jul 1992, C. Díaz S. et al. 5072 (MO sheet 6060058). Zona "El Caucho-Campo Verde". Parcela 2 × 500 m ( evaluación florística) paralela a parcela “V” de evaluación forestal permanente, 03°50'29"S, 080°15'30"W (-3.8413800, -80.2583300), 500 m, 11 Feb 1993, C. Díaz S. et al. 6272 (MO sheet 6060051) ; ibid. loc., 11 Feb 1993, C. Díaz S. et al. 6277 (MO sheet 6060053) ; ibid. loc., 11 Feb 1993, C. Díaz S. et al. 6282 (MO sheet 6060057). Zona "El Caucho-Campo Verde", Parcela “E” evaluación permanente, No. 326, 03°50'29"S, 080°15'30"W (-3.8413800, -80.2583300), 500 m, 16 Feb 1993 (fr), C. Díaz S. et al. 6545 (MO, US) ; ibid. loc., 17 Feb 1993, C. Díaz S. et al. 6575 (MO sheet 6060055) ; ibid. loc., No. 359, 17 Feb 1993, C. Díaz S. et al. 6605 (MO sheet 6060066) ; ibid. loc., 17 Jan Feb 1995 (fr), C. Díaz S. et al. 7430 (MO sheet 5707408) .

Figures

Figure 3. Illustration of Bahiana occidentalis A habit B shoot tip with spinose stipules C staminate inflorescence in bud D androecium E staminate bract F staminate bractlet G fruit H fruit valve (coccus) I columella J seed (ventral). Sources: A, B, H-J C. Diaz et al. 6288, US C-F C. Diaz et al. 6148, MO G C. Diaz et al. 7340, MO.

Figure 5. Morphology of Bahiana occidentalis A anther ventral B stamen dorsal C androecium with outer stamens removed to show hirsute receptacle (young bud) D stipule inner structure (split longitudinally) E leaf gland (abaxial) F leaf surface with prismatic crystals poking through epidermis along veins (adaxial) G leaf acarodomatia bounded by primary and secondary veins (abaxial) H leaf acarodomatium (clearing) I leaf gland with crystal along vein indicated by arrow (clearing) J whole leaf (clearing; tiled from 418 images) K glandular tooth at leaf margin (clearing) A-G SEM H, J brightfield LM I, K darkfield LM; sources A-C C. Diaz S. et al. 5522, MO D C. Diaz S. et al. 6148, MO E-K C. Diaz S. et al. 6288, US.