Swartzia yasuniensis Torke & A. J. Pérez, 2013

Torke, Benjamin M. & Pérez, Álvaro J., 2013, Notes on the genus Swartzia (Leguminosae) in Ecuador, with descriptions of two new species, Phytotaxa 147 (1), pp. 13-25 : 18-23

Swartzia yasuniensis Torke & A. J. Pérez , sp. nov. ( Figs. 3 , 4 )

Ebracteolate pedicels, a nearly glabrous gynoecium, with the ovary ca. 3.5 × longer than wide, and a frequently branched inflorescence belie a close phylogenetic relationship between the new species and several species of Swartzia section Pittierianae (R. S. Cowan 1968: 24) Torke & Mansano (2009: 921) , to which it is assigned; in the context of the section, it is singular in the following combination: stipules 1.6–13 mm long, abaxial leaflet surface pilose, bracts 3.1–6.6 mm long, buds 6.4–7.1 mm long, calyx segments 4–6, larger stamens abaxial, smaller stamens 74–95, ovary stipe 4–6.5 mm long, ovary 6.1–8.1 mm long, ovules ca. 14.

Type: ECUADOR. Orellana: Estación Científica Yasuní, Rio Tiputini , al NO de la confluencia con el Río Tivacuno , 6 km E de la carretera Maxus, km 44, desvio hacia el pozo Tivacuno, Sendero Botánico , 0°38’S, 76°30’W, 200–300 m elev., 7 November 1995 (fl), K . Romoleroux & R . Foster 1958 (holotype: QCNE-130955!; isotypes: F!, QCA!) .

Evergreen tree to ca. 35 m tall and 56 cm dbh; pubescence mostly of golden or ferruginous, erect to subappressed, fairly straight to weakly twisting, simple trichomes, these mostly 0.1–0.7 mm long; current season, leaf-bearing branchlets 1.2–3.5 mm thick at middle of internodes, densely pilose-tomentose. Leaves imparipinnate, with 3–5 pairs of opposite to subopposite lateral leaflets; stipules 1.6–13 × 0.8–2.3 mm, narrowly lanceolate, widest at base, often falcate, glabrous adaxially, densely villous-tomentose abaxially, glabrescent, caducous; petioles 0.8–3.2 cm long, 1.1–2.2 mm thick at middle, terete to subterete, longitudinally bicarinate adaxially toward apex, densely pilose-tomentose, the pulvinus 2.7–5.8 × 1.4–2.5 mm; rachis 3.5–18 cm long, 0.6–2.2 mm thick at middle of segments, densely pilose-tomentose, longitudinally bicarinate along segments adaxially, the ridges terminating in stipels, these 0.3–1.7 mm long, triangular to subulate, densely sericeous; petiolules 1.3–3 × 1–2.1 mm, pilose; laminas (1.5–) 2–3.5 × longer than wide, (1.9–) 4.2–14.4 × (0.9–) 1.9–5.5 (–7.6) cm, chartaceous, the basal ones smaller and less elongate than the others, usually elliptic, the medial and distal ones elliptic, obovate or weakly oblong, the base acute, obtuse or rounded, the apex usually acuminate, sometimes acute or obtuse, the tip rounded, the adaxial surface mostly glabrous, pilose on the primary vein and margin, the abaxial surface often somewhat glaucous or canescent, pilose, fairly densely so on the major veins, the primary vein impressed and other venation immersed adaxially, all venation prominent abaxially, the secondary veins ca. 6–12 on each side of the primary vein, initially ascending at 35°–55°, curving upward, fading or weakly brochidodromous submarginally. Inflorescences racemes, frequently compound, with 1–2 orders of branching, borne from leaf axils or from annotinous branchlets just below leaves, to ca. 50-flowered; axes (1.3–) 2.7–15.5 cm long, ca. 1.2–2.2 mm thick at base, densely pilose-tomentose; bracts 3.1–6.6 × 1.6–3.3 mm, elliptic to obovate, abaxially convex, the apex acute or shortly acuminate, glabrous adaxially, densely sericeous-tomentose abaxially, caducous; pedicels 4–12 mm long, 1.2–1.6 mm thick at middle, dorso-ventrally compressed, densely pilose-tomentose; bracteoles absent; flower buds 6.4–9 × 4.5–7.1 mm, ellipsoid, shortly umbonate, densely sericeous-tomentose. Calyx segments 4–6 in number, 2.4–5.7 mm wide, recurved, glabrous adaxially, densely sericeous-tomentose abaxially. Corolla monopetalous, the petal yellow, mostly glabrous, sparsely sericeous on the base of the primary veins abaxially; claw ca. 1.2 mm long, 0.4 mm wide at base, 1.1 mm wide at apex; limb membranous, broadly elliptic, ca. 9.5 × 8.2 mm, the venation palmate, with ca. 7 primary veins. Androecium zygomorphic, the stamens dimorphic, most of two size classes; larger stamens 4–5 in number, abaxial, often with 1–2 smaller and less robust than the others, the filaments ca. 9–11.5 × 0.3–0.5 mm, somewhat dorso-ventrally compressed, dilated basally, yellow, glabrous to sparingly villous, the anthers 1.2– 1.6 × 0.6–0.8 mm, elliptic or oblong-elliptic in outline, light tan, glabrous; smaller stamens ca. 74–95 in number, adaxial, glabrous, the filaments ca. 4–7 × 0.1 mm, terete to somewhat dorso-ventrally compressed, yellow, the anthers 0.8–1.1 × 0.6–0.8 mm, elliptic in outline, light tan. Gynoecium unicarpellate, dull yellow; ovary stipe 4–6.5 mm long, 0.4–0.6 mm thick at middle, more or less terete, dilated at base and apex, sparingly villous; ovary proper 6.1–8.1 × 1.8–2.3 mm, arcuate, inequilaterally and narrowly elliptic in outline, laterally compressed, sparingly villous on the abaxial (dorsal) suture, otherwise glabrous, the locule glabrous; ovules ca. 14; style 1.8–2.2 mm long, 0.3–0.4 mm thick at middle, terminal, terete, glabrous; stigma roundedtruncate, green. Fruits 1–several-seeded, glabrous; stipe 9–17 × 1.7–2.8 mm, more or less terete, somewhat dilated basally; body ca. 7–18 × 2.1–2.6 cm, inequilaterally elliptic to oblong-lanceolate in outline, laterally compressed, the valves little or not at all constricted between seeds, the base and apex acute to somewhat acuminate, the surface smooth to superficially rugose, with the ridges longitudinal to oblique.

Distribution, habitats and conservation: — Swartzia yasuniensis is known only from the northwestern section of Yasuní National Park, thus the epithet, and the adjacent Huaorani Ethnic Reserve in the province of Orellana in the Ecuadorian Amazon, where it occurs at less than 400 m elevation in the upper drainages of the Tiputini and Yasuní Rivers, southern tributaries of the Napo River ( Fig. 2 ). The actual distribution is probably larger, as much of the surrounding region has been little collected. The species occurs in humid lowland tropical rainforest, often in hilly dissected terrain, with a thin organic layer over red clay. According to specimen label notes (Jaramillo & Tapia 18679A; Pérez & Santillán 4682), associated tree species include Astrocaryum chambira Burret , Brownea grandiceps Jacq. , Cedrelinga catenaeformis (Ducke) Ducke , Iriartea deltoidea Ruiz & Pav. , Iryanthera hostmannii (Benth.) Warb. , Parkia nitida Miq. , Protium nodulosum Swart , and Rinorea lindeniana (Tul.) Kuntze (see also: Valencia et al. 2004).

The new species is one of several species of Swartzia found in the well-studied 50-hectare Yasuní Forest Dynamics Plot. In 25-hectares of the plot, there were 103 individuals of Swartzia yasuniensis with dbh greater than or equal to 1 cm, an average of four individuals per hectare. Of these, eight individuals exceeded 30 cm dbh, while 21 individuals had a dbh exceeding 10 cm but less than 30 cm. Between 2002 and 2007, the annual mortality rate for the species in the plot was 0.8%; recruitment rate was 0.4 individuals per year, and average growth rate was 0.9 mm per year.

Swartzia yasuniensis is assigned to the IUCN Redlist category of Near Threatened (NT). The documented extent of occurrence (EOO, criterion B1) is quite small (less than 5000 km 2), and on its periphery, encroaching settlement and deforestation are apparent in satellite images. However, the larger region is still mostly covered by intact and poorly explored Amazonian plant communities, and the species is present in at least two large, nationally protected areas.

Phenology: —Flowering has been observed in November, fruiting in January.

Additional specimens examined (paratypes):— ECUADOR. Orellana: Parque Nacional Yasuní, carretera y oleoducto de MAXUS , km 40, parcela permanente #10 de 1 hectárea, árbol marcado #06.21, 0°39’S, 76°26’W, 250 m elev., 15–17 May 1994 (st), M . Aulestia 2223 ( MO, NY, QCNE); Carretera Pompeya, Sur-Iro–Parque Nacional Yasuní, km 38.7, junto a la Estación de Monitoreo de Fauna Onkonegare Ecuambiente S . A ., 0°39’31.7”S, 76°27’7.5”W, 200–300 m elev., 26 June 1994 (st), X. Buitrón et al. 632 ( QCA); Cant. La Joya de Los Sachas, Yasuní National Park, km 14–15 of the Maxus pipeline road, E of Juan Tapuy's finca, Plot Shipati 3, tree #458, 0°31’S, 76°32’W, 250 m elev., October 1997 (st), N . Pitman & T . Delinks 2448 ( QCA); Parque Nacional Yasuní, km 9 via NPF– Pozo Tivacuno , 0°38’S, 76°30’W, 220 m elev., 7 June 1997 (st), J . Jaramillo & I . Tapia 18679 A ( QCA) ; Estación Científica Yasuní, Parcela de 1 ha, km 8.2 de la carretera NPF– Tivacuno , 0°40’51”S, 76°23’12”W, 200–300 m elev., 11 February 2002 (st), J . Jaramillo et al. 23061 ( QCA); Estación Científica Yasuní, parcela de 1 ha, km 8.2 de la carretera NPF– Tivacuno , 0°40’51”S, 76°23’12”W, 200–300 m elev., 1 March 2002 (st), J . Jaramillo et al. 23257 ( QCA); Parque Nacional Yasuní, km 34.6, carretera Pompeya-Iro , parcela 6, 0°37.637’S, 76°27.736’W, 250–300 m elev., 12 August 1997 (st), M . J . Macía et al. 1135 ( QCNE); Parque Nacional Yasuní ECY, Sendero “Laguna,” 0°40’40”S, 76°23’40”W, 200–300 m elev., 28 January 2010 (fr), A . J . Pérez & W . Santillán 4682 ( QCA); Añangu, Parque Nacional Yasuní , 0°31’– 0°32’S, 76°23’W, 260–350 m elev., 30 May–21 June 1982 (st), SEF 8869 ( QCA, QCNE, US) ; 21 June 1982 (st), SEF 8993 ( QCA, QCNE) .

Discussion:— Swartzia yasuniensis is assigned to the small section Pittierianae (R. S. Cowan 1968: 24) Torke & Mansano (2009: 921) , which comprises five species. Sectional characters include the lack of bracteoles, a glabrous or nearly glabrous gynoecium, a relatively compact ovary and a frequently branched inflorescence. Among consectional species, it differs from S. pittieri Schery (1952: 263) and S. trianae Bentham (1870: 39) of the northern Andes, the Orinoco basin, and northwestern Amazonia most obviously in having more numerous calyx lobes, larger floral bracts, and typically more densely pubescent leaflets ( Table 2). Probably more closely related are S. jorori Harms (1915: 39) and S. juruana Torke (2004: 358) of southwestern Amazonia, the former also ranging southward to the Brazilian Pantanal, but it differs from them in its longer stipules, floral bracts and ovary stipe, more strongly zygomorphic androecium, more numerous smaller stamens and ovules, and more frequently multi-seeded fruits ( Table 2).

The documented distribution of S. yasuniensis is similar to that of S. bombycina R. S. Cowan (1985: 303) . Both species appear to be restricted to the so-called Napo ecoregion in the Ecuadorian Amazon, giving credence to the classification of the ecoregion as a distinct biogeographical province (e.g., Silva et al. 2005).

A key to the species of Swartzia occurring in Ecuador

1. Petal white, violet or pink; leaves multifoliolate; mature fruits often more than 3 cm broad; Amazonian Region ..... 2

- Petal yellow (or the flowers apetalous); leaves multifoliolate or unifoliolate; mature fruits less than 3 cm broad; Amazonian region, Andean slopes, and Pacific lowlands ............................................................................................ 5

2. Ovary and ovary stipe densely pubescent, the fruits usually retaining at least some pubescence on the stipe, sutures and/or valves ................................................................................................................................................................ 3

- Ovary and stipe glabrous or essentially so, the fruits entirely glabrous ...................................................................... 4

3. Stipules 2–32 mm long; abaxial surface of leaflets drying with secondary and higher-order veins darker than or similar in color to the lamina; calyx appreciably sericeous-strigose on the adaxial surface, particularly toward center .... ............................................................................................................................................ S. bombycina R. S. Cowan

- Stipules not apparent or not exceeding 1 mm long; abaxial surface of leaflets usually drying with the secondary and higher order veins discernibly lighter than the lamina; calyx essentially glabrous on the adaxial surface ................... ................................................................................................................................................ S. rosea Mart. ex Benth.

4. Leaflet venation raised-reticulate on both surfaces; inflorescence axes, pedicels and flower buds glabrous; flower buds 10.4–19.4 mm long .............................................................................................................. S. calva R. S. Cowan

- Leaflet venation immersed and inconspicuous on both surfaces; inflorescence axes, pedicels, and flower buds strigulose; flower buds 4.2–8.1 mm long .................................................................................................... S. polyphylla DC.

5. Leaves unifoliolate....................................................................................................................................................... 6

- Leaves multifoliolate ................................................................................................................................................. 10

6. Pedicels supplied with a pair of bracteoles (not to be confused with stipules that sometimes subtend bracts); ovary stipe at least twice as long as the ovary proper; fruits maturing green, leaflets strongly discolorous; trunk slash with red-oxidizing exudate ....................................................................................................... S. klugii (R. S. Cowan) Torke

- Pedicels lacking bracteoles; ovary stipe not more than 1.5 × the length of the ovary proper; fruits maturing orange, yellow, green or brownish-green; trunk slash lacking red-oxidizing exudate ............................................................. 7

7. Androecium semi-actinomophic, the stamens more or less isomorphic, or at least not clearly divided into two size classes; flower buds 3.2–5.4 mm broad; petal 4.4–12.3 mm broad, the base of the limb acute to truncate ................... ........................................................................................................................................ S. arborescens (Aubl.) Pittier

- Androecium strongly zygomorphic, the stamens dimorphic, with an abaxial cluster of larger stamens and an adaxial or central cluster of smaller stamens; flower buds 5.8–12.2 mm broad; petal 16.1–45.9 mm broad, the base of the limb cordate ................................................................................................................................................................. 8 8. Leaf stalk almost entirely pulvinular, auriculate on the adaxial side just below apex, but not obviously winged; leaflet blade often more than 2.5 × longer than wide; inflorescences frequently borne from defoliate nodes of branches, but also from leaf axils; widespread in Amazonian lowlands .................................................... S. calophylla Poeppig

- Leaf stalk usually with a short “rachis” between the pulvinus and pulvinulus, this typically marginate or winged; leaflet blade usually less than 2.5 × longer than wide; inflorescences borne mostly in the axils of current leaves; Pacific lowlands, frontal ranges, and Andean slopes ................................................................................................... 9

9. Larger stamens 8–15; leaflets acute to obtuse at base, the secondary veins raised to plane on the adaxial surface; eastern Andean slope, Cordillera del Condor, and other eastern slope frontal ranges ............ S. simplex (Sw.) Spreng.

- Larger stamens 17–25; leaflets often rounded or subcordate at base, the secondary veins usually noticeable impressed on the adaxial surface; Pacific lowlands and western Andean slope ............... S. aff. simplex (Sw.) Spreng.

10. Pedicel supplied with a pair of bracteoles (not to be confused with stipules that sometimes subtend bracts); larger stamens 2–3 ................................................................................................................................................................ 11

- Pedicel lacking bracteoles; larger stamens 2–ca. 18 or the stamens essentially isomorphic..................................... 13

11. Lateral leaflets mostly 6–8-paired; petal 2.9–4.1 cm wide ..................................................... S. haughtii R. S. Cowan

- Lateral leaflets mostly 3–6-paired; petal 4.2–8.4 cm wide ....................................................................................... 12

12. Ovary densely sericeous-lanate; bracts 1–1.5 mm long; pedicels 2.9–5.5 cm long; western Andean slope ................. ...................................................................................................................................... S. decidua Torke & A. J. Pérez

- Ovary glabrous; bracts 5.4–12 mm long; pedicels 0.9–3.1 cm long; eastern Andean slope and adjacent Amazonia.... ..................................................................................................................................................... S. macrosema Harms

13. Primary vein raised-cariniform on the adaxial leaflet surface; lateral leaflets 1–3-paired; leaf rachis winged; flower buds and abaxial surface of calyx glabrous ................................................................................................................ 14

- Primary-vein impressed or immersed on the adaxial leaflet surface; lateral leaflets 2–6-paired; leaf rachis usually unwinged; flower buds and abaxial surface of calyx pubescent ................................................................................ 15

14. Androecium semi-actinomophic, the stamens more or less isomorphic, or at least not clearly divided into two size classes; flower buds 3.2–5.4 mm broad; petal 4.4–12.3 mm broad; gynoecium unicarpellate; fruit maturing green or brown-green; Amazonian lowlands ............................................................................... S. arborescens (Aubl.) Pittier

- Androecium strongly zygomorphic, the stamens dimorphic, with an abaxial group of ca. 9–18 larger stamens and an adaxial or central group of much more numerous smaller stamens; flower buds 7.5–12 mm broad; petal 25–53 mm broad; gynoecium often composed of two to several free carpels; fruit maturing orange or yellow; Pacific lowlands and Cordillera del Condor … S. littlei R. S. Cowan

15. Ovary excluding the stipe densely pubescent; fruits retaining at least some pubescence on the stipe, valves or sutures

................................................................................................................................................................................... 16 - Ovary excluding the stipe glabrous or nearly so; fruit glabrous ................................................................................ 17

16. Lateral leaflets 2–3-paired; flower buds 7–11 mm broad; ovary 12–18 mm long; Pacific lowlands ............................ .................................................................................................................................................. S. aff. amplifolia Harms

- Lateral leaflets 4–6-paired; flower buds 4.4–5.2 mm broad; ovary 6–7.5 mm long; Amazonian lowlands ................. ................................................................................................................................................ S. aff. leptopetala Benth.

17. Calyx segments 2; ovary 12.6–25 mm long; petal 4–5 cm broad ....................................................... S. trianae Benth. - Calyx segments 4–6; ovary 6.1–8.1 mm long; petal less than 1 cm broad ....................................................................

................................................................................................................................. S. yasuniensis Torke & A. J. Pérez

Figures

FIGURE 2. Geographical distributions of S. decidua and S. yasuniensis.

FIGURE 3. Swartzia yasuniensis. A: Leafy branchlet and inflorescence, with detail of stipule; B: Apex of inflorescence with submature flower buds subtended by bracts; C: Leafy branchlet with inflorescence; D: anthesis flower, lateral view; E: Petal, adaxial view; F: Post-anthesis flower with fertilized gynoecium; G: Submature fruit, fresh; H: Submature fruit, dried; I: Leaf. A, B, E, F from Romoleroux 1958 (F); C, D, G, from photo by Á. J. Pérez; H. from Pérez & Santillán 4682 (QCA); I from Macía et al 1135 (QCNE); drawn by Bobbi Angell.

FIGURE 4. Swartzia yasuniensis. A: Leafy branchlet with inflorescence; B: Leaf, abaxial view; C: Flowers; D: Infructescences; E: Sub-mature fruits; photographed by Álvaro J. Pérez.