Syagrus yungasensis Moraes (1996: 89)

Noblick, Larry R., 2017, A revision of the genus Syagrus (Arecaceae), Phytotaxa 294 (1), pp. 448-450 : 448-450

65. Syagrus yungasensis Moraes (1996: 89) . Type :— BOLIVIA. La Paz: Prov. Sud Yungas, 30 km del camino entre Chulumani y La Asunta, 900 m, 9 December 1994, M. Moraes 1874 (holotype LPB, isotypes FTG!, NY)

Figure 89 plate, Figure 86 map.

Small to medium-sized, solitary palm. Stem ca. 3–6 m × 7–15 cm, erect, columnar, light gray, somewhat prominently ringed with closely spaced leaf scars less than 1 cm apart. Leaves 12–18; sheathing leaf base ca. 12– 25 × ca. 13 cm; pseudopetiole 80–100 cm long; petiole 20–40 × 1.5–2.0 cm, 0.7–0.8 cm thick covered with a grayish tomentum; rachis 1.2–1.6 m long; leaflets a lustrous dark green on the upper or adaxial surface, slightly lighter on the abaxial surface, 90–120 along one side, in clusters of (2–)3–5(–10) and inserted at various angles, giving the leaf a plumose appearance, ramenta scales present where the leaflets are inserted on the rachis and fairly closely spaced along the abaxial midvein on the lower 2/3 of the leaflet, midveins of leaflets tomentose; basal leaflets 39–68 × 0.4–0.5 cm, middle leaflets 45–63 × 1.0– 1.5 cm, apical leaflets 4–20 × 0.1–0.3 cm. Inflorescence erect to pendulous, spirally branched; prophyll 20–30 × 3.5–4 cm, lanceolate with flattened margins; peduncular

222 • Phytotaxa 294 (1) © 2017 Magnolia Press

NOBLICK A REVISION OF THE GENUS SYAGRUS

Phytotaxa 294 (1) © 2017 Magnolia Press • 223 bract 80–120 cm long, expanded portion 50–66 × 4.5–7.0 cm, including a 2–3 cm beak, 7.5–8.5 cm perimeter, 2 mm thickness, narrow, woody, sulcate, exterior with thin indument on at least the apex and base; peduncle ca. 35– 56 × 1.1–1.3 cm, 0.5–0.8 cm thick, elliptical in cross-section, glabrous; inflorescence axis 24–38 cm long; rachis, 10–13(–30) cm long, glabrous; rachillae 32–46, 2.5–17 cm long at the apex, 25–32 cm long at the base, glabrous, but with only ca. 15 basal branches with pistillate flowers located at the base of the rachillae, at times only one rachilla with pistillate flowers, the rest of the rachillae with staminate flowers, 1 or 2 fruits per rachilla; staminate flowers 8–10 × 3–4 mm, green to yellow, sepals 1 × 1 mm, glabrous, no raised nerves, petals 6–10 × 3–4 mm with acute tips, nerves indistinct to slightly raised at the base, stamens 6 mm long, anthers 4–5 mm long, filaments ca. 2–3 mm long, pistillode up to 2 mm long; pistillate flowers conical, 9–13 × 9–13 mm, yellow, glabrous, sepals 8– 13 × 7–10 mm, glabrous, fleshy, with raised veins near the tips, petals 10–11 × 5–7 mm, glabrous to lepidote tomentose on the lower part of the petal, valvate tip 2/5 to ½ the length of the petal, ca. 2–3.5 mm long, pistil globose to ovoid, 7–8 × 4 mm, glabrous to lepidote or short tomentose at the base, with slightly raised veins, stigmas less than 2 mm long, glabrous, staminodal ring ca. 2 mm high, undulate. Fruit ellipsoid to ovoid, 3.5–4.5 × 2.5–3 cm, green when mature, glabrous, epicarp less than 0.5 mm thick, smooth, glabrous, green, with tomentum adpressed near the apex, mesocarp not measured, thin, succulent to dry-fibrous; endocarp ovoid, 3.0–3.4 × 2.2 cm, hard, boney with persistent fibers, 3–5 mm thick, with three crests or ridges that go from the base to the apex, slightly more raised apical crests or ridges near the apex, seed ovoid to broadly ellipsoid, 1.8–2.5 × 0.8–1.5 cm, endosperm homogenous, milky white, hard, with a small central cavity ( Moraes 2004, Moreno 2006). Germination remote-tubular.

Common name:— none known

Etymology:— The specific epithet, yungasensis , refers to the locality from which it was originally collected in La Paz, province of Sud Yungas, Bolivia.

Distribution and habitat:— Endemic to Bolivia ( Moraes 2004). Found southeast of La Paz in the province of Sud Yungas, between the towns of Chulumani and La Asunta. Restricted to narrow valleys and rocky slopes in semideciduous forests in the eastern Cordillera of the Andes with Anadenanthera , at 700–1000 m elevation.

Conservation:— This palm is threatened, because it grows in a zone of expansion of cultivated crops where farmers are accustomed to clearing the upper slopes ( Moreno & Moreno 2006). Based on Moreno’s description, this species is classified as vulnerable, VU A4.

Phenology:— This species has been seen flowering and fruiting in December.

Uses:— This palm has ornamental potential with its medium size, small trunk and attractive, full crown of plumose leaves.

Notes:— Syagrus yungasensis has inflorescences that have very few pistillate flowers per rachillae. They usually have only 2–4 flowers, although the basal rachilla usually can have 5 or 6(–10). As a consequence, there are also few fruits per rachilla. Both Moraes (2005) and Moreno & Moreno (2006, 2013) wrote how similar S. yungasensis is to S. cardenasii . They are both similar in having apiculate perianth in the fruiting stage, clustered leaflets and ellipsoid fruit (Moraes 2005). However, they differ in that S. yungasensis usually has a more robust solitary trunk with closely spaced internodes, slightly larger fruit (3.5–4.5 × 2.5–3 cm vs. 2.0–4.2 × 1.7–2.0 cm) and more rachillae in the inflorescence (32–46 vs. 6–18).

Representative specimens:— BOLIVIA. La Paz: Sud Yungas, 82 km de Chulumani en camino a La Asunta , 700 m, 30 May 1986, Beck 12636 ( LPB) ; 9 km del camino de Chamaca a Chulumani, Río La Paz , 900 m, –16.28, –67.28, 3 October 1995, Kessler et al. 5732 ( LPB) ; 30 km del camino entre Chulumani y La Asunta, 900 m, 9 December 1994, Moraes 1874 (holotype LPB, isotypes FTG!, NY) .

HYBRIDS

Hybrids occur where populations of closely related, natural occurring, species overlap. If the two species have synchronous phenologies, if there is a successful transfer of pollen, if no mechanical nor chemical barriers exist, and if they are genetically compatible, a hybrid may occur. Suspected hybrids are mainly recognized by the intermediate character states between the two suspected parents and their low frequency of occurrence. They are also often characterized by low fruit production, low seed germination, and by hybrid vigor resulting in the hybrid being more robust and vigorous than either of its parents.

A number of naturally occurring hybrids have been discovered in the genus Syagrus and some nurserymen and

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NOBLICK palm enthusiasts have attempted to hybridize others. One can only speculate why this occurs with greater frequency in this genus than in other palm genera. As of this writing, no one has attempted to answer that question. There is no conservation assessment given for hybrids as most would be classified as critically endangered based on their rare occurrence and small population size. However, they are not threatened, vulnerable or endangered, because, theoretically, we should be able to reproduce them again from their parents. The following is our current knowledge of the hybrids found in Syagrus , and they are summarized in Table 2.

Figures

FIGURE 86. Distribution maps of Syagrus vermicularis, S. weddelliana, S. werdermannii and S. yungasensis.

FIGURE 89. Syagrus yungasensis. A. Palm with J. Roca. B. Crown. C. Habit with Luis Moreno. D. Inflorescence. E. Infructescence. F. Infructescence of isotype showing only 1 or 2 pistillate flowers per rachilla (Moraes 1874). Grid is in centimeters. All photos except F by Oscar Moreno (Moreno & Moreno, 2006, 2013).