Schefflera prancei Fiaschi & G. M. Plunkett, 2016

Fiaschi, Pedro & Plunkett, Gregory M., 2016, Two new species of the Didymopanax clade of Schefflera (Araliaceae) from the Brazilian Amazon, Phytotaxa 245 (2), pp. 153-160 : 157-160

Schefflera prancei Fiaschi & G. M. Plunkett , sp. nov.

Type:— BRAZIL. Acre: Cruzeiro do Sul, Serra da Moa, Rio Moa, 6 km above school , 25 April 1971 (fr), G. T. Prance, P. J. M. Maas, K. Kubitzki, W. C. Steward, J. F. Ramos, W. S. Pinheiro & J. F. Lima 12446 (holotype NY-02212661 ! ; isotypes INPA!, K!, MG-42953 !, MO-4228031 !, R!, US-01212148 !) . Figures 1L–O , 3A–B , 4 .

This new species can be distinguished from Schefflera confusa ( Marchal 1878: 244) Harms in Engler & Prantl (1894: 37) by the narrow elliptic to oblanceolate (vs. elliptic to ovate) leaf blades, light brown to grayish sericeous (vs. glabrescent) abaxially, chartaceous to subcoriaceous (vs. membranaceous to subchartaceous), with the apices acuminate or cuspidate (vs. caudate); from S. decaphylla ( Seemann 1865: 266) Harms in Engler & Prantl (1894: 37) it can be distinguished by the leaves with 10–25 (vs. 7–15) leaflets, in 2–3 whorls [vs. in 1(–2) whorls], the blade abaxially light brown to grayish sericeous (vs. usually glabrescent), and the larger fruits (12.5–14 × 11–11.5 vs. 8–9 × 10–11 mm).

Trees 14–15 m; branchlets 1.5–2 cm diam., striate longitudinally, light brown sericeous. Leaves palmately compound, clustered at branchlet apices, internodes barely noticeable; stipules 10–13 mm long, adaxial surface glabrous, abaxial surface light brown sericeous, apex slightly bifid, lobes c. 2 mm long; petiole 26–36 cm long, cylindrical to laterally compressed, longitudinally striate, persistently light brown to grayish sericeous or glabrescent; leaflets simple, 10 to 25, grouped in two or three terminal whorls, held horizontally; blade plane, chartaceous to subcoriaceous, adaxial surface glabrous, abaxial surface light brown to grayish sericeous; median leaflet of outer whorl with petiolules 8.5–11.5 cm long, compressed laterally, canaliculate adaxially; blades 12–17 × 4–5.4 cm, narrowly elliptic to oblanceolate, base cuneate to attenuate, symmetrical, margin entire, revolute, apex acuminate to cuspidate, tip sometimes mucronulate; basal leaflets of outer whorl with petiolules 2.5–7 cm long, blade 13.7–14.5 × 3.5–4.6 cm, otherwise similar to median leaflets; venation brochidodromous; primary vein prominent abaxially, impressed to slightly prominent adaxially; secondary veins 12 to 14, prominent abaxially, impressed adaxially; intersecondary veins sometimes present; higher orders of venation inconspicuous. Inflorescence terminal, probably initially erect, becoming pendent when fruiting, light brown to grayish sericeous; main axis to c. 5 mm long; primary branches 2, both terminal, 17.5–20 cm long, with bracts c. 5 mm long; each bearing 9 to 10 secondary branches, with 2 to 3 terminal branches, 4.8–8.4 cm long, with bracts c. 2.5 mm long; tertiary branches 1.3–2.7 cm long; ultimate inflorescence units umbellules, number of flowers unknown; floral bracts not seen. Flowers unknown. Drupes 12.5–14 × 11–11.5 mm, broadly ellipsoid, 5-costate when dry, glabrescent; pedicels 6–11 mm long; pyrenes 5, c. 12–12.5 × 6 mm, laterally compressed, semi-oblate in outline, transversely narrowly elliptic, cartilaginous.

Distribution and ecology:— Schefflera prancei is known only from the type locality, at the westernmost tip of Brazil, in the Serra do Divisor National Park, Acre state ( Fig. 4 ). This species is very likely to occur in adjacent Peru, but no collections have been made to date in this country. Schefflera prancei grows in terra firme rainforests on sandy to clayey soils, at about 225 m elevation.

IUCN Red List category:— We consider this species as DD for conservation purposes, as the area where it is found is very poorly known botanically, despite recent efforts towards enhancing floristic knowledge of Acre state ( Medeiros et al. 2014).

Phenology:— Schefflera prancei was collected with fruits in April.

Etymology:— The new species epithet honors the type collector, Sir Ghillean Tolmie Prance (born 1937), whose extensive collections in Neotropical America support our better understanding of the flora.

Discussion:— Based on our preliminary analysis, Medeiros et al. (2014) cited this taxon as Schefflera sp. nov. in their updated checklist of the Flora of Acre state. Schefflera prancei can be readily distinguished from the remaining species of the Didymopanax group by the bundled, compound leaves with leaflets grouped in two or three whorls, and the perfect flowers with a 5-carpellate ovary. This species is similar to Schefflera confusa ( Fig. 3C ), from which it can be distinguished by the leaflets with blades that are narrowly elliptic to oblanceolate (vs. elliptic to ovate), the acuminate to cuspidate (vs. caudate) blade apex, and the light brown to grayish sericeous indument on the abaxial blade surface (vs. glabrescent). In addition, the fruits appear to be smaller in S. prancei (12.5–14 × 11–11.5 vs. 15–16 × 13–16 mm), but this may be due the fact that they were unripe in the type collection. Unlike Schefflera confusa , which grows mostly on white sand campinarana forests, S. prancei grows in terra firme forests on sandy to clayey soils.

From Schefflera decaphylla , S. prancei can be distinguished by a unique combination of character states, including leaflets arranged in two to three [vs. one (less often two) whorls in S. decaphylla ], leaves with light brown sericeous (vs. glabrescent) blades abaxially, with an acuminate to cuspidate (vs. usually rounded or obtuse) apex, and larger fruits (12.5– 14 × 11–11.5 vs. 8–9 × 10–11 mm). A few collections of S. decaphylla , however, do have either the leaflets arranged in two whorls or with a persistently sericeous undersurface, or the leaflet blades with an acuminate apex (e.g., Ferreira et al. 6597 and 7055, INPA), but the geographic distributions of the two species do not seem overlap (see Fig. 4 ).

Paratypes:— BRAZIL. Acre: Mâncio Lima, PARNA Serra do Divisor, Trilha para a Cachoeira Formosa , 07°26’47.4” S, 73°39’27.4” W, 225 m, 22 August 2008 (st), P. Fiaschi, H. M. Oliveira, J. E. S. L. Cucker, M. R. S. Melo & E. F. Silva 3309 ( NY, RB) .

Figures

FIGURE 1. A−K. Schefflera pubicarpa. A. Fruiting branch. B. Stipule, lateral view. C. Basal leaflet, abaxial view. D. Median leaflet, abaxial view. E. Bisexual flower, one petal and stamens removed, lateral view. F. Bisexual flower, stamens removed, lateral view. G. Petal, lateral view. H. Stamen, adaxial view. Stamen, abaxial view. J. Terminal inflorescence unit. K. Fruit, lateral view. L−O. Schefflera prancei. L. Fruiting branch. M. Median leaflet from outer whorl. N. Median leaflet from inner whorl. O. Fruit, lateral view. [Drawings by P. Fiaschi].

FIGURE 3. Schefflera prancei and the similar species S. confusa. A−B. Schefflera prancei. A. Branch, showing leaf undersurfaces. B. Leaf, showing leaflets in three whorls. C. Schefflera confusa, branch. [Photos by P. Fiaschi].

FIGURE 4. Geographic distribution of Schefflera prancei, S. pubicarpa, and similar species from the Amazonian lowlands (see text for morphological comparison between species).