Croton beccarii J.Beyer, 2023

Beyer, J., Esser, H. - J., Eurlings, M. C. M. & Welzen, P. C. van, 2023, A revision of the genus Croton (Euphorbiaceae) in Sumatra (Indonesia), Blumea 68 (1), pp. 1-25 : 10

3. Croton beccarii J.Beyer , sp. nov.

Resembling C. laevifolius vegetatively but differing in stipule shape and width (filiform, 0.3–0.5 mm wide in C. beccarii vs subulate, 0.5–1 mm wide in C. laevifolius ), leaf indument (abaxially scattered trichomes in C. beccarii vs (sub)glabrous in C. laevifolius ); also C. beccarii has shorter inflorescences (2–7 cm long vs 5–23 cm long), densely pubescent sepals and pedicels in pistillate flowers, and densely pubescent small, globose, hardly sulcate capsules (4–5 mm diam), while C. laevifolius has overall more glabrous inflorescences and larger distinctly 3-lobed obovoid capsules (5–8(–13) mm high by 4–7 mm diam) with scattered trichomes. — Type: Beccari PS 973 (holo L [L.2203857]!,iso FI-B!), Indonesia, Sumatera Barat,Sungei Bulu, Sept.1878.

Trees or shrubs, young branchlets densely pubescent, soon glabrescent. Indumentum consisting of creamy to amber stellate trichomes with a darker centre, 0.1–0.3 mm diam, flat to slightly erect, often with a short central porrect radius and 10– 20 free radii. Stipules filiform to subulate, 2–6(–8) by 0.3–0.5 mm, densely pubescent on both sides, caducous. Leaves pseudo-verticillate; petiole 0.5–3.5 cm long, grooved above, with scattered trichomes to slightly pubescent (denser at very base and very apex); glands elevated to slightly stalked discs, lateral on the very apex of the petiole, 0.3–0.5 mm diam, elevation/stalk 0.1–0.4 mm high; blade elliptic, 7–15 by 3–7 cm, 1.6–2.6(–3) times longer than wide, chartaceous, base obtuse to acute, margin slightly serrulate to subentire, teeth 4–6 mm apart, without apical trichomes nor marginal glands, apex acuminate, adaxial side glabrous, abaxial side with scattered trichomes (denser near base and large veins), epidermis visible; venation distinct, sunken above, not triplinerved, secondary veins 7–11 pairs, higher order nerves slightly indistinct. Inflorescences 1–2(–5) per apical whorl, 2–7 cm long, erect, basally 1–18 pistillate flowers, rarely 1 or 2 staminate flowers at the same node as a pistillate flower, apically 1– 2 staminate flowers per node; bracts triangular-ovate, c. 0.5 by 0.2 mm, slightly pubescent on both sides, with a patch of simple trichomes on apex, caducous. Staminate flowers 3.5–4 mm diam; pedicel 1– 2 mm long, round to slightly flattened, slightly pubescent; sepals triangular-ovate, 1.5–2 by 1–1.5 mm, outside with scattered trichomes to slightly pubescent; petals oblong, c. 1.7 by 0.5 mm, outside glabrous; stamens c. 11, filaments 1–2 mm long, anthers c. 0.4 by 0.4. Pistillate flowers 3.5–4 mm diam; pedicel 0.5–1.5 mm long, densely pubescent; sepals triangular-ovate, 2–2.5 by 0.8–1.5 mm, slightly longer than ovary, outside densely pubescent, glabrescent near apex and margin, with a patch of very short simple trichomes on apex; petals absent; ovary 3-lobed, globose, c. 2 by 2 mm long, sulcate, very densely yellowish pubescent to almost hispid; style nearly absent to 0.2 mm long, densely pubescent; stigmas c. 2.3 mm long, fused at base, once divided to c. 2 mm from apex. Capsules globose, 4–5 mm diam, rough, hardly sulcate, very densely yellowish pubescent; pericarp very thin (c. 0.1 mm). Seeds probably obovoid, c. 3.5 by 2 mm, glabrous, likely carunculate.

Distribution — Endemic to Sumatra (Sumatera Barat).

Habitat & Ecology — Flowering: September.

Affinities — Unknown, as molecular data are lacking, but morphologically highly similar to C. laevifolius (which is also not included in the phylogeny) and other species within the ‘ Riau pocket’ clade ( Fig. 1 : group I 4), based on the lack of colleters and similarities in trichomes and leaf shape.

Note — The description of seeds and capsules is based on very limited material, only three capsules were present and one seed, all very distorted.

Figures

Fig. 1 Bayesian phylogram based on ITS sequences excluding the 5.8S region. The values at nodes represent the Bayesian-inference posterior-probability support values. Astraea and Brasiliocroton are outgroups. Black names: New World, yellowish brown: Africa–Madagascar, green: mainland Asia, blue: Aus- tralia–West Pacific,red: Malesia.Accessions with bold names correspond to the newly sequenced taxa, all ocurring in Sumatra. Bar: nucleotide substitutions.