Saurauia denticulata C.B.Rob. (1908: 205)

Mazo, Kean Roe F. & Aribal, Lowell G., 2025, Rediscoveries, lectotypifications and new species record of the genus Saurauia (Actinidiaceae) from southwestern Philippines, Phytotaxa 704 (1), pp. 69-78 : 71-73

1. Saurauia denticulata C.B.Rob. (1908: 205) ; Fig. 2 A–J

Type:— PHILIPPINES. Mindanao, District of Zamboanga (now Zamboanga City): Talisayan, San Ramon, Sax River (=Sas River), 14 February 1905, 240 m elevation, Williams 2167 (holotype: NY 00428854!, isotypes: NY 00428855!, US 00110084!, K 000761715!).

Description: — Small tree, up to 7 m tall, 12 cm in diameter at breast height, outer bark yellowish, lenticels sparse. Branchlets terete, pale green. Distal portions of the twigs with dense pale green (brownish when old) indumentum and scales; longer scales, appressed to slightly ascending, triangular to lanceolate, 3–6 mm long; shorter scales linear to lanceolate, up to 1.5 mm long. Leaves alternate, simple, chartaceous; petiole terete, pale green, 0.8–2.5 cm long, 3–4 mm in diameter, indumentum similar to that of distal twigs; young leaves brownish red; blade subpeltate, obovate to oblong-elliptic, 30–35 × 8–14 cm, adaxially olivaceous, glabrous except the midrib with brownish appressed acicular hairs, abaxially pale green, with appressed acicular hairs (0.8–1.0 mm long), denser in the midrib, secondary veins and reticulations; secondary veins 16–18 pairs, prominent on the lower surface, 15–23 mm apart along the midrib, reticulately veined, arching and fading towards the leaf margin, base truncate to subcordate, margin denticulate (hairs on each denticulation up to 1 mm long), apex acute to acuminate. Inflorescences cauliflorous, ramiflorous, borne on tubercles, fascicled cymose, many-branched, 3–6 cm long; flowers rotate, 7–15 per peduncle, 1.5–2.0 cm in diameter, odorless; peduncle pale green, 6–10 mm long, with dense, appressed, reddish, acicular hairs (0.5–0.8 mm long); bracts 2, green, triangular to ovate, 1.4–1.9 × 0.5–1.0 mm, with dense, appressed, reddish-maroon, acicular hairs (1–2 mm long); bracteoles 2, green, narrowly triangular, 3.5–4.0 × 0.7–1.0 mm, indumentum similar to that of bracts; pedicel reddish, 8–17 mm long, indumentum similar to that of peduncles. Sepals 5, white, pale green in fruits, outer sepals 2, elliptic-ovate, 4.2–4.8 × 3.0– 3.5 mm (excluding setae), adaxial surface glabrous, abaxial surface with appressed, pinkish to red, acicular hairs (up to 1.2 mm long), margin entire, apex bluntly acute-obtuse to truncate; intermediate sepal present, partly covered with indumentum similar to that of outer sepals and partly glabrous similar to inner sepals; inner sepals 2, elliptic-ovate, 5.3–5.6 × 3.0– 3.5 mm (excluding setae), adaxial surface glabrous, abaxial surface with indumentum similar to that of outer sepals but only at the median portion, margin entire, apex bluntly acute-obtuse. Petals 5, white, elliptic to ovate, 8.4–9.2 × 4.5–5.5 mm, glabrous on both surfaces, apex unequally retuse, sinus 0.5–0.7 mm long. Stamens 15–20, in two series, adnate to the base of corolla; filaments yellow, 1.0– 1.2 mm long, glabrous; anthers dorsifixed, longitudinally dehiscent, oblong, 1.7–2.5 mm long, 0.1–0.2 mm wide, apex divided into 2 lobes, each lobe 0.15–0.20 mm long. Ovary white, ovoid, 2.0–2.2 × 3.0– 3.5 mm, glabrous; locules 3, placentation axile, ovules numerous. Styles 3 (rarely 4), white, turning reddish in fruit, filiform, proximal 10–15% fused, upper arms free, 4.5–5.0 mm long; stigma capitate, minutely corniculate. Fruits baccate, translucent green, globose to subglobose, 5.5– 6.5 × 7.0– 8.6 mm (styles excluded), glabrous, styles persistent. Seeds numerous, brown to black, irregularly rhomboid to oblong, 0.5–0.7 × 0.2–0.7 mm, embedded in mucilaginous matrix.

Distribution and Ecology:— Endemic to the Philippines. Prior to its rediscovery, Saurauia denticulata was only known from its type specimen, which was collected more than a century ago in the lowland primary forest (240 m elevation) of Barangay Talisayan, Zamboanga City. Recently, new populations of S. denticulata were discovered in Barangay Tinuyop, Municipality of Leon B. Postigo. This species was observed to be thriving along rivers and streams in secondary tropical lowland forest at 350–700 m elevation. Notably, it has been recorded to be flowering and fruiting from January to April.

Provisional IUCN conservation assessment:— The area of occupancy (AOO) of Saurauia denticulata is estimated to be 176.00 km 2 ( Bachman et al. 2011). Based on our field observations, there are only about 10–20 mature individuals at the type locality (Barangay Talisayan, Zamboanga City), and about 5–10 mature individuals in Barangay Tinuyop, Leon B. Postigo, Zamboanga del Norte. At the type locality, the habitat is facing the threat of ecotourism and water facilities development. Moreover, agricultural expansion and small-scale mining operations pose significant risks to the newly discovered populations in Barangay Tinuyop, Leon B. Postigo. Due to the limited distribution and existing threats to its habitat, we categorized it as Endangered (EN B2b(iii)), in accordance with IUCN red list categories and criteria ( IUCN, 2022).

Notes: —In Zamboanga Peninsula, Saurauia denticulata resembles S. zamboangensis in having indumentum and scales on the distal twigs, cauliflorous inflorescence, and ovoid and 3-locular ovary. However, S. denticulata can be easily recognized by its dense pale green (vs. reddish) indumentum and scales, longer scales being triangular to lanceolate (vs. narrowly lanceolate to triangular), shorter scales being linear to lanceolate (vs. acicular to linear) and up to 1.5 mm (vs. 2 mm) long, subpeltate (vs. non-peltate) and obovate to oblong-elliptic (vs. lanceolate) leaves, truncate to subcordate leaf bases (vs. acute), 16–18 pairs of secondary veins (vs. 12–14 pairs), 4.5–5.0 mm long styles that are 10–15% proximally fused (vs. 3.5–4.0 mm long and 25–28% proximally fused), and smaller fruits (5.5–6.5 × 7.0– 8.6 mm vs. 8.5–10.0 × 7.5–9.5 mm).

Additional specimen examined: PHILIPPINES. Mindanao, Zamboanga del Norte Province, Municipality of Leon B. Postigo , Barangay Tinuyop , 8°3’49.39” N, 122°55’48.03” E, elevation 322 m, 6 February 2021, K. R. F. Mazo 15 ( PNH 258578 !; CMUH!)

Figures

FIGURE 2. Saurauia denticulata C.B.Rob.A. Leafy branchlet; B. Distal portion of twig; C. Leaf (adaxial view); D. Leaf (abaxial view); E. Portion of leaf showing petiole and leaf base; F. Cauliflorous inflorescences; G. Inflorescence showing flowers. H. Petals; I. Sepals, in (inner sepals), it (intermediate sepal), ot (outer sepals); J. Infructescences. Photos by K.R. Mazo.