Boehmeria heterophylla Wedd.

Wilmot-Dear, C. M. & Friis, I., 2013, The Old World species of Boehmeria (Urticaceae, tribus Boehmerieae). A taxonomic revision, Blumea 58 (2), pp. 85-216 : 109-110

5. Boehmeria heterophylla Wedd. — Fig. 4e–l ; Map 6 , 7

Boehmeria heterophylla Wedd. (1856) 351, non Boehmeria heterophylla (Wedd.) Blume (1857) , nom.illeg. (see Note 1 under var. blumei ). ― Type: Cuming 1561 (iso BM, G, K, M, P), Philippines, Luzon , Manila .

Small subshrub or shrub, 0.5–2(–4) m tall, rather juicy; ultimate branches slender, up to 1 mm diam, with abundant hairs, these either ± adpressed, fine, uniform, straight and up to 0.2 mm long or a mixture of two kinds, usually spreading, some very short (0.2 mm long), others much longer (0.4 mm long), stems sometimes later glabrescent. Stipules lanceolate, long-acuminate, membranous, ((in specimens from Mindanao only) 3–)6–9 by (1–) 1.5–2 mm. Leaves alternate or subopposite, dimorphic in size and relative width, often also in shape with the ‘larger’ ones (at least those on main stems) 3–10 × as large as the ‘smaller’; larger leaves (slightly or) usually markedly asymmetrical (outline of one side ovate, of other elliptic) and sometimes slightly sideways-curved at apex, narrowly ovate or linear-lanceolate (rarely ± obovate), medium or large, (6–)8–16 by 1.4–4 cm, length 2.5–5(–6) × width; margin with (15–)25–40 teeth either side, these broad, relatively shallow, acute or rounded, 1–3(–4) mm long, 2–5(–7) mm broad; leaf apex short-acuminate or attenuate-long acuminate; base asymmetrically rounded or slightly cuneate; basal veins extending to middle of lamina or less (narrow side) or distal third (wide side) of lamina, number of upper lateral veins 3–4 on wide side, 1–2 on narrow side, all arising in distal 1/2 or 2/3 of lamina, finely impressed adaxially, thinly prominent abaxially; tertiary venation finely prominent abaxially; texture very thin-chartaceous or slightly thicker and leaves somewhat bullate, adaxial surface with hairs abundant, adpressed or spreading (longer than on stem); abaxial surface with hairs sparse or abundant, longer, more or less spreading; petiole short but variable relative to size of lamina, 0.1–0.3 × lamina length, pubescent like stem, sometimes also with longer spreading hairs; ‘smaller’ leaves relatively broader, rounded to broadly acute (rarely narrowly acute) and often subsessile with cordate base. Flower­clusters axillary, male clusters 2–4 mm diam, with flowers few or up to 15(–20), not very densely congested, female clusters up to 5(–8) mm diam, with flowers 50–70(–more than 100) in number, densely crowded; some clusters with both sexes; bracteoles in male clusters conspicuous, up to 0.8(–2) by 1 mm, ovate or obovate, rounded or acute at apex, pubescent like stem, bracteoles in female clusters mostly inconspicuous linear-elliptic, <0.5 mm long. Male flowers 4-merous, subsessile or on pedicel up to 0.5 mm long, mature buds globose up to 1.3 mm diam, tepals with prominent dorsal appendage, pubescent like the leaves. Female flowers mostly subsessile but in larger clusters sometimes grouped into highly reduced cymes with peduncle and pedicels lengthening in fruit, overall length of peduncle becoming up to 2 mm long; perianth narrowly ovoid, 1 by 0.3–0.4 mm, often flattened towards apex; stigma 1–3 mm long, extremely slender. Fruiting perianth 1–1.8 by 0.6–1 mm, broad or narrow, very variable in shape often even in one cluster, ± oblong in outline or ovoid, (slightly or) markedly asymmetrical, achene occupying only basal half, base ± narrowly rounded, distal part either inflated to markedly dorsiventrally flattened giving winged or shouldered appearance, ± without beak (2-toothed) or else narrowed into abrupt long beak up to 0.3 × total length. Achene 0.7–1 by c. 0.4–1 mm, obovoid slightly laterally flattened but usually markedly asymmetrical, swollen on one side in apical part and with style slightly asymmetrically inserted, yellowish, with sometimes tuberculate surface.

Distribution ― Indonesia (restricted to Sulawesi), Philippines (Luzon, Mindanao, Mindoro, Panay), Papua New Guinea (West Sepik, Milne Bay ).

Habitat & Ecology ― Secondary forest, evergreen forest margins; 200–1100 m altitude.

Conservation status ― Near Threatened (NT). The species is known from c. a hundred collections, but most of them are more than 50 years old and as discussed under B. beyeri , the Philippines have been subject to severe and continuing degradation of their natural habitats. The three widely scattered records from outside the Philippines make the figure for EOO (355 398 km 2) rather misleading. The AOO is calculated as less than 500 km 2. Although it appears to occur in too many localities to qualify formally for Endangered status it is probably under threat. Of the two varieties, var. blumei , almost entirely restricted to Luzon, is probably the more endangered.

Notes ― 1. Boehmeria heterophylla was hitherto thought to be a Philippine endemic and the few records from Indonesia (one from Sulawesi, two from the island of New Guinea) suggest that it is under-collected.

2. This and B. beyeri form a distinct small group mainly or entirely found in the Philippines, unique among the Old World taxa in having a combination of consistently alternate to subopposite (rather than variable or consistently opposite) arrangement of leaves and simple axillary flower-clusters. Boehmeria heterophylla is distinguished from B. beyeri by its markedly asymmetrical and dimorphic leaves, female clusters many-flowered and fruiting perianth apically inflated or with abrupt beak rather than gradually tapering to beak.

3. It can be confused with the widespread Pouzolzia sanguinea (sympatric in Indonesia) which sometimes has flower-clusters large and densely congested and appears superficially rather similar. Leaves in P. sanguinea are not markedly asymmetrical but the only consistent gross morphological distinctions are the male tepals without dorsal appendage and the conical, only slightly laterally flattened, bilaterally symmetrical fruiting perianth with several longitudinal ribs. Boehmeria heterophylla can also be confused with B. clidemioides which differs in leaves dimorphic only in size and not markedly asymmetrical, and fruiting perianth markedly laterally flattened with a distinct wing, often symmetrical.

4. The two varieties here recognised were hitherto considered as separate species, and at the extremes of the variation (as represented by the respective type collections) they do look very different, var. blumei having two markedly different lengths of indumentum on the stem, relatively broader thicker bullate leaves, marginal teeth longer and mostly relatively broader with convex rather than concave upper margin; stipules also seem to be often longer-persistent. However, there is overlap with var. heterophylla in leaf proportions and in tooth size and shape and considerable variation in leaf texture; many collections are difficult to assign to either entity, being somewhat intermediate in indumentum with the two sizes of hair only moderately different (longer indumentum only 0.2 mm long) or with most characters as in var. heterophylla but leaves subopposite.There also appears to be little difference in flower and fruiting perianth, except the tendency to larger female clusters and sometimes tuberculate achene surface in var. blumei . It therefore seems better to recognise these two entities only as varieties. They are only partly sympatric, var. blumei being apparently less widespread in the Philippines and absent from the island of New Guinea but also recorded from Sulawesi (see above). It is unfortunate that there is very little habitat information for var. blumei , to ascertain whether the variation may be correlated with habitat differences.

5. Type material of the following name is intermediate between the two varieties.

Boehmeria villosa C.B.Rob. (1911) 3. ― Type: Fenix BS 3754

(holo PNH n.v.; iso BO, NY), Philippines, Batan Islands,

Santo Domingo de Basco.

One collection from Luzon ( Ramos BS 13580, BM. K, L) has narrowly obovate (rather than ovate) cuneate leaves only sparsely hairy adaxially and minute pubescence abaxially, and stigma with unusually long hairs giving a ‘bottle brush’ appearance. In other respects it conforms to B. heterophylla s.lat. and is therefore included here.

Key to varieties

1. Hairs on stem short (up to 0.2 mm), fine, adpressed, uniform; leaves clearly alternate, thin-chartaceous, relatively narrow (length (3–)4–7 × width), marginal teeth with concave upper margin......................... a. var. heterophylla

Figures

Map 6 Distribution of Boehmeria heterophylla Wedd. var. blumei (Wedd.) Friis & Wilmot-Dear (●) and B. beyeri C.B.Rob. (ä).

Map 7 Distribution of Boehmeria heterophylla Wedd. var. heterophylla.

Fig. 4 a–d: Boehmeria beyeri C.B.Rob. a. Part of stem showing leaves dimorphic in petiole length; b male flower; c. axillary female flower-cluster (inflo- rescence); d. female perianth. — e–j: Boehmeria heterophylla Wedd. var. heterophylla. e. Stem with alternate dimorphic leaves and axillary flower-clusters (inflorescences); f. detail of stem with fine adpressed indumentum; g. leaf with adpressed indumentum on adaxial surface; h. axillary female flower-cluster (inflorescence); i, j. fruiting perianths of different form (from same plant).— k–m: Boehmeria heterophylla var.blumei (Wedd.) Friis & Wilmot-Dear.k. Stem with subopposite dimorphic leaves; l. detail of stem with coarse and fine spreading indumentum; m. male flower in bud (a–d: Beyer 13540; e: Cuming 1561; f, h: Borbon 8866; g: Elmer 15627; i, j: Edano 19876; k, l: Cuming 731; m: PPI 11815; all K). — Scale bars: a, e, g, k = 2 cm; c, h = 2 mm; b, d, f, i, j, l, m = 1 mm.