Boehmeria tsaratananensis Leandri

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 : 143-145

21. Boehmeria tsaratananensis Leandri — Fig. 19 ; Map 21

Boehmeria tsaratananensis Leandri (1950) 59. ― Syntypes: Humbert 18285 (syn P, n.v.), Madagascar, Centre Tsaratanana and Sambirano,Andavaka; Perrier de la Bâthie 15501 (P) & 9972 (P), Madagascar,Tsaratanana; Perrier de la Bâthie 17678 (P), Madagascar,Ambre.

Boehmeria platyphylla D.Don var. masoalensis Leandri (1950) 59. ― Type: Perrier de la Bâthie 9973 (holo P), Madagascar, Masoala. – See Note 2.

Shrub, ± scrambling, 1–3 m tall, branches rather fleshy; ultimate branches slender, c. 1 mm diam, hairs dense, minute (up to 0.1 mm long), fine, closely-adpressed, eventually glabrescent. Stipules broad- or narrow-triangular (shortest in high altitude specimens), 3.5–10 by 1–1.5 mm, fused for 0.3–0.5 × length, usually cordate in basal part, sparsely hairy outside as stem. Leaves opposite and slightly or moderately dimorphic with length of ‘larger’ leaves up to 1.5 × ‘smaller’ ones, elliptic or elliptic-obovate, sometimes asymmetrical with one half slightly wider, small or medium, 5–16 by 2.5–7 cm, length 1.7–2.2 (–2.8) × width; margin entire in basal quarter or half, distal part indistinctly serrate, teeth 10–15(–20) either side, these very shallow but broad, 0.3–1(–1.5) by 3–8 mm, length usually 5–10 × width, the longest near apex; leaf apex broadly rounded terminated abruptly by short acumen tapering to fine point; base broadly rounded to broadly cuneate, often slightly oblique; basal veins extending to distal quarter of lamina, upper lateral veins (1–)2 on wide side, 1(–2) on narrow side, all arising in distal third or near apex, inconspicuous or (in thick leaves) deeply impressed adaxially, prominent abaxially, recorded as purple when live, coarser tertiary venation ± scalariform, prominent abaxially; texture thin- or thick-chartaceous to ± coriaceous (leaves sometimes slightly bullate), adaxial surface hairy, hairs like the stem but sparse, extremely inconspicuous and often lying in a rather regular pattern pointing towards the centre of areoles; abaxial surface with similar hairs on veins and reticulation but denser and even smaller; petiole long with respect to lamina, half of to almost equalling lamina length, pubescent like stem. Flower­clusters borne along leafless inflorescence-bearing axes, these extremely slender, (0.2–0.5 mm diam when dry), (red in live state) 1–several arising from thicker basal part which is extremely short 2–5 mm long; axes rarely bisexual, more often unisexual but both sexes sometimes on same plant with male axes in upper axils; male axes 3–10 cm, erect, female ones (10–) 15–40 cm, pendulous; flower-clusters often rather wide-spaced, 2–20 mm apart, up to 2.5 mm diam, with only 1–5(–10) flowers; bracts broadly ovate, acuminate 1.5 by 1 mm; bracteoles very conspicuous, triangular or elliptic, acute, 0.5–0.8 mm long. Male flowers 4-merous, subsessile, male buds globular, large c. 1.5 mm diam, with slight dorsal thickening and sparse hairs as stem. Female perianth small, c. 0.5 mm long, ovoid without distinct beak; stigma 1–1.5(–2) mm. Fruiting perianth ellipsoid short and broad 1–1.2 by 0.6–0.7 mm, slightly laterally flattened with marginal rim and short beak, hairs sparse, minute, spreading. Achene ± filling fruiting perianth.

Distribution ― Madagascar (northern and eastern part).

Habitat & Ecology ― Cloud forest, moss forest, wet hollows in dense undisturbed primary forest, on siliceous soil; 400– 1000 m altitude.

Conservation status ― Endangered (EN). The species is known from c. 10 collections from five localities. The material is both old and relatively recent, the latest from 2005. There is habitat destruction on Madagascar, but also conservation efforts, and forest reserves exist. The EOO is 96 172 km 2, which would give it a conservation status as Near Threatened (NT) but, the AOO is only 24 km 2. Taking into account the few, small and scattered populations in restricted habitats it can be given a status of Endangered with the criteria EN 2Bab(iii).

Notes ― 1. This species is endemic to Madagascar (one of only three taxa native to the region, the other being two varieties of B. virgata subsp. macrophylla ) and does not closely resemble any other taxon. It is distinctive in its leaves obovate to elliptic-obovate with teeth sharply-up-curved but very shallow and wide-spaced, these progressively shallower proximally and finally absent in basal part of leaf margin, upper veins only 1–2, arising close to apex, its petiole very long relative to lamina; its inflorescence-bearing axes extremely slender with large male flowers and its short broad fruiting perianth.

The character of partly-entire leaf margin is also seen only in two allopatric and otherwise very dissimilar species. The extremely rare Burmese endemic B. didymogyne is a slender herb with leaves membranous and flower-clusters axillary. The Papua New Guinean endemic B. subintegra has leaves much narrower (length 3.5–4 × width), glabrous and shiny above with apex gradually attenuate, marginal teeth only up to 0.2 mm long, petiole relatively much shorter (0.1–0.25 × lamina length), leaves often markedly more dimorphic with length of ‘larger’ leaves up to 4 × ‘smaller’ ones.

2. Leandri (1950), at the same time as describing B. tsaratananensis , also described material of it as B. platyphylla var. masoalensis . Subsequently ( Leandri 1965), he remarked on the long petiole and shallow teeth, but had presumably not seen a sufficiently wide range of variation of B. tsaratananensis to define its other distinguishing characters of leaf shape, venation and progressive change in form of marginal teeth.

Figures

Map 21 Distribution of Boehmeria tsaratananensis Leandri.

Fig. 19 Boehmeria tsaratananensis Leandri. a. Habit of stem with inflorescence-bearing axes; b, c. leaves of different form (from different plants); d. leaf, detail of adaxial surface; e. detail of abaxial surface; f. detail of stem and stipules; g. detail of male inflorescence-bearing axis with flower-clusters (inflores- cences) and bract; h. detail of female inflorescence-bearing axis with flower-clusters (inflorescences) and bract; i. fruiting perianth (a, f: Schatz 2402, K; b, g: Andrianantoanina 343, K; c-e, h: Lowry 4084, K; i: Bathie 9972, P). — Scale bars: a–c = 2 cm; d, e = 5 mm; f-i = 1 mm.