Macairea thyrsiflora DC.

Authority

Renner, Susanne S. 1989. Systematic studies in the Melastomataceae Bellucia, Loreya and Macairea. Mem. New York Bot. Gard. 50: 1-112.

Family

Melastomataceae

Scientific Name

Macairea thyrsiflora DC.

Description

Species Description - Shrub or treelet, 0.5-2(-8) m tall; branchlets, petioles, and peduncles sericeous or strigulose with slightly curied, rust-colored, basally rough ened hairs and with globose sessile glands. Leaves elliptic, 4.5-13 x (2-)3-4.5 cm, obtuse, acute or acuminate, basally obtuse, attenuate or subacute, 3(-5)-nerved, the lateral primaries arising at the blade base, basally close to or to 6 mm from the margin, apically close to the margin, upper surface vermcose or scabrous, with stout conical hairs with downward curved tips, lower surface on the mid-vein and lateral primary veins more or less densely strigose with basally broad and roughened, apically slender, slightly curled hairs, the lateral secondary veins and veinlets with shorter hairs, areoles with short, few-branched = papillae-like hairs and with sessile glands; petioles (0.2-)0.5-1.6 cm long. Inflorescence a manyflowered terminal paniculate cymes. Flowers with pedicels 1-4 mm long; pedicels, bracts, hypanthium, and calyx lobes sericeous with rust-colored, slightly curled hairs, with sessile glands; hypanthium 3-4 x 2-3 mm; calyx lobes broadly to narrowly triangular, 2-3-5 mm long; petals basally white, tuming red with age, apically pink, or petals white, 7-9 x (4-)6.5-8 mm; filaments 8-9 or 5-8 mm long, ventrally with short-stalked glands; thecae 3.5-5 mm long, the connective distinctly prolonged and expanded dorsi-basally; ovary apically with short glandular hairs, sometimes with 4 lobes surrounding the base of the style, 4-locular. Fruits capsular. Seeds 0.7-0.8 mm long, subcochleate.

Distribution and Ecology - Distribution and ecology (Fig. 33A): Macairea thyrsiflora occurs from the Gran Sabana in Venezuela, east into Guyana, south through Brazilian Amazonia into Mato Grosso and Bolivia, and west into Venezuelan, Colombian, and Pemvian Amazonia. It grows in humid locations, sometimes with the roots in water and is common in disturbed areas; lowlands to 1700 m.

Discussion

Type: Brazil. Amazonas: Upper Rio Negro (ff), Ferreira s.n. (holotype: P!; isotypes: K!, LISU!).

Figs. 22A-C; 23A; 28J-L.

Macairea albiflora Cogniaux in Martius, Fl. bras. 246. 1885. Type: Colombia (Vichada or Guainia) or Venezuela (Amazonas). Nr. Maypures or on the Atabapo, Jun 1854 (fl). Spruce 3719 (holotype: K!, H. A. Gleason photo s.n.; isotypes: BM!, K!, P!, F photo neg. 36139!, WI, F photo neg. 32323!).

Macairea aspera N. E. Brown, Trans. Linn. Soc. London 6: 27, pl. 2. 1901. Type: Guyana. Upper slopes of Mt. Roraima, 1894 or 98 (fl), McConneU& Quelch 31 (holotype: K!).

Macairea scabra Cogniaux, Bot. Jahrb. Syst. 42: 133. 1908 [1909]. Type: Pem. Loreto: Rioja, W of Moyobamba, 800-900 m, Sep 1904 (fl), Weberbauer 4708 (holotype: BR!; isotypes; G!, isotype at B destroyed, but represented by a photo, F neg. 16704!).

Macairea rosea Cogniaux, Comm. Linh. Telegr. Estr. Matto Grosso, Publ. 10, Annexo 5, Bot. 3: 4. 1912. Type: Brazil. Mato Grosso: Juruena, Apr 1909 (fl), Hoehne 1800 (lectotype, here designated: BR!, photo US s.n.!).

Macairea arirambae Huber, Bull. Soc. Bot. Geneve 6: 193, fig. 6. 1914. Type: Brazil. Para: Campos de Ariramba, Trombetas, 23 Dec 1906 (fl), Ducke 8087 (lectotype, here designated: MG!, F photo neg. 2602!; isolectotypes: G!, MG!).

Macairea villosa Hoehne, Mem. Inst. Butantan, Sec. Bot. 1: 59, pl. 8, fig. 1. 1922. Type: Brazil. Mato Grosso: Morro Podre, Chapada Central, Mar/Apr 1911 (fl), Hoehne 2476 (holotype: R!).

Macairea schultesu Wurdack, Bot. Mus. Leafl. 18: 164. 1958a. Type: Colombia. Comisaria del Vaupes: Rio Kuduyari, Cerro Yapoboda, savannas on quartzite base, 450 m, 5/6 Oct 1951 (fl), Schultes & Cabrera 14358 (holotype: NY!).

Macairea maguirei Wurdack, Phytologia 20(6): 36. 1970. Type: Venezuela. Terr. Fed Amazonas: Edges of sabana El Venado, left bank of Cano Pimichin, 2 km above Pimichin, 120-140 m, 10 Oct 1957 (fl). Maguire, Wurdack & Keith 41800 (holotype: US!; roughisotypes: B!, G!, NY!, P!, VEN!).

Macairea thyrsiflora is superficially similar to M. theresiae, from which it differs in the mst color of the lower leaf surface (vs. a greenish lower surface in M . theresiae), the finer reticulation of the veinlets, and the glandular ovary indument (see also under M . theresiae). Macairea thyrsiflora and M . theresiae are sympatric near Oriximina, Belem, and Santarem; they maintain their distinctness at these localities. Macairea thyrsiflora is exceedingly polymorphic in the length ofthe pubescence and the calyx lobes. Specimens from the Rio Negro-Pacimoni area have quite smooth leaves with a vermcose upper leaf surface and a velvety lower surface covered with very short, papillose hairs; plants from Guyana have rougher (scabrous) leaves with short, conical hairs with downward curved tips on the upper surface and a more or less strigose lower surface. This east to west cline is found only in the northem part of the species' range. Collections from the area south of the Amazon are homogeneously intermediate in their pilosity. Those from savannas just north ofthe lower Amazon (Oriximina and the Campos de Ariramba), in tum, are intermediate between Guyana specimens and the specimens of southern provenance. The quality of the indument is the same in all collections. The length of the calyx lobes ranges from two to five m m and seems to vary randomly.

In some savannas, the rough-leafed and the smooth-leafed morphs occur together; for example, at the base and on the plateau of Serra Araca, around Esmeralda, near Mitu on the Rio Vaupes, and in a savanna at k m 350 ofthe Manaus-Caracarai road. A savanna colonized by seedlings from several different areas would contain the different plant types growing next to each other for prolonged periods of time if gene exchange between the individuals were low. I suspect this is the case; the pollen grains of M . thyrsiflora are often malformed and there are very few grains per anther. In M . theresiae, agamospermy has already been demonstrated experimentally (see Pollination and Dispersal), and it is possible that the capacity to form seeds asexually is also present in M . thyrsiflora. Such off"- spring would have the advantage of having genotypes already tested for suitability in a particular savanna environment. Asexual reproduction results in clones, with major discontinuities between them and little heterogeneity within them. This would fit well the situation observed in M . thyrsiflora.

N. E. Brown (1901) provides an illustration of the species.