Miconia dimorphotheca Jan.M.Burke & Michelang., 2018

Burke, Janelle M. & Michelangeli, Fabian A., 2018, Six new species of Miconia (Miconieae, Melastomataceae) from the Andes, Phytotaxa 361 (2), pp. 131-150 : 139-140

Miconia dimorphotheca Jan.M.Burke & Michelang. , sp. nov. ( Fig. 5 )

Diagnosis: Similar to other dioecious species of Miconia section Cremanium , containing anthers opening by 2 or 4 broad pores, but can be distinguished by presence of red sessile glands on abaxial leaf surface, base of petiole with small, oval paired appendages and stems bluntly quadrangular and deep purple.

Type:— BOLIVIA. [La Paz]: Unduavi in Nor Yungas , 3100 m, December 1931 (fl), O. Buchtien 8998 (holotype: NY!; isotype: US!) .

Treelet, up to 1– 8 m. Young stems terete becoming blunty quadrangular, glabrous or scabrous when young, to glabrous when mature, internodes with narrow longitudinal fissues, nodal line faint, deep red to maroon, with a pair of white, ovoid or oblong glands at base of each petiole. Leaves isophyllous; the petiole (0.5) 1–2.6 cm long, the indumentum absent to scabrous; the blade 4.4–10.1 × 1.9–3.4 cm, oblong (elliptical, obovate), membranaceous, the apex cuspidate to acuminate (0.5 –0.75 cm), the base round to slightly attenuate, the margin inconspicuously serrate with 0.25 mm teeth; secondary veins 2 pairs, basally nerved, with faint marginals, tertiary veins percurent, 1.5–3 mm apart, often inconspicuous, reticulate, veins slightly impressed on the adaxial surface and raised, light to deep red on the abaxial surface; adaxial surface green, the indumentum on the surface glabrous, and sessile, translucent glands on the primary and secondary veins; abaxial surface light green, the indumentum on the surface glabrous except for red sessile, pigmented glands, veins glabrous. Inflorescences terminal, narrow panicles of cymose units, 4.8–9 cm long; peduncles slightly flattened, brown to deep purple, the indumentum glabrous to scabrous; bracts ca. 1 × 0.3 mm, lanceolate, caducous; bracteoles ca. 1 mm long, linear, caducous. Flowers 5-merous, functionally unisexual, with pedicel 0.5–1 mm long. Hypanthium 1.77 mm long, semi-hemispherical, 2.3 mm wide at the torus, external indumentum of few sessile translucent glands, internal surface glabrous, androecial fringe absent. Calyx open in bud, the tube 0.2 mm long at anthesis, the lobes vestigial to 0.3 mm × 0.2 mm, vestigial to round, glabrous, hyaline; calyx teeth round, 0.2 mm × 0.2 mm, glabrous, as hypanthium. Petals 0.75 × 0.6 mm, obovate, spreading, white at anthesis (drying yellow), glabrous, the apex round, the base attenuate, the margin slightly erose. Male flowers diplostemenous; stamens isomorphic, exserted and actinomorphic at anthesis; stamen filaments 1.3–1.4 mm long, glabrous, white, anthers with 2 locules, thecae 1 × 0.5–0.55 mm, obovate to cuneate, opening by 1 ventral broad, 0.4 mm wide pore, white at anthesis, connective 0.25 mm. Ovary 3-locular, 10% free, the free portion projecting 0.3 × 1.5 mm, slightly convex, glabrous, ovules present, the apex without a corona; style 1 mm long, straight, white, glabrous; stigma truncate, 0.4 mm wide. Female flowers diplostemonous; stamens isomorphic, exerted and actinomorphic at anthesis, stamen filaments 1 mm long, glabrous, white at anthesis, anthers with 2 locules, thecae 0.9 × 0.3 mm, oblong, collapsed, pollen not present, with 1 ventral pore, white at anthesis, dorsal bump 0.25 mm, glabrous. Ovary 3-locular, 10% free, 0.2 × 1–1.5, slightly convex, glabrous, ovules present, the apex without a corona; style 2.3mm long, slightly curved, white, glabrous, peltate, 0.5–0.7 mm. Berries only seen in immature state. Chromosome number not known.

Distribution.— Humid montane forest, 2000–3300 m in La Paz and Cochabamba, Bolivia (Fig. 3).

Phenology.— Flowering in October–December.

Etymology.— The epithet refers to the dimorphic morphology of the anthers between the functionally pistillate and staminate flowers.

Conservation Assessment.— The extent of occurrence (EOO) of M. dimorphotheca is 11,654 km 2 (5 data points), all of it at high elevation dwarf or cloud forests in Bolivia. Most of this distribution is outside protected areas. Given its restricted distribution, we recommend that this species is categorized as vulnerable, VU B1ab(iii) ( IUCN 2001).

Additional specimens examined: BOLIVIA: La Paz: Nor Yungas, Unduavi, 3300 m, November 1910 (male fl), Buchtien 2912 (US) ; Prov. Franz Tamayo, Pelechuco, bajando a pie el Río Pelechuco, 3000 m, 14˚46’ S, 69˚02’ W, 19 October 1999, (male fl) Beck 25210 ( LPB, US) ; Corani, Chapare, 2000 m, October 1959 (fem. fl), Cardenas 5721 ( US) ; Prov. Inquisivi, “Chaca Jahuira”, lower slopes N of the Rio Chaca Jahuira, ca. 1.5 km down river from the falls at Jalancha, 13 km NW of Choquetanga, 3300 m, 16˚47’ S 67˚25 ’ W, 21 July 1991 (bud), Lewis 39411 ( MO, US). Cochabamba: Bosques de Incachaca paia Sacaba, 2500 m, 12 November 1921 (sterile), Steinbach 5923 ( NY) ; Sailapata, 3500 m, November 1935 (fem. fl.), Cardenas 3217 ( NY) ; km 104 camino al Chapare, 3100 m, 3 December 1966 (fem fl.), Steinbach 567 ( NY, US) .

Miconia dimorphotheca is a dioecious species endemic to Bolivia. It is most similar morphologically to another recently described species from Bolivia, Miconia neei Burke and Michelangeli (2013:175) . In both species, the flowers retain vestigial organs of the opposite sex. Here, the pistillate flowers have exserted stamens, however the anthers are smaller, collapsed, and without pollen. The staminate flowers have a gynoecium, but the style is not exserted, as in the pistillate plants. Miconia dimorphotheca is also morphologically similar to M. theaezans Cogniaux (1888:419) a species that, as currently circumscribed, is distributed throughout much of South America. See Table 1 for distinguishing characters among these three species. One specimen, Cardenas 6154 ( US) is intermediate between M. dimorphotheca and M. neei . The leaves are more ovate with finely serrulate margins, as in M. neei , but with distinctive petiole appendages as in M. dimorphotheca .

Figures

FIGURE 5. Miconia dimorphotheca A. Habit. B. Staminate flower in bud (L) and at anthesis (R). C. Staminate flower in longitudinal section, with detail of stigma. D. Stamens from staminate flower, from left to right: ventral, dorsal and side view. E. Node of vegetative axis, with detail of node showing paired glands at base of petioles. F. Inflorescence cyme. G. Pistillate flower at anthesis. H. Longitudinal section of pistillate flower. I. Stamens of pistillate flower, from left to right: side, ventral and dorsal view. Drawn from Buchtein 8998, NY and Cardenas 3217, NY.