Monographs Details – Ericaceae

Monographs Details:

Authority:

Pedraza-Peñalosa, Paola. 2010. (Ericaceae, Vaccinieae). Fl. Neotrop. Monogr. 108: 1-126. (Published by NYBG Press)

Family:

Ericaceae

Scientific Name:

Disterigma humboldtii (Klotzsch) Nied.

Synonyms:

Vaccinium humboldtii Klotzsch, Vaccinium myrtifolium (Klotzsch) Willd., Vaccinium pachyphyllum Hemsl., Disterigma pachyphyllum (Hemsl.) S.F.Blake, Disterigma mayanum Lundell, Disterigma pilosum Wilbur, Disterigma ecuadorense Luteyn

Description:

Species Description - Epiphytic (especially in Central America) or terrestrial shrubs, scandent, pendent, or erect, 1–3 m tall. Young branchlets ridged, ± smooth, pubescent, puberulous, villosulous, or occasionally pilose, the hairs eglandular and light brown, the indumentum of the mature branches similar but glabrate or pilulose. Leaves 1–7 per cm, apparently distichous or spirally arranged, diffuse; petiole 1–2.5(–3.5) mm long, glabrate or puberulous, the hairs eglandular; lamina coriaceous and sometimes succulent, ovate, elliptic, or rarely obovate, 0.6–2(–2.5) × (0.2–)0.3–0.8(–1.3) cm, basally obtuse or cuneate, marginally entire or rarely crenulate towards apex, slightly revolute toward base, apically ciliolate or ciliate with deciduous eglandular hairs, apically subacute, obtuse, or rarely blunt-acute, drying wrinkled, adaxially and abaxially glabrate or rarely pilosulose with eglandular hairs and sometimes with glandular hairs, the venation adaxially obscure or hyphodromous with the midvein impressed, abaxially obscure, hyphodromous, or 3-nerved with the midvein raised. Axillary solitary flowers and rarely 2–3- flowered fascicles; bracts 5–8, chartaceous, ovate or transverse-elliptic, 0.4–2 × 0.6–2.2 mm, marginally eciliate or minutely ciliolate with eglandular hairs, apically obtuse, abaxially glabrous; pedicel 0.7–1.5(–2) mm long, reduced and hidden by overlapping bracts or rarely evident or at least with a portion of it not completely obscured by overlapping bracts, glabrate with eglandular or glandular hairs; differentiated apical bracteoles 2, distinct, chartaceous, enveloping entire calyx tube or to upper limb, covering 40–85(–100)% of calyx, obovate, ovate, or reniform, 1.8–4(–4.8) × 1.6– 4 mm, marginally eciliate or sometimes ciliolate with minute eglandular hairs, apically obtuse, the surface smooth and often keeled, abaxially glabrous or glabrate with eglandular hairs at base, adaxially glabrous. Flowers 4-merous. Calyx aestivation valvate, campanulate, 3–4.8(–5.5) mm long; tube angled, 1.1–2 mm long, abaxially glabrous or glabrate with eglandular or glandular hairs; limb 1.7–3.3 mm long, abaxially glabrous or glabrate (especially apically) with eglandular hairs, adaxially glabrous; lobes triangular, (1–) 1.3–2.5 × (0.8–)1–1.8 mm, marginally eciliate or rarely ciliolate with eglandular hairs, apically acute; sinuses acute (V-shaped). Corolla very light pink or white, thin-fleshy, bistratose, tubular or urceolate, (4.5–)6.5– 13.5 mm long, 2–3.5 mm diam., 1.3–2.8 mm wide at throat, abaxially glabrate with eglandular or glandular hairs, adaxially glabrous (especially in South America) or glabrate with minute hairs (although the presence of indumentum may vary within the same population); lobes 0.7–1.5 × 0.8–1.3 mm, apically acute, adaxially rugose. Stamens 8, (4–)6.5–11.8 mm long, included or rarely the tips exserted; filaments distinct, straight, ± linear with parallel sides or broader at base, (2.5–)4– 7.5 mm long, abaxially and adaxially glabrate, pilose, or pilulose; anthers distinct, papillae only on thecae; thecae 1–1.5(–1.8) mm long, with or without basal appendages; tubules 2, distinct, 1.3–2.5(–3.1) mm long, dehiscing introrsely by longitudinal slits, 0.9–1.1 mm long. Ovary 4-locular; style 5.7–10(–12) mm long, exserted. Berry white (few unconfirmed reports of light purple fruits; fruiting specimens have not been collected in Central America), ± spherical, the persistent calyx lobes erect or spreading, becoming succulent (at least at base), same color as mature berry; embryo color unknown.

Distribution and Ecology - Disterigma humboldtii is the second most frequently collected species of the genus, and 85% of the collections come from Central America, mainly from Costa Rica (71%); fewer are the specimens from Mexico, Guatemala, Honduras, and Panama. In South America, this species is found scattered in Colombia, Venezuela, Ecuador, and Peru (Fig. 31). It grows in premontane and montane cloud forests at (1000–)1500–3500 m. Flowering year-round; fruiting year-round except for Jan and Apr.

Local Names and Uses - This species is known as "muras" in Morona-Santiago, Ecuador.

Discussion:

Disterigma humboldtii (Figs. 29, 30A) is characterized by its leaves subacute, obtuse, or rarely bluntacute; solitary flowers with the pedicel usually reduced and hidden by the overlapping bracts; differentiated apical bracteoles enveloping the entire calyx tube or up to the upper limb; corollas white, tubular or urceolate, (4.5–)6.5–13.5 mm long, with equally long variable stamens; stamens with the thecae papillate; and white berries and embryos (amazingly, fruiting specimens have not been collected in Central America). Unlike the adaxially puberulous corollas of D. alaternoides, a species frequently thought to be close to D. humboldtii (Luteyn, 1996; Smith, 1933; Wilbur, 1992), the corollas of D. humboldtii are adaxially glabrous in South America (although inconspicuous hairs may occasionally be found within the same population) or mostly glabrate with inconspicuous hairs in Central America. These two taxa are discussed in more detail under D. alaternoides. The continuous variation in leaf and flower size observed in Disterigma humboldtii is reflected in the number of synonymized taxa, each one of them originally describing a different combination of traits (i.e., long corollas with small leaves, short corollas with large leaves, small corollas with small leaves, etc.), but all with essentially the same floral characteristics (see Fig. 29 for an example of D. mayanum). Differences in size are likely to be shaped by micro-environmental factors, thus D. ecuadorense and D. pilosum are here synonymized. The external indumentum can also be shaped by the environment or it can be manifested differently with age; for example, the pilulose indumentum of D. pilosum has been found also in representative specimens of D. humboldtii on the young shoots, but not in the mature branches.

Common Names:

muras

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