Monadelpha guayanensis (L.J.Gillespie) L.J.Gillespie & Card.-McTeag., 2020

Gillespie, Lynn J., Cardinal-McTeague, Warren M. & Wurdack, Kenneth J., 2020, Monadelpha (Euphorbiaceae, Plukenetieae), a new genus of Tragiinae from the Amazon rainforest of Venezuela and Brazil, PhytoKeys 169, pp. 119-135 : 119

Monadelpha guayanensis (L.J.Gillespie) L.J.Gillespie & Card.-McTeag. comb. nov. Figures 1 , 2

Tragia guayanensis L.J.Gillespie, Novon 4: 330-338. 1994.

Type.

Venezuela. Amazonas: Río Casiquiare entre la boca del [Rio] Siapa y el caño Momoni, 18 Feb-4 Mar 1986, B. Stergios & G. Aymard 9182 (holotype: MO-260419! - staminate; isotype: NY-00076710! - pistillate).

Description.

See Gillespie (1994b). Emended here (based on Ule 5013): Leaves: petiole 2-8 cm long, blade elliptic, ovate-elliptic, broadly elliptic, broadly ovate-elliptic, or suborbicular, 12-25 × 6-17 cm, apex with acumen 1-2 cm long, base cordate with narrow sinus 0.8-2.5 cm deep, margins irregularly serrulate or denticulate. Staminate inflorescences ~3-18 cm long.

Etymology.

The specific epithet is derived from Guayana, and refers both to the Guayana Shield region of northern South America and to the Guayana Region of Venezuela where the species is native. Guayana is of Amerindian derivation by European colonists, and may come from the tribe Guayanos or the Indigenous word uayana, meaning pale (see Berry et al. 1995).

Additional collections examined.

Brazil. Amazonas: Rio Juruá, Nov 1900, E.H.G. Ule 5013 (L-0160690, K-001205092). Venezuela. Amazonas: En la isla de Trapichote, Delta del Ventuari, [3°57'31.45"N, 67°12'7.45"W], alt. 125 m, 21 Apr 1942, L. Williams 14990 (paratypes: F-1189188, US-1833601).

Distribution and preliminary conservation status.

Known from only three collections. The two from Venezuela are ~220 km apart in lowland rainforests of the upper Orinoco Basin and Río Casiquiare of western Amazonas. The Brazilian collection occurs at least 500 km to the south along the Rio Juruá (locality imprecise) in Amazonas. They occur in remote, pristine rainforest and their IUCN Red List Category presently should be Data Deficient given limited information of distribution and threats.

Notes.

Monadelpha guayanensis is newly reported here from Brazil based on one 1900 collection by E.H.G. Ule. Staminate inflorescences on this collection (L-0160690 sheet) are considerably longer than previously described, and are closer in length to the pistillate inflorescence. It appears that the staminate inflorescence on the holotype may be damaged and partly missing or possibly less mature. Leaf blades are more variable in size and shape than on the two Venezuelan collections, some blades being very similar, others larger and relatively broader.

Monadelpha guayanensis has unisexual inflorescences and is likely monoecious (rather than dioecious). Although unisexual inflorescences are not found on the same branch, the type collection, Stergios & Aymard 9182, has inflorescences of both sexes, and is thus monoecious if one assumes branches originate from a single individual. Further collections are needed to confirm this character.

Figures

Figure 1. Illustration of Monadelpha guayanensis. A habit showing staminate inflorescence B staminate flower C habit showing infructescence D pistillate flower E mericarp of dehisced capsule with enclosed seed F seed, lateral view with hilum at top. Sources: A, B based on Stergios & Aymard 9182 (MO) C-F based on Stergios & Aymard 9182 (NY). Illustration by Cathy Pasquale reproduced from Gillespie (1994 b) with permission from the Missouri Botanical Garden Press.

Figure 2. Pollen morphology of Monadelpha guayanensis A SEM of pollen grain showing polar view with five colpi B closeup of mesocolpium and two colpi. Source: Stergios & Aymard 9182 (MO). Figure reproduced from Gillespie (1994 b) with permission from the Missouri Botanical Garden Press.