New species of Gymnanthes (Euphorbiaceae) from Bolivia and Colombia, and taxonomic notes on the genus in Venezeula

Abstract: New, locally endemic species of Gymnanthes are described from Bolivia (G. microphylla) and Colombia (G. hirsuta). Both species are characterized, among other features, by a specific indumentum different from each other and from other, related species. In addition, two species from Venezuela are discussed: G. apiculata is proposed as a synonym of Actinostemon caribaeus, and the name G. hypoleuca is lectotypified. Citation: Esser H.-J. 2017: New species of Gymnanthes (Euphorbiaceae) from Bolivia and Colombia, and taxonomic notes on the genus in Venezuela. — Willdenowia 47: 217–224. doi: https://doi.org/10.3372/wi.47.47304 Version of record first published online on 9 November 2017 ahead of inclusion in December 2017 issue.


Introduction
Gymnanthes Sw. (Euphorbiaceae) is a pantropical genus that is most common in dry tropical regions of South America, but also has a few species in wet tropical areas in the Neotropics and Palaeotropics, with many of them local and rare. Originally restricted to a few Neotropical species (Pax & Hoffmann 1912), the genus has recently been expanded to include species formerly classified in Sebastiania Spreng. (Esser 2001;Esser & al. 2010), and currently includes c. 45 known species (Esser 2001;Webster 2014).
Distribution and ecology -So far known only from the type locality. In very dry tropical forest (bosque muy seco tropical, or bms-t), on rocky substrate on bare soil, at elevations of 930 -975 m. The Hacienda Churimal is located in the northernmost of two very dry forest enclaves in the Cauca Valley, 6 km S of the town of Roldanillo. Flowers and fruits were found in March and October.
Remarks -There are a few Neotropical species of Gymnanthes with distinctly pubescent fruits and leaves, such as G. vestita Müll. Arg. from Brazil (Esser & al. 2010).  Esser: Gymnanthes from Bolivia, Colombia and Venezeula None of these, however, is as densely hirsute as this new species on most surfaces (except for the only sparsely pubescent upper leaf surface and staminate flowers), and few are as distinctly sclerophyllous and scleromorphic, with the short, leafy side branches terminating in spiny tips. This last character is shared with G. microphylla, described below from Bolivia, but the latter is otherwise sufficiently distinct.
Gymnanthes hirsuta is presumably the second species of Gymnanthes known from Colombia. Webster & al. (1999) cited Colombia in the distribution data of G. hypoleuca Benth., which was later included by Murillo (2004), but no specimen was cited and this record might therefore be doubtful. The World Checklist of Euphorbiaceae (Govaerts & al. 2000) did not mention Colombia. Diagnosis -The new species is similar to Gymnanthes schottiana Müll. Arg., but differs in particular by branches and pedicels that are pubescent with very short hairs less than 0.1 mm long (but not glabrous), broadly elliptic leaf blades (1.45 -2 × as long as wide, versus narrowly elliptic to obovate, 2.7 -3.5 × as long as wide), and larger, 5 -7 mm long, often muricate fruits (versus 2 -3 mm long, never muricate).
Distribution and ecology -The species is known from three departments of Bolivia (Chuquisaca, Cochabamba and Potosí). It is locally frequent on rocky slopes with sparse vegetation, on nearly bare, flat rocks, dry bushland, and dry, xerophytic forest (where often in more humid microclimate), at elevations of 1850 -2850 m (3750 m probably recorded in error). Flowering plants were collected in December and January; fruiting ones from November to April.

Vernacular name -tikira.
Remarks -Most specimens of this species were collected in fruit. Staminate flowers are rarely collected, but these are very small and easy to miss. The type collection is the only one with abundant flowers and fruits.
The genus Gymnanthes has hitherto been known from three species in Bolivia (Esser 2014), all more widespread in dry vegetation in South America and rare in Bolivia (see also Oliveira & al. 2013). This new species is the first Bolivian endemic, locally frequent in dry vegetation types.
This new species is similar to Gymnanthes schottiana from Brazil, formerly known as Sebastiania schottiana (Müll. Arg.) Müll. Arg., with which it has sometimes been confused. Both species share comparatively small leaves, small, axillary staminate inflorescences of similar size, and solitary, axillary fruits on long pedicels; however, the leaves of G. microphylla are even smaller and are presumably the smallest in the genus. The unusual indumentum of the new species is unique, being always present at least on some parts but consisting of very short (less than 0.1 mm long) hairs that are barely visible without magnification.
Several of the specimens had previously been determined as Sebastiania haploclada Briq. However, the latter is endemic to Peru and, although a shrub with a similar spinescent habit and smaller leaves, it belongs to Sebastiania and differs by large and fleshy floral bracts c. 1 mm long, sessile staminate flowers, leaves elliptic-  sí -Sucre, 2620m, fr., 28 Feb. 1991; prov. Zudañez, ladera oeste del río Pilcomayo, cerca Oronkhata, 2100m, sterile, 27 May 2004, R. Lopéz & al. 868 (LPB). -Potosí: prov. Chayanta, 1.5 km W de Maragua, 3750 m (?), sterile, 18 Nov -3 Dec 1998prov. Saavedra, pasando Retiro, 2600m, fl., 30 Mar. 1993; prov. Linares, valle de Oronkhota, subiendo de Oronkhota hacia Jatum Palmar, 2520 m, fr., 4 Apr. 1993, G. Torrico & C. Peca 316 (LPB). The name Gymnanthes apiculata was validly published by Badillo in a checklist (Badillo & al. 1984), but has been widely overlooked. It was not included in the World Checklist of Euphorbiaceae (Govaerts & al. 2000) and, at the time of writing this manuscript, it is still missing in IPNI (http://www.ipni.org). The genera Actinostemon Mart. ex Klotzsch and Gymnanthes are similar, differing, among other features, in the floral buds (individual cymules covered and protected by the bracts in Gymnanthes, versus the whole inflorescence covered and protected by large bud scales in Actinostemon with the bracts reduced) and some leaf characters (leaves mostly serrate with marginal glands in Gymnanthes, versus leaves entire with laminar glands in Actinostemon). Mature inflorescences and fruits are indeed very similar and can be confused easily. Badillo did not include Actinostemon in his checklist and probably did not study authentic material of the genus, so he might have confused the genera. Actinostemon caribaeus is known from N Venezuela (Jablonski 1969), and G. apiculata fits well into the known distribution area of the species. There is a some confusion about the types of Gymnanthes hypoleuca in the literature. Bentham (1854) cited two collections from different localities, but he did not mention collecting numbers. Both syntype collections are in fact numbered 2806. Spruce 3780 (sometimes considered a syntype, as seen in several herbaria and by Gillespie 1993) was collected only after the description of the species (Brazil, Amazonas, insula secus ostia fl. Marauiá, Dec 1854) and cannot therefore be a type for the name, but is instead the type gathering of G. hypoleuca var. angustifolia Müll. Arg. The lectotype designated here was chosen because it has the larger number of duplicates,