Two new species of Dendrophthora (Viscaceae) from the Venezuelan Andes

Abstract Two new species of Dendrophthora Eichler (Viscaceae) from northwestern Venezuela are described and illustrated. Both mistletoes, D.apiculata Canelón et al., sp. nov. and D.coronata Canelón et al., sp. nov., are confined to subpáramo and páramo ecosystems of the Venezuelan Andes and are, at present, only known from Guaramacal National Park (Portuguesa and Trujillo states). Ecological aspects and possible taxonomic affinities are discussed. A distribution map also is presented.


Introduction
Dendrophthora Eichler (Viscaceae) is the second most diverse genus of mistletoe in the New World comprising over 125 species distributed in Mexico, Central and South America, and the Caribbean (Nickrent in press). We follow Nickrent et al. (2010Nickrent et al. ( , 2019 in placing Dendropthora in the Viscaceae, even though Stevens (2020) places the genus in a more broadly construed Santalaceae (tribe Visceae Horan.). In South America, the vast majority of Dendrophthora species are found at high elevations along the Cordillera de los Andes, ranging from Colombia and Venezuela south to Ecuador, Peru, and Bolivia (Kuijt 1961). Approximately 28 species of Dendrophthora have been reported from Venezuela, including 13 endemic species (Rizzini 1982, Kuijt 2008, Tropicos 2019. For Guaramacal National Park, which is located in the northeastern portion of the Venezuelan Andes (Portuguesa and Trujillo states, Fig.  1), Dorr et al. (2000) reported three species of Dendrophthora: D. ambigua Kuijt, D. elliptica (Gardner) Krug & Urb. and an unidentified species. Continued research and collection, focusing on the flora of Guaramacal National Park, revealed an additional unidentified species. Inasmuch as both unnamed species do not match any previously published description of Dendrophthora found in the Andes of Venezuela or in the rest of the Americas, we describe them as new and provide information on their habitats and known hosts. Both species apparently are restricted to the subpáramo and páramo ecosystems of the Venezuelan Andes and are, at present, only known from Guaramacal National Park.

Materials and methods
We studied herbarium specimens of Dendrophthora collected in the Venezuelan Andes and deposited in the following herbaria: PORT (Portuguesa, Venezuela) and US (Smithsonian Institution). We also examined the type collection of the latter herbarium, examined specimens in COL (Universidad Nacional de Colombia herbarium, Bogotá, Colombia), and accessed specimens at MO (Missouri Botanical Garden) via the Global Plants JSTOR (2019) and Tropicos (2019) online portals. We also exhaustively reviewed the many articles, monographs, and checklists treating Dendrophthora published by Kuijt (1961Kuijt ( , 2000Kuijt ( , 2003Kuijt ( , 2008Kuijt ( , 2011Kuijt ( , 2016 and our terminology follows his. Species descriptions were made combining information from fresh and dried specimens, with inflorescences and flowers rehydrated using Aerosol OT solution (Ayensu 1967). Diagnosis. Dendrophthora apiculata is distinguished from congeners by its rough striate stems; minute, ca. 0.5 mm long cataphylls surrounding all nodes; leaf blades 5-20 × 3-6 mm, apex apiculate with an apiculum 0.2-0.5 mm long; inflorescences usually 1(2) per leaf axil, staminate inflorescences triseriate and pistillate ones uniseriate; flowers ca. 1 mm long; and mature fruits globose-compressed, ca. 0.8-2 × 2-3 mm when dried.
Distribution and hosts. Dendrophthora apiculata is known only from Guaramacal National Park (Trujillo state) between 2600-3100 m on both its northeastern and southwestern mountain slopes. This mistletoe grows in open areas of the páramo and evidently is uncommon throughout its distributional range. Its host range seems to be limited, as the only hosts recorded so far are the shrubs Cybianthus marginatus (Benth.) Pipoly (Primulaceae), Hypericum juniperinum Kunth (Hypericaceae), and Espeletia griffinii Ruiz-Teran & López- Fig. (Asteraceae). Interestingly, the mistletoes found so far on the first host listed were observed on lower and middle branches, while in the last one they were found at the tips of branches.
Phenology. Reproductive individuals of Dendrophthora apiculata have been observed with flowers and fruits all year round, and the fruits seem to be an important source of food for the bird fauna present in the páramo and subpáramo habitats.
Etymology. The specific epithet is derived from "apiculate," which describes the minute sharp apiculum observed at the apex of leaves.
Discussion. Dendrophthora apiculata is similar to D. lindeniana Tiegh., but the latter has stems up to 1 m long, dense papillose trichomes covering the entire plant, leaves with rounded apices with papillose edges, and the cup subtending the inflorescence is usually bifid. In contrast, D. apiculata has stems up to 40 cm long, coarsely striate stems with scarce papillose indumentum or papillae absent; leaves with a smooth margin and a persistent, minute apiculum 0.2-0.5 mm long at the apex; and a cup subtending the inflorescence that is usually whole (or rarely rounded).
Distribution and habitat. This species has been found in the transition between cloud forest and subpáramo in Guaramcal. This vegetation is influenced by multiple factors including high rainfall (3200+ mm/year), elevation above sea level (2400-3100 m), as well as relative humidity (100% for most of the year) (Cuello and Cleef 2011). Dendrophthora coronata is found in these Andean/high Andean forests characterized by woody vegetation of low stature with numerous individual shrubs and small trees, and a thin understory with a carpet of thick leaf litter. The canopy can reach between 6-14 m tall, with some emerging trees that reach 16 m, among them: Phenology. As with most other species of tropical mistletoe, Dendrophthora coronata can be observed bearing flowers and fruits throughout the year. Its white fleshy fruits seem to be an important food source for forest birds.
Etymology. The species name is derived from the coroniform trichomes (i.e., papillae crowned by 2-6 minute, simple hairs) that cover the entire plant and that resemble small crowns.
Discussion. At first sight, Dendrophthora coronata resembles D. apiculata and D. lindeniana. However, D. coronata can be readily recognized by its marked parallel striations along the stems, small, 0.5-1 mm long basal cataphylls, which sometimes are found 1-2 cm above nodes in old branches, and its dense layer of predominantly coroniform trichomes that cover the entire plant. In contrast, D. apiculata and D. lindeniana have stems sparsely covered by simple trichomes and lack basal cataphylls (or rarely have a few very small, 0.5 mm long cataphylls and then always at the nodes) (Table 1)  Entire plant abundantly papillate.

Stem
With longitudinal striations (not pronounced).

Cataphylls
Cataphylls surrounding nodes 0.2-0.5 mm long; only located at the base of a node.