Three new species of Columnea (Gesneriaceae) from the western Andean slopes of Ecuador and Colombia

Abstract Three new species of Columnea (Gesneriaceae, tribe Gesnerieae) are described from the western Andean slopes of northern Ecuador and southern Colombia. Columneaangulata J.L. Clark & F. Tobar and Columneafloribunda F. Tobar & J.L. Clark are described from northern Ecuador. Columneatecta J.L. Clark & Clavijo is described from southern Colombia and northern Ecuador. The three new species are facultative epiphytes with dorsiventral shoots and are readily recognized by bright red tips on the abaxial and adaxial leaf surfaces. The species described here are vegetatively similar to the sympatric species Columneapicta H. Karst. and are readily differentiated by floral features that are illustrated, described and featured with digital images.


Introduction
The flowering plant family Gesneriaceae, with over 3400 species and 150+ genera (Weber 2004;Weber et al. 2013), is in the order Lamiales. The family is divided into three subfamilies and seven tribes (Weber et al. 2013(Weber et al. , 2020, which represent monophyletic lineages (Ogutcen et al. 2021). The majority of New World members are in the subfamily Gesnerioideae and are represented by 1200+ species and 77 genera . Columnea L. is classified in the tribe Gesnerieae and subtribe Columneinae (Weber et al. 2013(Weber et al. , 2020. The genus Columnea is primarily epiphytic. It ranges from Mexico south to Bolivia, and is most diverse in the northern Andes of Colombia and Ecuador. With over 210 species , Columnea is the largest genus in the subfamily Gesnerioideae (Weber et al. 2013(Weber et al. , 2020. The genus is distinguished by fruits that are indehiscent berries in contrast to fleshy bivalved capsules in closely related genera. Columnea is strongly supported as a monophyletic genus based on molecular phylogenetic studies (Smith et al. 2013;Schulte et al. 2014). The species described here were discovered during exploratory research expeditions and ongoing taxonomic research of herbarium specimens. The three newly described species are similar to many taxa recognized in the section Collandra (Lem.) Benth. or previously classified as members of the genus Dalbergaria Tussac. We refrain from classifying the new species to a subgeneric rank because most are artificially defined and not supported by phylogenetic studies (Smith and Carroll 1997;Smith 2000;Clark and Zimmer 2003;Clark et al. 2012;Smith et al. 2013;Schulte et al. 2014). The three species described here are distributed on the western Andean slopes of northern Ecuador and southern Colombia (Fig. 1). Herbarium specimens representing these three species are often annotated as "Columnea aff. picta" or "Columnea cf. picta" because they share a similar vegetative feature of apical red leaf apices on the upper and lower leaf surfaces. In contrast, most species of Columnea have red leaf apices on the lower leaf surface, but not on the upper leaf surface.   (asterisks). Note that C. picta ranges from southern Ecuador to northwestern Colombia (exceeding the range of the currently described species) (Map generated by Marco Monteros). Description. Facultative epiphyte with dorsiventral shoots to 1.5 m long, subwoody, suffrutescent, glabrescent below, sparsely pilose above; internodes 7-10 cm near base, then clustered at branch apex. Leaves opposite, strongly anisophyllous, papyraceous when dry; larger leaf nearly sessile, petioles 0.1-0.4 cm long, pilose; blade asymmetric, oblanceolate to oblong, 7-28 × 2-9.5 cm, base oblique, apex acuminate, margin serrate, adaxially uniformly dark green to red with dark red apex, glabrous, abaxially light green, upper regions of margins, and apical third of leaf dark red, sparsely pilose to densely pilose along the venation, lateral veins 7-15, primary and secondary veins occasionally red; smaller leaf sessile, sometimes appressed to the dorsal surface of stem; blade asymmetric, lanceolate 0.5-2 × 0.4-0.6 cm, base oblique, apex acuminate, margin serrate, green with red apex on both surfaces, glabrous adaxially, sparsely pilose to densely pilose along the venation and margins abaxially. Inflorescence reduced to a single axillary flower (rarely 2-3); peduncles absent or highly reduced (< 0.2 cm); bracts 1-2, light green, lanceolate, 0.7-1.2 × 0.2-0.4 cm, glabrous on both sides. Flowers subtended by elongate pedicels, 1.5-2.5 cm long, sparsely to densely pilose, tightly appressed to the abaxial leaf surface when immature, becoming pendent during anthesis; calyx lobes 5, nearly free, mostly equal in size and shape, dorsal lobe slightly smaller, lobes appressed to flower when immature and spreading during anthesis, from uniformly yellow, to red with yellow margins, to yellow with a large reddish midregion, 1.5-3.5 × 0.5-1 cm, ovate to broadly oblong, apex acuminate to acute, margin serrate, pilose on both surfaces; corolla tubular, appearing perpendicular to calyx via a sigmoid-shaped corolla tube, 2.1-3.5 cm long, outer and inner surfaces pilose, base appearing laterally compressed, limb shallowly bilabiate, white suffused with yellow on lower two thirds, more yellow toward apex, splotches of dark red on lower portion of lateral and ventral lobes, light yellow patch below lobes, red streaks abaxially, lobes 0.3-0.4 × 0.3-0.5 cm. Androecium of 4 stamens, filaments connate at the base and forming a filament curtain for 0.2-0.4 cm, free portion of filaments 3-3.5 cm long, Phenology. This species has been found with flowers in two periods: February to May and August to October.
Etymology. The specific epithet is in reference to the angulate or bent corolla tube. The corolla is nearly perpendicular to the calyx lobes because of the sigmoid-shaped tube.
Distribution and preliminary assessment of conservation status. Columnea angulata is locally abundant in forests along the western slopes of the Ecuadorian Andes in the provinces of Cotopaxi, Imbabura, Pichincha, and Santo Domingo de los Tsáchilas ( Fig. 1) where it grows in mature forests and the shaded understory of recently cleared forests, from 1500 to 2600 m in elevation. It is especially common along the old highway between Quito and Santo Domingo. It has been documented in two protected areas: Reserva Florística-Ecológica Río Guajalito and Bosque Protector Los Cedros. According to the IUCN Red List criteria (IUCN 2001) for limited geographic range (B1, less than 20,000 km 2 ) and considering the uncertain future of habitat conservation of western Andean forests (B2b, c), Columnea angulata should be listed in the category Vulnerable (VU).
Comments. Columnea angulata is unique from other Columnea by the posture of the pendent mature flowers where the corolla tubes are oriented oblique to perpendicular relative to the calyx (Figs 2A, 3B). Another defining character is a constriction at the base of the corolla tube that makes it appear laterally compressed (Fig. 2C). Columnea picta and C. angulata are vegetatively similar and grow sympatrically. These two species are differentiated by the presence of deeply bilabiate corolla tubes in Columnea picta (Fig. 6A) in contrast to the shallowly bilabiate corolla tubes in C. angulata (Fig. 2B, C). Columnea angulata differs from C. tecta by an elongate corolla tube (vs. corolla tube that does not exceed the calyx lobes in C. tecta) and single axially flowers (rarely 2-3) in contrast to the abundant clusters of 3-5 axially flowers in C. floribunda. Columnea picta and C. angulata are the two most commonly collected species in this complex and readily differentiated by the entire calyx margin in C. picta and serrate calyx margin in C. angulata. Diagnosis. Differs from Columnea picta by a nearly tubular corolla (vs. deeply bilabiate corolla). Differs from Columnea angulata by the straight corolla relative to the calyx (vs. oblique to perpendicular corolla relative to the calyx). Differs from Columnea tecta by corollas that exceed the length of the calyx lobes (vs. corollas that are equal to or less than the length of the calyx lobes).
Phenology. Collections of Columnea floribunda are documented with flowers between January and April and between June and October. Fruits have been recorded during March.
Etymology. The specific epithet refers to axillary clusters of several flowers (3-5). Distribution and preliminary assessment of conservation status. Columnea floribunda is locally abundant in the Mashpi Rainforest Biodiversity Reserve (900-1340 m) and the surrounding roads, a Chocó biogeographic forest relict in northern Ecuador. It is likely that additional populations are located in the adjacent provinces of Imbabura and Esmeraldas. Future research expeditions to unexplored areas of the Cotacachi Cayapas Ecological Reserve will hopefully result in additional documented populations of C. floribunda. According to the IUCN Red List criteria (IUCN 2001) for limited geographic range (B2a, less than five locations) and considering the uncertain future of habitat conservation, Columnea floribunda should be listed in the category Endangered (EN).
Comments. Columnea floribunda is readily distinguished from all other congeners by the elongate corolla tubes that exceed the length of the calyx lobes (Fig. 4A), in contrast to the corolla tubes of C. tecta that are equal to or less than the length of the calyx lobes (Fig. 7C); the corolla posture relative to the calyx that is straight (Fig. 4A), in contrast to the oblique to perpendicular corolla relative to the calyx of C. angulata ( Fig. 2A); and the axillary clusters of three or more flowers (Fig. 4D). Diagnosis. Differs from Columnea picta by a nearly tubular corolla (vs. deeply bilabiate corolla) that is equal to or shorter than the calyx lobes (vs. corolla that extends beyond the calyx lobes). Type. Ecuador Esmeraldas: cantón San Lorenzo, remnant patch of forest along highway Ibarra-San Lorenzo, between the towns of Durango and Alto Tambo, 0°57'21"N, 78°33'38"W, 664 m, 3 Jun 2009, J.L. Clark & 2009; isotypes: MO, NY, QCNE, SEL).
Phenology. This species was documented with flowers in June and May. Fruits have been recorded in June.
Etymology. The specific epithet tecta refers to the "hidden" or relatively short corolla tube that does not exceed the length of the calyx lobes, an unusual character in Columnea.
Distribution and preliminary assessment of conservation status. This species has not been found in any formally protected areas. According to the IUCN Red List criteria (IUCN 2001) for limited geographic range (B2a, less than five locations) and considering the uncertain future of habitat conservation of western Andean forests, Columnea tecta should be listed in the category Endangered (EN).
Comments. Columnea tecta is readily distinguished from all other congeners by relatively short corollas that barely exceed the length of the calyx lobes (Fig. 7). The corollas of Columnea tecta have limbs that are shallowly bilabiate (Fig. 7A) in contrast to the deeply bilabiate corollas of Columnea picta (Fig. 6A). Columnea tecta and C. picta are vegetatively similar by the presence of a dorsiventral habit with red apices on both leaf surfaces. The corolla tubes of C. tecta are short (less than the length of the calyx lobes and shallowly bilabiate) relative to the longer corolla tubes of C. picta (exceeding the length of the calyx lobes and deeply bilabiate). Columnea tecta differs from C. angulata by a straight orientation of the corolla relative to the calyx (vs. oblique to perpendicular in C. angulata).