Introduction

The subtribe Catasetinae Lindl. includes eight genera (Catasetum Rich. ex Kunth., Clowesia Lindl., Cyanaeorchis Barb.Rodr., Cycnoches Lindl., Dressleria Dodson, Galeandra Lindl., Grobya Lindl., and Mormodes Lindl.) (Chase et al. 2015), and is well represented in Colombia, except for Cyanaeorchis and Grobya. The neotropical genus Catasetum comprises 169 species and 28 natural hybrids (Milet-Pinheiro & Gerlach 2017, Romero-González 2009, POWO 2023). It is characterized by its unisexual flowers exhibiting sexual dimorphism (Holst 1999, Romero & Jenny 1993, Romero-González 2012, Milet-Pinheiro & Gerlach 2017, Van der Pijl & Dodson 1969). Among the genera in Catasetinae, Catasetum is notably speciesrich, representing over 40 species in the Colombian orchid flora (Bonilla-Morales et al. 2016a). This count has grown with several recent additions (Bonilla-Morales et al. 2017).

In Colombia, Catasetum is widely distributed. It is most abundant in the Andean, Amazon, and Orinoquía regions (Betancur et al. 2015, Ortiz & Uribe 2019). The most significant species concentration occurs in forests of the eastern and central mountain ranges, ranging from above sea level to 1200 m in elevation. However, it is worth noting that certain Colombian regions, such as the Amazon (particularly departments like Vaupés) and areas in the Andes (like Norte de Santander), as well as the Atlantic region (departments including Atlántico, Córdoba, Sucre, Guajira, and Cesar), have sparse collections of Catasetum species (Bonilla-Morales et al. 2016a).

During our field studies in the Department of Caquetá, Colombia, we discovered a unique Catasetum specimen. After exhaustive comparison with representative species of Catasetum from Colombia and its neighboring countries, we found that this specimen did not correspond to any previously described species. Consequently, we propose this Colombian entity as a new species, accompanied by comprehensive color photographs and comparison with morphologically similar species.

Material and methods

The plant material of the new species was collected during botanical exploration in June 2020 at one of the Universidad de la Amazonia campuses located in Florencia, Caquetá. This region serves as a transition between the Andean and Amazonian ecosystems. The plant was found as a single individual, but it was not in a fertile state. Consequently, it was transferred to a greenhouse to await flowering, which occurred in October. The flowers of the new species were then collected and preserved in FAA solution (5:5:50:40 Formaldehyde, Glacial Acetic Acid, 95% ETOH, and distilled Wat) (Díaz 2019).

Herbarium specimens of Catasetum from COL, JAUM, JBB, LLANOS, HPUJ, COAH, and HUAZ (acronyms according to Thiers 2021) were carefully examined. In addition, digital images of other specimens and type collections housed at AMES, F were reviewed through the JSTOR portal (https://plants.jstor.org/) and GBIF (https://www.gbif.org/). A stereoscope (Leica EZ4) was used to examine each available Catasetum flowering specimen. A map was plotted using the DIVA-GIS 7.5 software to visualize the distribution of specimens. In cases where specimen coordinates were not available, they were inferred using Gazetteers and Google Earth Pro 7.3.6.9345 (64-bit) (Hijmans et al. 2001).

Taxonomic treatment

Catasetum caquetense R.A.Calderón-Álvarez & M.Bonilla, sp. nov. (Fig. 1).

Figure 1
Catasetum caquetense R.A.Calderón-Álvarez & M.Bonilla.

TYPE: COLOMBIA. Caquetá: Municipality of Florencia, tropical humid forest -campus Universidad de la Amazonia, 1°36’29.86” N 75°36’22.36” W, 273 m, 3 June 2020, R.A. Calderón-Álvarez 244 (holotype: HPUJ030774; isotype: HPUJ030775).

Diagnosis: Catasetum caquetense is morphologically similar to C. tuberculatum Dodson; however, it differs by the rectangular lip (vs. elliptical), with smooth to somewhat denticulate edges (vs. entire), the abaxial surface not entirely tuberculated (vs. fully tuberculated lip on the abaxial surface), and a prominent apiculate basal callus (vs. slightly prominent), which is encircled by minor crown-shaped protrusions, with an extra callus towards the apex that partially narrows towards the saccate mid-lip, a characteristic absent in C. tuberculatum.

Epiphytic herb, caespitose, 15-25 cm long. Roots 1-2 mm thick, terete, whitish. Pseudobulbs ca. 13 × 5 cm, heteroblastic, cespitose, terete, ellipsoid-fusiform, up to 6 internodes, green. Leaves ca. 25 × 4 cm, oblong-lanceolate, distichous, plicate, flat, nerves sunken adaxially and prominent abaxially, green, slightly discolor, deciduous. Inflorescence basal, 30 cm, racemose, 1-2 by pseudobulb, up to 12 staminate flowers; peduncle up to 24.0 × 0.5 cm, terete, greenish; peduncle bracts up to 1.2 × 1.0 cm, clasping, lanceolate, acute, pale green; rachis up to 20 × 0.1-0.3 cm, terete, pale green; floral bracts up to 3.0 × 0.9 cm, lanceolateovate, acute, pale green. Staminate flowers are fragrant, ovary and pedicel up to 4.00 × 0.15 cm, terete, brown-reddish; dorsal sepals up to 3.6 × 0.7 cm, oblong-elliptical, base cuneate, margin entire, apex acute, concave, brown-reddish; lateral sepals up to 3.0 × 0.7 cm, elliptical, base cuneate, margin entire, apex acute, convex, brown-reddish; petals up to 3.2 × 0.9 cm, elliptical, convex, superimposed on the dorsal margins of the dorsal sepal in natural position, base acute, margin entire, apex acute, brown-reddish; lip 20 mm long × 10 mm wide × 5 mm deep, fleshy, sacciform, elliptical, denticulate margin, basal calli, greenish yellow. Staminal column 1.6 × 0.4 cm, trigonous, apex apiculate ca. 7 mm, brown; antennae 2, ca. 5 mm length, parallel, equal, filiform, pale brown. Anther ca. 10 × 3 mm, apiculate, opercular, unilocular, green-yellowish; viscidium 0.8 × 0.8 mm, rounded, whitish; stipe ca. 3.0 × 1.0-1.5 mm, oblanceolate, white-brownish; pollinia 2, ca. 3.5 × 1.8 mm, obovate, flattened, yellow. Pistillate flowers not observed. Fruit and seeds not seen.

Distribution and Ecology: A single collection of C. caquetense has been identified in the Department of Caquetá, specifically in the municipality of Florencia, Amazon region, between 270-280 m of elevation (Fig. 2). Catasetum caquetense was found growing as an epiphyte on a tree of Zygia longifolia (Humb. & Bonpl. ex Willd.) Britton & Rose. It grows in shade in the humid forest, similar to C. tuberculatum. Tree ferns, bromeliads, and various tree species from the Fabaceae family characterize the surrounding vegetation in this area.

Figure 2
Distribution of C. caquetense R.A.Calderón-Álvarez & M.Bonilla in Caquetá Department.

Phenology: Catasetum caquetense is known to flower in October under cultivation.

Etymology: The specific epithet “caquetense” refers to the Caquetá Department in Colombia, which is the geographical location where the species was discovered.

Discussion

Catasetum caquetense is morphologically similar to the C. tuberculatum and C. juruenense Hoehne. Distinguishing features of Catasetum caquetense include a lip with two calli on the abaxial surface, one at the base and another one that gives prominence and apiculation to the apex; therefore, the lip is not fully tuberculated.

Catasetum caquetense and C. tuberculatum exhibit parallel antennae, whereas C. juruenense has convergent and short antennae (Mauad et al. 2022). In addition, the lip of C. caquetense and C. juruenense are rectangular, in contrast to the elliptical lip of C. tuberculatum. Moreover, C. caquetense forms a crown-like structure with its basal callus, nearly closing with filiform prominences. In contrast, C. tuberculatum possesses rough to completely filiform or tuberculate basal calli and C. juruenense is slightly roughened (Fig. 3B-C).

Figure 3
Comparison of morphologically similar species of Catasetum.

Catasetum caquetense has a prominent callus and non-tuberculate edges at the base. Additionally, the antennae of C. juruenense are short and convergent, reaching the middle of the staminal column, while those of C. caquetense are of the same size and reach the base of the lip. While C. tuberculatum is distributed from Colombia to Peru, C. juruenense is endemic to Brazil (Betancur et al. 2015, Bonilla-Morales et al. 2016a, Romero-González 2009, Ortiz & Uribe 2019). In addition, these three species (C. caquetense, C. juruenense, and C. tuberculatum) are distributed in the Amazonian Forest life zone, although C. tuberculatum extends to the Andean-Amazonian piedmont area.

Currently recognized species in the Department of Caquetá from Colombia include C. discolor (Lindl.) Lindl., C. ochraceum Lindl., C. roseo-album (Hook.) Lindl., C. tabulare Lindl., C. tuberculatum Dodson, C. villegasii G.F.Carr (Arias et al. 2023), the latter being considered endemic. Also present in the department of Caquetá are C. caquetense R.A.CalderónÁlvarez & M.Bonilla and C. collare Cogn. (Table 1). However, C. villegasii is similar to Catasetum moorei C.Schweinf., which is known from Ecuador, Peru, and Brazil (Romero-González & Gerlach 2008). Given its distribution in neighboring countries, it is highly likely that C. moorei is also found in Colombia.

Catasetum collare, while extensively documented in the broader Amazon region, is scarcely recorded in the Colombian Amazonia. The specimens from this region show subtle variations in the lip, suggesting the possibility of intraspecific variation. Such variations could broaden our understanding of the current species circumscription (Bonilla Morales et al. 2016a,b, Romero-González 2009) (Fig. 4).

Figure 4
Catasetum collare Cogn.

Acknowledgements

We thank Professor Lilia Roa and Alexander Damián for carefully reviewing the document, Marcela Morales-S. for the illustration, and Juan Fernández for the photograph. We thank the Universidad de la Amazonia for the support provided throughout this study and for granting the framework permission (Resolution 01140 of September 30, 2016, Autoridad Nacional de Licencias Ambientales ANLA) for collecting biological specimens. Also, we thank Carlos Rubiano from the Academia Iberoamericana de Idiomas AIDI for thoroughly reviewing the English language used in this work.

Literature cited

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