A new species, Miconia garagoana, from riparian environments of the northern Cordillera Oriental of Colombia, is described. This is the second species exclusive to rheophytic conditions that grows in the Andean forest in Colombia and is characterized by the presence of stellate-lepidote trichomes on young structures and inflorescences, terminal inflorescences, 4-merous (rarely 5-merous) flowers, oblong-subulate anthers with an apical pore and 2-locular ovary. The differences with other rheophytic species occurring in Colombia are noted and it is argued that it is related to other Andean species with bluish-green ripe fruits such as M. squamulosa and M. symplocoidea. This new species is so far known only from Colombia and its threat category is suggested as Critically Endangered” (CR).

Se describe una nueva especie, Miconia garagoana, de ambientes riparios del norte de la Cordillera Oriental de Colombia. Esta es la segunda especie exclusiva de condición reofitica que crece en bosques andinos de Colombia y se caracteriza por la presencia de cubiertas de tricomas estrellado-lepidotos en las estructuras jóvenes e inflorescencias, inflorescencias terminales, flores 4-meras /raras veces 5-meras), anteras oblongo-subuladas con un poro apical y ovario 2-locular. Se establecen las diferencias con otras especies reofíticas presentes en Colombia y se argumenta que está relacionada con especies de andinas de frutos maduros color verde-azuloso como M. squamulosa y M. symplocoidea. Esta nueva especie hasta ahora se conoce sólo de Colombia y se sugiere su categoría de amenaza como En Peligro Crítico (CR).

Eastern Mountains, endemism, Miconieae, northern Andes, rheophytic plants, riparian environments

Ambientes riparios, Cordillera Oriental, endemismo, Miconieae, norte de los Andes, plantas reofíticas

The genus Miconia Ruiz & Pav. is one of the largest in the Melastomataceae family and among the largest exclusive to the Neotropical region (Goldenberg et al. 2008). Recently, phylogenetic analyses (Michelangeli et al. 2016, 2022) redefined this genus to include all Neotropical Melastomataceae species characterized by fleshy fruits, small flowers, and multiflorous inflorescences. Previously, these species were grouped under the tribe Miconiae, which included 18–20 genera exclusively distributed in the Neotropics. The genus comprises an estimated 1900 species, with about 600 found in Colombia (Almeda et al. 2016; Mendoza Cifuentes et al. 2021; Michelangeli et al. 2022).

Miconia species grow in variety of environments at all altitudes, but are particularly rare along rivers and streams, especially in lowland areas of tropical rainforests. For example, Miconia aplostachya (Bonpl.) DC. and M. riparia Triana are found along blackwater rivers and streams in Amazonia and Antioquia department in Colombia, while M. rheophytica Posada-Herrera & Almeda is the only specie restricted to rocky margins of torrential rivers in the Andes of Colombia (Hoyos-Gómez and Bernal 2018; Posada-Herrera and Almeda 2018).

In order to document the floristic diversity of Sub-Andean forest remnants in Colombia, numerous expeditions have been carried out in the departments of Boyacá and Santander, with the discovery of a new species of Miconia from riparian environments. This manuscript describes this new species, exclusively associated with stream margins at elevations near 2000 meters above sea level. The habitat characteristics of the species are outlined, and an assessment of its extinction threat is provided.

This new species was discovered through a comprehensive review of collections housed in regional herbaria, coupled with field expeditions conducted in previously unexplored regions of the Eastern Cordillera in Colombia. Several collections were located in the herbaria UDBC and JBB. Measurements of vegetative parts were made in dry herbarium material using a digital caliper with a precision of 0.1 mm. Measurements of the floral parts and fruits were based on fresh flowers preserved in alcohol from the plants designated as types. Trichome types follow Wurdack (1986). Field photos were compiled and a map of the occurrence of this new taxon in Colombia was generated using Arc-GIS version 10.2.1. Preliminary conservation status was assessed by estimating the Area of Occupancy with GeoCat (http://geocat.kew.org/editor) and applying the IUCN Red List Category criteria (IUCN 2012, 2017).

Miconia garagoana exhibits distinctive morphological characteristics. It is recognized by the rheophytic condition and its abundant branching, occasionally featuring plagiotropic main branches that incline under the influence of water currents. This species displays an indumentum of stellate-lepidote trichomes on its distal branches, inflorescences, and the underside of its leaves. The linear-elliptic leaf is a distinguishing feature commonly found in species inhabiting the banks of rivers and streams, representing an adaptation to withstand the constant impact of water currents (van Steenis 1987). Furthermore, other remarkable morphological traits of Miconia garagoana include terminal inflorescences with few flowers (1–14), predominantly 4-merous flowers, oblong-subulate anthers featuring a ventrally oriented pore, and a 2-locular ovary. In addition, this species is characterized by its mature fruits, which feature an bluish-green color, and its large and relatively few seeds (less than 20).

The most vegetative similar species to Miconia garagoana is M. riparia, also present in Colombia, but the latter has dense rufous indumentum of pinoid trichomes on stems (vs. stellate-lepidotes in M. garagoana), and 5-merous flowers (vs. predominantly 4-merous) and dark purple or black fruits (vs. bluish-green). It is also similar to Miconia rheophytica, but the latter has branches with dense rufous indumentum of dendritic trichomes, ciliate leaf margins, dichasial axillary inflorescences, 5-merous flowers, yellow anthers, 3-locular ovary, globose to subglobose fruit with a bright indigo blue colour, and seeds ovoid with lateral and antiraphal symmetrical planes elliptic to elliptic-ovate (Posada-Herrera and Almeda 2018). Additionally, Miconia riparia and M. rheophytica grow below 1000 m, while M. garagoana grows around 2100 m elevation.

According to the number of petals, M. garagoana could be associated with the Ulmarioides complex (recently revised by Tiernan and Michelangeli (2018). However, all species of this complex always present 4-locular ovary and pink or fuchsia connective of the anther, so there is not full certainty.

Perhaps the species most closely related to Miconia garagoana are M. squamulosa (Sm.) Triana, and M. symplocoidea Triana, considering that they share the indumentum of stellate-lepidote thrichomes in vegetative parts and flowers, the shape of the stamens, and especially the bluish-green ripe fruits with angled ovoid seeds with smooth testa. Miconia squamulosa is part of section Cremanium, while M. symplocoidea is part of section Miconia (Goldenberg et al. 2013). However, these sections proposed by Cogniaux (1891) are considered artificial (Goldenberg et al. 2008).

The rheophytic condition is one of the distinctive characters of Miconia garagoana. Rheophyte is a term coined by van Steenis in 1987 to describe a biological group of flood-tolerant plants that are confined to the beds of swift-running streams and rivers in nature, growing there up to flood level, but not beyond the reach of regularly occurring flash floods (van Steenis 1987; Santana Costa et al. 2020).

In Melastomataceae, about 23 rheophytic species are reported, of which six, including the present novelty, correspond to the genus Miconia (Hoyos-Gómez and Bernal 2018; Posada-Herrera and Almeda 2018; Santana Costa et al. 2020). Among these species are Miconia linearis (Gleason) Michelang, M. mulleola Wurdack, M. rheophytica, Miconia riparia and Miconia salicina (Ser. ex DC.) Mabb. However, there are gaps in the information on the hábitat of the species, so it is not known with certainty how many, and which, species are restricted to this rheophytic condition. On the other hand, some of the species on record as being rheophytic are not exclusive to riparian environment, as is the case with Miconia mulleola. In order to guide conservation plans for riparian environments, the addition of this type of information would be very useful.

We are grateful to Fernando Fernandez for his hospitality at the El Secreto Reserve and his support in the field, Milton Rincon for creating the plates, the staff of Herbario Forestal (UDBC), and Jardín Botánico de Bogotá (JBB). We also extend our thanks to the reviewers for their valuable comments on the manuscript.