Acianthera is a genus of orchids in the family Orchidaceae, order Asparagales, comprising approximately 302 accepted species. The genus is native to the tropical regions of the Western Hemisphere, with Brazil forming the primary centre of diversity, though members are found throughout tropical Central and South America.
The genus was first formally described in 1842 but remained obscure for much of its history. For most of the twentieth century, the vast majority of species now placed in Acianthera were classified within Pleurothallis subgenus Acianthera, a large and complex group of mostly small-flowered, epiphytic orchids collectively known as pleurothallids. The modern, expanded circumscription of Acianthera as a distinct genus is the direct result of molecular phylogenetic work — DNA sequencing revealed that the group forms a natural, coherent lineage that warrants recognition at the genus level.
Like most pleurothallids, Acianthera species are typically small epiphytes of humid montane and lowland tropical forests, often growing at intermediate to high elevations. They are characterized by their diminutive habit, fleshy or leathery leaves, and small, often intricately structured flowers that can be produced singly or in succession along short inflorescences.
Taxonomy Notes
Acianthera was first described in 1842 but was not widely recognized as a distinct genus until recent decades. Most of its species were previously accommodated in Pleurothallis subgenus Acianthera, and the segregation into a separate genus reflects the results of molecular DNA sequencing that supported its monophyly within the pleurothallid alliance (Orchidaceae: Asparagales).
Distribution
Acianthera is native to the tropical Western Hemisphere, with its greatest diversity centred in Brazil. Species occur across tropical Central America and South America, typically in humid forest habitats.
