Deamia is a small genus of climbing and pendent (hanging) cacti in the family Cactaceae, order Caryophyllales. Its species are native to a narrow range from southern Mexico through Central America to Nicaragua.
The genus was erected in 1920 by Nathaniel Lord Britton and Joseph Nelson Rose, initially as a monotypic genus containing only Deamia testudo. The name commemorates Charles C. Deam, a plant collector who supplied the type material to Britton and Rose. Taxonomically the genus has had an unsettled history: Franz Buxbaum folded it into Selenicereus in 1965, and it remained submerged there until botanist Alexander Doweld revived Deamia in 2002, at which point the species then known as Selenicereus chontalensis was transferred into it. Molecular phylogenetic studies in 2017 and 2018 subsequently confirmed the genus as monophyletic, placing it within tribe Echinocereeae, subtribe Pachycereinae, as one of the earliest-diverging lineages in that tribe. Even so, some authorities have been slow to follow: as recently as 2021, Plants of the World Online still classified D. chontalensis under Selenicereus rather than Deamia, reflecting ongoing disagreement over the genus's circumscription.
Species of Deamia are climbing or pendent shrubs, structurally similar to their relatives in the "moonlight cactus" alliance (Selenicereus, Strophocactus). Their flowers are marked by hairs and spines and are followed by red fruit with clear pulp. The genus currently comprises four recognized species — D. testudo (the type species), D. chontalensis, D. montalvoae, and D. funis, the last described as new to science in 2022 — making it one of the more recently stabilized small genera within Cactaceae.
Etymology
The genus name Deamia honours Charles C. Deam, a plant collector who sent the type material to Nathaniel Lord Britton and Joseph Nelson Rose, who erected the genus in 1920.
Distribution
Deamia species are native from southern Mexico through Central America to Nicaragua.
Taxonomy Notes
Erected in 1920 by Britton & Rose as a monotypic genus (Cactaceae, order Caryophyllales), Deamia was submerged into Selenicereus by Franz Buxbaum in 1965 and remained there until Alexander Doweld revived it in 2002. Molecular studies in 2017 and 2018 confirmed the genus as monophyletic and placed it in tribe Echinocereeae, subtribe Pachycereinae, as an early-diverging lineage. As of March 2021, however, Plants of the World Online still treated D. chontalensis under Selenicereus, showing the classification is not universally settled.
