Leuenbergeria is a small genus of flowering plants in the family Cactaceae (order Caryophyllales), comprising eight species of trees and shrubs native to the Caribbean basin and adjacent regions of the Americas. Unlike the vast majority of cacti, members of Leuenbergeria retain true, persistent leaves throughout their lives and develop bark on their stems at an early stage of growth — a combination that makes them among the most morphologically unusual plants in the cactus family. The stems, once bark-covered, lack stomata and cannot serve as photosynthetic organs, in contrast to the green, water-storing stems that define most cacti.
Plants in the genus grow as trees or large shrubs, reaching up to 10 metres in the tallest species, Leuenbergeria lychnidiflora. Like all cacti, they bear areoles — specialized structures that produce spines; in most species the areoles also carry leaves. Flowers are most commonly pink, orange, or red, though L. aureiflora and L. guamacho — the only sister pair within the genus — are distinguished by yellow flowers.
The genus was created in 2012 by French botanist Joël Lodé to accommodate what molecular phylogenetic studies had identified as the "Northern clade" within a previously broad circumscription of Pereskia. By 2016, all three recovered clades of the old Pereskia had been recognized as separate genera. Leuenbergeria, along with Pereskia sensu stricto and Rhodocactus, is considered basal to all remaining cacti, meaning these leafy, bark-forming plants represent the ancestral condition from which the more familiar leafless, succulent cacti evolved. Leuenbergeria is the sole genus placed in the subfamily Leuenbergerioideae.
Etymology
The genus name Leuenbergeria honours Beat Ernst Leuenberger, a Swiss botanist known for his work on cacti. The genus was established in 2012 by Joël Lodé when molecular studies demonstrated that the species warranted separation from the broadly circumscribed Pereskia.
Distribution
Most species of Leuenbergeria are native to southwest Mexico and the Caribbean region, including both the West Indies and northern South America, with a discontinuous distribution across these areas. The sole exception is L. aureiflora, which occurs in eastern Brazil, geographically isolated from the rest of the genus.
Taxonomy Notes
Leuenbergeria was segregated from Pereskia in 2012 following molecular phylogenetic studies that revealed three distinct clades within the older, broadly circumscribed genus. The three clades were formally recognised as separate genera — Leuenbergeria, Pereskia sensu stricto, and Rhodocactus — by 2016. Leuenbergeria is placed as the sole genus in the subfamily Leuenbergerioideae and, together with its two sister genera, is considered basal to the rest of the Cactaceae, representing an early-diverging, leafy grade from which more derived cacti evolved.
