Monanthes is a genus of small succulent plants in the family Crassulaceae (order Rosales), comprising around fifteen accepted species. The genus is concentrated almost entirely in Macaronesia: most species are endemic to the Canary Islands, with the greatest diversity on Tenerife, where seven species occur. One species is endemic to the nearby Savage Islands, and one — an unusual case — reaches the High Atlas mountains of Morocco, making Monanthes a rare example of a group that re-colonized a continental landmass from an island after its ancestors originally colonized the island from the continent.
Plants in the genus are small and subtropical, and are not frost-resistant. Morphologically and genetically, Monanthes is closely allied with related Macaronesian genera including Sempervivum, Aeonium, Greenovia, and Aichryson, a relationship reflected most clearly in the similarity of their flowers — the genus name itself derives from the Greek for "single flower." Species vary markedly in growth form: M. icterica is annual and is also the most genetically distant member of the genus, while all remaining species are perennial. On the islands of Fuerteventura and Lanzarote, only a single species, M. laxiflora, is found.
Etymology
The name Monanthes derives from Greek, meaning "single flower," a reference to the characteristic flower morphology shared across the genus.
Distribution
The genus is centered on the Canary Islands (Macaronesia), with its greatest species richness on Tenerife. One species is endemic to the Savage Islands, and one extends to the High Atlas mountains of Morocco. On Fuerteventura and Lanzarote, only Monanthes laxiflora is present. The genus offers a documented case of island-to-continent re-colonization.
Ecology
Monanthes species are subtropical succulents that are not frost-resistant, restricting them to mild oceanic island climates. The genus shows an unusual biogeographic pattern: while most island groups derive their flora from continental colonists, at least one Monanthes lineage subsequently re-colonized the African continent from the islands.
