Ayenia is a genus of flowering plants in the mallow family, Malvaceae, placed in the order Malvales. In its modern, broadly circumscribed sense the genus comprises approximately 217 accepted species of subshrubs, shrubs, small trees, and twining lianas. The genus is perhaps most remarkable for its flowers: though very small, they are morphologically complex and highly distinctive within Malvaceae.
Species of Ayenia are distributed across the tropical and subtropical Americas — from the southwestern United States south through Central America and the Caribbean to tropical South America — with additional representatives in tropical Africa and tropical Asia. Within this range they occupy a wide variety of habitats, from open, seasonally dry scrublands and xeric woodlands to humid forests and gallery forests along river banks, and from lowland coasts to higher elevations.
The genus reached its current broad circumscription in 2018, when Christenhusz and Byng formally transferred the species of Byttneria and the monotypic Brazilian genus Rayleya into Ayenia. That reclassification was prompted by phylogenetic analyses demonstrating that the old Byttneria was paraphyletic and that Ayenia (as then defined, a Neotropical genus) was nested within it; Ayenia held nomenclatural priority, making it the correct name for the expanded group. Ayenia was first described by Linnaeus in 1756, published in K. Vet.-Akad. Handl. 17: 23.
Taxonomy Notes
Ayenia was originally a Neotropical genus, with Byttneria treated as a separate pantropical genus and Rayleya as a monotypic Brazilian genus. Phylogenetic work showed Byttneria to be paraphyletic with Ayenia nested inside it, and Rayleya as a sister clade. In 2018, Christenhusz and Byng transferred both into Ayenia, which held nomenclatural priority, expanding the genus to its current circumscription of approximately 217 species. Ayenia was first described by Linnaeus (1756) in K. Vet.-Akad. Handl. 17: 23.
Distribution
Ayenia is native to the tropical and subtropical Americas, including the southwestern United States, Central America, the Caribbean, and South America, with additional species in tropical Africa and tropical Asia. Within this range, species occupy habitats from dry and seasonally dry open areas to humid forests and river banks, and occur from lowland to high-elevation zones.
Ecology
Species of Ayenia grow across a broad ecological spectrum, from open, xeric habitats in dry and seasonally dry regions to humid forests and riparian zones. The genus spans a wide elevational range, from lowlands to high elevations. Some former Byttneria species (now included in Ayenia) are documented host plants for insects, including beetles of the genus Lonchophorellus.
