Andesanthus is a genus of flowering plants in the family Melastomataceae (order Myrtales), native to the Andes and surrounding mountain ranges of Colombia, Costa Rica, Ecuador, Panama, Peru, and Venezuela. The genus was established in 2019 when molecular phylogenetic work revealed that the long-used, broadly circumscribed genus Tibouchina was paraphyletic, and its species were redistributed into four genera: a narrower Tibouchina, the re-established Pleroma and Chaetogastra, and the newly named Andesanthus.
Members of the genus range from shrubs 1–3 m tall to trees reaching 5–20 m at maturity. Their leaves are opposite and petiolate. The inflorescence is a terminal panicle or a modification thereof. Flowers are perigynous, with a bell- or urn-shaped hypanthium that is externally pubescent in most species. Each flower bears five free petals colored pink, purple, magenta, or white — in some species the petals open magenta or rose-red and fade to lavender with age. There are ten stamens, either uniform or dimorphic (two distinct size classes). The stamen connective is prolonged into a characteristic bilobed ventral appendage. Seeds are cochleate (spiral-shaped).
Andesanthus is distinguished from related genera by its lepidote (small flattened scales) indumentum, glabrous (hairless) stamens, and anther coloration: in single-sized-stamen species all anthers are yellow; in dimorphic species the larger anthers are yellow and the smaller ones pink or red.
As of 2022, Plants of the World Online accepted nine species, all distributed across cool montane forests and forest margins in the Andes and the mountains of Costa Rica and Panama, with Colombia hosting the greatest species richness. One species, Andesanthus lepidotus (formerly Tibouchina lepidota), is cultivated as an ornamental tree or shrub outside its native range, including in Australia, where the cultivar 'Alstonville' was developed in New South Wales.
Etymology
The name Andesanthus is a compound reflecting the geographic center of the genus: Andes, the mountain range where most species are found, combined with Greek anthos (flower). The genus was named when it was formally described in 2019.
Distribution
Andesanthus is native to the Andean and adjacent mountain ranges of northern South America — Colombia (the most species-rich country), Ecuador, Peru, and Venezuela — and extends into Central America in the highlands of Costa Rica and Panama. Species grow in cool montane forests and along forest margins at altitude.
Taxonomy Notes
Andesanthus was erected in 2019 by Guimarães & Michelangeli after molecular phylogenetic analyses (2013 and 2019) demonstrated that Tibouchina as broadly circumscribed by Alfred Cogniaux in 1885 — which accumulated roughly 470 taxa — was paraphyletic. The data resolved four well-supported, morphologically and geographically coherent clades. The proposed solution split Tibouchina sensu lato into a more narrowly circumscribed Tibouchina, the re-established genera Pleroma and Chaetogastra, and the new genus Andesanthus. Phylogenetically, Andesanthus is sister to Chaetogastra or to a clade combining Chaetogastra and Brachyotum, depending on the analysis.
Cultivation
Some species of Andesanthus are grown as ornamental shrubs or trees outside their native Andean range. Andesanthus lepidotus (long sold under the synonym Tibouchina lepidota) is particularly popular in Australia, where the cultivar 'Alstonville' — developed in Alstonville, New South Wales — is widely planted for its showy flowers.
