A revision of the Neotropical Costaceae: results from sixty years of taxonomic struggle

Here we present a taxonomic revision of all neotropical Costaceae represented by 90 species, distributed in four monophyletic genera, Chamaecostus (9 spp.), Costus (76 spp.), Dimerocostus (5 spp.), and Monocostus (1 sp.). The work resulted in three new combinations, several nomenclatural changes, and four insufficiently known species are mentioned to demonstrate the need for continued and ongoing work on this charismatic yet often cryptic lineage of plants. We highlight the seventeen species of Costus and one species of Chamaecostus that were recently described (Maas et al. 2023) based on knowledge that emerged during this complete revisionary work, 60 years in the making. Included in this revision are details concerning the morphology, distribution, ecology, and phylogenetic relationships among the species studied. All currently recognized species are fully described, including notes on taxonomic synonymy, lectotypification, information on distribution and ecology, conservation status (either as evaluated and published in the IUCN Red List of Threatened Species or as estimated for this publication), vernacular names (when given) and short taxonomic notes. For each species, a distribution map is prepared and at least one colour photograph is included to assist in species identification. Dichotomous keys that include all species are provided, as is a list of all (c. 11.000) exsiccatae studied and an index to scientific names.