The taxonomy and ecology of the genus Hoya R.Br, are unclear, especially in the core area of its distribution: Sumatra, Borneo, Sulawesi and Irian Jaya. This paper summarises the available information on the ecology of Hoya species, and describes eight species from central Sulawesi. An important ecological trait of many Hoya species is their association with ants. Four types of mutualistic relationships with ants occur in the genus: 1) species with specialised leaves to house ants; 2) a single species that provides housing for ants under imbricate leaves; 3) species growing on the carton of ant nests; and 4) species that root in ant inhabited cavities in tree trunks and branches. Four of the eight described species grew in association with ants (types 2-4). Taxonomically, Hoya sussuela (Roxb.) Merr. is placed in synonymy with H. coronaria Blume, and H. maxima (H. Karst.) Warb. and H. pseudomaxima Koord. are reduced to H. imbricata Decne. Three new species are described.

Hoya, Marsdenieae, Sulawesi, ant gardens, ant plants, epiphytes
Blumea: Biodiversity, Evolution and Biogeography of Plants

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Kleijn, David, & van Donkelaar, Ruurd. (2001). Notes on the taxonomy and ecology of the genus Hoya (Asclepiadaceae) in Central Sulawesi. Blumea: Biodiversity, Evolution and Biogeography of Plants, 46(3), 457–483.