Glochidion is a genus of approximately 170 species of flowering trees and shrubs in the family Phyllanthaceae, order Malpighiales. Distributed across the Old World tropics — from Madagascar through South and Southeast Asia to the Pacific Islands — the genus is commonly known as cheese trees or buttonwood in Australia, and leafflower trees in botanical literature.
Plants in this genus are ecologically remarkable for their highly specialised obligate mutualism with small moths of the genus Epicephala (leafflower moths). The moths are the exclusive pollinators of Glochidion flowers, actively transferring pollen to ensure seed set, but simultaneously lay their eggs inside the flowers' ovaries. The developing moth larvae consume a fraction of the seeds as food. This relationship closely parallels those of figs with fig wasps and yuccas with yucca moths — textbook examples of mutualistic coevolution.
Taxonomically, Glochidion has long been placed in Phyllanthaceae (formerly within the broader Euphorbiaceae), and its placement in order Malpighiales is well established. A 2006 revision proposed merging the genus into Phyllanthus; while new combinations under Phyllanthus have been published for populations in Madagascar and the Pacific Islands, the majority of species retain their Glochidion names and the genus continues to be broadly recognised.
Among the best-known species, Glochidion puberum is native to East Asia and has become naturalised in the US state of Alabama. Glochidion calocarpum is used medicinally by the Nicobarese people, who employ its bark and seeds to treat abdominal disorders linked to amoebiasis.
Distribution
Glochidion is native to the Old World tropics, ranging from Madagascar eastward through South and Southeast Asia to the Pacific Islands, with the highest species diversity in tropical Asia. Although entirely Old World in its native distribution, the East Asian species Glochidion puberum has become naturalised at several locations in the US state of Alabama.
Ecology
Glochidion species are the hosts of one of botany's most celebrated obligate mutualisms: leafflower moths of the genus Epicephala are the sole pollinators of Glochidion flowers, actively collecting and depositing pollen, while also ovipositing into the floral ovaries. Their larvae then consume a portion of the maturing seeds. The two partners are thus simultaneously mutualists and antagonists — a situation that mirrors the fig/fig-wasp and yucca/yucca-moth systems. Several Glochidion species also serve as larval food plants for Lepidoptera such as Aenetus eximia and Endoclita damor.
Taxonomy Notes
Glochidion has traditionally been recognised as a distinct genus within Phyllanthaceae. A 2006 monographic revision recommended sinking it into the larger genus Phyllanthus on phylogenetic grounds; new Phyllanthus combinations have been published for species from Madagascar and the Pacific Islands, but most of the roughly 170 species have not yet been formally transferred, and Glochidion remains the name in widespread use.
Cultural Uses
The Nicobarese people of the Nicobar Islands have documented medicinal use of Glochidion calocarpum, using the bark and seeds to treat abdominal disorders associated with amoebiasis.
