The circumscription of Antirhea was very broad at one time, but has been narrowed significantly in recent years. It was treated for some time as a genus found from the Indian Ocean through Asia and the Pacific well into the Neotropics, but Chaw & Darwin (1992) showed that the Paleotropical plants are distinct from the Neotropical species. This web page clarifies the identites of the Antirhea species described from the Neotropics; the Paleotropical plants are not treated here.
Chaw & Darwin (1992) restricted Antirhea to include only Paleotropical plants, which range from Madagascar to the islands of the western Pacific. Antirhea now includes dioecious, small to medium-sized trees with the leaves usually 3 per node, the inflorescences axillary with markedly scorpioid axes, small sessile flowers, and succulent drupaceous fruits that are relatively small and contain a single pyene or stone with 2-4 locules. Chaw & Darwin separated 3 subgenera, two distributed entirely outside Madagascar while Subg. Antirhea is restricted to Madagascar and the Mascarene Islands, with 1 species restricted to the Mascarenes, 1 found in both the Mascarenes and Madagascar, and 1 restricted to Madagascar. Their Subg. Mesocarpa included 5 species from Australasia and the western Pacific, and Subg. Guettardella included 28 species found from southeastern Asia, including China and the Philippines, through Australasia to the western Pacific.
Chavez et al. (2021) addressed Paleotropical Antirhea in more detail with molecular sequence data, and noted the separation of six genera (Fig. 4) within this group: Antirhea, in the western Indian Ocean; Timonius, in southeast Asia through the Pacific; Guettardella, from southeast Asia through the western Pacific; the new genus Achilleanthus, from eastern Indonesia through New Guinea to the western Pacific; Tinadendron, from the western Pacific; and the genus "Gea", is found in the western Pacific, that has not yet been described. They formally treated Antirhea s. lat. of previous authors in three genera, to which they provided no key: Antirhea, Achilleanthus, and Guettardella. The presented generic descriptions and a list of species and synonyms for each of these, noted that the species lists for these latter two genera are not complete.
The systematics of the Neotropical plants that were previously included in Antirhea are not completely clear, and this group of speces has not been studied in detail with modern techniques. These species are currently treated in three Neotropical genera, Neolaugeria, Stenostomum, and Resinanthus; few other species were inaccurately described in Antirhea, due to incomplete knowledge of the species or of the characters of Antirhea. See the web pages for these other three genera for more information about them. The Neotropical plants have also at times been variously treated in Terebraria and Laugeria Vahl ex Hook. f. (not Laugeria L.), and confused with Guettarda.
Author: C.M. Taylor
The content of this web page was last revised on 3 February 2022.
Taylor web page: http://www.mobot.org/MOBOT/Research/curators/taylor.shtml