On the nominal species of Acropora (Scleractinia: Acroporidae) described from eastern Australia

Context Recent phylogenomic studies have highlighted substantial discordance between the taxonomy proposed in revisionary monographs from the late 20th century and results from modern integrated approaches for the species-rich coral genus Acropora. In particular, numerous species synonymies proposed during the 1970s to 1990s, prior to the routine application of molecular data, have proven inconsistent with genomic evidence. Aims We aimed to comprehensively reassess the nominal species of Acropora with type localities in eastern Australia using an integrative, topotype-anchored phylogenomic framework, testing whether historical synonymies reflect true evolutionary relationships. Taxon Acropora Oken, 1815 (Scleractinia: Acroporidae). We evaluated 53 nominal Acropora species, comprising 40 species with type localities in eastern Australia and 13 additional species from the wider Indo-Pacific considered senior synonyms of eastern Australian taxa. Methods Using targeted sequence capture of ultraconserved elements (UCEs) and exonic loci, we reconstructed a phylogeny from 369 specimens, including four sequenced holotypes and 49 topotypes, and compared phylogenomic lineages directly against name-bearing type material. Key results Of the 53 nominal species evaluated, 47 were supported by congruent phylogenomic and morphological evidence. Twelve species are removed from synonymy: Acropora syringodes (Brook, 1892) from A. longicyathus (Milne-Edwards, 1860); A. patula (Brook, 1892) from A. latistella (Brook, 1892); A. affinis (Brook, 1893) from A. florida Dana, 1846; A. australis (Brook, 1892) from A. gemmifera (Brook, 1892); A. fruticosa (Brook, 1892) from A. humilis (Dana, 1846); A. wallaceae Veron, 1990 from A. samoensis (Brook, 1891); A. otteri Crossland, 1952 from A. secale (Studer, 1878); A. azurea Veron & Wallace, 1984 from A. nana (Studer, 1878); A. laevis Crossland, 1952 from A. muricata (Linnaeus, 1758); A. murrayensis Vaughan, 1918 from A. loripes (Brook, 1892); A. pacifica (Brook, 1891) from A. robusta (Dana, 1846); and A. squamosa (Brook, 1892) from A. millepora (Ehrenberg, 1834). Four species previously listed as taxa inquirenda are recognised as valid: A. bullata (Brook, 1892), A. jeulini Crossland, 1952, A. secundella Verrill, 1902, and A. brooki Crossland, 1952; the latter is an invalid junior homonym of A. brooki (Bernard, 1900), for which we designate Acropora crosslandi nom. nov. as the replacement name. Acropora cardenae Wells, 1985 is newly synonymised with A. tenella (Brook, 1892); A. ambigua (Brook, 1892) and A. decipiens (Brook, 1892) are transferred from synonymy with A. robusta to A. pacifica (Brook, 1891), pending further investigation; and three existing junior synonymies, A. leptocyathus (Brook, 1891), A. baeodactyla (Brook, 1892), and A. exilis (Brook, 1892), are retained. Conclusions Our results show that many Acropora species with type localities in eastern Australia, previously treated as junior synonyms, are distinct evolutionary lineages supported by both phylogenomic and morphological evidence. Current species counts for Acropora are therefore underestimated due to the synonymisation of valid nominal species, and endemism in the genus is more common than previously recognised. Our topotype-anchored integrative framework links phylogenomic lineages to existing species names through direct comparison with name-bearing types, offering a scalable approach for resolving species boundaries and nomenclatural uncertainty across Scleractinia and other species-rich coral taxa requiring comprehensive reassessment. ZooBank: urn:lsid:zoobank.org:pub:F202DB49-58BD-4879-8C3F-8548F87F48C0