A team of 11 coral researchers has used phylogenomic techniques to resolve the taxonomy of the genus Acropora. Historically, coral taxonomy was based almost exclusively on skeletal morphology, resulting in the description of some 400 species of Acropora, with two-thirds of them demoted to junior synonyms.
But this latest molecular study using DNA extracted from corals has resurrected five of those species, as well as describing two brand new ones. They also took a deep dive into the perennial reef aquarium favorite, Acropora tenuis.
The study by Tom C L Bridge and others says that Acropora is the most species-rich and numerically abundant coral genus on most Indo-Pacific reefs, with species like Acropora tenuis thought to be pandemic and exhibiting morphological plasticity. Previously, our favorite Acro was thought to be as widespread as French Polynesia in the South Pacific to the Indian Ocean, South Africa, and the Red Sea, but experts have been muttering about the real tenuis and its origin for a while.
Acropora bifaria
Using samples taken from far and wide, the super popular Rainbow tenuis we all covet from Indonesia has been revealed as Acropora bifaria, the type specimens coming from Java, in Indonesia. Acropora tenuis from the Great Barrier Reef and Western Australia has also been revised, and they are now called Acropora kenti. There are no Acropora tenuis growing naturally now, in either Indonesia or the whole of Australia. The real Acropora tenuis now only comes from Fiji and Tonga. New species Acropora tenuissima also only comes from Fiji, while new species Acropora rongoi is described from the Cook Islands.
“Our study represents the first taxonomic revision of Acropora based on phylogenomic data, and our results are clearly incongruent with recent taxonomic revisions based on morphology.”
“Our results demonstrate that: (1) the diversity of Acropora is higher than currently recognized; and (2) the putatively widespread nominal species, A. tenuis represents multiple distinct species with restricted geographical distributions.”
The authors also move away from traditional species groups created via morphology, and divide Acropora into six clades instead, with Acropora tenuis and its close relatives being in Clade I.
Implications
So how does this affect us and our favorite Acro? In short, it doesn’t, as CITES is super slow/not willing/not caring about updating the names of the hard corals they regulate, so Indonesian Acropora bifaria will still be recognized as, permitted, and travel as Acropora tenuis, a species which is widely maricultured in that country. The same for wild Acropora kenti from Australia.
On a conservation level however, Acropora tenuis now has a much smaller geographic range, with implications for climate change and the long-term conservation and management of that species.
Only if Fijian Acropora tenuis receives extra protection do we need to worry, as then that blanket, catch-all, pandemic name could affect former tenuis trading countries if their policy makers don’t read and take notice of these taxonomic changes, the new names, and what really comes from where. But spread the word – true Indonesian Acropora tenuis is no more.
Citation
Tom C L Bridge and others, A tenuis relationship: traditional taxonomy obscures systematics and biogeography of the ‘Acropora tenuis’ (Scleractinia: Acroporidae) species complex, Zoological Journal of the Linnean Society, 2023;, zlad062, https://doi.org/10.1093/zoolinnean/zlad062
