Author: Andrew Baird
Species: Acropora tanegashimensis Veron, 1990
Acropora tanegashimensis was named by Veron for a species of table coral from Tanegashima, a subtropical island just south of Kyushu and the site of the northern-most coral reef in Japan. There has long been some confusion as to how to identify this species in the field.
The holotype is a small nubbin from a much larger colony and has fairly thick branches, mostly between 5-10 mm wide (Fig. 1), which is fairly unusual for a table Acropora and definitely not that common in the field. However, Dr. Takuma Mezaki has been exploring this question in detail and has observed that the branches in one of the A. hyacinthus like species at Misaki often vary widely in width within a typical corallum, from between 5-10 mm towards the centre of the corallum, to less than 5 mm on the periphery (see Fig. 2 b & c). On this basis, Dr. Mezaki is convinced that A. tanegashimensis has field characters suggesting an affinity with A. hyacinthus. Indeed, it appears to be one of the four or five clades in the A. hyacinthus species complex of Japan (Suzuki et al. 2016)
In our phylogeny using targeted capture of conserved regions, specimens from Sesoko in Okinawa that are remarkably similar morphologically to those from Misaki, form a clade that is recognised as distinct by the species delimitation approaches we are using and it is a distant cousin of A. hyacinthus (Dana 1846). On balance this suggests that A. tanegashimensis Veron 1990 is a good species with highly variable branch width that can look a lot more like A. hyacinthus in the field than might be guessed from the holotype. Hopefully, the samples collected at Misaki will allow us to confirm this although a topotype from Tanegashima would be better. Unfortunately, I did not get permits to collect from Tanegashima. If these specimens are all the same beast, the distribution of the species extends from Misaki in Kochi in the north to Sesoko in Okinawa in the South. Both Veron (2000) and Wallace et al. (2012) suggest it is endemic to Kagoshima so these samples represent a considerable expansion in range both north and south of the type location. I do not recall having seen this morphotype anywhere else in my travels.
Suzuki G, Keshavmurthy S, Hayashibara T, et al. (2016) Genetic evidence of peripheral isolation and low diversity in marginal populations of the Acropora hyacinthus complex. Coral Reefs 35:1419-1432
Veron JEN (2000) Corals of the world. AIMS, Townsville
Wallace CC, Done BJ, Muir PR (2012) Revision and catalogue of worldwide staghorn corals Acropora and Isopora (Scleractinia: Acroporidae) in the Museum of Tropical Queensland. Mem Queensl Mus 57:1-255