Changing coral taxonomy: What can we do in the meantime?

Author: Hanaka Mera

As a PhD student, if someone told me that the species I am working with (or planning on) for my research project actually might be something entirely different or might be five different species, it would be quite overwhelming, maybe feel a bit devastated. This could be true for any researcher or the general public who are interested in what they are seeing.

Here is what I learned so far to keep moving forward:

1. Be consistent!
If you are running experiments which involve collecting certain species, make sure to observe your species very carefully, familiarise yourself with it, and only collect specimens you can be confident that it is the one. This will minimize the risk of getting variations in your study that stem from…well, different species.
If you are conducting field studies which require you to identify species but unsure of the actual name, take photos, take notes of what they look like and give it a made-up name (e.g. Acropora cf. florida_1, Porites phoenix_1) and stick to it.

2. Photos, photos, and photos!
As part of assisting with being consistent, take photos of what you are calling who, essentially to create your own database of species identification. I believe this could also be done on video transects which you analyse after the fact – take screenshots of what you will be calling Acropora sp.1 for example. This will also help if the field study runs over several months or years, and/or if someone else needs to take over the study in the future. Once Project Phoenix makes an easily accessible database for original description and holotype/topotype materials, you can cross reference with your photos as well. Keep in mind that there are limits to what you can identify with a photo, however it is better to have some than none at all.
EDIT: When taking those photos in the field, it will help to have a scale and take multiple shots: a wide shot (habitat and gross morphology), mid shot (variation within the colony), and close up shot (branch shape and corallite size). Thank you Russ for pointing this out!

3. Take note of geographical and depth differences
Species found in Hawaii, USA may not be in the Great Barrier Reef, Australia. They could be, but if you are unsure, there is probably a reason why. Similarly, species found at 2-meter depth can look different at 15 m. Phenotypic plasticity? Maybe. But can you be sure? Not yet.  Make use of an open nomenclature to capture any uncertainty in your identification such as  ‘aff.’ (has affinity to but different; see more in detail in Cowman et al. 2020) and take note of where exactly you saw the species. It is easier to pool your data later if you find more evidence that they are one species.

4. Not all corals are confusing
Some families and genera have solid evidence for being ‘good’ species. My personal favourite is Diploastrea heliopora (Lamarck 1816), the only species in the family Diploastreidae and morphologically distinct from any other group. Though words of caution as no study to date has compared D. heliopora from different geographic locations. Oh no. Another I find very characteristic is Turbinaria heronensis Wells 1958. Among the diverse genus Acropora, A. palmata and A. cervicornis (both Lamarck 1816) are the two out of three Acropora species found in the Caribbean. My point is, if you are looking for a scleractinian species but not a specific one, a literature search will show you which one has fairly good lines of evidence. Our publications list is a good place to start. If your study species needs to be a specific one but you cannot find literature with good lines of evidence, you just found yourself a new research question.

5. Know that there is a light at the end of the tunnel!
Members of Project Phoenix are working on different research projects simultaneously, some of which are:
Collecting topotypes with tissue to allow DNA sequencing plus detailed field and skeleton photos
Documenting biodiversity from a particular region including detailed photographs of species
These will dramatically help with the above points when they become available. But good taxonomy takes time.

A pretty photo of a reef to conclude this article. Photo credit: Hanaka Mera

Literature cited

Cowman, P. F., A. M. Quattrini, T. C. L. Bridge, G. J. Watkins-Colwell, N. Fadli, M. Grinblat, T. E. Roberts, C. S. McFadden, D. J. Miller, and A. H. Baird. 2020. An enhanced target-enrichment bait set for Hexacorallia provides phylogenomic resolution of the staghorn corals (Acroporidae) and close relatives. Mol. Phylogenet. Evol. 153:106944.

2 thoughts on “Changing coral taxonomy: What can we do in the meantime?

  1. Hi Hanaka

    Enjoyed this article. I agree with the emphasis on taking good images for coral ID. But as someone who has taught coral ID to nearly a thousand people I think you should go further by suggesting they shoot an ID sequence: wide shot, mid shot, close up and close up with scale. I use a dedicated ‘muck stick’ with scale graduations but at the very least put a finger in one of the shots. With practice the field worker will rattle off the sequence almost as quickly as a single image.

    Taking a sequence is important for the beginner because it creates some real world post-dive context and the scale is critical for eliminating options. It save a lot of hand wringing.




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