There are definitely cases.
But the actual, scientific debate on whether or not there are multiple species of Erythrinus erythrinus is very much still out.
To be calling them anything than different morphs or local variants is very forward as any fish biologist is concerned.
Maybe someday they will run DNA testing and find that due to the somewhat extensive range there is on average a 1.5-2% difference between these and they will give some guy his species of fish as a bone for a life time of taxonomic work.
These most likely should not be split in my mind, unless there is substantial (at least 3-4%) genetic difference between them, which I doubt there is.
On an evolutionary timescale - these differences are nothing.
We Homo sapien have been around for a fragment of a second - and yet we have highly (morphologically) different relatives. Genetically I believe that difference is what it looks like when two species have just split, which, in the big scheme of things we have.
The division of Erythrinus erythrinus I believe is something similar, genetics maintained in some areas of collection are enough different that you might notice different patterning.
At worst it is a myth, and age, and just difference between individuals is what is amounting to all this confusing.
I am more more hesitant rather than less to go off declaring things a species without any scientific basis other than coloration; in training to become a fish biologist, they often teach us to identify species without the coloration because it can be misleading, and it varies quite widely within species.
