As with both of you, I'd love to see some more work with Brachyplatystoma. I'm particularly interested in the phylogeny of the group, especially following the work of Dr. Lundberg on the genus and how he split capapretum off of filamentosum. Finding specific morphological traits to validate the difference was evidently quite difficult, and was done with the shape and number of teeth.
Of course now, many of us in the hobby can look at young filas and capas and spot them instantly, but those differences could certainly fit within the range of genetic variability of one species, similar to what we're seeing with the variability in tigrinum or juruense. The possibility exists for sister species to exist within both of these species, forming a sister complex. This is what happened with the ATF; when a genetic diversity study was done, it was found that that there were three undescribed sister species or subspecies to VATF. The original VATF would be correctly referred to as
H. vittatus sensu stricto, with the three VATF sister species/subspecies being referred to as
H. vittatus sensu lato until such time as they're formally described and named. TATF was found to be an extremely closely related sister species to the vittatus complex, but just outside of it. It is a VATF complex species that underwent allopatric speciation to become something unique. The VATF species complex will eventually do the same if something should prevent them from being able to continue to swap genetic information.
FATF has the same species complex thing going on, with at least one undescribed species or subspecies. There was also a cryptic species unrelated to anything previously known found, but it is most closely affiliated to the VATF complex.
Due to finally acquiring firm and reliable location data for what we were calling in the hobby TATF, we now know they're from the lower Congo from the same waters as GATF. It is impossible for them to be TATF with this reality, so following
fugupuff
's naming convention, I ascribed the name big eye to them. I *strongly* suspect that this fish is the undescribed crypic species. I'm working on a description, which will name this fish Hydrocynus acutus. In the hobby we also have a VATF
sensu lato species, which I refer to as H. cf. "stout vatf". It is in every way a VATF, and comes from VATF territory, but the scale counts are slightly off, they get a little bigger and they grow a little faster.
Without that genetic study, we'd never know of the mess that exists in Hydrocynus. The cryptic species, three sisters of VATF, at least one sister of FATF and more would all be completely unknown because they all *look* basically the same unless you're actively looking for differences that you know should be there due to genetics.
The same type of situation could easily exist within Brachyplatystoma, as is strongly inferred by Dr. Lundberg's definition of B. capapretum. I find this to be incredibly likely actually, given the high variability that we've seen in many species. The main issue that we'll run into however is how interconnected many of the rivers of South America are through the flood season, genetic drift may be difficult. There's also the issue of people not realizing the genetic diversity of things that are present, such as with the dorados (almost all the fish in the hobby are hybrids between franciscanus and brasiliensis due to farms mixing them and stocking them before it was clear they were different species; suppose I need to address that in that sticky, too).
All that is to say that it's possible that even if there
was additional speciation within Brachyplatystoma, it is entirely possible that we may no longer be able to define it, only recognize that it once existed, due to anthropogenic meddling in the gene pool (accidentally or otherwise).
Apologies for rambling on, sometimes I just allow a line of thought to meander through my mind to see what grows like the Nile meanders through the desert.
