Except that it's an on-going problem, and one there are no easy answers to. Hobbyists can help by not guessing at the ID of a plant, as we see SOOOO often when someone posts a "what is this plant" post with a photo and no other information on Face Book. Then the poster goes and spreads that plant around the hobby with their "favorite" crowd-sourced guess.
Growers can help by not selling plants with KNOWN faulty ID's (for instance, selling Rotala indica as "Ammania sp.'Bonsai'"!!!)
But many plants look quite different grown under different conditions, AND there are cultivars (man made varieties, like all the different forms of Echinodorus hybrids) or spontaneous mutations like Rotala rotundifolia 'Colorata' developed by Anubias.
Then there are the plants that have tremendous variation, even in the wild... like many Rotala sp., Cryptocoryne sp. or like Pogostemon erectus. We found very different looking versions of this plant, often even growing in the same stream or river. Different species? Or just genetic variation? My bet is on the later, considering that in the wild, these plants reproduce from seed after flowering in the dry season. We "fix" these traits by only propagating the versions we like vegetatively or through tissue culture. (which is also vegetative of course) But they don't (and shouldn't) have different scientific names, as they are truly one species.
Clearly a Pogostemon, and based on emersed, flowering plants found nearby, I would say P. erectus. But it doesn't look like what we have in the hobby as P. erectus.
Pogostemon (probably erectus) from another locality, not TOO far away from the first, but very different looking... More like what we have in the hobby. We didn't find flowers at this site, though.
That is true with many Cryptocoryne sp. also. I've shared photos of the many C. crispatula types from various parts of Thailand. They not only LOOK different, their growth habits are COMPLETELY different. But the DNA work has been done on these plants, they ARE all the same species. (at least in the way that we understand and use the word)
Cryptocoryne crispatula from the Mekong River in north Thailand
Cryptocoryne crispatula from the Myanmar border at the Pogostemon helferi locality. How can this be! They look so different? True, but the genetic work has been done, and they ARE the same species.
And, of course,finally we get to plants like the mosses and Eriocaulons that are very, VERY difficult to determine. In some cases, like E. parkeri, we could get a determination because there aren't too many Erios in that region. In places like India? Good luck. There is a different one in every stream. Often things get into the hobby LONG before the scientists have time to figure out what they are. That is also what is happening with Bucephalandra.
In the case of chain swords, (which, BTW, were removed from the genus, Echinodorus a long time ago now, even though many growers still use the wrong genus... They are now Helanthium) I have seen three distinct types of H. tenellum. One has consistently short green leaves, one has consistently short leaves that turn red in bright light, and one has green leaves that grow quite a bit longer in poor light. I can't tell you whether these were different collections from the wild (most probable, since these plants have been in the hobby in these three forms for many years) or whether they diverged in the greenhouse somewhere.
The problem is, very few botanists have any direct contact with, or for that matter, particular interest in aquarium plants (funnily enough, most botanists work mostly from dried materials, even in this day and age) So you have to find someone who has the expertise, the interest, the TIME and the funding to take it on. Even then it takes time.
