What does the 'Apply establishment means to descendent places' button (in check lists) actually do?

I suspect I’m just being a bit slow here and missing something obvious, but I’m struggling to see how this button actually performs any function. To explain:

As a test this morning I picked a random insect species and set it as introduced (I have the only observation) for the Australia checklist. I then searched for that species under some descendent places of Australia, eg NSW and Sydney, and it was showing as introduced for them as well. When I looked at the checklists for NSW and Sydney, the establishment means field had been auto-populated and ‘introduced’ was shown as the status; so even though I didn’t manually set those checklists as introduced, the status had automatically flowed down from the Australia checklist. Note that this did not require me to click the ‘Apply establishment means to descendent places’ button.

This behaviour is exactly what I would expect. If something gets listed as introduced for any given place X, then by definition it must also be introduced within all descendent places it occurs. If this isn’t the case for 100% of descendent places, then it shouldn’t get marked as introduced for the entire parent place, but rather should get marked at the relevant descendent places manually.

So already from this simple exercise, this button starts to seem a little bit useless if descendent places inherit their parent’s status automatically anyway.

But then I think about another situation. For some species, lots of individual curators apply lots of different statuses on places idiosyncratically and sometimes in conflict with each other. So let’s imagine a situation where there are hundreds of manually applied statuses for a single species in country X across all kinds of descendent places (states, counties, towns, etc), including a mixture of introduced and native statuses. Unfortunately some of them are wrong/were based on erroneous information, and this species should actually only have a status of introduced across all the places within this country. I can go to the country level checklist and amend that to introduced, however, this doesn’t actually change the descendent place statuses once they’ve already been filled in.

So I think finally, a use case for the ‘Apply establishment means to descendent places’ button. All I have to do is set the country to introduced, click the button, and then that status will override all the wrong descendent ones. But this is not what will happen. That button comes with the message that clicking it “won’t change existing values, just fill in blank ones.” But as I already demonstrated in my first example above, setting the parent place status already automatically fills in the blank statuses in descendent places without needing to press the button.

So what is the actual purpose of the button? If it isn’t required to auto-populate descendent places, and it cannot override erroneous descendent statuses, I cannot see what use it actually serves. It’s especially confusing given that, if you do click it, you get this warning pop up:

if clicking it does not change existing values, then what work could it possibly undo?

I’m not 100% sure how this works, but I do not think that descendant places automatically inherit status and I don’t think that they should.

So I disagree with part of the reasoning here:

This is not the way that I have seen invasive/native determinations/designations made. For instance, especially in a larger place, like a large country, a species can be native to one portion of the country but introduced/invasive in another. In the US, many species of fish are good examples of this - they are native to part of the country, but stocked in other places where they have become invasive (example: https://www.nwf.org/Educational-Resources/Wildlife-Guide/Threats-to-Wildlife/Invasive-Species). The same goes for the bullfrog - native to much of the eastern US, invasive in the Western US: https://wildlife.ca.gov/Conservation/Invasives/Species/Bullfrog

In the example of the American Bullfrog it is considered native to the US (it is naturally found within its borders), but invasive to specific places (eg, California) within the US.

It’s my understanding that the button does populate places entirely within a larger one, but should be used very carefully, and only in instances where the status would be correct for all descendant places. If I put bullfrog as Native for the US and ticked “all descendants”, it could set a bunch of places in Cali as native (which is definitely not true). However, in the case of the bullfrog, which was never found in California prior to human intervention, I could mark bullfrogs as invasive in Cali and apply to descendant places. I still might not do this, though, because bullfrogs aren’t found everywhere in Cali, because this might create a lot of unnecessary checklist entries. For a state where bullfrogs were native to the entire state (like Georgia perhaps, guessing a little), it would probably be safe to apply bullfrog as native to the entire state and all descendant places, since the species is pretty ubiquitous.

This is what I see:

So I think this is what happens:

That screenshot seems to explain the difference.

that’s what I initially assumed, but they definitely do (at least some) based on my testing this morning. Just to elaborate on my point more:

  1. I picked a silverfish, Subtrinemura epigea, for which I knew 100% a status had never been applied to any checklist at all (I have the only observation in existence).
  2. I set it as introduced in the Australia checklist.
  3. I then checked the NSW and Sydney checklists, and they had been automatically filled out as introduced as well, even though I did not manually fill those statuses out and I did not press the button

I see the same message, I was just quoting the relevant portion of it. Could you explain to me what you think the entire message conveys that I’m missing here (as I said, pretty sure I’m being stupid here and missing something obvious)

this is definitely not the case, I have already tested this. Pre-existing statuses will not be overriden

This will change the establishment means of all listings of this taxon on all descendant places of North America to “introduced” .

To me this sounds like it will change all current statuses (introduced, native, or endemic) to introduced. It will not update unknowns, although if you’ve already marked it as introduced that should’ve already happened.

This sounds like a bug then? I haven’t really used this much so I can’t speak to whether it works.

I searched on the forum and found some relevant threads:

This probably explains the situation most pithily:

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right, the first part of that does make sense

but the second part

still doesn’t seem to align with the button’s message that it will explicitly not change everything?

The part about just filling in blank values refers to just changing the status. Subsequently applying to descendent places changes (or should change) all values.

The wording of the button’s message would probably be clearer like this:

Changing the establishment means to “introduced” without using this tool will have roughly the same effect, but it won’t change existing values, just fill in blank ones.

And my understanding was that this is a special case for the “introduced” establishment means, and is not applicable to the other possible establishment means values.