Native vs Immigrant plants?

Question

**Is this statement applicable to any known plant/region combinations?** > Plant species X, Y, and Z are truly indigenous to region R. Other "immigrant" species can be destroyed by drought or harsh weather, but these species will always be part of the region R. (all species in question are "benign" - like wheat; please disregard climate change and other global disasters like nuclear wars). PS. Background: I heard this statement (with specific X,Y,Z,R) attributed to a "leading botanist" (probably 20th century), but I don't really see how this can be true (my biology education ended in high school though; I am a mathematician by training).

Answer 1

The red flag in this question for me would be the use of the word 'always' in terms of any ecological system. The earth is constantly changing, species evolve and outcompete each other on large timescales. Even barring human activities, which has caused the quickest large-scale change our biosphere has ever seen aside from events like asteroids, always is never used regarding how well a living thing can survive. Forests grow into plains, plains breach into forests, fires strike, islands get new seeds, earthquakes disturb the ocean floor, a moth gets lost in a storm and ends up in the wrong place at the wrong time, and so on and so forth.

' Other "immigrant" species can be destroyed by drought or harsh weather, but these species will always be part of the region R.  '

So we would need a plant that cannot be destroyed by drought or harsh weather. Every plant needs water, so if a place is above ground, drought is not impossible. Forgetting even that, there is no place on planet Earth that has remained with the same exact climate over the last billion years.

Also invasive species are constantly able to out compete native species. A plant has evolved to be vine like and suffocate trees. The ecosystem has some way to adapt to balance this out, say by a monkey that eats the vine, or a special resistance the trees can build. Well, I'm going to take this plant and put it in the middle of another continent where they've never seen such a thing. There are no adaptations against it, and this immigrant plant will survive. This isn't always the case, as sometimes the climate just won't allow for this specific plant, the native plants are able to hold their own just fine, and so on and so forth - but it's a case that can happen to anything on this planet provided the right species.

To say a plant is 'immune' to any competition in its environment would mean we would have to test it with every possible plant out there, with every varying adaptation they hold.

Most plants will not be able to survive whatever drought or weather this one endures, but nothing is stopping a single plant species from being better at nutrient uptake, or placing shade over the plant to stop its growth, or stop it from constricting, or maybe it makes the soil more acidic and changes the environment for its own benefit, etc etc etc.

Hopefully I was able to help with this, but invasive plant science is a whole field of it's own full of many intricacies, so let me know if you have any questions or if there is a specific area of the world this quote was taken from, so I can help provide better examples!