don't talk to me about invasive species unless you want to summon the MegaNuance Beam 9000 there will be no survivors
invasive species are a real thing, but there is a reason why (in USAmerica and elsewhere I reckon!) invasive species are the most widely understood and easy to teach about ecological concept.
this reason is very bad and has nothing to do with ecology
invasive plants and invasive animals tend to be different in some ways, and also all invasive species are different from all other invasive species. so basically don't generalize this
but the history of many invasive species is totally inseparable from the ways the landscape was altered to create niches for those species. European style farming, surface/strip mining, construction, roads and railroads, etc. created novel ecosystems with novel disturbance regimes that the "invasive" species are highly capable of taking advantage of.
There is nothing wrong about Kudzu that makes it invasive in Appalachia, but there is something wrong with Appalachia that makes it so extraordinarily invasible by kudzu, and that thing is "you exploded the tops off the mountains, scraped the whole entire surface of the land away, and put a bunch of fucking highways through the wreckage."
I believe that the history of destruction and exploitation could possibly still be present in the evolutionary history of the invasive species even when the destruction is no longer visible.
In the case of Kudzu, Chinese scientists have compared USAmerican kudzu to Chinese kudzu and found evolutionary changes in the USAmerican kudzu's DNA that come from its adaptation in the environments in the introduced range. I can't find the article right now I'll look for it later
but, think of this: entire eastern half of the USA was laid waste, logging strip mining and destructive methods of farming obliterating the soil and previous landscapes. during the same time non-native species are introduced. The wasteland left over is poorly suited for native species, but the non-native species are weeds, they are adapted for this stuff. So the non-native populations become huge because there is so much destroyed habitat, and they have lots of genetic diversity. They breed and breed and breed and they evolve and evolve and evolve. Then, even when the forests are partly restored and the land starts to heal, the non-native species are highly adapted to the new environment due to having been able to breed, evolve, and spread widely in the previous state of destruction.
that is my thought anyway, I would have to study it more to confirm.
Cities, at least in the contemporary, concrete-jungle sense of the word, are novel ecosystems; they have notably different climate than the surroundings due to urban heat island effect, and the soils can be highly depleted or highly over-fertilized, depending. They have tons of non-native species that wouldn't otherwise survive being kept alive in landscaping and gardens. Basically it creates lots of tiny local niches where non-native species can survive, and where a population survives and reproduces, it evolves.
Within the special novel ecosystems of cities, populations evolve and evolve and evolve and with every generation there is a chance that an individual will emerge that is capable of surviving a little outside the novel ecosystem. And then, when the species is able to expand to live in new conditions, the new genes are spread widely because they are so helpful.
humans introduce species to new places, but we also cause evolution of species through our creation of new habitats. there is even a word for plants that are adapted only to live in human created habitats, and have no apparent "wild" populations because human habitats ARE their habitat: they are called anecophytes and the word has mostly been used by urban ecologists studying central Europe but it is a very intriguing concept. here is PDF of an inventory of Czech Republic flora that uses the term extensively.
Kudzu itself is adapted to live alongside humans: it has been used by human beings for over 6,000 years in its native range and its genetics have been strongly affected by human selection and breeding for various traits. It is considered possible that kudzu is not controlled by "natural enemies" because its "natural enemy" is, in fact, humans. here is article about it
the history of destruction and exploitation of the land has profoundly affected the evolution of invasive species. the presence of invasive species on the land often communicates the violence that was done to the land.
the natural state of an ecosystem is seen as passive, whereas invasive species are considered beings with destructive agency. But the invaded territory is not a passive state of nature, it is a bleeding wound in need of immediate attention and care, and a state of chaos and upheaval that invites WEEDS to intervene
In the case of Kudzu, the plant arrived to stop the bleeding, quickly growing and overtaking the obliterated wasteland to which it was introduced and beginning to reverse the loss of soil. you can read here about it in this article about Copper Hill, Tennessee, a place where literally all vegetation was dead from sulfuric acid pollution from mining and refining copper.
