But from the last discussion, in science nothing native can be invasive, invasive is at first introduced.
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Invasive: a species introduced to an area where it becomes established and does serious ecological/economical harm.
Naturalized: a species introduced to an area where it becomes established but is relative benign.
Aggressive: the term used to describe native species that have weedy or āinvasive-likeā tendencies.
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OK so here are the definitions of āinvasive speciesā I have found after a brief google. Some are even from reputable sources.
My emphasis belowā¦
Nat Geo:
āAn invasive species is an organism that is not indigenous, or native, to a particular area. Invasive species can cause great economic and environmental harm to the new area.ā
Wikipedia (yeah, I know, I know):
" An invasive or alien species is an introduced species that becomes overpopulated and harms its new environment."
US NOAA:
" An invasive species is an organism that causes ecological or economic harm in a new environment where it is not native."
USGS:
āAn invasive species is an introduced, nonnative organism (disease, parasite, plant, or animal) that begins to spread or expand its range from the site of its original introduction and that has the potential to cause harm to the environment, the economy, or to human health.ā
Nature dot org:
āInvasive species are any species that are non-native and harm the local ecosystem. When these non-native plants and animals establish themselves in our local ecosystems, they outcompete and dislodge species that have evolved specifically to live there.ā
USDA:
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In UK, invasive does not imply non-native. The acronym INNS is widely used, standing for Invasive Non-native Species, which would be a tautology if all invasives were non-native. As I understand it, an invasive species is one that can displace an established species or community. That is, it is not just taking over empty ground like thistles after a field is ploughed but is taking over habitat that was already occupied. Bracken Pteridium aquilinum is probably the worst invasive native plant in UK. It occupies a significant percentage of the northwest.
Now someone is going to say āBut one species ousting another is just competition or succession, happens all the timeā. Yes, that is true and I am not going to try to come up with a definition that distinguishes the phenomena. I guess it is a case of you know an invasive when you see one. Or perhaps it is subjective according to your point of view: if you prefer woodland to grassland, colonisation by oak trees is fine. If you prefer grassland, oaks are invasive.
Going back to the original question, otters (native) apparently feed on the introduced mink in Britain and have given a lifeline to water voles (native) which were being eliminated by mink among other factors.
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Calling succession an invasion is an astonishing view, not sure what are the reasons and gain from doing that. There would be no differences between those in such paradigm, everything is an invasion if something starts to dominate.
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Can you cite an example? My understanding is, by definition, a native species in its native territory cannot be invasive. It may be described as aggressive in its growth habit, but thatās not the same.
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I usually see things like plants being referring to as āaggressive nativesā or āwith weedy tendencyā instead of invasive. American trumpet vine, for example, is actually native to the eastern US, but grows like crazy, in a āweedy manner.ā A few other examples include boxelder, eastern poison ivy, sumac, goldenrod, and ragweed, which are all aggressive in their native range.
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As an invasion ecologist, my quick note is: There has been ongoing discussion around these (and more!) terms in the field for decades that has mostly gone around in circles. In the primary literature, there are different papers using and advocating for different definitions for a variety of terms, and no 100% consensus on any of them. A good approach is for people to define a term as they are using it in a given source so the audience knows specifically what they mean (and, as a reader/audience member to look for how an author defines the term when they use it). Trying to create consistent definitions that everyone will agree with isā¦not likely to end well (or at all!).
iNat does include a definition with its little exclamation point symbol text which says:
āIntroduced in [location]: arrived in the region via anthropogenic meansā, so it is really referring to whether a species was introduced or not, not whether it is āinvasiveā.
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Longhorn Crazy Ant (Paratrechina longicornis), introduced, versus Bolbonota leafhopper, native.
Longhorn Crazy Ants, introduced, versus unidentified Common Land Snail (Stylommatophora), unknown if native or introduced.
Mostly what I see here are large Western honeybees, introduced, driving smaller native bees away from flowers. But the smaller bee circles back when the larger bee leaves, and all their legs seem to be loaded with pollen; there are flowers enough for all it seems, for the moment.
Here is a palate cleanser, native on native, Unstable Paper Wasp (Polistes instabiles) versus Gulf Fritillary (Dione vanillae).
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āInvasive non-nativeā would only be tautologous if all invasives are non-native and all non-natives are invasive. It is possible to be a non-invasive non-native, but I do think it is oxymoronic to call something a ānative invasiveā. To me, and apparently the definitions above, āinvasiveā basically means ānon-native pestā
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Indeed. A non-native pest is the conclusion I came to as well.
I would say to the people advocating for still-relevant terms to suddenly mean something else: Go and get some new words - these ones are taken.
Speaking of interactions between introduced / alien and native organisms, this iNat project (called Interactions (s Afr)) based in southern Africa is just amazing ā¦ it documents the interactions between any and all organisms, ranging from native species on both sides, native-alien interactions, and sometimes alien-alien interactions in a country that neither is native to.
Link to observations for above project
The best observations in my opinion have to be the observations of introduced biocontrols doing their job in helping to keep invasive aliens in check!
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Itās technically an oxymoron but it is a valid term used by ecologists. It joins the ranks of jumbo shrimp, old news, freezer burn, living dead, loyal opposition and others of oxymorons that actually mean something.
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Well, I guess nobody said ecologists would ever make it as lexicographers. 
The key to language is mutual intelligibility, so if ecologists understand each other clearly I guess that works for them :), but it seems rather messy to me, and conflicts with the definitions used by others, so I wish they hadnāt!
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Both species are technically invasive to New York but a Cross Orbweaver (Araneus diadematus) making a meal out of a Spotted Lanternfly.
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Great picture
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