Can you find one? Is there at least one species of an introduced plant or animal to North America from anywhere else in the world that has become a new species since europeans arrived on the continent? Other than plants that were deliberately bred by humans of course. I’ve looked. I can’t find anything.
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We actually can see species appear in a lifetime, glapagos finches are one example, but you need a good place and good gene situation to make it happen.
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You’d want to look at lineages with multiple related species, and locations with a long archaeological record. If you find archaeological remains associated with a human use site, and they turn out to be related to, but not the same as, species present there now, you have a beginning. But then you still have to establish whether the ancient humans brought the ancestral species there or it was already there and they began using it.
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Tragopogon mirus is a hybrid species that arose from a cross between an introduced european Tragopogon and a native NA species, it’s polyploid and thus isolated from its parent species.
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I would think that with deliberate artificial selection you could create a new species with near total reproductive incompatibility in just a few generations for some branches of the tree of life; there has to be clades where flipping expression of just a few uncommon recessive genes would be enough.
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It’s certainly a fun thought experiment, thinking about which species can and will speciate given time.
As others have pointed out though, the timelines along which evolution operates is gradual enough and takes so long that it is immaterial to us currently (and certainly so in terms of conservation).
The only time, I think, where conservation of an invasive species would be relevant is where the invasive species is endangered enough in its native range (which is the case for some species), that the eradication of the extralimital population would be counterproductive to the preservation and continued survival of that species.
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Interesting point. Do you think conservationists would then capture members of the invasive population and establish them back into their native range?
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Let me say that in this case the word “invasive” should be substituted by “alien”.
Invasive is a status of an alien species and, of course, not all alien species present in a given area are invasive.
Anyway, yes, certain alien species can speciate and even rapidly. Think about Oenothera sect. Oenothera subsect. Oenothera (those species referred by many simply as Oe. biennis). There are many microspecies that originated after the introduction outside the area of origin of their ancestors.
http://dspace.bsu.edu.ru/bitstream/123456789/3455/3/Tokhtar_Mikro.pdf
They should not deserve a particular protection as they are still alien even though there could be a certain interest in their possible properties or potential usage.
Other alien unfortunately can produce hybrids, sometimes also fertile, with the native congeners.
There are other cases.
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Some ungulates that are rare in their native ranges have been bred and released here in Texas. These exotics, in many cases, are now running wild. So if they went extinct in their native range, the individuals here in TX could be used to restore them back to their native range (if suitable habitat remained).
Most animals do not speciate rapidly, but come visit Texas in a few million years and these alien ungulates would be different species than those in their native range.
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Marbled crays first showed up in the European aquarium trade, but likely did not arise there. My personal pet theory for the origin of them is that they honestly might have just come out of some random ditch in Florida, possibly found by people collecting wild crayfish for sale as feeders
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That’s interesting. A fine distinction though - Zebra Mussels, Noctua pronuba and the Emerald Bark Beetle I would consider to be invasive to NA. Others that migrate here on their own I would not consider as invasive. This thread - https://forum.inaturalist.org/t/great-tailed-grackle-in-north-america-introduced-or-not/30425/2 - would illustrate that difference.
The distinction may be defined by how much of a pest (which is another category!) the organism is. If, like the Emerald Bark Beetle - the species causes the reduction of native species (American Elm) I would call it invasive. Agricultural pest species, like Flea Beetles introduced to to NA, I would class as something else. I don’t know what. I don’t think that they bother the local Cruferiadae much but can devastate a Canola crop.
In New Zealand they have a category of ‘Self Introduced’ mostly for birds that have migrated in some way across the sea from Australia. It’s all very complicated!
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I don’t think we can paint all of evolution the same. Speed of evolution is a function of reproductive mode, generation period, mutation rates, and selective pressure. Each of these factors can vary wildly for different organisms and at different times. At the rapid end of the spectrum, consider evolution of antibiotic resistance in bacteria, novel viruses, etc. Or the example of successful polyploid hybridization already mentioned, in which new species can emerge instantaneously.
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I am mainly interested in plants.
There are many definitions of invasive species. Some focusing more on the ability of an alien species to spread on a vast territory, others on the impacts desumed on the literature. As far as I am concerned, I would prefer to keep the ability to spread and the potential or actual impacts separated. Thus, in my scheme an invasive species (able to spread on vast territories) can be either impacting (making damages at the ecological level) or non-impacting (no damages or negligible). There are consequently four combinations and the worst case is that of an impacting invasive (e.g. here in the Mediterranean Robinia pseudoacacia, Ailanthus altissima, Carpobrotus spp., Myriophyllum aquaticum and their bad company). One could add two more cases: impacts not known.
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Sounds interesting. I hadn’t considered ‘spreadability’, but that’s also a factor for insect invasive species. If they can’t live in cold winters, they can only get so far north. It would likely work with plants as well.
I was mainly thinking out loud about the distinction between ‘invasive’ and ‘alien’, and whether there was a difference.
I think your concept of the invasive species adapting to better survive their new habitat is partly in error. The biggest change is actually in the new habitat due to anthropogenic habitat alteration, climate change, and other invasive species. Many invasive plants in America are thriving due to their predilection for disturbed soil, tendency to keep their leaves longer, leaf out earlier, and resistance to invasive pathogens. In my area’s deciduous forests November and March are great times for invasive species removal. If you can identify a Shortleaf Pine and an Eastern Red Cedar then you can pretty much guarantee that anything else with leaves doesn’t belong. It’s not that these species are evolving to match our weather patterns. Instead, climate change is causing our weather patterns to better match those of the Asian temperate forests these species were originally adapted to.
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