Anthrodemics and the Evolution of Introduced Life

Nature Talk
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What happens when two non-native species are introduced into an area, they hybridize and subsequently speciate in that area? As in the case of Salsola ryanii, a species endemic to California, but introduced to California at the same time. It’s a species with no native range. The definition of a native species is as follows:

A native species is an organism (plant, animal, etc.) that naturally lives, evolved, or historically dispersed into a specific region or ecosystem without human help

This means that Salsola ryanii and a whole host of other taxa introduced by people worldwide and subsequently speciated, are not native to anywhere. They are simultaneously endemic and introduced to their respective areas, but cannot be native. Below I have compiled more information on these species, and a term to classify them, since they do not fit into the classic “native/introduced/endemic” bubble.

I and some other naturalists have been compiling a list of all of the examples of these with this project here: https://www.inaturalist.org/projects/introduced-endemics

Criteria for inclusion in the project:

  1. Must be a species or subspecies that arose in a particular area, making it endemic to that area
  2. Species are hybrids, polyploids, or otherwise evolved/derived from at least one non-native parent taxa

Island Foxes, in California for example likely evolved from mainland Gray Foxes that were introduced to the Channel Islands by indigenous peoples. In the fossil record of the island, you can directly see a cutoff with flightless birds, large rodents existing on the islands prior to human and fox arrival, with all of those fossil species disappearing after the fact.

Thousands of years ago people moved Agave around to various locations in the Southwestern US, which ended up in highly localized locations, each speciating into very rare forms today, as with Agave verdensis, etc.

I call all of these species “Anthrodemics” or “Anthropogenic Endemics”. I encourage you to check out the project list, and I can provide sources for any of the taxa I listed if someone is curious about why I included certain species. If you have another example of an Anthrodemic, I would love to hear about it and include it on the list.

From a conservation standpoint it is odd, because there are critically endangered species of real conservation concern on my list, but also novel, highly invasive species like Salsola ryanii, Tragopogon mirus, etc. I ranked these simply on the fact that they all more or less share the same origin. These taxa did not exist before humans intentionally or unintentionally moved their ancestors around. The oldest confirmed example I have found of this is the Manus Island Spotted Cuscus (Spilocuscus kraemeri), which evolved from one of the mainland PNG Spilocuscus species when people introduced them to the island of Manus around 20,000 years ago. Dingos are older, but we all are generally fairly familiar with them.

Humans have been moving species around for a long time, causing speciations without even realizing it. There are surely countless more examples of this phenomena worldwide that we will simply never know about.

I also have an umbrella project called “ https://www.inaturalist.org/projects/anthropogenic-life ” That includes this project and two others, encompassing species that evolved alongside us, and species we have domesticated.

Edit: This post is not to promote my projects but rather start the discussion on what these species actually are and how to handle them going forward. There have already been a few other posts regarding this topic, but people have been left confused/debating, so I am hoping this helps outline things better going forward. An example of another post regarding this from earlier this year: https://forum.inaturalist.org/t/species-arising-through-hybrid-speciation-with-alien-parents-are-these-native/65600/16

Edit 2: Moved to Nature Talk as that seems like the better fit than General

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I’m not intending to detract from your interesting discussion of the problem, but the definition seems unambiguous here. Note that the conjunction in this definition is “or” rather than “and”, so in the case of your example, the species evolved in California, therefore it is “native” regardless of it’s origin before it evolved into it’s current species.

This premise is logically incorrect according to the definition. Salsola ryanii (as you describe its origin) would be endemic to California, but would NOT be considered introduced. It’s two parent species were introduced, then evolved into a new species in situ. The newly evolved species thus DOES have a native range.

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Some other definitions of native do include and outright say “without human intervention.”

a native species is indigenous to a given region or ecosystem if its presence in that region is the result of only local natural evolution with no human intervention during history.

I agree I could have worded the introduced status of Salsola ryanii better, yes, it itself cant be introduced, by definition, because it itself evolved in situ. I still stand by it not being native however- its endemic, certainly, but under the definition of “native” that I go by, none of these species would be considered under it. I used “introduced” in this context in the beginning because we had no word for these specific species cases, hence “Anthropogenic Endemics”

Edit: a lot of this does just hinge on one’s own definition of native/introduced/endemic and I’m sure a lot of people would argue back and forth about this all day, haha. I’m mostly interested in the discussion of these species from a conservation standpoint, if they should be conserved at all. I can see how you could have both sides of the argument- people who think we should just get rid of all of them because they aren’t “natural” vs people who argue that every species, regardless of origin, is important for biodiversity and needs to be conserved. I tend to fall in the middle.

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The ‘native vs. introduced’ binary often feels a bit too rigid for modern ecology, and ‘Anthrodemics’ fills that gap perfectly. It’s wild to think about species that are technically endemic to a place but wouldn’t exist without human intervention. Have you considered looking into how these might be categorized in conservation legislation? I imagine it’s a legal gray area!

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They’re handled very differently depending on their effects on the environment and prior perceptions of where these taxa came from. I looked into it a bit and found that Salsola ryanii, the tumbleweed that arose in California, is defined as an invasive species in state materials. This is because while technically it’s a different species, it’s a major threat to crops and rangeland, and so, I think, people aren’t all that motivated to see it as being all that “different” from other tumbleweed species that are straightforwardly invasive.

However, this brings up the fact that ecosystems are dynamic, as is speciation. As safron referred to, the Channel Islands Gray Fox likely had a role in causing flightless bird extinction from those islands at the time of its introduction, so if you hopped in a time machine to 7000 years ago and observed that introduction, you would have been right to call the Gray Fox invasive to those islands. But in the thousands of years since, the fox has evolved a unique island form and the memory of those extinct birds is long gone. Now it’s a beloved endemic.

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On top of what shauna1 said, even modern anthrodemics have had some conservation funding put towards them, such as the case of York Groundsel (Senecio eboracensis), A species that only came into existence in the 1970s, subsequently went extinct due to herbicide applications, and then was subsequently revived from old seed stored in a seed bank, before being introduced into the wild. The very first successful reintroduction of an extinct species, the first successful de-extinction, was an anthrodemic that has only existed for around 50 years!

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It reminds me of the quote, “A weed is an out-of-place flower”