Exotic Invasives and Other Threats to Your Mental Health

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Australian dingoes aren't really native and aren't really exotic
Australian dingoes… kind of native, kind of exotic. Photo by TheGirlsNY from Brooklyn, NY, CC BY-SA 2.0, via Wikimedia Commons

Do you ever hear someone talk about an endemic species and wonder if maybe that’s something that lives in your bowels? Do you think an “exotic invasive” sounds like what you call it when a stripper breaks in to your house? Or maybe you get the general idea, a sense that they’re positive or negative terms, but you’re not 100% clear on exactly what all this stuff means. If you read articles about endangered species, or watch documentaries about wildlife conservation, or god forbid, listen to a bloody podcast about environmental issues, you’ll probably come across these and other terms on a regular basis. Sometimes they do a good job of explaining what they mean, but other times, they forget that not everyone speaks biology-nerd. And it may not always be clear why these terms are even useful or why we should care.

Well, it’s back-to-school time for a few minutes while we go over this stuff and why it matters. Don’t worry, this isn’t another stress dream where you’re wandering around a giant building, possibly nude, trying to remember where your 3rd period class is. You don’t have an assignment due today that you totally forgot about. You’re awake, and this is just a blog post. So relax and let the information flow into your brain space. Let it ooze down into the cracks and crevices, feel the knowledge fill up your mind-holes.

What’s a native species?

Let’s hit the most common one first. You probably know what the term “native” means, since it means pretty much the same in ecology as it does in every day life. A native species is simply a species that was originally found in an area and is a natural part of the ecosystem. A native species could be native to a forest, a river, a state or province, a geographic region, a continent, or even broader areas spanning multiple continents or oceans. It’s also important to note that just because a species is native to an area, doesn’t mean it’s not native to other areas also. In other words, when we say that that the honey badger is native to Kenya, that doesn’t mean that it isn’t also native to other places, like Tanzania. Likewise, when we say that the honey badger is native to Africa, that doesn’t mean that it’s native to the entirety of the continent. It isn’t found in the northern areas such as Egypt and the Sahara region, for example. The context of the statement matters when you’re talking about a native species. Oh, and by the way, the term “indigenous” means basically the same thing as “native”, and the two terms are used interchangeably in biology.

Honey badgers are native to Africa, but not ALL of Africa.
Honey badger does care. About its baby. And where it’s native to.
Photo by Derek Keats from Johannesburg, South Africa, CC BY 2.0 , via Wikimedia Commons

Easy peasy, right? Ah… but there’s a little wrinkle. What if a species has been present in an area for a long time, but did not evolve there or hasn’t always been present there? Generally, if we know a species hasn’t always been present somewhere, we won’t consider it to be a native species. For example, the common carp has been present in North America pretty much since Europeans started settling there and brought the fish over with them. No one living remembers a time when the animal wasn’t present in North America, but it’s still not considered to be native to the continent.

But where do you draw the line? If a species has been present for 500 years, is it native? What about 5,000? That’s the conundrum we have with the Australian dingo. Dingoes are basically wild dogs, descended from grey wolves just like our more familiar domestic dog. However, wolves are not native to Australia, nor were they ever present there. So, dingoes did not originate on the continent. The current thinking is that humans from one of the Indonesian islands to the north traveled by boat to Australia around four to five thousand years ago, and brought dingoes along with them. So… after 5,000 years, do we call dingoes native? If not, then where do we draw the line? They’re certainly part of the ecosystem at this point, for better or for worse.

Who cares if they’re native?

Perhaps the better question is, who gives a shit? What difference does it make if something is native or not? Well, it matters because of evolution. See, species don’t evolve in a vacuum. That wouldn’t make any sense. I mean, you have to at least have some air, or water. One or the other, at least, preferably both.

Yeah, sorry, bad joke. What I meant was, species don’t evolve completely separately from other species. They adapt to the presence of other species in their ecosystems. Some species rely exclusively on certain other species for a food source. Others evolve to avoid being prey. If you’re a plant, there’s a decent chance you’ve evolved to rely on other species for your own reproduction. Flowering plants are perverts, y’all. Whether it’s a collaboration or a competition, different parts of the ecosystem can become intricately tied to one another. When you drop an entirely new species in there, it starts interacting with everything else. It can wreck the elaborate arrangements the native species have.

Rockhopper penguins would be exotic if you put them in the Mojave desert, but they wouldn't last long
You’re not likely to find penguins in the Mojave
photo by Ben Tubby, CC BY 2.0 , via Wikimedia Commons

This introduced, non-native species is often called an exotic species. In every day use, we might say “exotic” to mean something unfamiliar, unusual, or interesting. That’s not the case in biology. All it takes for a species to be exotic is for it just not be native to that exact place. Say you have two lakes next to each other, and one has three species of fish while the other has the same three plus one more species. If you then took that extra species from one lake and dropped it in to the other, that fish would be an exotic species in that lake. It would be native to the area, but an introduced exotic in that lake. It could be incredibly common in the other lake just next door, and very similar to fish in its new home, but it would still be an exotic species. Often an exotic species won’t do well, because it’s not well adapted to its new environment. Drop a rockhopper penguin into the Mojave Desert, and it’s not gonna live long. But sometimes, the opposite happens. Sometimes the native species aren’t adapted to advantages the new species has. Just by accident, the exotic species will be a sort of ecological Superman… ordinary in their native land, but extraordinary in their new home.

In this case, the introduced species becomes what we call an invasive species. An invasive species, by definition, is a trouble maker. And not the fun, sexy kind, either. At the very least, an invasive species competes with native species for food and habitat. At the worst, it can wipe out native species and degrade the entire ecosystem. A great (or, horrible?) example is a lovely flower called purple loosestrife. This European native was introduced to North America both intentionally, as a garden flower, and accidentally, as seeds in mud that ships took on as ballast in Europe and then dumped in America. It’s a great garden flower… tall stalks with vibrant purple flowers that last all summer. The problem is, nothing in North America can eat it. Not deer, not rabbits, not any sort of insect. Nothing.

That’s bad enough. But purple loosestrife has another superpower that contributes to its status as an invasive species. In its native habitat, there are things that eat it, so it’s evolved to deal with this by breeding like crazy. Like if rabbits and roaches started making babies together, and then THOSE babies got religion and started making as many of their own babies as possible. Each plant can produced a gazillion seeds a year. Well, technically, between 1.5 and 2.3 gazillion. A new plant can grow from a broken piece of root left in the ground. Even a section of stem can grow into a new plant under the right conditions. Combined, these superpowers are a lot more impressive than being able to fool people by wearing glasses.

Canadian marsh that's been completely taken over by purple loosestrife
Canadian marsh that’s been completely taken over by purple loosestrife
Photo by Saffron Blaze, CC BY-SA 3.0 , via Wikimedia Commons

In North America, purple loosestrife can completely take over an area, especially in its favored habitat of moist soils, shorelines, or marshy areas. Since nothing eats them, they out-compete the native plants that have natural predators. They can then blanket the area with seeds, which germinate and grow easily since there’s nothing to munch on them. After a few years, there’s nothing left but a sea of loosestrife. There’s fewer species of plants in the ecosystem as a result, and any species that relied on those missing plants are gone now, too. There’s fewer herbivores because they can’t eat the loosestrife, which means fewer carnivores to eat the herbivores. The entire ecosystem is degraded. Basically, purple loosestrife is the mother-fucking devil. So, that’s why invasive species are a problem, why it’s important to know about them and understand what makes them invasive. It’s why we’d rather stick with native species as much as possible.

The easy going naturalized species

It’s not always all or nothing, of course. There’s a middle ground where exotic species manage to survive in their new habitat without wrecking it. You sometimes see these species referred to as being “naturalized”. Technically, a naturalized species is any exotic species that doesn’t die out in its new environment, and so that would include the overly successful invasives. But in practice, you tend to only hear “naturalized species” used to describe a species that’s reproducing and persisting, but that’s not a threat to the entire ecosystem or likely to aggressively spread.

A good example of a naturalized species is a another pretty flower, the grape hyacinth. Grape hyacinths are a group of plants native to Europe and Asia. They are popular garden flowers in North America, where they are exotics. Under the right conditions, grape hyacinths planted as landscaping in North America can start reproducing and spreading out into the surrounding areas. However, they spread relatively slowly and don’t tend to compete well with native species, so you rarely see them naturalized in truly wild areas. You’ll find them growing “wild” in grass lawns and in landscaped areas where they weren’t planted, but it’s pretty rare to find them in an actual meadow or forest, no matter how much they reproduce in a suburban landscape. They’re exotic, and they can become naturalized, but they’re not really invasive.

Grape hyacinths can become naturalized in North America, but rarely invasive
Grape hyacinths aka your buddy Chris
Photo: Bff CC by SA-4.0 via Wikimedia Commons

So, think of it like having people over to your house. Your house guests are all exotic. They’re not supposed to actually live there. Most of them will leave after a few hours, or maybe the weekend. But your buddy Chris is going to stay for “just a couple of weeks” until he sorts things out with his girlfriend, but then they split up for real and he’s looking for a new apartment but you suspect he’s not really looking too hard and other than the fact that he apparently is physically incapable of doing the dishes you don’t mind so much so eventually you start asking him to help out with the rent and utilities and now he’s become naturalized.

But, maybe instead of your buddy Chris, it’s your Aunt Cindy. She insists she’s only staying for a bit and that she really just wants to help you get settled in to your new place, but you’ve been living there for three months already so that seems a little weird, and you never liked her as much as she seems to think you do, but it’s hard to say no to her because she’s your mom’s sister after all, and it’s nice that she wants to redecorate your bathroom you suppose but she did it all up in bubble-gum pink and you hate pink I mean if it had been a paler pink that would have been okay but the entire bathroom is now the color of Pepto-Bismol and also she also apparently bought you a big mixer for the kitchen which really was nice of her but you wish she hadn’t spent the money because you hate baking so you’re never going to use it but you can’t tell her that because it’d hurt her feelings so now it’s just going to sit there until you try to use it once just out of guilt, plus now she is having guests over to drink wine while they watch NCIS on your Netflix account and congratulations! You now have an exotic invasive living with you.

Could you en your demic in private, please?

Next up, an easy one called “endemic species”. Endemic species are a particular type of native species. When a native species is only found in a particular area, and nowhere else, it’s endemic to that area. Normally this is a small or restricted area, like an island, lake, or mountain range, but technically could be just whatever their native range is regardless of the size of it. So, if you wanted to be a real smart-ass, you could say that pigeons are endemic to the planet Earth. But more commonly you’d say that the island fox, for example, is endemic to the Channel Islands off the coast of California. They are only found there and nowhere else. Golden eagles, on the other hand, are also native to the Channel Islands, but not endemic to them, since they are also native to vast swaths of the Northern Hemisphere.

Adorable island fox pup, endemic to the Channel Islands
A kind of adorable island fox pup, endemic to the Channel Islands

We often use the term “endemic” to indicate that a species is special or unique, in part because it has a very restricted range and probably a naturally low population, making that species vulnerable to extinction. An endemic species warrants special attention, even if they’re not immediately in any threat of extinction. On the other hand, we rarely say that a species is endemic to, say, the Amazon rain forest, because that’s not particularly special or helpful. It’s a huge area and thousands of other species are also endemic there. Technically it might be correct, but you won’t often hear it. You would just say it’s native there.

Cheap beer for science

Finally, here’s a fun one for you: Keystone species. A keystone species is one that depends largely on canned light beer for survival… shit, never mind, I already did that joke in the last post. Actually, a keystone species is named for the top stone in an archway, the keystone. That keystone is the only thing holding the archway together, and without it, the whole thing would collapse. In an ecosystem, a keystone species is one that shapes the ecosystem in ways beyond just what they eat and what eats them. Their very presence has dramatic effects on the rest of the ecosystem. Most species fit into an ecosystem, but keystone species make the ecosystem fit them. Like the stone in that archway, they keep everything hanging together.

As mentioned in the last post, beavers are a keystone species. By removing large trees and building dams across streams, they physically reshape their environment. They alter the stream flow and create new habitat for other species, all of which also serves to make the habitat better for the beaver. Elephants are another keystone species. They eat and destroy small trees and shrubs, maintaining the savanna by preventing forests from taking over. They also distribute the seeds of many species they eat in their dung as they travel long distances. This helps propagate those species and ensures they have good genetic diversity. Elephants shape and maintain the character of their own environment.

Beavers are a classic example of a keystone species
Beavers are a classic keystone species
NPS Photo / Emily Mesner, Public domain, via Wikimedia Commons

When you eliminate a keystone species from an area, it can have a cascading effect on everything else, usually in ways that weaken the ecosystem and make it less diverse and more vulnerable to further disturbance. Identifying keystone species allows us to understand which species are absolutely critical to protect, and by focusing conservation efforts on them, we end up helping many other species as well. Keep the population of keystone species healthy, and they’ll do a lot of the conservation work for you.

Okay, class. Those are the different classifications of species types you’re most likely to run in to, but may not have fully understood before. Biologists toss these terms out all the time, but we rarely take the time to make sure people know what we’re talking about. And it matters, as I hope you can see. Invasive species do a hell of a lot of damage. Endemic species are inherently rare and special and impossible to replace. Keystone species let us see where to focus our efforts, how to get the best bang for our conservation bucks. Preserving native species is always better than allowing exotics to run amok, because the other species in the ecosystem are already adapted to them. And when we all understand these things, we’re better equipped to make decisions, both as individuals and as societies. We know how to pressure our leaders and governments to act, and maybe we can even educate them a little bit, too.

More importantly, I hope you now know to be careful about who you let in to your home. Sure, usually it’s no big deal, but if you let someone like Aunt Cindy take root, before you know it, she’ll be driving you out of your home. If you don’t believe me, just think about what happens when she starts breeding uncontrollably. In your home. Where you can hear it. You don’t want to be around for that, do you? Of course not. You’ll wish you’d payed better attention in biology class then, I guarantee it.

Dingoes to remain classified as non-native wild dogs under reform to Western Australian law
Beavers as a Keystone Species
Restoring the Channel Islands: the “Galápagos of North America”

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