Evolution Awesomeness Series #1: Red Queen and TTX
First, let me throw out there that I love when a scientific theory is named for a character in a story written by a guy on LSD. That being said, The Red Queen Hypothesis is hands-down one of my favorite things about evolutionary development upon which to geek out. The fact that it’s considered a truism (something hardly worth pointing out because it’s so obvious, my new word for the day) by science doesn’t dampen my enthusiasm a bit.
“Now, here, you see, it takes all the running you can do, to keep in the same place. If you want to get somewhere else, you must run at least twice as fast as that!” says the Red Queen to Alice (in Wonderland), when Alice points out that at home, running typically gets you somewhere.
Thus the Red Queen Hypothesis describes a process also known as the “arms race” between predator and prey. In essence, two living things (one of which eats the other) are forever evolving adaptations to deal with the adaptations that the other is also developing. Did you catch that?
In other words, there is a relationship between the development of better defenses by prey, and the subsequent development of better offenses by predators. A newt, eaten by a certain kind of snake, develops toxins to defend against said snake. The snake, over time, develops a tolerance for that toxin and continues to eat said newts. The newts evolve to have a more potent toxin, and the snake develops a higher tolerance again. (That is to say, by natural selection, newts with higher toxin levels survive better than those with lesser toxin levels, and snakes with better toxin resistance survive more often than snakes without.)
A giraffe likes to eat acacia trees. The acacia trees, over time and random genetic mutation, develop huge thorns. Similarly, the giraffe develops tougher mouthparts and a fancy tongue designed especially for pulling on foliage. Some acacias develop a symbiotic relationship with ants, whereby the ants feed on the tree and attack herbivores (thus defending the tree) that may also want to browse.
Remember, evolution isn’t conscious – the animals and plants aren’t thinking to themselves, “Gee, I’m really tired of being terrorized and eaten.” The adaptations are a result of an obstacle in the living thing’s environment. It’s natural selection, where positive mutations lend an edge to the survival of certain individuals. Now, some things aren’t doing a whole lot of obvious evolving at the present moment because, well, there aren’t any new, dangerous obstacles in their environments.
Even though an animal may not evolve on the outside (think alligators and crocodiles) for millions of years, their genetics *are* changing. A croc from the time of the dinosaurs isn’t genetically the same as a croc at the San Diego Zoo; they can’t be the same, because of that whole mutation thing. Genes are forever mutating, and so what’s fascinating (as pointed out by my Evolutionary Biology PhD-possessing boss) is this: the question isn’t exactly “Why haven’t they changed over millenia on the outside?”, it’s “Why have they stayed the same?” What about their environments/situations/etc determine that they’ll look the same for a million years, even when they’re different at the genetic level? AWESOME!
But, I digress. Let’s go back to the snakes and newts, because this is a really cool example.
Garter snakes (Thamnophis) prey on rough-skinned newts (Taricha granulosa), which possess the poison tetrodotoxin (TTX). TTX is also found in puffer fish, that fish that some lunatic people take the risk of eating. (If not prepared correctly, puffer fish can kill you before you leave the restaurant.) TTX is one of the most toxic… toxins on the planet. A single rough-skinned newt contains enough TTX to kill an adult human, easy-peasy. So it was a little surprising to researchers when they discovered that garter snakes were eating the newts with no problem. Garter snakes living in areas without newts around, however, died when subjected to the toxin, suggesting that the two had a very special relationship.
From the Stanford Report: “Why would a small animal produce such an excessive amount of poison? The answer lies in the evolutionary back-and-forth between newts and garter snakes. Throughout much of their shared territory, newts and snakes have been locked in a kind of arms race: TTX-resistant snakes cause natural selection to favor ever-more poisonous newts, and the new-and-improved newts drive selection for higher resistance in snakes.”
On Principia Cybernetica Web, F. Heylighen sums up the Red Queen Principle perfectly: “In a competitive world, relative progress (“running”) is necessary just for maintenance (“staying put”).”
Look around you the next time you go outside. Can you find other examples of the Red Queen theory/natural selection? Watch for butterflies and moths with eyespots, meant to deter birds from eating them. Imagine the terrible taste of sagebrush, their leaves full of volatile oils meant to deter browsers. If you notice a good one, leave it in the comment area!
Posted on August 5, 2010, in Biology/Ecology and tagged coevolution, garter snake, natural selection, naturalist, nature, red queen hypothesis, roaming naturalist, rough skinned newt, taricha granulosa, thamnophis. Bookmark the permalink. 3 Comments.