Hello, students.  This is [inaudible] in Southern California.  So we have these newts and newts have in their skin toxins.  And these toxins are -- they'll like shut down your nervous system, so don't eat newts.  That's the main message.  It turns out that there's garter snakes that can eat newts.  And they are stunned.  Like you know, eating a newt is like eating a jalapeño pepper or something, right?  But it's -- if you're a garter snake.  And so they kind of [inaudible].  But they recover from it and of course, newts are not only delicious but they are nutritious.  And so it turns out that certain populations, certain populations, of garter snakes have adapted to be able to handle the tetrodotoxin.  So they can eat newts and it just stuns them a little bit, but they are able to get the food out of the newt and do quite well.  And the interesting thing about this, is that there's been a co-evolutionary exchange between the newts and the garter snakes as they vary geographically.  So there's a co-evolutionary geographic process whereby, certain locations have garter snakes that are highly tolerant to the toxin, and they also have newts that make a lot of toxin.  And then other places have garter snakes that are not particularly tolerant to the toxin and they have newts that only make the normal amount of toxin.  And there's a lot of different levels of this co-evolutionary process that's occurred in different populations of newts and garter snakes.  

So the way I would imagine it would happen is that start out with newts all being poisonous.  Of course we think this because not just our local newt, but lots of species of newts all have this tetrodotoxin in their skin.  And then, a mutation arises in some garter snakes or maybe garter snakes are forced to eat newts or something like that.  And so then there's selection on the garter snakes and they -- the mutations that allow them to be tolerant to the toxin, spread in that little local population.  So then, you have garter snakes eating newts in that little, local area.  And then, there's selection for the newts to be more toxic.  You know, any newt that is more toxic, when a garter snake bites into it, they say, "Oh, too hot."  And it let's go, right?  And so those are the newts that go on to be the parents of future newts who will also likely have the genes that make them even more toxic.  

Meanwhile, there are other areas where the garter snakes haven't adapted to eat newts.  You know, they don't ever eat newts.  And so in those areas, the newts are toxic but they're just the normal level of toxin.  And this is a co-evolutionary process that's kind of specifically at the population level as opposed to say diffuse co-evolution between bees and flowers, where there's a lot of flowers and then bees start collecting pollen.  And the bees adapt to flowers, but they don't -- they adapt to a lot of different types of flowers, not just you know, one type of flower.  And then flowers adapt to bees, but they're not the same bees.  You know, it's much -- it's millions of years later.  This is -- this newt-garter snake thing is much more in the same time period, almost synchronous coadaptation of the animals to one another.  Though that's coadaptation.  That's all I really have to say about that.