Science Sundays: Speciation, or the 3 ways we get new species

By: Meradeth Houston on 11:59 AM

Hi everyone! Hope you are all enjoying (or enjoyed) a nice weekend. Things have been kind of warm in Montana, so I'm happy :) Also, I have a little giveaway going on here, which is super easy to enter (just leave a comment!) and I'd love it if you stopped by and entered!

Also, something has been bothering me about my Science Sundays posts and I thought I'd mention it here before I talk a little about how to speciate. I worry that I come across as some kind of know-it-all when I talk about science stuff, which is totally not my intention at all. I just like science :) I have spent a lot of time studying these things and hope that someone enjoys reading about them, remembering things they've heard about before, or can possibly use it to ensure things they're writing follow some of the real-world science that's out there. Anyhow, I just kind of felt like putting that out there...

Anyhow, speciation. How we get new species. I personally find this to be a really intriguing part of evolution. I mean, it's how we fundamentally get so much of the variation in species we see in the world. In general there are three basic ways this happens: allopatric, parapatric, and sympatric speciation.

The simplest and most common type of speciation is allopatric. Basically what happens here is some kind of barrier to mating develops between two groups within a population and keeps them separate. This can be something like a river running through a population of some animal that separates them into two groups--one on either bank. Or it could be a behavioral change that develops that splits off part of the population in the way they "attract the ladies" :) By doing this, and given enough time, the two groups become separate and even if they come in contact with one another, they won't be able to interbreed.

The second kind of speciation, parapatric, happens when there's two different environments/niches that are next to one another. A single species may live in both of these niches, but some of them may do better in one or the other due to some variable. I always use coat color and a mountainside as an example: say there are rabbits that have light coat color--they would do better at the top of the mountain in the exposed rock area as they would blend in there. The dark-coat rabbits would do better in the forest area at the bottom of the mountain, because they blend in better there. So, while they might be the same species to start with, over time it would be in the rabbit's best interest to mate with others that have a similar coat color as they do, as their offspring will be able to fit in better in the niche of their parents. A light-coat and dark-coat rabbit mix (hybrid) might have offspring that can't live in either of their parent's niches. So selection will benefit those who don't interbreed and eventually lead to distinct species that can't mix with one another.

The last kind of speciation is a little bit more tricky. What happens in sympatric speciation is that two species evolve in the same spot (not just next to each other) because within this same environment there are two niches, or ways to exploit the environment. What happens then is that again we have selection keeping the two groups apart (and it has to be really strong selection at this point!) so that again it is in the best interest of the individuals mixing within their own niche so that their offspring are best able to exploit that environment.

So, my question is, have you heard of these before? Can you think of any examples?