Too cool, part 24: Ring species

Over at Why Evolution Is True, Jerry Coyne talks about new research that shows that the we no longer have any examples of ring species (which actually means we never did in the first place.) What’s a ring species, you ask? Go ahead, I did myself. Coyne explains it best, and you need to go there to get the full understanding, but in a nutshell, it’s a peculiar classification where a species population may spread around a geographical barrier and meet when they complete the ring surrounding the barrier, but because of the distance covered and time it took for them to do so, the outlying ‘fingers’ that meet again have diverged enough genetically to fail to interbreed, one of the ways we classify speciation in the first place. However, the species can interbreed with the population behind it, and this trait extends back through the population and around the ring to the other ‘finger’ – while each individual can mate with its immediate neighbor, there remains some minor genetic variation between them, and the further the species has spread, the more variation can occur between distant sections of it, to the point where bringing the most distant portions together again may result in genetic incompatibility. In essence, it shows one of the problems with divergence and when to consider something a separate species.

It highlights something often missed: we make up words to help us communicate things, but sometimes the concept we want to communicate doesn’t have the clear distinctions that we want them to have. Many people believe that ‘species’ has a firm definition, and moreover, an easy way to tell one from another. This is not at all the case. After using the word/concept for centuries, we found that living things just cannot be separated so distinctly. Even with the working definition that we’ve adopted, the concept of a ring species defied it – it represented a continuum of reproduction with a speciation barrier at the far ends.

The fact that it is not shown to exist does not solve the problem, either; it demonstrates how we cannot have a definition that holds for all circumstances. It’s not much of a stumbling block – those in the field and many outside know the issues, and it only presents a problem in a few cases. Sometimes, this is when someone is trying to determine whether or not a new name is necessary.

It is a good example of correction, though, and Coyne puts it succinctly when he talks about the removal of the greenish warbler (Phylloscopus trochiloides) from the examples of potential ring species – the last one on the list, by the way:

But nature is nature, and what happened is what happened.

That’s science, and moreover the practical frame of mind that it engenders – make the correction, accept the results, and move on. All of it is useful information and adds to our knowledge base, so the only thing lost is the emotional desire anyone might have had to know a species defined a particular trait – it’s strictly personal, in other words. From time to time, one hears arguments (I’ll let you guess from what subset of our population) that science changes all the time, as if this is a detriment. But science is actually very good at correcting itself, or to be more accurate, the structure serves to help us gain a more precise understanding of our world, realizing that we’ve never been perfect and neither is knowledge, and improvement is a good thing. Which would you rather have: a system that can correct its mistakes and improve constantly, or one that ignores all flaws and believes that never admitting to gross, blatant errors somehow means they don’t exist?