Tree of life has more leaves than expected

It turns out being a descendent isn’t as clear cut as it seems. As sequences of genomes fill the digital world, their analyses surprise many evolutionary biologists. It is hard to define exactly what a species is. Where do you draw the line between species? Wolves and dogs are clearly different. What about wolves and coyotes? Wolves and huskies? Coyotes and dogs? Labs and Newfies? Mutts and purebreds?

We have a habit of standing where we are and looking back in increments. How else can we learn about our world? Well, scientifically, we are growing up very fast, and need new perspectives. Just because the only information we have is that of clear, distinct species in a neat branching tree doesn’t mean that act of speciation is a neat business. In fact, I’m willing bet the farm that as we study genomes, we will find speciation is messy and “blurry” and species can only be distinctly identified long after the “speciation event”.

If there is even a single event. In some cases there may be a single change that allowed a new species to survive and the old to become extinct. I suspect that for many species (most?) it’s a continuum and that once you get far enough along the continuum, the species are then very distinct. Kind of like the visible spectrum. What’s the difference between 695nm and 700nm? Both are still red light. Once you get to 600nm, however, the light is very clearly orange. Can’t confuse those two colors. I think speciation is likely to the same way. At the very least, different species have interbred in the distant past, making the creation of family trees a bit more challenging.

Here are few stories about finding the “blurriness” in species by comparing genome sequences.


About Dr.B.

I teach upper and lower level biology course at CCBC and UMBC.

Posted on March 19, 2012, in Evolution and tagged , , . Bookmark the permalink. Leave a comment.

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