Bugs Within Bugs

Earlier I had mentioned Epigenetics and how entities other than individuals play a role in natural selection.

Thusly, when reading the Journal of Biology, (the free open source version) I ran across an article that interested me. Now there’s people who claim that would be “synchronicity,” or a hell of a coincidence, but we skeptics know that this is a confirmation bias.

The article (which you have to be a member to read – you can join up as a member of the Jackson Skeptical Society) lays out a few interesting points and has the super-science journal title “Genome degeneration affects both extracellular and intracellular bacterial endosymbionts.”

First up – parents (in this case, termites) are transferring symbiotic bacterium to their young! That’s a sort of epigenetic inheritance. with pics!) But think about what this means to the bacterium within! They have virtually no selection pressure on their metabolic genes – and that was how the scientists (in Germany) “clocked” these guys as playing all sorts of crazy with their genetics – compared to the DNA of buggers surviving in the “real” world, the isolated ivory tower gut-dwellers had DNA that looked a head on good frothy mug of ale.

These enslaved microbes could probably not survive outside the host organism. This is great for the host organism, and, at this point, good for the microbes, who have to stay put and keep breaking down cellulose for their arthropoidal lords and masters.

The key is imprisoning them. In termites, there are special cellular structures, bacteriocytes, which house them. In stinkbugs and many other organisms, it is simple “pocketing” of the gut that leads to this arrangement – where a single, small (but dense) population exists, it will frequently go through “bottlenecks” that rapidly evolve it to exist in this tiny niche.

All this genetic change can be measured against similar bacteria existing outside the plantation and compared to the evolutionary clock. And since they don’t need to keep up to date on the latest and greatest in predator-evasion, food-gathering and metabolic pathways, these bugs mutate FAST.

Its a fascinating exploration of the real tenets of evolution. Here, it is not the strength or miserliness or hardiness of the individuals that makes the difference – it is not even the rate of reproduction. Here, we are seeing the often blurry boundaries of parasitism and symbiosis.

So – what is the individual unit of natural selection? The gene? The individual? The group? The species? And what actions constitute being the “most fit?” As with any scientific endevour, questions are what you want, they are the starting points, not the ending points.

So, coming up soon – parasite or symbiote? It’s a fun game until someone gets a liver fluke…


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