Thursday, August 23, 2012

Energy Rate Density, Fitness and Reproduction

As you (Ian and Yasha) know I have been struggling with the idea of differences between absolute and relative fitness. I just typed out something that just occurred to me. Let me know what you think. 

Not all traits/behavior may contribute to reproductive success. If we consider reproduction as a special case, then those traits become relevant that contribute to reproductive success as they can get selected and evolve. 

If reproduction does not occur in a system, then those traits will evolve (by means that do not specifically require reproduction/heredity) that contribute to...well just living and increasing/maintaining the bearers free energy rate density (Chaisson, 2011).

If the above has some meaning then bringing together the two ideas of "reproduction is a special case" and "is there a difference between absolute and relative fitness" leads you to this conclusion, traits that contribute to increasing free energy rate density can be broken down into two types those that rely on reproduction and thus contribute to increasing reproductive fitness and those that do not contribute to in any conceivable way to increasing reproductive fitness. 

In the second scenario those traits that rely on reproduction and contribute to a increase in reproductive fitness are traits that increase relative fitness of an organism in a population over time. 

The first scenario describes contribution of a trait to absolute fitness, where a trait might not have anything to do with reproduction or reproductive success. It just contributes to maximizing free energy rate density..just living. 
        Chaisson, E. J. (2011). Energy rate density as a complexity metric and evolutionary driver. Complexity, 16(3), 27–40. doi:10.1002/cplx.20323


  1. I'm going to give Chaisson a read and comment in full.

  2. I'm afraid I'd have to read Chaisson, too, before I could really comment. One thing that occurs to me at the moment, though, is that what seems to be lacking in your description is a consistent definition of fitness. As usually conceived, absolute fitness is still concerned with reproduction. The only difference between it an relative fitness is, again usually, that absolute fitness generally doesn't account for an individual's reproductive success relative to other individuals. Within the common usage of these terms, then, it's hard to see how a trait could contribute to absolute fitness without having at least something to do with reproductive success. My guess is that you're using an expanded definition of fitness which, as you know, I'm on board with. Nevertheless, if that's the case then it would be helpful to now just how you are using the term in this instance.