Over at PhysOrg.com, a recent article on ecosystems has shown up. It seems that, studying parasites, of all things, a new “rule” of ecosystems has been established.
A team from UCSB studied various ecosystems on the California coast and discovered that the ‘number’ of individuals in any species population can be predicted not only by its ‘size (an already known ‘rule’), but also by where it resides (top end, or bottom) on the feeding heirarchy.
How, then, does this fit in with Darwin’s Malthusian thoughts? Darwin wants to tell us that fitness is related to ecological niches, and that differential reproduction (NS) is what brings this fitness about. [Malthus, of course, pointed out that many more members of a species is produced each generation then survives to reproductive age.]
But if a species size and location on the feeding order determines how many “numbers” of the species will be found in the ecosystem, then doesn’t this mean that population of any particular species will remain relatively constant from one generation to another?
If so, then what, exactly, does ‘fitness’ mean in such a scenario? What does “differential reproductive success” mean in a, more or less, static population?
The “rule” of the ecosystem isn’t that as you become more fit, you increase in numbers; rather, it is simply that given your size and eating habits, there will be only so many of you in any particular ecosystem. Under these circumstances, then, what is the motivation for changing your phenotype?
This seems, overall, to be an argument for stasis. And, of course, this is what overwhelmingly is seen in the fossil record.
Let the “just-so” stories begin!