Evolution and Increased Diversity

In a previous, exceptionally off-topic (even for me) thread digression, an interesting discussion occurred concerning the relationship of natural selection to biodiversity between myself (obviously a proponent) and Elmer, who feels the concept of natural selection is vacuous - and hence meaningless in the context of biodiversity. I thought that this would be a good place to continue that conversation.In order to avoid a descent into too scattershot or rambling a discussion, I’d like to try and frame the question a bit more clearly. In essence, there is a direct observation of a phenomenon that needs explaining.Note: to avoid confusion, I’d like to clarify three terms that I will be using: biodiversity, guild composition, and selection pressure.1. Biodiversity: When discussing biodiversity in this context, I will be focusing on RAZD’s second definition: number of species in a given location. This is the definition most relevant to the example, and also the one I’m most familiar with because this is the scale (landscape) at which I work.2. Guild composition (or composition tout court): I’ll be using “composition” as a shorthand for a combination of quantitative measures: species diversity, functional distribution, relative abundance, etc. It is the differences observed in these measures which are most relevant to the example.3. Natural selection: The non-random action of the suite of environmental factors (“selection pressures”) that affect a population. Both biotic and abiotic factors extant in the area under consideration are subsumed under “selection pressure”. If it becomes necessary, more detail can be examined.Enough preamble, here is the observation that needs explaining:Dung beetles (Coleoptera: Scarabaeinae) represent a speciose group of organisms with critical functional roles (decomposition, nutrient recycling) in many ecosystems. They are especially common in the tropics, in both the Old and New Worlds. At the landscape level, they form complex, multi-species guilds whose composition is differentiated by habitat type. The group appears highly sensitive to environmental change, and in fact guild composition can be directly mapped to different environmental gradients; for instance, that between disturbed habitat, ecotone (or transitional habitat) and mature forest. Any changes in habitat are directly reflected in changes in guild composition, whether the habitat change is “negative” (in the sense of anthropogenic impacts such as defaunation, introduction of exotic species like cattle, deforestation, etc), or “positive” (in the sense of habitat restoration, natural succession, etc). In fact, this guild’s composition is so sensitive to environmental change and so tightly correlated to habitat integrity that it has been proposed as a valid surrogate for monitoring the health of the entire landscape - including all its other species assemblages and the ecosystem processes on which they depend. As the habitat changes, so too does the composition and structure of the guild.So here’s the question before the board: What is the explanation (i.e., mechanism) which accounts for the tight correlation between guild structure/composition and habitat/habitat change with these organisms?My answer: The observed differentiation can be accounted for by subtle differences in the environmental factors existing at each microsite along the given gradient. The interplay of these factors as they affect the specific species populations composing the guild at each microsite - subsumed under the term “natural selection” - is the mechanism by which guild composition changes in lockstep with changes in these environmental factors. These factors (“selection pressures”) either favor or inhibit the survival and reproduction of specific species which comprise the guild at each site, thus changing species diversity, relative abundance, or the other observed measures of guild structure and composition.Elmer’s explanation is:??????????

I'm afraid you appear to be making a lot of noise with little substance, Elmer. I thought better of you. Simply answer the question posed in the post: what mechanism do you propose that explains the observation I outlined? We know you think natural selection is vacuous. Now tell us what the alternative is. Then, perhaps, we can go back and discuss why you think the concept has no merit. Okay?Just a quick note on "random" vs "non-random" in the context in which I used it. The effect of the various environmental factors on the guild is NOT random in the sense that the outcome will vary all over the place. Whereas we may not be able to actually predict the specific outcome (due to the complexity of the variables and their interactions, not because of randomness) the actual observations in the field conducted by myself and other scientists demonstrate beyond reasonable doubt that the guild composition of the Scarabaeinae can be directly and positively correlated to the environmental factors present at each microsite. IOW, it is at least partially (and I think mostly) deterministic. Else why would changes in the factors correlate so precisely to changes in composition, and why would we be able to use these organisms as effective surrogates for monitoring biodiversity?Answer the question posed in my previous post, then maybe we can go on to something else besides your repetitious rant against natural selection.

Nope, doesn't work that way. I gave you a scientific observation, then asked the question about a mechanism to explain the observation. I then did you the courtesy of providing my explanation. Once you get around to providing yours, then we can move forward. Your repeated attempts to avoid addressing the specific example provided aren't doing your cause much good, because it is starting to appear you don't actually have an explanation.You're right, I probably will get tired of you beating around the bush and avoiding the question. I have a low tolerance for evasion.

Exactly. This is the explanation that fits the observation perfectly: a fairly straight-forward application of the concept of natural selection as accepted by biologists, ecologists, and others of that ilk, including me. Because of the sensitivity to environmental change of the organisms in question, subtle differences in conditions at different microsites along an ecological gradient either select for or select against (depending on how you want to look at it) different species of this subfamily, thus changing the guild composition at each location. I'm not sure how fine-grained the studies have been, but certainly in general terms this is the case - hence their utility for biodiversity studies.And therein lies the rub: Elmer has, in multiple threads, completely discounted the concept of natural selection. He terms it vacuous, empty, circular, and many other epithets. Although he has yet to provide any substance supporting those assertions beyond rhetoric and constant repetition, all the conversations thus far have degenerated into little more than "is too", "is not" infantile posturing. So my goal with my example was to present a quite replicable (and replicated) observation, and then ask him to provide an explanation or mechanism that explains the observation that is better than natural selection. IOW, if natural selection is meaningless scientifically, then there must be another explanation for the observation. As you can see from the discussion up to this point, Elmer is doing his absolute best to avoid providing that. It surely must give any reader cause to believe there is no such explanation.I plan on giving it one more go-around, then bagging the conversation with the conclusion that there is nothing of substance on the other side.

Since he's posted to another thread in the last day or so, and this thread has dropped to the fourth page.