Hyena

Hi everyone, I have a general question-ish/ proposition, but more or less I would like this thread to serve as a sort of disorganized compendium of thoughts related to specific questions of what I want to call evolutionary plasticity. What I mean by evolutionary plasticity is basically an account of the differences in evolutionary histories (speed of evolution, outcomes, influences) of whatever lineage you may imagine. I'm interested in what drives evolution, and how these different driving forces may alter the outcome of a particular situation. My question is sort of a long-winded one, and it's difficult for me to ask without giving some back-story first. I was thinking about the differences in life-histories of birds, and that some birds, after they hatch are basically ready to leave the nest (precocial, like ducklings) and other birds are born blind and helpless (altricial, like many songbirds). These birds thus have very different life-histories, related to feeding and predation and protection of the nest and everything else that accompanies these two strategies. From my understanding of evolution, there was a common ancestor of these two types of strategies, that may have had a similar life-history pattern or may have been different (I'm not interested in the specifics of the basal lineage). However, at some point there must have been a divide between the precocial strategy and the altricial strategy. Perhaps it was some sort of intermediate strategy, of which which I'm sure there are examples present today. I'm assuming that slight variations in these strategies (a chick is born with slightly more feathers, or less developed, etc.) must have existed and over time diverged into what we see now. However, these two strategies are so different that they impact the behavior, ecology, etc. of the species that use them, and now it is to the point that a clutch of duck eggs isn't going to have any altricial ducklings, and vice versa. Essentially, there is little to no variation anymore on this trait, yet at one time it was a driving force of evolution that at some point must have had some phenotypic flexibility. My main general question is this (assuming what I've said makes sense): "What explains the variability of a trait in the past that is no longer variable?" In other words, why don't we see variation in a trait that at one point must have been variable? I'm sure there are exceptions, and really I don't think this is even a valid question, because it's probably presuming something that isn't always true. I don't know enough about birds to know whether or not the trait I've chosen is a good example to set the stage, but nevertheless, it got me thinking. I want you guys to think and ask questions too!

Aye, thank you. I didn't think I had a novel idea in that regard. More or less just an observation that, at least with my education on the matter, is sometimes... overlooked. So, then, the aforementioned debate as to whether or not DNA alters itself is correct? It does so indirectly through 'host' co-evolution with the environment. And, possibly (probably) off-topic, what, if anything, is there to say about this co-evolution when considering introduced species and their successes? Is it an underlying trait of successful invasives to more readily capitalize on the changes associated with the co-evolution of species and environment? On another, more personal note, I apoligize for coming across as arrogant or entitled to this idea, if it is indeed the case that I have done so. I just enjoy thinking about this kind of stuff, and as such, my passion for the subject sometimes tends to accidentally project an air of superiority. I do admit that I often get ahead of myself, sometimes to the point of reiterating ideas conceptualized long before my time. I'm just uncovering the same thoughts that others before me have understood with the same level of intensity and enthusiam, because that's what I like to do. -Hyena

I think the difference between my hypothesis and standard Darwinian theory is the incorporation of a self-perpetuated selection loop. That probably makes no sense. What I am trying to describe is the relationship between the agent (in this case, any organism) and its manipulation of the environment; a loop exists between agent and interactions with the environment. The organism changes the environment in a way that creates a more optimal environment for its causes* (reproductive success) and in turn, alters the way that natural selection drives evolution for that species (and others in the same environment, as well). Really, the only difference between my hypothesis and Darwin's is that I'm considering the changes that any organism may implement on its surroundings, which in turn alter Natural Selection over a longer period of time. The result is that species evolve to be suited for their habitat not only through random genetic mutations selected for by the environment (and certainly not through changes in that specific organism in its own lifetime, as you think I've been suggesting), but also indirectly through the changes that organism incurs to the environment (because the environment, Natural Selection, drives evolution). It is not so much a novel hypothesis(?) as it is a proposed consequence of Natural Selection combined with agent-based environmental change. Since all organisms alter their environment in some way, I think that this consequence, if it holds true, is important when considering the evolutionary history of all organisms. *An important caveat is that changes made to the environment are not necessarily beneficial to the organism. However, it still holds that these changes direct the 'direction' of Natural Selection (with the understanding that Natural Selection is in fact directionless, but for lack of a better word). -Hyena

I understand that most of the genome evolves neutrally. What is it, +90% of all mutations result in neutral or deleterious changes? I am not arguing that. But, consider, chad, that despite this fact you have just presented, evolution still occurs. Phenotypic change can only be the result of a change in the genetic code, which is, as we all know, either the result of mutations, epigenetic impacts, or viral incorporation (as far as novel genetic material is concerned), or the result of natural selection (as far as 're-assortment' of pre-existing DNA is concerned ie. no new genetic material). Natural selection is the driver of evolution, yet it rarely directly impacts the genetic code, as far as changing what is written, so to speak. Yet how is it that a hummingbird's beak fits perfectly into the flower to get nectar and pollinate the plant? Yes, the genetic material responsible for coding for these specific phenotypes was the result of (most likely) neutral evolution, but the fine-tuning, so to speak, is the result of natural selection; birds with sleeker beaks could get more nectar, and in turn, those birds had more offspring. The chain continues, as specific DNA is selected for by the environmen ie the plant that the bird feeds on. So, consider a situation where the organism actually manipulates its own environment. All organisms do it; otherwise there would be no interactions, they could not eat, drink, build a nest, etc. Would not natural selection also impact these interactions, the same interactions that were originated by the organism, and traceable back to that organism's genetic code? In response to the next question I will delve more deeply into specific situations, but consider these points: -All organisms interact with their environment -Behaviour (interactions) is due to chemical, physiological, mechanical constraints -Constraints are induced by availability of genetic material (ie an organism's genetic makeup determines what it can and cannot do) -Environment, through natural selection, drives evolution -Interactions between organisms and environement drive environmental change We see a loop where organisms interact with their environment, and the environment selects for individuals with the highest reproductive success. Therefore, organisms will be the most successful if they can manipulate the environmen to give them the highest total reproductive success. These manipulations are due to the genetic code. So, it follows that DNA is using its 'host' as a proxy to select for the most reproductively successful individuals, to continue passing on the DNA. In short, the point that new genetic material is the result of random mutations is moot. It is not Lamarkian. It is simply Natural Selection. Individuals with the highest propensity to pass on their genes survive, and their offspring will thus have a better chance to pass off their genes. It is assumed that these individuals have some advantage (ie reproductive success) over their competitors, otherwise it would be a case of neutral evolution, or genetic drift, or something of that sort. If the attributes responsible for increasing reproductive success are ones that capitalize on sellf-inflicted changes in the environment, then it follows that the genes that code for the behaviour that modifies the environment in such a way are effectively altering natural selection to continue to select for the reproduction of individuals with those genes (both ones that incite initial modificational behaviour and ones that capitalize on the results of that behaviour). Lamarck posited more of an epigenetic approach (which is, as we continue to understand more and more, accurate in some instances), whereby organisms changed during their lifetime and passed on those changes to their offspring. I am suggesting no such thing. I'm enjoying this thoroughly. Please continue to question! -Hyena Edit: Ah! Evidence! I've not the time at this exact moment. I have... obligations. But, in my next post, (or if I can edit this one still when I have time again) I will provide you with ample evidence, hopefully.

It's both. I apologize for the confusion - I often feel the need to be more specific when trying to explain concepts that to me are difficult to understand. I'm proposing that DNA directs selection on itself through the processes of Natural Selection, using the 'host' as its vector of sorts. On a side note, I'm not so used to communicating these ideas to people who actually have a good grasp on the concept of evolution and Natural Selection, so I beg your pardon with my mostly unneccesary reiteration. I'm simply trying to continue on the 'template altering template' idea posted before me. The idea that the genome indirectly alters itself through the actions of the organism. I'm playing with two ideas here: one is that the organism isn't much more as a walking sack of DNA, ultimately subject to what's written in its genetic code, and secondly that the genetic code, through Natural Selection, alters itself. It's quite the same as what one would observe in your typical case of natural selection, but there is one more layer of complexity involved. Rather than, let's say, a species evolving over time due to uncontrollable agents in its environment, that species evolves due to controllable agents in its environment, ie the changes that it has made. Thus I incorporated the whole ecosystem engineer idea, because it's the most plain to see. Those organisms obviously alter their environment in easily observable physical ways. Of course the most successful species (and in turn, the most successful 'strain' of genes) will capitalize on these changes. I apologize for my point being lost in my verbosity (as unfortunately is often the case), but the main point I was trying to configure is that there exists a positive feedback loop between organisms and their interactions with the environment, and that this feedback loop is subject to change via Natural Selection; in essence, organisms are increasing the pressure of Natural Selection on themselves. I fear that the misunderstandings have arisen when I continued on this path, talking about how the DNA is the root of these interactions with the environment. For this I apologize. I hope this clears a few things up. Please feel free to continue to ask question, or PM me (if that's a thing here). -Hyena

First, I want to acknowledge that this is an interesting and important thread. Props, OP. I understand that this is a 9-yr old thread. This caught my attention: I have a bit of an... obsession with feedback loops. Your observation piques my interest, and I, lately, have been tinkering with my own ideas as to how one could explain something like this. I'm assuming that by 'template alter the template', you mean that DNA (or whatever means of propagating genetic information) alters itself in a way that allows for further success (read: continued "existence" of that biological molecule). If I understand correctly, your question is asking how DNA can react to itself, in a way. How can DNA continue to make changes to itself over the course of time to continue to be successful, biologically speaking? This is a bona-fide positive feedback loop. To answer your question, I must first preface that it is not a simple answer. In fact, it is not an answer at all, but just a couple ideas I've strung together that could help to shed some light on the issue. The first idea to consider is that of 'Ecolgical Perception', or in philosophy, as it is called, Direct Perception. It is the idea that organisms react solely to the information given to them by their environment. Action is preceded by interpretation - cause and effect, if you will - and thus whatever the agent can identify/percieve, it can act accordingly. What use does this have when considering your question? From one of my writings: "If it is the case that an organism is substantiated through the results of its own actions, and therefore its actions in reponse thereafter, then there exists some positive feedback loop in which the responses to the effects of said organism's actions interact with its previous responses. That is to say, how an organism responds to its environment is in some way intrinsically tied to how it responded before." This is from a line of thought dealt with a little more in depth here, where I consider a term I've coined an invasive loop if you will, or a sel-fulfilling prophecy: autopropagation (initially developed through consideration of a universal set of traits inherent in invasive species). The idea is that a successful species capitalizes on the impacts it has made in the environment. As the most observable instance, zebra mussels (or any other ecosystem engineer) literally use themselves as the substrate, using their ability to reproduce quickly and efficiently to their advantage by living rooting themselves to each other. Who better than to utilize self-created niche space than the creator? (population-wise in this instance). The philosophical equivalent is Reciprocal Determinism. So, what does this mean in accordance to 'template altering template', as you've asked? Doesn't the genetic makeup of an organism determine its life history, and in some way its ability to percieve and react to the environment? The ability of zebra mussels to use each other as a substrate is certainly not present in all organisms, and as such, that particular trait is not present in all living things. However, the concept, I argue, is; the ability to capitalize on the changes that organism has made. "In effect, the actions of an organism are determined by the interactions between responses, which are determined by the genetic code; over time, when a population can evolve via natural selection, portions of DNA in that population's genetic background code for the most successful outcomes of these interactions, and thus, the DNA itself is actually indirectly selecting for other portions of DNA through positive feedback loops between organismal behavior and coded responses to implications of that behavior, ie. reciprocal responses" From a link in the OP: "Selfish Gene Theory regards the visible organism (the cat, human, flower, amoeba or whatever) as the host" What better way to ensure (or at least give a better chance of) continuation of genetic code by capitilazing on the changes your 'host' has made in the environment? Not to say that it is a conscious effort of DNA to replicate and choose to do such a thing, but if it is indeed a successful (assuming it actually exists) blueprint, then its place in evolution wouldn't be surprising. -Hyena

For your question, should it matter? Even if all nitrogen from the soil is utilized by the clover, would it not then return to fixation of atmospheric nitrogen? Assuming there is enough N produced by the clover to sustain your tree (hoping it's a small one) from its fixation, the result should simply be that the resources available in the soil will be utilized until no more is available - at that point, intake by the tree would be limited to what the clover can produce; if it enough to sustain structural and metabolic processes (mostly implemented towards chlorophyll, methinks), then the tree should at least be able to survive. -Hyena