Re: Maldaptation, Extinction and Natural selection
Warren, If you want succinct, then I believe Endler does the job: If you have: 1. Phenotypic vaiability that 2. comes from genotypic variability, and that gives 3. Differential reproductive success (due to that phenotypic variability). We call this fitness. Then you will have natural selection, which is just a different genotype frequency in subsequent generation. If that continues in the same way for generations, then we are likely to have Evolution by Natural Selection. These are all necessary and sufficient conditions for natural selection. We can also see that fitness differences CAN come from competition, but they do not HAVE to. And, we must remember that while Darwin coined the term, he knew nothing of genetics, which has come a long way since then. And, there was the New Synthesis that put Darwin's ideas into a more modern framework, with Fischer, White, Mayr. And, then, we have Dawkins and Gould, who might have argued between themselves, but who, by reading, WE can all come to understand evolution better. Cheers, Jim Warren W. Aney wrote: I've been trying to follow this discussion with little profit until I read this last posting from Wirt Atmar. This is the most intelligent, succinct, evocative and accesible (and inspiring) explanation I've ever read on the topic of basic evolution. Maybe it's old-hat to evolutionary biologists, but it's going to be part of this wildlife ecologist's permanent lexicon. Thanks, Wirt, for persisting on this topic. Warren Aney Senior Wildlife Ecologist Tigard, OR -Original Message- From: Ecological Society of America: grants, jobs, news [mailto:[EMAIL PROTECTED] Behalf Of Wirt Atmar Sent: Tuesday, 18 July, 2006 14:20 To: ECOLOG-L@LISTSERV.UMD.EDU Subject: Re: Maldaptation, Extinction and Natural selection Dan writes: I am not an expert on evolution (far from it) but I have a hunch that relates to Hutchinson's quote and analogy about the evolutionary play in the ecological theater. Let me say that you can do no wrong by reading and memorizing G. Evelyn Hutchinson, and especially his student, Robert MacArthur. The metaphor I tend to use however invokes a different art form, that of a movie. The study of ecology, which entails investigations into the totality of the biotic interactions we find on earth, is like the last, current frame of a movie that has been running at 24 frames per second for the last several hundred years. When we do ecology, we're looking only at the last frame of the movie. Ecology is evolution in now time, captured in the current frame, but no matter how intricately we tease apart the ecological physics of those interactions in this last frame, the interactions will never make complete sense unless they are examined over the course of the entire movie. The ghosts of competitions past, where pronghorn antelope run at high speed from a cheetah that's no longer present on the North American plains, is as good an example as we have of the necessity of imposing time into our studies, making Hutchinson's the evolutionary play in the ecological theater phrase all the more relevant. Why are developing these metaphors important? On one hand, saying all of this is obvious. On the other, these discussions have almost no practical value when you're in the field, taking detailed measurements. But science doesn't mean data. The mathematician Henri Poincare wrote, Science is built of facts the way a house is built of bricks, but an accumulation of facts is no more science than a pile of bricks is a house. Science literally means understanding, and without developing these perspectives, we really don't understand much of anything. Evolving truly accurate mental metaphors and models is fundamental to doing science, of any stripe. Saying this, what then of the idea of the evolutionary algorithm? In that regard, you write: My hunch combined with your analogy below of evolution as algorithm might be considered ecology as operating system. This focuses on ecology at the ecosystem and biosphere level. Your description of the algorithm seems to explain and characterize selection well, but it does not seem to account for 1) generation of novelty, other than via random or error-related mutation, 2) feedbacks that result when the organisms and communities/ecosystems alter the environment and then have to adapt to their own alterations (as studied in niche construction and ecosystem engineers) and 3) the infrastructure and maintenance of elements, energy, materials that make the instantiation or materialization of new forms (actors) possible, participates in juxtaposing them in new plays and cleans up the mess after the play (i.e. decomposition and recycling) so that the theater is not cluttered from past performances. I could convert these to algorithm or application/program vs operating system examples relation
Re: Evolution Environment Adaptation Re: Maldaptation, Extinction and Natural selection
Joerg, I like your analogy, and many studies have compared fitness landscapes to your topography that you describe here. Note, those are fitness landscapes, not Natural Selection landscapes. So, if you are in a wide flat plane, you might compare that to Gould's equilibrium in his context of punctuated equilibrium. That is, no natural selection is taking place. You may go extinct because you run out of space, a disease comes along and so forth, but, no natural selection needs to be taking place. An analogy from maths (where I come from): in global optimization, if you are on a wide flat plane and you have no clue in which direction to go to find the valley, you are stuck with the solution you have at hand. It might be a rather bad one (extinction) but anywhere you turn it doesn't get (much) better. That doesn't mean that in many cases optimization algorithms won't work they do even in quite bad conditions if you have a lot of time to search. So I think it just comes down to the degree of maladaptation versus the likely rate of change. And, we must understand that while adaptation is the process whereby natural selection over time (evolution) forms features that permit organisms to do well, we cannot think that maladaptations are formed by the same process. Accidents (meteors, floods, continental drift, climate change) may make something that was once useful into something that is no longer useful, but the maladaptation was not made for that new scenario through natural selection. So, care must be used in thinking about the process. Cheers, Jim -- - James J. Roper, Ph.D. Universidade Federal do Paraná Depto. de Zoologia Caixa Postal 19020 81531-990 Curitiba, Paraná, Brasil = E-mail: [EMAIL PROTECTED] Phone/Fone/Teléfono: 55 41 33611764 celular: 55 41 99870543 e-fax:1-206-202-0173 (in the USA) = Zoologia na UFPR http://zoo.bio.ufpr.br/zoologia/ Ecologia e Conservação na UFPR http://www.bio.ufpr.br/ecologia/ - http://jjroper.sites.uol.com.br
EVOLUTION Higher concept Re: Maldaptation, Extinction and Natural selection
At 02:19 PM 7/18/2006, Wirt Atmar wrote: In Darwin's alternate universe of death and famine, we unfortunately have a simple, easy-to-understand mechanism, one that does eventually builds the most exalted objects which we are capable of conceiving, the production of the HIGHER [capitals mine, since italics and bold are rejected by the program--WT] animals. Honorable Forum: Many years ago my wife was being interviewed by a radio host. He asked her about how we were BETTER than the other species. We're not better, we're just different, she said. That was one of my proudest moments, in many proud moments, of her long career of simply doing, not bragging (that, obviously, is what I am doing here, entirely without her permission and knowledge, but it's germane to the issue). I can't help but wonder if the evolution of culture was not the ultimate maladaptation, and that the consequences of all population booms is a downslope trend, if not the last frame of the movie called, with ironic arrogance, Homo sapiens sapiens. Doubly wise, indeed! FIN wt
Evolution Environment Adaptation Re: Maldaptation, Extinction and Natural selection
Kim: Excuse my ignorance, but what's the contradiction? WT At 09:36 PM 7/8/2006, Kim van der Linde wrote: Hi all, I am having an interesing discussion at the moment about Natural selection. The context is a single population of individuals that, due to changes in the environment, are now maladapted and the population is reducing in size. Based on the often used definition of differential reproduction, when there is not much to differentiate with, there is no longer differential selection, and as such, no natural selection. However, they are maladapted, so unfit to survive. Any opinions about this nice contradiction? Cheers, Kim -- http://www.kimvdlinde.com
Re: Maldaptation, Extinction and Natural selection
Dan writes: I am not an expert on evolution (far from it) but I have a hunch that relates to Hutchinson's quote and analogy about the evolutionary play in the ecological theater. Let me say that you can do no wrong by reading and memorizing G. Evelyn Hutchinson, and especially his student, Robert MacArthur. The metaphor I tend to use however invokes a different art form, that of a movie. The study of ecology, which entails investigations into the totality of the biotic interactions we find on earth, is like the last, current frame of a movie that has been running at 24 frames per second for the last several hundred years. When we do ecology, we're looking only at the last frame of the movie. Ecology is evolution in now time, captured in the current frame, but no matter how intricately we tease apart the ecological physics of those interactions in this last frame, the interactions will never make complete sense unless they are examined over the course of the entire movie. The ghosts of competitions past, where pronghorn antelope run at high speed from a cheetah that's no longer present on the North American plains, is as good an example as we have of the necessity of imposing time into our studies, making Hutchinson's the evolutionary play in the ecological theater phrase all the more relevant. Why are developing these metaphors important? On one hand, saying all of this is obvious. On the other, these discussions have almost no practical value when you're in the field, taking detailed measurements. But science doesn't mean data. The mathematician Henri Poincare wrote, Science is built of facts the way a house is built of bricks, but an accumulation of facts is no more science than a pile of bricks is a house. Science literally means understanding, and without developing these perspectives, we really don't understand much of anything. Evolving truly accurate mental metaphors and models is fundamental to doing science, of any stripe. Saying this, what then of the idea of the evolutionary algorithm? In that regard, you write: My hunch combined with your analogy below of evolution as algorithm might be considered ecology as operating system. This focuses on ecology at the ecosystem and biosphere level. Your description of the algorithm seems to explain and characterize selection well, but it does not seem to account for 1) generation of novelty, other than via random or error-related mutation, 2) feedbacks that result when the organisms and communities/ecosystems alter the environment and then have to adapt to their own alterations (as studied in niche construction and ecosystem engineers) and 3) the infrastructure and maintenance of elements, energy, materials that make the instantiation or materialization of new forms (actors) possible, participates in juxtaposing them in new plays and cleans up the mess after the play (i.e. decomposition and recycling) so that the theater is not cluttered from past performances. I could convert these to algorithm or application/program vs operating system examples relation to hardware realizations, memory and/or disk space/clutter. Algorithms are great, but for them to work one needs an operating system that can continue to run and allow many programs to run and that is robust and does not itself crash. There is also work by folks following up on Robert Rosen that suggests that much of the essence of life process is non-computable, not algorithmic and non-mechanistic. Some of the work here focuses on ambiguity and circularity, both of which algorithms do not handle well but life seems accustomed to. I previously wrote the evolutionary algorithm as: Given self-reproduction, Darwinian evolution is composed of only these five components: o a bounded arena o a replicating population which must eventually expand beyond the bounds of the arena o thermodynamically inescapable replicative error, guaranteeing variation within the reproducing population o competition for space in that arena among the inevitable variants o the consequential competitive exclusion of the lesser fit But it's important to note that Darwin probably would have said the same thing, if the word algorithm had been in use 150 years ago. What he did write, in the final paragraph of his last chapter in The Origin of Species, was this: It is interesting to contemplate an entangled bank, clothed with many plants of many kinds, with birds singing on the bushes, with various insects flitting about, and with worms crawling through the damp earth, and to reflect that these elaborately constructed forms, so different from each other, and dependent on each other in so complex a manner, have all been produced by laws acting around us. These laws, taken in the largest sense, being Growth with Reproduction; inheritance which is almost implied by reproduction; Variability from the
Re: Maldaptation, Extinction and Natural selection
I've been trying to follow this discussion with little profit until I read this last posting from Wirt Atmar. This is the most intelligent, succinct, evocative and accesible (and inspiring) explanation I've ever read on the topic of basic evolution. Maybe it's old-hat to evolutionary biologists, but it's going to be part of this wildlife ecologist's permanent lexicon. Thanks, Wirt, for persisting on this topic. Warren Aney Senior Wildlife Ecologist Tigard, OR -Original Message- From: Ecological Society of America: grants, jobs, news [mailto:[EMAIL PROTECTED] Behalf Of Wirt Atmar Sent: Tuesday, 18 July, 2006 14:20 To: ECOLOG-L@LISTSERV.UMD.EDU Subject: Re: Maldaptation, Extinction and Natural selection Dan writes: I am not an expert on evolution (far from it) but I have a hunch that relates to Hutchinson's quote and analogy about the evolutionary play in the ecological theater. Let me say that you can do no wrong by reading and memorizing G. Evelyn Hutchinson, and especially his student, Robert MacArthur. The metaphor I tend to use however invokes a different art form, that of a movie. The study of ecology, which entails investigations into the totality of the biotic interactions we find on earth, is like the last, current frame of a movie that has been running at 24 frames per second for the last several hundred years. When we do ecology, we're looking only at the last frame of the movie. Ecology is evolution in now time, captured in the current frame, but no matter how intricately we tease apart the ecological physics of those interactions in this last frame, the interactions will never make complete sense unless they are examined over the course of the entire movie. The ghosts of competitions past, where pronghorn antelope run at high speed from a cheetah that's no longer present on the North American plains, is as good an example as we have of the necessity of imposing time into our studies, making Hutchinson's the evolutionary play in the ecological theater phrase all the more relevant. Why are developing these metaphors important? On one hand, saying all of this is obvious. On the other, these discussions have almost no practical value when you're in the field, taking detailed measurements. But science doesn't mean data. The mathematician Henri Poincare wrote, Science is built of facts the way a house is built of bricks, but an accumulation of facts is no more science than a pile of bricks is a house. Science literally means understanding, and without developing these perspectives, we really don't understand much of anything. Evolving truly accurate mental metaphors and models is fundamental to doing science, of any stripe. Saying this, what then of the idea of the evolutionary algorithm? In that regard, you write: My hunch combined with your analogy below of evolution as algorithm might be considered ecology as operating system. This focuses on ecology at the ecosystem and biosphere level. Your description of the algorithm seems to explain and characterize selection well, but it does not seem to account for 1) generation of novelty, other than via random or error-related mutation, 2) feedbacks that result when the organisms and communities/ecosystems alter the environment and then have to adapt to their own alterations (as studied in niche construction and ecosystem engineers) and 3) the infrastructure and maintenance of elements, energy, materials that make the instantiation or materialization of new forms (actors) possible, participates in juxtaposing them in new plays and cleans up the mess after the play (i.e. decomposition and recycling) so that the theater is not cluttered from past performances. I could convert these to algorithm or application/program vs operating system examples relation to hardware realizations, memory and/or disk space/clutter. Algorithms are great, but for them to work one needs an operating system that can continue to run and allow many programs to run and that is robust and does not itself crash. There is also work by folks following up on Robert Rosen that suggests that much of the essence of life process is non-computable, not algorithmic and non-mechanistic. Some of the work here focuses on ambiguity and circularity, both of which algorithms do not handle well but life seems accustomed to. I previously wrote the evolutionary algorithm as: Given self-reproduction, Darwinian evolution is composed of only these five components: o a bounded arena o a replicating population which must eventually expand beyond the bounds of the arena o thermodynamically inescapable replicative error, guaranteeing variation within the reproducing population o competition for space in that arena among the inevitable variants o the consequential competitive exclusion of the lesser fit But it's important to note that Darwin probably would have said the same thing, if the word
Re: Maldaptation, Extinction and Natural selection
All, I think this question is important, in that apparently there are a variety of opinions out there as to what Natural Selection does and does not. In all this discussion, nobody that believes NS favors extinction has put NS into a logical framework (premises, assumptions, - basically, a syllogism) that would explain the process. AND, it seems to me that most that opine that NS favors extinction, seem also to think that extinction only occurs by evolution by NS. I would say that extinction can occur for many reasons that have nothing to do with natural selection. In today's world, habitat loss, disease, exploitation, and so on. Probably was true in the past as well. It is not true that every extinction was the result of a struggle between a winning species and a losing species. The syllogism that best explains (in my book) NS is the following: IF 1. Individuals vary phenotypically for some trait or traits, AND 2. Those traits are due to genotypic variability, AND 3. Fitness is associated with those phenotypic trait or traits, THEN, Individuals with the trait associated with greater fitness will leave MORE genes of that phenotypic trait in subsequent generations. Ergo, Natural Selection. If conditions favor that same process for many generations, we are likely to have evolution by natural selection. And, remember, phenotypic variation may be only environmental. Now, I would say, with this syllogism, just like the expression SH__ HAPPENS we can say extinction happens with or without natural selection. . Finally, we can think of evolution by natural selection as a process that generates adaptations. Adaptations are advantages given a certain set of environmental circumstances. Sure, adaptations in the wrong circumstances can become hindrances, but natural selection did not make them to hinder the organism. Rather circumstances changed (Ice Age, for example). Difficult to imagine natural selection favoring a maladaptation Fitness is defined as differential reproductive success, not natural selection. Cheers, Jim Jane Shevtsov wrote: Imagine a stable population in which a favorable new genotype has appeared and is increasing. That sure looks like selection FOR the new genotype to me. On the other hand, if we start with the same population and change the environment so some of the old genotypes no longer do well, I'd call that selection AGAINST those genotypes. This is all just semantics. If confused, stick to differential reproduction. Jane At 07:16 AM 7/13/2006, Malcolm McCallum wrote: Am I understanding you correct? =20 Natural Selection selects against unfavorable phenotypes. Sexual Selection selects for favorable phenotypes. =20 =20 =20 VISIT HERPETOLOGICAL CONSERVATION AND BIOLOGY www.herpconbio.org = http://www.herpconbio.org=20 A New Journal Published in Partnership with Partners in Amphibian and = Reptile Conservation and the World Congress of Herpetology. =20 Malcolm L. McCallum Assistant Professor Department of Biological Sciences Texas AM University Texarkana 2600 Robison Rd. Texarkana, TX 75501 O: 1-903-223-3134 H: 1-903-791-3843 Homepage: https://www.eagle.tamut.edu/faculty/mmccallum/index.html =20 From: Ecological Society of America: grants, jobs, news on behalf of = James J. Roper Sent: Thu 7/13/2006 6:37 AM To: ECOLOG-L@LISTSERV.UMD.EDU Subject: Re: Maldaptation, Extinction and Natural selection But Wirt, Natural selection doesn't cull but rather it favors. And selecting for something is very different than selecting against something.=20 Favoring a trait leads to adaptation. That is, those with a trait leave more descendents. Even so, it is not that simple. At any rate, John Endler does a wonderful job of clearing things up with Natural Selection in the Wild and I highly recommend it for anyone who has not read it, and, don't forget, The Extended Phenotype by Dawkins, that should also be required reading. Interpreting literally what I wrote leads to a condition that I = normally rail against myself. Selection never selects for anything. Selection = operates only as a culling mechanism, removing the least appropriate, least = competitive phenotypes of the demic excess that currently fills the competitive = arena. =20 What the heck does demic excess really mean? Cheers, Jim == The whole person must have both the humility to nurture the Earth and the pride to go to Mars. --Wyn Wachhorst, The Dream of Spaceflight Jane Shevtsov co-founder, http://www.worldbeyondborders.org/World Beyond Borders visit my blog, http://perceivingwholes.blogspot.com/Perceiving Wholes Perhaps one day... the world, our world, won't be upside down, and then any newborn human being will be welcome. Saying, Welcome. Come. Come in. Enter. The entire
Re: Maldaptation, Extinction and Natural selection
Jim writes: But Wirt, Natural selection doesn't cull but rather it favors. And selecting for something is very different than selecting against something. Favoring a trait leads to adaptation. That is, those with a trait leave more descendents. Even so, it is not that simple. At any rate, John Endler does a wonderful job of clearing things up with Natural Selection in the Wild and I highly recommend it for anyone who has not read it, and, don't forget, The Extended Phenotype by Dawkins, that should also be required reading. Let me try one more time, if you don't mind. To do that, let me begin at the beginning and write evolution as an algorithm. Given self-reproduction, Darwinian evolution is composed of only these five components: o a bounded arena o a replicating population which must eventually expand beyond the bounds of the arena o thermodynamically inescapable replicative error, guaranteeing variation within the reproducing population o competition for space in that arena among the inevitable variants o the consequential competitive exclusion of the lesser fit If resources are more abundant than the population's current demands, then, as a first order approximation, there is no effective competition among the population's members, thus there is no selection. The competitive exclusion of the least fit only begins in earnest when the resource space fills. These few statements are the essence of Darwinian evolutionary ecology. THE NATURE OF SELECTION Let me apologize for stating the obvious, but given the comments on the list, I thought it best to be as clear as possible. However, the simplicity of the evolutionary algorithm doesn't mean that it can't be substantially misinterpreted. In that regard, Malcolm asked a pertinent question: Am I understanding you correctly? Natural Selection selects against unfavorable phenotypes. Sexual Selection selects for favorable phenotypes. No, unfortunately, you are misunderstanding me. The selective processes of sexual and natural selection are similar, but the agents of selection are quite different. They are similar however in that they both act to cull the least appropriate individuals from the population. Natural selection can be said to be the consequence of all of the extrinsic forces that impinge on a population, but sexual selection is quite different, startlingly so if you think about it for a minute. It is a mechanism of selection that was invented within the phyletic lineage. It is a form of selection which the lineage imposes on itself, and it can be quite intense. Two forms of error bedevil populations. They can be described as: o design error o manufacturing error NATURAL SELECTION CORRECTS DESIGN ERRORS Design error is associated with the population not being currently centered on a local optimum, and thus rendering a population not as competitive as it might be. Design error is quickly mitigated however by selection inexorably moving the population across an apaptive topography to that point of maximum optimality that is achievable in the current situation. This movement is accomplished by constantly culling the least appropriate (fit) of the excess population (that inevitable fraction of the population above the carrying capacity of the current arena). At every stage of this evolutionary movement, fitness is a relative quality. Some phenotypic trials will be more competitive than others, and their stochastic survival is more likely than their less-competitive conspecifics. I earlier gave the examples of longer tarsal hairs in barn flies and a 32 base-pair deletion in an allele of the CCR5 chemokine receptor in humans as simple, point mutation instances that allowed populations to move extremely rapidly in the face of a drastically changed environment. Because these examples are so simple, it seems perfectly reasonable to say that selection is selecting for these properties, but this is not the normal condition, nor does it present an accurate representation of the evolutionary process. The interaction of a lineage's underlying genetic code with its manufactured phenotypes is an extraordinarily complex process, being both highly polygenic and pleiotropic. Because of this, selection cannot select for any single quality in isolation of the remainder of the genotype. Rather, evolutionary movement across an adaptive topography, as exemplified by the onset of either endemism or the full speciation of a population as the lineage partitions a new niche for itself, must involve a genotypic revolution, precisely as Ernst Mayr argued. SEXUAL SELECTION MITIGATES MANUFACTURING ERROR The second form of error is manufacturing error. Although design error can be effectively quelled by natural selection moving a population to a new point of optimality, manufacturing error is inevitable and persistent, even when
Re: Maldaptation, Extinction and Natural selection
But Wirt, Natural selection doesn't cull but rather it favors. And selecting for something is very different than selecting against something. Favoring a trait leads to adaptation. That is, those with a trait leave more descendents. Even so, it is not that simple. At any rate, John Endler does a wonderful job of clearing things up with Natural Selection in the Wild and I highly recommend it for anyone who has not read it, and, don't forget, The Extended Phenotype by Dawkins, that should also be required reading. Interpreting literally what I wrote leads to a condition that I normally rail against myself. Selection never selects for anything. Selection operates only as a culling mechanism, removing the least appropriate, least competitive phenotypes of the demic excess that currently fills the competitive arena. What the heck does demic excess really mean? Cheers, Jim -- - James J. Roper, Ph.D. Universidade Federal do Paraná Depto. de Zoologia Caixa Postal 19020 81531-990 Curitiba, Paraná, Brasil = E-mail: [EMAIL PROTECTED] Phone/Fone/Teléfono: 55 41 33611764 celular: 55 41 99870543 e-fax:1-206-202-0173 (in the USA) = Zoologia na UFPR http://www.bio.ufpr.br/zoologia/ Ecologia e Conservação na UFPR http://www.bio.ufpr.br/ecologia/ - http://jjroper.sites.uol.com.br
Re: Maldaptation, Extinction and Natural selection
Am I understanding you correct? =20 Natural Selection selects against unfavorable phenotypes. Sexual Selection selects for favorable phenotypes. =20 =20 =20 VISIT HERPETOLOGICAL CONSERVATION AND BIOLOGY www.herpconbio.org = http://www.herpconbio.org=20 A New Journal Published in Partnership with Partners in Amphibian and = Reptile Conservation and the World Congress of Herpetology. =20 Malcolm L. McCallum Assistant Professor Department of Biological Sciences Texas AM University Texarkana 2600 Robison Rd. Texarkana, TX 75501 O: 1-903-223-3134 H: 1-903-791-3843 Homepage: https://www.eagle.tamut.edu/faculty/mmccallum/index.html =20 From: Ecological Society of America: grants, jobs, news on behalf of = James J. Roper Sent: Thu 7/13/2006 6:37 AM To: ECOLOG-L@LISTSERV.UMD.EDU Subject: Re: Maldaptation, Extinction and Natural selection But Wirt, Natural selection doesn't cull but rather it favors. And selecting for something is very different than selecting against something.=20 Favoring a trait leads to adaptation. That is, those with a trait leave more descendents. Even so, it is not that simple. At any rate, John Endler does a wonderful job of clearing things up with Natural Selection in the Wild and I highly recommend it for anyone who has not read it, and, don't forget, The Extended Phenotype by Dawkins, that should also be required reading. Interpreting literally what I wrote leads to a condition that I = normally rail against myself. Selection never selects for anything. Selection = operates only as a culling mechanism, removing the least appropriate, least = competitive phenotypes of the demic excess that currently fills the competitive = arena. =20 What the heck does demic excess really mean? Cheers, Jim -- - James J. Roper, Ph.D. Universidade Federal do Paran=E1 Depto. de Zoologia Caixa Postal 19020 81531-990 Curitiba, Paran=E1, Brasil =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D E-mail: [EMAIL PROTECTED] Phone/Fone/Tel=E9fono: 55 41 33611764 celular: 55 41 99870543 e-fax:1-206-202-0173 (in the USA) =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D Zoologia na UFPR http://www.bio.ufpr.br/zoologia/ Ecologia e Conserva=E7=E3o na UFPR http://www.bio.ufpr.br/ecologia/ - http://jjroper.sites.uol.com.br
Re: Maldaptation, Extinction and Natural selection
SWYgSSB1bmRlcnN0YW5kIHRoaXMgY29ycmVjdGx5OyB0aGUgaW5pdGlhbCBzY2VuYXJpbyBkZXNj cmliZXMgYSByZWR1Y3Rpb24Kb3IgZWxpbWluYXRpb24gaW4gcGhlbm90eXBpYyB2YXJpZXR5IGlu IGEgc2luZ2xlIHBvcHVsYXRpb24gdGhhdCBpcyB0aGVuCnJlbmRlcmVkIHVucHJlcGFyZWQgZm9y IHNvbWUgaW1tZWRpYXRlIGVudmlyb25tZW50YWwgb3IgZWNvbG9naWNhbCBjaGFuZ2UgKAppLmUu IG1hbGFkYXB0ZWQpLiAgVGhpcyBzb3VuZHMgbGlrZSBhbiBlZmZlY3Qgb2YgaW5icmVlZGluZywg YnV0IGl0IGNvdWxkIGJlCmFuIG9yZ2FuaXNtIHdpdGggYSB2ZXJ5IHNwZWNpZmljIG5pY2hlIHRo YXQgaGFzIGxpbWl0ZWQgdmlhYmlsaXR5LgoKVGhlcmUgYXJlIGFuIGluY3JlYXNpbmcgbnVtYmVy IG9mIGV4YW1wbGVzIHdlcmUgaW5icmVlZGluZyBwbGF5cyBhIHJvbGUgaW4KZGVtaWMgZXh0aXJw YXRpb24uIEhldGVyb2NlcGhhbHVzIGdsYWJlciwgYW4gZXhjZXB0aW9uIHRvIHRoaXMgcnVsZSwg Y2FuCnRvbGVyYXRlIGVsZXZhdGVkIGluYnJlZWRpbmcgaW4gcGFydCBkdWUgdG8gdGhlIGNsaW1h dGljIHN0YWJpbGl0eSBvZiBpdHMKZm9zc29yaWFsIGV4aXN0ZW5jZS4gIFVyc3VzIG1hcml0aW11 cyBwb3B1bGF0aW9ucywgYnkgY29tcGFyaXNvbiwgYXJlIG1vcmUKZ2VuZXRpY2FsbHkgZGl2ZXJz ZSBidXQgdGhleSBhcmUgbW9yZSB2dWxuZXJhYmxlIGNsaW1hdGUgY2hhbmdlIG93aW5nIHRvCnRo ZWlyIGhpZ2ggZGVncmVlIG9mIGVjb2xvZ2ljYWwgYW5kIGRpZXRhcnkgc3BlY2lhbGl6YXRpb24u CgpOYXR1cmFsIHNlbGVjdGlvbiBkZXNjcmliZXMgdGhlIHByb2Nlc3Mgb2YgZXZvbHV0aW9uIHdo aWNoIGluY2x1ZGVzCmV4dGluY3Rpb24gYXMgd2VsbCBhcyBzdXJ2aXZhbC4gIERlbGV0ZXJpb3Vz IGluYnJlZWRpbmcgZWZmZWN0cyBsZWFkaW5nIHRvCmdlbm90eXBpYyBob21vZ2VuZWl0eSBhcmUg d2VsbCB1bmRlcnN0b29kLiBUaGUgcm9sZSBvZiBwaGVub3R5cGUgYW5kIG5pY2hlCm9jY3VwYXRp b24gaW4gZXh0aW5jdGlvbiBldmVudHMgaXMgY2xlYXJseSBkZW1vbnN0cmF0ZWQgYXQgdGhlIEsv VApib3VuZGFyeS4gIElmIGEgcG9wdWxhdGlvbiAid2lua3Mgb3V0IiBvciBhIHNwZWNpZXMgZ29l cyBleHRpbmN0LCBzb21ldGhpbmcKd2lsbCBldmVudHVhbGx5IHJlcGxhY2UgaXQgYXMgbG9uZyBh cyB0aGUgbmljaGUgZXhpc3RzLgoKTWF5YmUgdGhlIHF1ZXN0aW9uIG9mICJjb250cmFkaWN0aW9u IiB3aXRoICJuYXR1cmFsIHNlbGVjdGlvbiIgY291bGQgYWxzbyBiZQpjb25zaWRlcmVkIHdpdGgg cmVzcGVjdCB0byBzY2FsZT8gIENhbiBhIHdob2xlIHN5c3RlbSBiZSBtYWxhZGFwdGVkPwpEaW5v c2F1cnMgbWlnaHQgYWdyZWUgdG8gdGhpcy4KCkppbSBTcGFya3MKCk9uIDcvMTIvMDYsIEphbWVz IEouIFJvcGVyLCBQaC5ELiA8ampyb3BlckBnbWFpbC5jb20+IHdyb3RlOgo+Cj4gPiBJdCBzZWVt cyB0byBtZSBhIGJpdCBhcmJpdHJhcnkgdG8gYWNjZXB0IHRoYXQgbmF0dXJhbCBzZWxlY3Rpb24g aXMKPiA+IHRha2luZyBwbGFjZSB3aGVuIGEgY2VydGFpbiBmcmFjdGlvbiBvZiBpbmRpdmlkdWFs cyBhcmUgc2VsZWN0aXZlbHkKPiA+IGN1bGxlZCBmcm9tIGEgcG9wdWxhdGlvbiwgeWV0IHdoZW4g dGhhdCBmcmFjdGlvbiByZWFjaGVzIDEwMCUgdGhhdAo+ID4gc29tZXRoaW5nIGRpZmZlcmVudCBp cyBuZWNlc3NhcmlseSBnb2luZyBvbi4gVG8gYmUgc3VyZSwgdGhlIFJFU1BPTlNFCj4gPiBvZiBh IHBvcHVsYXRpb24gdG8gbmF0dXJhbCBzZWxlY3Rpb24gd2hlbiBtb3J0YWxpdHkgaXMgMTAwJSB3 aWxsIGJlIGEKPiA+IG1vb3QgcG9pbnQgKHVubGVzcyBvbmUgaXMgY29uc2lkZXJpbmcgc2VsZWN0 aW9uIG9mIGhpZ2hlciBzY2FsZQo+ID4gZW50aXRpZXMsIGRhcmUgSSBzYXkgZ3JvdXBzPyksIGJ1 dCB0byBkZW55IHRoYXQgdGhlIHNhbWUgcHJvY2Vzc2VzIGFyZQo+ID4gYXQgd29yayBzZWVtcyBs aWtlIGEgYmlkIGZvciBzcGVjaWFsIHRyZWF0bWVudC4KPiBJbmRpdmRpdWFscyBhcmUgbm90IHNl bGVjdGl2ZWx5ICJjdWxsZWQiIGZyb20gYSBwb3B1bGF0aW9uLCBidXQgcmF0aGVyCj4gdGhleSBs ZWF2ZSBmZXdlciBkZXNjZW5kYW50cyB0aGFuIG90aGVycy4KPgo+IEkgd291bGQgc2F5IHRoYXQg YSBwb3B1bGF0aW9uIGRlY2xpbmUgaXMgcHJvYmFibHkgY29tcGxldGVseSBpbmRlcGVuZGVudAo+ IG9mIG5hdHVyYWwgc2VsZWN0aW9uLCBpbiB0aGF0IHNvbWV0aGluZyBlbHNlIGlzIGNhdXNpbmcg dGhlIGRlY2xpbmUuCj4gTmF0dXJhbCBzZWxlY3Rpb24gaXMgb25seSBhYm91dCB0aGUgZGlmZmVy ZW50aWFsIHJlcHJlc2VudGF0aW9uIG9mIGdlbmVzCj4gaW4gc3Vic2VxdWVudCBnZW5lcmF0aW9u cywgaW4gd2hpY2ggc29tZSBpbmRpdmlkdWFscyB3aXRoIHNvbWUgdHJhaXRzCj4gbGVhdmUgbW9y ZSBkZXNjZW5kZW50cyAtIFdIRU4gbmF0dXJhbCBzZWxlY3Rpb24gaXMgb2NjdXJpbmcuCj4KPiBT bywgbXkgcG9pbnQgaGFzIG5vdGhpbmcgdG8gZG8gd2l0aCBob3cgbWFueSBpbmRpdmlkdWFscyBh cmUgaW52b2x2ZWQuCj4gQmVzaWRlcywgbmF0dXJhbCBzZWxlY3Rpb24gd29ya3Mgd2l0aCBpbmRp dmlkdWFscywgbm90IHBvcHVsYXRpb25zLi4uCj4KPiBDaGVlcnMsCj4KPiBKSW0KPgo+IC0tCj4g LS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0tLQo+IEphbWVzIEouIFJvcGVyLCBQ aC5ELgo+IFVuaXZlcnNpZGFkZSBGZWRlcmFsIGRvIFBhcmFu77+9Cj4gRGVwdG8uIGRlIFpvb2xv Z2lhCj4gQ2FpeGEgUG9zdGFsIDE5MDIwCj4gODE1MzEtOTkwIEN1cml0aWJhLCBQYXJhbu+/vSwg QnJhc2lsCj4gPT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PQo+IEUtbWFpbDog ICAgICAgICAgICAgampyb3BlckBnbWFpbC5jb20KPiBQaG9uZS9Gb25lL1RlbO+/vWZvbm86ICAg NTUgNDEgMzM2MTE3NjQKPiBjZWx1bGFyOiAgICAgICAgICAgICAgIDU1IDQxIDk5ODcwNTQzCj4g ZS1mYXg6ICAgIDEtMjA2LTIwMi0wMTczIChpbiB0aGUgVVNBKQo+ID09PT09PT09PT09PT09PT09 PT09PT09PT09PT09PT09PT09PT0KPiBab29sb2dpYSBuYSBVRlBSCj4gaHR0cDovL3d3dy5iaW8u dWZwci5ici96b29sb2dpYS8KPiBFY29sb2dpYSBlIENvbnNlcnZh77+977+9byBuYSBVRlBSCj4g aHR0cDovL3d3dy5iaW8udWZwci5ici9lY29sb2dpYS8KPiAtLS0tLS0tLS0tLS0tLS0tLS0tLS0t LS0tLS0tLS0tLS0tLS0tCj4gICBodHRwOi8vampyb3Blci5zaXRlcy51b2wuY29tLmJyCj4KCgoK LS0gCkphbWVzIEwuIFNwYXJrcyBKci4KRnJlZWxhbmNlIEVjb2xvZ3kKUmljaG1vbmQsVmlyZ2lu aWEK
Re: Maldaptation, Extinction and Natural selection
Part of this disagreement seems to stem from a detachment of ecological processes (death and reproduction) and resulting evolutionary patterns. Various ecological processes act in a non-random ways to remove phenotypes (and indirectly genotypes) from populations. I am hesitant to reserve the term natural selection for only those occasion when there is subsequent response to selection. Doing so unnecessarily entangles selective pressures (ecological processes or events that affect reproduction and mortality in a non-random fashion) with mechanisms of inheritance (primarily genetic variability). Imagine the case where you have two phenotypically identical populations that have different underlying genetics. If these populations have different heritabilites, application of the identical selective pressures could lead to dramatically different outcomes. In this scenario only the responses to selective pressures would differ. It would seem inconsistent to me to retro-actively claim that natural selection was only operating in the one case where there was a response. Rather, natural selection was only effective in producing evolutionarily relevant change in one case. James J. Roper wrote: Natural selection doesn't cull but rather it favors. And selecting for something is very different than selecting against something. Favoring a trait leads to adaptation. That is, those with a trait leave more descendents. Even so, it is not that simple. At any rate, John Endler does a wonderful job of clearing things up with Natural Selection in the Wild and I highly recommend it for anyone who has not read it, and, don't forget, The Extended Phenotype by Dawkins, that should also be required reading. Perhaps I should have not said the dreaded g-word so casually. Empirically speaking natural selection seems most effective operating within a population. However, theoretically speaking, there is no reason to think it can't operate on higher scale entities. Though we may both wish it to be true, we are unlikely able to commit this matter to the grave quite yet. Besides, natural selection works with individuals, not populations... -- Norris Z. Muth Department of Ecology and Evolution State University of New York at Stony Brook 650 Life Sciences Building Stony Brook, NY 11794-5245 [EMAIL PROTECTED] http://life.bio.sunysb.edu/~nmuth http://life.bio.sunysb.edu/ee/pigliuccilab/
Re: Maldaptation, Extinction and Natural selection
Imagine a stable population in which a favorable new genotype has appeared and is increasing. That sure looks like selection FOR the new genotype to me. On the other hand, if we start with the same population and change the environment so some of the old genotypes no longer do well, I'd call that selection AGAINST those genotypes. This is all just semantics. If confused, stick to differential reproduction. Jane At 07:16 AM 7/13/2006, Malcolm McCallum wrote: Am I understanding you correct? =20 Natural Selection selects against unfavorable phenotypes. Sexual Selection selects for favorable phenotypes. =20 =20 =20 VISIT HERPETOLOGICAL CONSERVATION AND BIOLOGY www.herpconbio.org = http://www.herpconbio.org=20 A New Journal Published in Partnership with Partners in Amphibian and = Reptile Conservation and the World Congress of Herpetology. =20 Malcolm L. McCallum Assistant Professor Department of Biological Sciences Texas AM University Texarkana 2600 Robison Rd. Texarkana, TX 75501 O: 1-903-223-3134 H: 1-903-791-3843 Homepage: https://www.eagle.tamut.edu/faculty/mmccallum/index.html =20 From: Ecological Society of America: grants, jobs, news on behalf of = James J. Roper Sent: Thu 7/13/2006 6:37 AM To: ECOLOG-L@LISTSERV.UMD.EDU Subject: Re: Maldaptation, Extinction and Natural selection But Wirt, Natural selection doesn't cull but rather it favors. And selecting for something is very different than selecting against something.=20 Favoring a trait leads to adaptation. That is, those with a trait leave more descendents. Even so, it is not that simple. At any rate, John Endler does a wonderful job of clearing things up with Natural Selection in the Wild and I highly recommend it for anyone who has not read it, and, don't forget, The Extended Phenotype by Dawkins, that should also be required reading. Interpreting literally what I wrote leads to a condition that I = normally rail against myself. Selection never selects for anything. Selection = operates only as a culling mechanism, removing the least appropriate, least = competitive phenotypes of the demic excess that currently fills the competitive = arena. =20 What the heck does demic excess really mean? Cheers, Jim == The whole person must have both the humility to nurture the Earth and the pride to go to Mars. --Wyn Wachhorst, The Dream of Spaceflight Jane Shevtsov co-founder, http://www.worldbeyondborders.org/World Beyond Borders visit my blog, http://perceivingwholes.blogspot.com/Perceiving Wholes Perhaps one day... the world, our world, won't be upside down, and then any newborn human being will be welcome. Saying, Welcome. Come. Come in. Enter. The entire earth will be your kingdom. Your legs will be your passport, valid forever. --Eduardo Galeano, Latin American writer
Re: Maldaptation, Extinction and Natural selection
Norris, I think you have a good point to illustrate the problem: Imagine the case where you have two phenotypically identical populations that have different underlying genetics. If these populations have different heritabilites, application of the identical selective pressures could lead to dramatically different outcomes. In this scenario only the responses to selective pressures would differ. It would seem inconsistent to me to retro-actively claim that natural selection was only operating in the one case where there was a response. Rather, natural selection was only effective in producing evolutionarily relevant change in one case. There is no inconsistency, because for natural selection to act, the phenotype must have a connection (heritability) with its underlying genotype. So, in your example above, let's just say that one population's phenotype was totally environmental (a good year, perhaps) while the other population's identical phenotype was genetic. Well, in both cases perhaps the individuals with the same, high quality phenotype would be favored (leaving more descendants) but only the population with a genetic basis would leave behind the tendency that was based on the phenotypic expression of the genotype. The other, in a different environment, would no longer show the same phenotype. Did I explain well? Cheers, Jim -- - James J. Roper, Ph.D. Universidade Federal do Paraná Depto. de Zoologia Caixa Postal 19020 81531-990 Curitiba, Paraná, Brasil = E-mail: [EMAIL PROTECTED] Phone/Fone/Teléfono: 55 41 33611764 celular: 55 41 99870543 e-fax:1-206-202-0173 (in the USA) = Zoologia na UFPR http://www.bio.ufpr.br/zoologia/ Ecologia e Conservação na UFPR http://www.bio.ufpr.br/ecologia/ - http://jjroper.sites.uol.com.br
Re: Maldaptation, Extinction and Natural selection
Jim writes: Sure, natural selection can be occurring while extinction is taking place, but the extinction is NOT the result of natural selection. If you don't wish to buy my examples, which I'll certainly stand by, it nevertheless might be useful to remember that Darwin labeled one of his sections in the Origin of Species, Extinction caused by natural selection. You can read the section on-line at: http://www.bartleby.com/11/4006.html Wirt Atmar
Re: Maldaptation, Extinction and Natural selection
Wirt, I will certainly disagree here! Friendly disagreement, of course. In my continuing bid to become the group's curmudgeon, Since there are no other candidates, I guess you will be elected! :-) Natural selection judges only whatever advantages it finds in populations in the moment. What it truly never does is assess the long-term consequences of its preferences. Natural selection is not a judge. It is only differential representation of genes in subsequent generations, in which more successful genes become more common from one generation to the next. Sure, natural selection can be occurring while extinction is taking place, but the extinction is NOT the result of natural selection. For example, we could say that natural selection is favoring longer bills, while habitat loss is eliminating the species. That is, those birds with longer bills leave relatively more descendents, but, it is a moot point because it was habitat loss that eliminated the species. The first is the reversion of a sexual lineage back to parthenogenesis. Parthenogensis is unaffected by natural selection, because one of the premises of natural selection is genetic variability among the population. And, the accident of becoming parthenogenetic also was NOT the result of natural selection, but rather a point event. Doing this offers the lineage a number of hypothetical advantages, most especially freeing itself from the burden of maintaining males Males are not a burden. Species do not suffer ecological costs, individuals do. And, you would not say often find a situation in which males compete with females, and both lose future reproductive success due to this competition. A population free of males is also capable of rapid expansions into recently vacated territories. But, not for reasons of natural selection. It can also survive in extremely adverse situations where a sexual population would go extinct, simply due to low population numbers and the difficulty in finding a mate. Often, species that reproduce both sexually and asexually do the sexual part exactly WHEN the conditions are adverse, presumably because it is precisely those conditions that favor genetic (and phenotypic) variability. Rotifers and aphids, for example. The second condition is the evolution of high-order polyploidy. High-order polyploidy is also the result of point changes in a population, not natural selection. This does not result from a gradual change, nor a genetic tendency? That is, adults do NOT reproduce a variable set of offspring, some polyploid and the rest normal, that after the fact leave a variable number of offspring There is no EVOLUTION for polyploidy, it happens by accident. After that, the polyploid often becomes genetically isolated from its ancestors, and then perhaps natural selection acts on it, and all its polyploid descendents, based on their phenotypic (and underlying genotypic) variability. High-order polyploidy seems on the surface to be an excellent information-assurance mechanism, mitigating the informational corruption of any body of information that is replicated generation after generation indefinitely. Accidents are not adaptations. While we find both types of populations in nature, their rarity is prima facie evidence that they are not strategies that are successful on the long-term, That is a circular argument. Also, there are examples of both that have probably been around since the cambrian. So, duration is also evidence of success. However, the phenomenon is unknown in mammals, and I have long attributed the evolution of differential imprinting of the chromosomes that pass through either maternal or paternal gametogenesis to be an evolutionary brake that prevents a reversion to parthenogenesis in mammals. You cannot call parthenogenesis a reversion, since ancestral vertebrates were probably not parthenogenetic. As accidents, there is nothing to explain. Mammals are just unable to have these kinds of accidents. Hybridizing lizards MAY become parthenogenic (Cnemidophorus), but they don't have to. There are no evolutionary brakes, as that implies planned evolution, and by your own accounting, evolution does not plan...nor does natural selection. Mutations are not planned, they just happen. Cheers, Jim -- - James J. Roper, Ph.D. Universidade Federal do Paraná Depto. de Zoologia Caixa Postal 19020 81531-990 Curitiba, Paraná, Brasil = E-mail: [EMAIL PROTECTED] Phone/Fone/Teléfono: 55 41 33611764 celular: 55 41 99870543 e-fax:1-206-202-0173 (in the USA) = Zoologia na UFPR http://www.bio.ufpr.br/zoologia/ Ecologia e Conservação na UFPR http://www.bio.ufpr.br/ecologia/ - http://jjroper.sites.uol.com.br
Re: Maldaptation, Extinction and Natural selection
Jim writes: Sorry, the scenario is to poorly defined to say anything about it, and there is probably no contradiction. But, there is also no reason to think that natural selection is always in action. And, certainly, natural selection CANNOT select for extinction. In my continuing bid to become the group's curmudgeon, let me say that natural selection can quite easily select for extinction. Natural selection judges only whatever advantages it finds in populations in the moment. What it truly never does is assess the long-term consequences of its preferences. Although there are probably a dozen hypothetical scenarios where natural selection of one attribute or another could drive a lineage to extinction, let me just mention two that are well-known and reasonably well-documented. The first is the reversion of a sexual lineage back to parthenogenesis. Doing this offers the lineage a number of hypothetical advantages, most especially freeing itself from the burden of maintaining males, who often represent substantial ecological costs to the species and who quite frequently do not participate in the economy of deme. A population free of males is also capable of rapid expansions into recently vacated territories. It can also survive in extremely adverse situations where a sexual population would go extinct, simply due to low population numbers and the difficulty in finding a mate. The second condition is the evolution of high-order polyploidy. High-order polyploidy seems on the surface to be an excellent information-assurance mechanism, mitigating the informational corruption of any body of information that is replicated generation after generation indefinitely. While we find both types of populations in nature, their rarity is prima facie evidence that they are not strategies that are successful on the long-term, and that any lineage that adopts them for whatever short-term gain it may accrue also soon disappears. Both mechanisms so evolutionary stabilize a lineage that it cannot adapt to changing conditions. Reversion to parthenogenesis is relatively common in the arthropods, but it also is known to occur in vertebrates as complex as reptiles and birds. It's very rare in these animals, but it does occur. However, the phenomenon is unknown in mammals, and I have long attributed the evolution of differential imprinting of the chromosomes that pass through either maternal or paternal gametogenesis to be an evolutionary brake that prevents a reversion to parthenogenesis in mammals. Syngamous chromosomes derived from either gender have been rendered incapable of producing a viable individual because some critical information has been suppressed on one chromosome or the other. Only when the chromosome is matched with the complementary gender's is the library complete and embryogenesis allowed to go forward. On a second. related subject, two people wrote privately and asked if I had a reference for the barn fly story that I told. Unfortunately I don't. I heard the story at the XII International Congress of Entomology at Canberra in 1972, as a contributed talk. Only the keynote and plenary talks were published. If there is any published work on the subject somewhere, it is probably published in an agricultural bulletin somewhere in Australia. Nonetheless, there is another virtually identical story regarding the CCR5 chemokine receptor in human immune systems that is more current and a great deal more readily available. Ordinarily, the CCR5 gene appears to be involved with the inflammatory immune response and thus serves an important purpose, but in some people bearing one particular allele of the gene, the gene is defective for its primary purpose. Very similar to the fly story, this defective allele also cripples one of two receptor molecules that the HIV virus requires when infecting a macrophage, and thus the homozygous bearers of the defective CCR5 appear completely immune to HIV infection, rendering them as completely protected from this plague as were the flies with the longer tarsal hairs. As this article from the CDC states: At least 23 alleles have been described for the coding region of this gene, and most of them are very rare. The most common and most studied is the 32 allele, a 32 base pair (bp) deletion that confers almost absolute protection from infection with macrophage tropic (M-tropic) viruses in homozygous individuals and provides an average 2 to 3 year delay in the progression to AIDS in those heterozygous for the deletion. --http://www.cdc.gov/genomics/hugenet/factsheets/FS_CCR5.htm If you're interested, you won't have any trouble finding articles on this example, where once again a mild genetic defect (in normal circumstances) proves to be of great benefit in a shifted environment. Indeed, if the selection coefficient were as strong in humans due to HIV as the toxin was to the flies, we too would all
Re: Maldaptation, Extinction and Natural selection
Perhaps there are valid points on both sides of this argument: James J. Roper, Ph.D. wrote: Natural selection is not a judge. It is only differential representation of genes in subsequent generations, in which more successful genes become more common from one generation to the next. Sure, natural selection can be occurring while extinction is taking place, but the extinction is NOT the result of natural selection. It seems to me a bit arbitrary to accept that natural selection is taking place when a certain fraction of individuals are selectively culled from a population, yet when that fraction reaches 100% that something different is necessarily going on. To be sure, the RESPONSE of a population to natural selection when mortality is 100% will be a moot point (unless one is considering selection of higher scale entities, dare I say groups?), but to deny that the same processes are at work seems like a bid for special treatment. Wirt Atmar writes: In my continuing bid to become the group's curmudgeon, let me say that natural selection can quite easily select for extinction. I might argue a semantic point here. While you make a valid argument that past natural selection can lead to evolutionary dead ends and extinction, I don't think it is accurate to say natural selection is selecting for extinction itself. Rather, natural selection for certain traits (other than extinction-proneness) may ultimately lead to extinction. A minor point perhaps, but an important distinction. Hope this is a helpful contribution to an interesting discussion. Norris -- Norris Z. Muth Department of Ecology and Evolution State University of New York at Stony Brook 650 Life Sciences Building Stony Brook, NY 11794-5245 [EMAIL PROTECTED] http://life.bio.sunysb.edu/~nmuth http://life.bio.sunysb.edu/ee/pigliuccilab/
Re: Maldaptation, Extinction and Natural selection
Norris writes: In my continuing bid to become the group's curmudgeon, let me say that natural selection can quite easily select for extinction. I might argue a semantic point here. While you make a valid argument that past natural selection can lead to evolutionary dead ends and extinction, I don't think it is accurate to say natural selection is selecting for extinction itself. Rather, natural selection for certain traits (other than extinction-proneness) may ultimately lead to extinction. A minor point perhaps, but an important distinction. No, what you write is not a small point. When I wrote that natural selection can quite easily select for extinction, I was simply being sloppy in my language. What I meant, and what I should have written was natural selection can quite easily select for [the short-term advantageous conditions that ultimately lead to the] extinction [of the lineage]. Interpreting literally what I wrote leads to a condition that I normally rail against myself. Selection never selects for anything. Selection operates only as a culling mechanism, removing the least appropriate, least competitive phenotypes of the demic excess that currently fills the competitive arena. If selection were only culling the black balls from an urn filled with red and black balls, what would be the harm in saying that it was selecting for the red balls? If the genetic representation of the individuals' code were that independent, there wouldn't be any, but no such situation can exist in a complexly interwoven informational system, especially one where the twin phenomena of polygeny and pleiotropy dominate. I've previously written about this misuse of language as being one of the fundamental philosophical errors that plagues evolutionary biology, so I'm more than a little embarrassed that I wrote that line myself, but it's not what I meant, and hopefully that's clear from the context of my other comments. One paper that is on-line which contains my criticisms of such language is at: http://aics-research.com/research/notes.html#IIIC This paper is on the simulation of evolution for purposes of evolving machine intelligence and was published in an engineering journal in 1994. Although the idiom of the paper is primarily engineering, engineers designing extremely complex systems face precisely the same problems that nature does in optimizing its designs, and thus the subjects of accurately determining what is being evolved, optimized and selected very rapidly converge. If you get these qualities wrong, you're offered every opportunity to quite completely misunderstand the evolutionary process, which is arguably a more serious consequence for engineers than biologists. Wirt Atmar
Re: Maldaptation, Extinction and Natural selection
It seems to me a bit arbitrary to accept that natural selection is taking place when a certain fraction of individuals are selectively culled from a population, yet when that fraction reaches 100% that something different is necessarily going on. To be sure, the RESPONSE of a population to natural selection when mortality is 100% will be a moot point (unless one is considering selection of higher scale entities, dare I say groups?), but to deny that the same processes are at work seems like a bid for special treatment. Indivdiuals are not selectively culled from a population, but rather they leave fewer descendants than others. I would say that a population decline is probably completely independent of natural selection, in that something else is causing the decline. Natural selection is only about the differential representation of genes in subsequent generations, in which some individuals with some traits leave more descendents - WHEN natural selection is occuring. So, my point has nothing to do with how many individuals are involved. Besides, natural selection works with individuals, not populations... Cheers, JIm -- - James J. Roper, Ph.D. Universidade Federal do Paraná Depto. de Zoologia Caixa Postal 19020 81531-990 Curitiba, Paraná, Brasil = E-mail: [EMAIL PROTECTED] Phone/Fone/Teléfono: 55 41 33611764 celular: 55 41 99870543 e-fax:1-206-202-0173 (in the USA) = Zoologia na UFPR http://www.bio.ufpr.br/zoologia/ Ecologia e Conservação na UFPR http://www.bio.ufpr.br/ecologia/ - http://jjroper.sites.uol.com.br
Re: Maldaptation, Extinction and Natural selection
Sorry, the scenario is to poorly defined to say anything about it, and there is probably no contradiction. But, there is also no reason to think that natural selection is always in action. And, certainly, natural selection CANNOT select for extinction. Read Natural Selection in the Wild by Endler. Jim Kim van der Linde wrote: Hi all, I am having an interesing discussion at the moment about Natural selection. The context is a single population of individuals that, due to changes in the environment, are now maladapted and the population is reducing in size. Based on the often used definition of differential reproduction, when there is not much to differentiate with, there is no longer differential selection, and as such, no natural selection. However, they are maladapted, so unfit to survive. Any opinions about this nice contradiction? Cheers, Kim -- - James J. Roper, Ph.D. Universidade Federal do Paraná Depto. de Zoologia Caixa Postal 19020 81531-990 Curitiba, Paraná, Brasil = E-mail: [EMAIL PROTECTED] Phone/Fone/Teléfono: 55 41 33611764 celular: 55 41 99870543 e-fax:1-206-202-0173 (in the USA) = Zoologia na UFPR http://www.bio.ufpr.br/zoologia/ Ecologia e Conservação na UFPR http://www.bio.ufpr.br/ecologia/ - http://jjroper.sites.uol.com.br
Maldaptation, Extinction and Natural selection
Hi all, I am having an interesing discussion at the moment about Natural selection. The context is a single population of individuals that, due to changes in the environment, are now maladapted and the population is reducing in size. Based on the often used definition of differential reproduction, when there is not much to differentiate with, there is no longer differential selection, and as such, no natural selection. However, they are maladapted, so unfit to survive. Any opinions about this nice contradiction? Cheers, Kim -- http://www.kimvdlinde.com
Re: Maldaptation, Extinction and Natural selection
Actually, in the below senario there is Natural Selection and it is = working. Since those organisms are now maladapted, and declining to = extinction Natural Selection is selecting them for extinction. =20 Natural Selection selects against unfit organisms, not for fit ones. = This is much different from selecting for the most fit organisms. This = is particularly important because it is this selection against = maladapted individuals that maintains diversity within a population. If = Natural selection selected for a particular genome, the entire = population would rapidly become homogeneous. The heterogeneity dictates = that the population has many different characteristics, some of which = are ideally adapted to the current climatic/habitat conditions, others = are only marginally adapted to this optima. As the climates change or = habitats success, dominance of different traits shifts do to = differential selection pressure across a continuum of from least to most = adapted. The least adapted will decline, possibly becoming extirpated. = The most adapted will proliferate and dominate. Another shift in optima = occurs and the population traits shift in response. =20 =20 This is not unlike a place of employment. People who can't do the job = are fired. But there is wide variation in the ability of employees to = do the same job. Some of these receive raises and promotions due to = their ability to excel while others are demoted or do not receive = raises. This array of employees remains employed and functioning in the = workplace, they all reproduce! =20 =20 To learn more about this interesting relationship it would be good to = get yourself a copy of Dawkin's The Selfish Gene. In my opinion, it = is the best evolution book out there (still) because anyone can grasp = what is written. My genetics class is required to read this! =20 =20 I hope that answers your question and if you need clarification, feel = free to send an email!=20 =20 VISIT HERPETOLOGICAL CONSERVATION AND BIOLOGY www.herpconbio.org = http://www.herpconbio.org=20 A New Journal Published in Partnership with Partners in Amphibian and = Reptile Conservation and the World Congress of Herpetology. =20 Malcolm L. McCallum Assistant Professor Department of Biological Sciences Texas AM University Texarkana 2600 Robison Rd. Texarkana, TX 75501 O: 1-903-223-3134 H: 1-903-791-3843 Homepage: https://www.eagle.tamut.edu/faculty/mmccallum/index.html =20 From: Ecological Society of America: grants, jobs, news on behalf of Kim = van der Linde Sent: Sat 7/8/2006 11:36 PM To: ECOLOG-L@LISTSERV.UMD.EDU Subject: Maldaptation, Extinction and Natural selection Hi all, I am having an interesing discussion at the moment about Natural selection. The context is a single population of individuals that, due to changes in the environment, are now maladapted and the population is reducing in size. Based on the often used definition of differential reproduction, when there is not much to differentiate with, there is no longer differential selection, and as such, no natural selection. However, they are maladapted, so unfit to survive. Any opinions about this nice contradiction? Cheers, Kim -- http://www.kimvdlinde.com
