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
Re: Evolution Environment Adaptation Re: Maldaptation, Extinction and Natural selection
Kim, I guess, there isn't really a contradiction. I would say the problem is that they might be so badly adapted that small changes won't help. But that is more of a problem of the rate of change and not an indication that the processes are not at work. They might just lead to extinction because the population can't change fast enough. That'll be selcetion, too for my amature understanding. 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. Cheers, Joerg 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 -- Jörg Kaduk jk61 at le.ac.uk Lecturer Department of Geography University of Leicester University Road Leicester LE1 7RH United Kingdom
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
