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Post by rsivertsen on Jul 2, 2011 3:20:18 GMT -10
Hey Gus, I had a similar discussion with John Turnbull some years ago, regarding some other plants, and he agreed that they may have originated from hybrid origins, but the fact that they are now a self sustaining population should warrant the separate species status; other Nepenthes species, such as N. hookeriana, (and many others) occur as isolated plants within the populations of two (or more) species that have overlapping, sympatric areas and never seem to become hybrid swarms. As for "speciation", I would rather regard this as the accumulation of genetic drift on an isolated population to the point where they really do have definable and consistent differences. - Rich
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Post by agustinfranco on Jul 2, 2011 12:49:45 GMT -10
Hey Rich:
Thanks for your comments, but i would still have to ask you: How much genetic drift is required to call them a new species then?
Gus
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Post by rsivertsen on Jul 2, 2011 13:12:19 GMT -10
Hey Rich: Thanks for your comments, but i would still have to ask you: How much genetic drift is required to call them a new species then? Gus Ahh, yes, the magic question indeed! I guess it all depends on the "eyes of the beholder" and the "authority" who makes that observation and determination, a perennial point of contention among taxonomists; I still have some reservations about several plants in Sumatra in the "N. singalana" group, which according to my opinion, could really be reduced to various geo-type forms instead of separate species status, just like the various forms of N. rafflesiana and N. mirabilis, but that's just my opinion, and nothing more. - Rich
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Dave Evans
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Post by Dave Evans on Jul 4, 2011 17:22:22 GMT -10
Hey Rich: Thanks for your comments, but i would still have to ask you: How much genetic drift is required to call them a new species then? Gus Dear Gus I really don't think genetic drift is going to drive evolution. Genetic drift more or less results in different varieties; might function more as starting place for speciation; getting the ball rolling so-to-speak.
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Post by agustinfranco on Jul 5, 2011 1:40:52 GMT -10
Hey Rich: Thanks for your comments, but i would still have to ask you: How much genetic drift is required to call them a new species then? Gus Dear Gus I really don't think genetic drift is going to drive evolution. Genetic drift more or less results in different varieties; might function more as starting place for speciation; getting the ball rolling so-to-speak. Dear Dave: As the rules for evolution are not tightly set by anyone, as far as I know then, who is qualified to say when a plant cross transforms from a complex hybrid to a species?. Perhaps we are looking too hard at a process which may have a very simple explanation Gus
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Dave Evans
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Post by Dave Evans on Jul 5, 2011 10:32:23 GMT -10
Hmm? Not sure what hybrization has to due with it...
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Post by rsivertsen on Jul 5, 2011 17:10:15 GMT -10
Hey Rich: Thanks for your comments, but i would still have to ask you: How much genetic drift is required to call them a new species then? Gus Dear Gus I really don't think genetic drift is going to drive evolution. Genetic drift more or less results in different varieties; might function more as starting place for speciation; getting the ball rolling so-to-speak. Well, according to all my college studies and books on Evolution, Genetic Drift and population isolation (also known as "Island Ecology") is EXACTLY what the driving force of Evolution is all about; of course Natural Selection takes a special course in these things which are local to the specific micro habitats. It's just how it works, in both plants and animal evolution. There are no shortages of examples either. - Rich
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Dave Evans
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Post by Dave Evans on Jul 5, 2011 17:42:10 GMT -10
Exactly Rich, the isolation results in populations living with different conditions and so each now each separate population reaches differently to a different environment, but it is the accumulation of useful traits that make for different species, not a couple of random mutations that happen all the time and get promoted via genetic drift.
Mutations, which cause evolution, are random. Evolution is not random. Most mutations result in cell death. Most mutations that don't kill are useless. But with natural selection, only useful traits are promoted and therefore the underlining specific mutations as well. The theory of genetic drift is more related to the mathematical properties of genes and it demonstrates how non-useful mutations can come to be present in most or all individuals in a given population, while no individuals in another population can inherit the mutation as it isn't available to them. Genetic drift can also kill off these useless mutations as well, and none are the wiser.
Genetic drift is in some ways anti-natural selection. This is similar to the slow kind of evolution that Darwin envisioned--not accurate all. The accumilation of useful traits can occurs rather quickly--natural selection works a lot faster than genetic drift and a lot faster than Darwin thought.
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Post by agustinfranco on Jul 6, 2011 0:31:10 GMT -10
Exactly Rich, the isolation results in populations living with different conditions and so each now each separate population reaches differently to a different environment, but it is the accumulation of useful traits that make for different species, not a couple of random mutations that happen all the time and get promoted via genetic drift. Mutations, which cause evolution, are random. Evolution is not random. Most mutations result in cell death. Most mutations that don't kill are useless. But with natural selection, only useful traits are promoted and therefore the underlining specific mutations as well. The theory of genetic drift is more related to the mathematical properties of genes and it demonstrates how non-useful mutations can come to be present in most or all individuals in a given population, while no individuals in another population can inherit the mutation as it isn't available to them. Genetic drift can also kill off these useless mutations as well, and none are the wiser. Genetic drift is in some ways anti-natural selection. This is similar to the slow kind of evolution that Darwin envisioned--not accurate all. The accumilation of useful traits can occurs rather quickly--natural selection works a lot faster than genetic drift and a lot faster than Darwin thought. Dave: biological entities whether they are plants or animals develop characteristics and traits for functionality. Natural selection is a combination of environmental pressure and genetic plasticity to change for survival. Genetic drift, in my opinion, is also part of evolution. Random mutations are usually repaired by specialized enzymes to maintain the accuracy of genome composition . If mutations occur and remain in the plant population, then they must offer an advantage to the plants having them, because if they don't, these are wiped out. Evolution needs mutations. By mutations, i am referring to all kinds not just single base pair changes, but large gene sections exchanged, deleted, or translocated elsewhere. We can't have new species with the same gene composition as their ancestral species. Gus
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Dave Evans
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Post by Dave Evans on Jul 6, 2011 5:35:03 GMT -10
So the theory is Nepenthes evolve by aimlessly meandering into different species?
Actually, it describes how non-selected for traits can come to dominate given populations in the absence of selective pressures. Traits that are neutral, like blond hair or blue eyes that don't define a species, but just add to back ground genetic diversity.
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