Understanding through Discussion


Welcome! You are not logged in. [ Login ]
EvC Forum active members: 78 (8896 total)
Current session began: 
Page Loaded: 03-22-2019 1:49 AM
37 online now:
Dredge, PaulK (2 members, 35 visitors)
Chatting now:  Chat room empty
Newest Member: WookieeB
Post Volume:
Total: 848,539 Year: 3,576/19,786 Month: 571/1,087 Week: 161/212 Day: 3/25 Hour: 2/1


Thread  Details

Email This Thread
Newer Topic | Older Topic
  
Prev12
3
4Next
Author Topic:   How many generations does speciation take?
custard
Inactive Member


Message 31 of 52 (189848)
03-03-2005 4:45 PM
Reply to: Message 29 by pink sasquatch
03-03-2005 4:33 PM


quote mine? Please.

Your definition is NOT the one promoted by TalkOrigins, rather it is a quote-mine, mistaken or not.
.

It would be a quote mine only if I were misreprenting the quote. Look back at the OP, I clearly stated I wanted to use a very restrictive definition of BSC.

If you like I'll REVISE it to say the "1937 Dobzhansky definition of BSC."

Regardless, this is the definition I stated that I am using and I have explained why I'm using it. I am NOT arguing that more liberal definitions of the BSC are incorrect.


This message is a reply to:
 Message 29 by pink sasquatch, posted 03-03-2005 4:33 PM pink sasquatch has responded

Replies to this message:
 Message 39 by pink sasquatch, posted 03-03-2005 6:05 PM custard has not yet responded

  
custard
Inactive Member


Message 32 of 52 (189850)
03-03-2005 4:55 PM
Reply to: Message 24 by pink sasquatch
03-03-2005 4:22 PM


Re: not my BSC
custard writes:

One reproductive anamoly does not a species make.

Pink responds:

Why yes, yes it does. That's all biological speciation is - reproductive incompatibility.

So Joe Lowspermcount is a separate species from homo sapiens because he is unable to reproduce? Are you really saying that?

Doesn't genetic similarity come into play at some point?

This message has been edited by custard, 03-03-2005 16:55 AM


This message is a reply to:
 Message 24 by pink sasquatch, posted 03-03-2005 4:22 PM pink sasquatch has responded

Replies to this message:
 Message 40 by pink sasquatch, posted 03-03-2005 6:15 PM custard has not yet responded
 Message 46 by Loudmouth, posted 03-04-2005 1:09 PM custard has not yet responded

  
Brad McFall
Member (Idle past 3109 days)
Posts: 3428
From: Ithaca,NY, USA
Joined: 12-20-2001


Message 33 of 52 (189852)
03-03-2005 5:06 PM
Reply to: Message 1 by custard
02-26-2005 9:52 PM


I am using the standard 10^-5 muts per gen ordered by symmetrical affects subject to "If any two molecules approach each other, there comes into importance within certain distances the attractive interaction, which is designated by London as teh dispersion force. The motion of the electrons in one of these molecules modifies that of the electrons in the other, so that they tend on the average to move in phase. This produces an atractive force proportional to the inverse seventh power of the distance between the molecules. It has been suggested that this force may be agent in the process of adsorption. This interaction is additive, and of sufficient influence to account in part for the cohesive forces in liquids. The more unlike the molecules that are involved in this interaction the less likely are their electrons to move in phase. This may account for the "squeezing out" action of liquids for small amounts of second substances . If the dispersion forces were responsible fro the "structure" found in a liquid the exclusion of impurities which would distort this structure would be easily pictured. In any case, dispersioin forces between adsorptive and adsorbant favor adsorption." in Cassidy's Asorptio and Chromatography 1951 Interscience

This is an analogue approach. one need only note that Newton perferred chemistry to explain cohesion than conspiring motions. The whole level of selection thing is framemable not factually as a conspiricy. Think of the small amount of substance as gene expressed >> codes compared to substance of original expression as ++ smmyetry. Photons might have some effect there however.


This message is a reply to:
 Message 1 by custard, posted 02-26-2005 9:52 PM custard has responded

Replies to this message:
 Message 35 by custard, posted 03-03-2005 5:18 PM Brad McFall has responded

    
custard
Inactive Member


Message 34 of 52 (189853)
03-03-2005 5:08 PM
Reply to: Message 24 by pink sasquatch
03-03-2005 4:22 PM


Put the snails to bed
pinksasquatch writes:

One mutation can result in reproductive incompatibility. I gave examples.

1- Here's the rebuttal I was looking for regarding the 'speciation' of the snails.

2- This doesn't meet the definition of speciation as stated in the OP.


This message is a reply to:
 Message 24 by pink sasquatch, posted 03-03-2005 4:22 PM pink sasquatch has responded

Replies to this message:
 Message 42 by pink sasquatch, posted 03-03-2005 6:28 PM custard has not yet responded

  
custard
Inactive Member


Message 35 of 52 (189854)
03-03-2005 5:18 PM
Reply to: Message 33 by Brad McFall
03-03-2005 5:06 PM


brad writes:

am using the standard 10^-5 muts per gen ordered by symmetrical affects subject to "If any two molecules approach each other, there comes into importance within certain distances the attractive interaction, which is designated by London as teh dispersion force. The motion of the electrons in one of these molecules modifies that of the electrons in the other, so that they tend on the average to move in phase. This produces an atractive force proportional to the inverse seventh power of the distance between the molecules. It has been suggested that this force may be agent in the process of adsorption. This interaction is additive, and of sufficient influence to account in part for the cohesive forces in liquids.

Did you state that the 10^-5 muts/generation are cumulative? How many generations are you estimating it takes to 'fix' a mutation?


This message is a reply to:
 Message 33 by Brad McFall, posted 03-03-2005 5:06 PM Brad McFall has responded

Replies to this message:
 Message 36 by Brad McFall, posted 03-03-2005 5:33 PM custard has not yet responded

  
Brad McFall
Member (Idle past 3109 days)
Posts: 3428
From: Ithaca,NY, USA
Joined: 12-20-2001


Message 36 of 52 (189863)
03-03-2005 5:33 PM
Reply to: Message 35 by custard
03-03-2005 5:18 PM


I am working on a DEDUCTIVE approach. I dont know that it exists in the literature. In the thread in response to Loudmouth. I indicated the need to work into Wright's equilibrium after this calculation will be performed. I did not even say how many base changes might go into a a part of a gene let alone a whole gene that is fixable.

Sorry if I mislead you into thinking I had progressed in my work father than I actually am. The base substitutions COULD INDEED be cummulative within the binding of their contributions to formal ++ and >> transformative grammers but I dont even take that approach. Instead I am interesting in directly deducing from Glaydhsev's law.

I am curious if it is possible to develop a "neutral" methodology so that assertions of creationists that Salmon only take 13 generations to speciate might be generalized. Maybe you should ask Mick how he thinks it. Deduction is itself a kind of "fixation" and so is minization. I was trying to discuss change ONLY in terms of gene caused and species caused sequence divergence. Population convergence may indeed have causes not even predictable in principle from what I was starting to propose. I am sorry that i started to post as I saw rather quickly the approach was going to get confused with the output. Again I apologize. I had seen you post when you first posted it but decided NOT to post until I might be in a position to state uncategorically. I can not. A mutation is not an electrotonic flow but flesh is possibly a conspircy of emotions.

This message has been edited by Brad McFall, 03-03-2005 17:35 AM


This message is a reply to:
 Message 35 by custard, posted 03-03-2005 5:18 PM custard has not yet responded

    
pink sasquatch
Member (Idle past 4099 days)
Posts: 1567
Joined: 06-10-2004


Message 37 of 52 (189865)
03-03-2005 5:49 PM
Reply to: Message 30 by custard
03-03-2005 4:42 PM


not genetic compatibility, genetic isolation
Do you honestly believe a Saint Bernard and a Chihuahua are seperate species simply because their reproductive organs don't fit together?

You just can't rule out genetics and rely solely on morphology. Our current taxonomy overemphasized morphology and needs to be re-evaluated with more emphasis on genetics.

If two populations cannot mate "because their reproductive organs don't fit together" they are reproductively isolated. Do you disagree with that?

They are genetically isolated from one another.

Now, this is NOT ruling out genetics AND it is NOT relying on a typological species concept.

Two fly species exist that have incompatible genitalia, they cannot interbreed, even though they are genetically compatible at the post-mating level, they are genetically incompatible at the pre-mating level. Just because morphology is mentioned does not mean this is a typological species definition.

It is a genetic species definition because the genomes of the two fly species do not have access to each other. They are genetically isolated from one another. Genetic isolation results from any form of reproductive isolation, premating or postmating.

It is not about injecting the DNA of the male of one species into the egg of another by in vitro fertilization to determine compatibility.

You're basically claiming that hundreds of species that never interbreed in the wild are the same species.

Defining species "genetically" (by the BSC) is about genetic isolation, not post-mating genome compatibility.


This message is a reply to:
 Message 30 by custard, posted 03-03-2005 4:42 PM custard has not yet responded

Replies to this message:
 Message 38 by DBlevins, posted 03-03-2005 6:00 PM pink sasquatch has not yet responded

  
DBlevins
Member (Idle past 1852 days)
Posts: 652
From: Puyallup, WA.
Joined: 02-04-2003


Message 38 of 52 (189870)
03-03-2005 6:00 PM
Reply to: Message 37 by pink sasquatch
03-03-2005 5:49 PM


Re: not genetic compatibility, genetic isolation
You're basically claiming that hundreds of species that never interbreed in the wild are the same species.

An example of this problem would be the Liger or the Tion. Tiger's and Lion's are considered seperate species but mating between them can produce a 'viable' though infertile offspring.

Or for that matter, horses and donkeys and mules.


This message is a reply to:
 Message 37 by pink sasquatch, posted 03-03-2005 5:49 PM pink sasquatch has not yet responded

  
pink sasquatch
Member (Idle past 4099 days)
Posts: 1567
Joined: 06-10-2004


Message 39 of 52 (189871)
03-03-2005 6:05 PM
Reply to: Message 31 by custard
03-03-2005 4:45 PM


not liberal, accurate
It would be a quote mine only if I were misreprenting the quote.

Exactly. By calling it "the TalkOrigins definitions"...

(Using the talkorgins defintions) the BSC definition I'm using, which I think I stated in the OP,

...when essentially the next line after the excerpt you posted was...

The definition of a species that is accepted as the BSC...

...followed by what TalkOrigins "accepts" as the accepted definition.

Look back at the OP, I clearly stated I wanted to use a very restrictive definition of BSC.

It's clear now that you've edited. It wasn't at all clear before you edited, which is why I presume you included the tentative "which I think I stated in the OP" in your above quote. I checked after I read "I think" the first time and it wasn't there.

Using an outdated, non-accepted (misunderstood?) version of the term "biological species concept" and trying to justify it with a historical view is kind of like using the term "theory of evolution" and then later claiming you meant and prefer Lamarckian evolution theory.

Regardless, this is the definition I stated that I am using and I have explained why I'm using it. I am NOT arguing that more liberal definitions of the BSC are incorrect.

I'm not sure why you see the accepted definition as liberal. It isn't that is is "liberal", it is that it is more accurate (and predictive), which is why it has become the accepted form of BSC, even accepted by Dobzhansky.

The form of the BSC you are using is less accurate.


This message is a reply to:
 Message 31 by custard, posted 03-03-2005 4:45 PM custard has not yet responded

  
pink sasquatch
Member (Idle past 4099 days)
Posts: 1567
Joined: 06-10-2004


Message 40 of 52 (189874)
03-03-2005 6:15 PM
Reply to: Message 32 by custard
03-03-2005 4:55 PM


the rooster has sex with all of them.
So Joe Lowspermcount is a separate species from homo sapiens because he is unable to reproduce? Are you really saying that?

You obviously read only the last line of the post (#24) you were responding to. Otherwise you would have read my rebuttal of this point already:

custard: In any case, I don't think the snails are a good example... they could still reproduce through artificial insemination. An analogy would be a man who has a low sperm count (genetic) and can't produce viable offspring with his wife without artificial means. Is he really a member of a different species?

PinkSas: No, because MOST males and females of the human species are reproductively compatible. However, NO individuals among "chirality left" and "chirality right" snail populations are reproductively compatible. This is a huge difference - and why species are defined at population levels, and not at individual levels.

It's pretty straightforward.

Doesn't genetic similarity come into play at some point?

You should probably use the term "post-mating" rather than "genetic" in this context. Reproductive isolation can be "pre-mating" (behavioral, for example) or "post-mating" (genomic incompatibilities you are referring to).

Both pre-mating and post-mating incompatibilities are the result of genetics.

Both pre-mating and post-mating incompatibilities result in reproductive isolation.

Both pre-mating and post-mating incompatibilities result in genetic isolation.


This message is a reply to:
 Message 32 by custard, posted 03-03-2005 4:55 PM custard has not yet responded

  
Wounded King
Member (Idle past 2171 days)
Posts: 4149
From: Edinburgh, Scotland
Joined: 04-09-2003


Message 41 of 52 (189876)
03-03-2005 6:20 PM
Reply to: Message 16 by pink sasquatch
03-03-2005 2:59 PM


Re: hormonal butterflies
Another example of premating isolation as the result of a single mutation was witnessed by researchers in a population of snails - snails with the mutation had the opposite shell chirality of the snails without, and their genitals couldn't line up for mating.

This still isn't right Pink. The offspring of homozygous mothers with the mutation have the sinistral chirality, not those who are themselves homozygous.

TTFN,

WK


This message is a reply to:
 Message 16 by pink sasquatch, posted 03-03-2005 2:59 PM pink sasquatch has responded

Replies to this message:
 Message 44 by pink sasquatch, posted 03-03-2005 6:31 PM Wounded King has not yet responded

    
pink sasquatch
Member (Idle past 4099 days)
Posts: 1567
Joined: 06-10-2004


Message 42 of 52 (189879)
03-03-2005 6:28 PM
Reply to: Message 34 by custard
03-03-2005 5:08 PM


Snails, stay up all night and party!
1- Here's the rebuttal I was looking for regarding the 'speciation' of the snails.

Right. I never said it was a speciation event. I said it was an example of premating isolation resulting from a single mutation. In fact, I pointed out that issue when I first brought it up. You can check my unedited post #16 in this thread. Here is the relevant text:

Another example of premating isolation as the result of a single mutation was witnessed by researchers in a population of snails - snails with the mutation had the opposite shell chirality of the snails without, and their genitals couldn't line up for mating. (I don't think it has been reported yet if the alleles have been fixed into separate extant breeding populations, so I don't know if true speciation has occurred.)

Wounded King's post clarified that it was not a speciation event. It did not rebut the point of my example, which is that the snails were reproductively isolated. Nowhere does Wounded King bring up your point, which is that artificial insemination between snails was the reason they hadn't speciated. Wounded King's issue was fixation of alleles in separate populations, which I qualified in my initial mention of the snails here with.

WK writes:

It may have produced speciation, in as much as two populations of homozygotes for the distinct alleles, after subsequent generations, but this is not documented in the paper.

See - here he is stating that speciation could occur with fixation.

The snail example states exactly what I said it stated, nothing more.
So the snails can stay up 'til the breaka breaka dawn...

2- This doesn't meet the definition of speciation as stated in the OP.

It did at the time I brought it up.


This message is a reply to:
 Message 34 by custard, posted 03-03-2005 5:08 PM custard has not yet responded

  
Wounded King
Member (Idle past 2171 days)
Posts: 4149
From: Edinburgh, Scotland
Joined: 04-09-2003


Message 43 of 52 (189880)
03-03-2005 6:28 PM


Snail Models
In relation to the snail chirality issue there is a paper, pre-dating the Nature paper Pink referenced, Which discusses a computer model used to investigate rates of speciation based on 'delayed prezygotic' isolation.

Delayed prezygotic isolating mechanisms: evolution with a twist
J. Stone and M. Björklund
Proc. R. Soc. Lond. B (2002),Volume 269, Number 1493, pp.861 - 865

Assortative mating characterizes the situation wherein reproducing individuals pair according to similarity. Usually, the impetus for this bias is attributed to some type of mate choice conferring benefits (e.g., increased fitness or genetic compatibility) and, thereby, promoting speciation and phenotypic evolution. We investigate, by computer simulation of an evolving deme-structured snail population, the ramifications ensuing from passive assortative mating wherein couples exhibiting opposite shell coil direction phenotypes experience a physical constraint on mating success: putative mating partners inhabiting stout dextral and sinistral shells are unable to exchange sperm. Because shell coil chirality genotype is encoded at a single locus by shell coil alleles that are inherited maternally, snails containing sinistral alleles can present the typical dextral phenotype. Consequently, the incidence of a sinistral allele in as few as one snail can be manifested as prezygotic reproductive isolation within a deme in a subsequent generation. However, because the efficacy of achieving this type of prezygotic reproductive isolation is affected by shell form, the likelihood and product of single-gene speciation should be determined by deme interaction (migration) and composition (morphological distribution). We test this hypothesis and show how stochastic migration interacts with passive assortative mating yielding morphologically induced prezygotic reproductive isolation to produce new species phenotypes. The results show that demes can achieve rapid macroscopic phenotypic transformation and indicate that sympatric speciation might be more plausible than naturalists recognize conventionally.

TTFN,

WK


    
pink sasquatch
Member (Idle past 4099 days)
Posts: 1567
Joined: 06-10-2004


Message 44 of 52 (189881)
03-03-2005 6:31 PM
Reply to: Message 41 by Wounded King
03-03-2005 6:20 PM


Re: hormonal butterflies
You are correct - I oversimplified (again) on that point.

I should have said, "the mutation results in snails with the opposite shell chirality...".


This message is a reply to:
 Message 41 by Wounded King, posted 03-03-2005 6:20 PM Wounded King has not yet responded

  
Loudmouth
Inactive Member


Message 45 of 52 (190053)
03-04-2005 1:05 PM
Reply to: Message 28 by custard
03-03-2005 4:31 PM


Re: Some numbers.
quote:
This makes me think that a variable (for a much grander model than what I'm futzing about with) would be some sort population plateau where the sheer number of an existing species would prevent continued evolution because any and all new mutations are eventually cycled back into the population at large; then the mutations are simply watered down and exist in isolated pockets, or just die out.

Let's look at an ideal stable ecosystem and an ideal ecosystem moving towards stability.

In an ideal stable ecosystem, all, or nearly all, of the available niches are filled by one species. Each species specializes in that niche and is so specialized that it can not survive outside of that niche. In this situation there will be no speciation (since we are dealing with an ideal situation). Natural selection will be pushing each species towards stability and away from change because every other possible "job" is already being done by another species and they are doing it better than your species could with just one generation of mutation. There are no ideal stable ecosystems, so this is a hypothetical situation. However, there are ecosystems that have been closestable for quite a long time and this is what we see.

In an ideal developing ecosystem, you start with two species. One is a prey species and the other is a predator species. This could be an herbivore/plant relationship or a carnivore/prey relationship. In this situation there are a lot of possibilities for change. There are empty niches all over the place. Plants will grow larger to prevent over grazing while other plants will grow smaller so that the fit into little cracks to avoid grazing. Prey species will either grow larger or get faster. I think you get the idea.

So in your model you also have to calculate the relative stability of the ecosystem. You could hypothetically calculate the maximum rate of speciation which would be tied in with the mutation rate and using the model of an initial two species ecosystem.

quote:
Once the species reaches a certain level, it would become extremely resistant to additional speciation because the baseline genes (for lack of a better phrase) would keep the overall species characteristics near the mean.

The phrase that is often used is "fitness peak". This is an analogy that works quite well for this discussion.

Think of adaption as an uphill walk towards a peak which represents specialization. Each niche is then a peak with valleys between each of the niches. For a species to move into another niche it must go "downhill" (become less specialized), cross the valley, and then climb the next fitness peak. What happens in stable ecosystems is that the valleys become extremely deep. So deep that species are not able to make the traverse to the next peak. In a developing ecosystem the species are not very far up their fitness peaks. They are in the valleys and each path up each peak is a path of speciation.

You must also remember that the mutation rate is the same for every species regardless of the stability of the ecosystem. In a stable ecosystem, beneficial mutations are rare because the species are all well adapted. Therefore, neutral mutations will be selected for in a stable ecosystem. In a developing ecosystem there are many possible beneficial mutations most of which will be selected for.

quote:
think this would be a sort of punctuated equilibrium argument, no?

Yeah, in a general sense. You will observe stasis in a stable ecosystem and punctuated evolution in developing ecosystems.


This message is a reply to:
 Message 28 by custard, posted 03-03-2005 4:31 PM custard has not yet responded

  
Prev12
3
4Next
Newer Topic | Older Topic
Jump to:


Copyright 2001-2018 by EvC Forum, All Rights Reserved

™ Version 4.0 Beta
Innovative software from Qwixotic © 2019