How many generations does speciation take?

Hey custard,Even if you make the assumption that rate of mutation is constant for all species, there is still another variable - speciation can occur with a single mutation, or may require countless mutations. Environment also plays a large role in speciation events. In other words, speciation cannot be distilled down to a simple equation of 'x' mutations = 1 speciation.Perhaps someone else might have an idea about approximating an 'average' number of mutations per speciation, but it would likely be pure speculation, unless perhaps it is limited to a single species group.

But Saint Bernards and Chihuahuas cannot. (And I'm not entirely sure that a wolf and a pug could successfully reproduce.) One, basically. A single mutation can result in reproductively incompatibility.Ernst Mayr references (in What Evolution Is) a single gene speciation that effects hormonal ratios in butterflies, causing premating reproductive isolation. I haven't been able to find the original research on this one, though - perhaps someone else has some info? 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.)An example of postmating speciation that comes to mind is the Robertsonian chromosomal fusions in wild mice (I believe a substantial body of work has been done characterizing these reproductively isolated populations in the Alps). The fusions cause chromosomal sorting problems if a mouse with a particular fusion mates with a mouse without the same fusion - most of the resulting offspring exhibit aneuploidy and don't survive, or have developmental defects. Thus this could serve as an example of single-mutation postmating reproductive isolation.Now, these mutations/reproductive incompatibilites arise in a single generation, but it may take several generations for fixation into separate populations.If a dominant, reproductively isolating mutation arose and segregated 50/50 in a single large birth group (like a brood of fish with several hundred individuals; or maybe those butterflies Ernst mentioned), then speciation could essentially occur in a single generation.

The same thing in terms of biological species. You've simply asked if the reproductive isolation is postmating or premating. Either way it is still reproductive isolation. The biological species concept you have been using includes premating isolation (as in the first two of the three examples I gave in my previous post).If the only way two populations can/will reproduce is by human transfer of semen, then those two populations are not the same species by the BSC definition.

Not "hypothetically". One mutation can result in reproductive incompatibility. I gave examples. No, it doesn't. At least not the popular biological species concept put forth by Mayr and used by evolution scientists. There are countless species in the wild that have only a premating reproductive barrier, yet never mate - these would collapse into single species using your version of the BSC.In fact, some species barriers involving complete morphological genital incompatibility would fail under your definition.We could even extend insemination to in vitro fertilization; and collapse a bunch more species whose barrier is sperm-egg incompatibilities...It's all about reproductive isolation. It doesn't matter if it is pre- or post- mating isolation, it is still reproductive isolation. 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. Why yes, yes it does. That's all biological speciation is - reproductive incompatibility.

Considering that speciation has been observed, I wouldn't say we'd have to wait that long: Observed Instances of Speciation
The article happens to also contain this bit relevant to my previous post (emphases mine): Neither description of the BSC includes human intervention as an exception.

Your definition is NOT the one promoted by TalkOrigins, rather it is a quote-mine, mistaken or not. It is taken from a passage describing the history of species concepts. I describe the accepted version of the BSC in my above post.

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.

Exactly. By calling it "the TalkOrigins definitions"... ...when essentially the next line after the excerpt you posted was... ...followed by what TalkOrigins "accepts" as the accepted definition. 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. 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.

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

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: It's pretty straightforward. 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.

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: 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. 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... It did at the time I brought it up.

You are correct - I oversimplified (again) on that point.I should have said, "the mutation results in snails with the opposite shell chirality...".