Art of Reasoning

Please first watch the 3:15-minute YouTube video (which opens in a new page/tab), and then come back to this page to read the analysis of the argumentation.

Now, let us consider the important points….

We do not find any hybrids between them. They cannot interbreed. Why is this? — In this one statement and question we find the crux of the entire argument for “ring species.” Notice that the entire basis for claiming that some sort of speciation event has taken place rests on the Biological Species Concept (BSC). If two species can interbreed with neighboring populations, then they are the “same species” as the neighboring populations. But when two neighboring species (with overlapping ranges) “cannot interbreed,” then it is believed that “reproductive isolation” has occurred, resulting in what properly must be considered as two separate species.

The gradual evolution of one parent species into two distinct daughter species —  Awesome! Here it is: evolution in action. If this claim can be sustained, it is indeed a compelling example of evolution in action. And so-called “ring species” are claimed by the heavyweights, including Ernst Mayr, as the most compelling examples of evolution in action that we know of.

Entered California’s coastal ranges from Oregon’s Cascade Mountains — This is a critical point, and we make the same point again when talking about the greenish warbler “ring species” example. The first point that scientists must establish to get the notion of a “ring species” off the ground is that of a starting point! Every ring species simply must start at one geographical point and then begin to migrate into territory it did not previously occupy. As we will see, the entire “ring species” argument is a non-starter if there were always Ensatina salamanders throughout their present range. The purported “starting point” of the “migration” is critical!

The Central Valley formed a barrier where the salamander could not inhabit — This is the second crucial point in the “ring species” argument. All “ring species” must start at one geographic point, then migrate, then encounter some geographical barrier that forces the population to “split” in its migration. So, already we see the theory being that the salamander started in Southern Oregon, migrated South into California, encountered the Central Valley (too dry for salamanders to inhabit), and part of the migrating population pushed South and West, while part of the migrating population pushed South and East, producing a “ring” around the Central Valley.

The two populations became isolated from each other —  It is critical to the “ring species” theory that the two populations become geographically isolated by the geographical barrier. This geographical isolation is the defining characteristic of “allopatric speciation,” which just is speciation produced by geographic isolation. If the two populations were interbreeding as they moved South, then the ultimate reproductive split between them when the “ring” joined would be inexplicable. Instead, because of the geographic isolation, which genetically isolated the two, distinct, Southward migrating populations, the “ring speciation” argument can easily assert that natural selection was playing is predicted role in genetic drift.

As the populations spread Southward, they faced unique environments to which they had to adapt —  And here is natural selection in action. Given that the populations are both geographically and genetically isolated, the only explanation for the differing genetic drift between the populations is that natural selection is doing what we would expect it to do: produce morphological and genetic changes in a population. And because these are “parallel” populations with a common ancestor, and differences we observe between them must be attributable to evolution at work. It is perfect! The changes produced by “adaptation” accumulate in each branch as each branch migrates ever Southward, and the “adaptations” are necessarily different, as the two populations encounter different conditions to the East and West of the Central Valley.

The descendants of these populations converged again at the South end of the valley — And here is the final component of the “ring speciation” model: The two distinct populations again encounter each other and have one range that they occupy. They started together, and then finish together.

By that time they had genetically drifted so far apart that interbreeding was no longer possible — So, they started together, then split around a geographical barrier, then evolved as they migrated South in parallel but isolated from each other, then combined ranges again at the South end of the valley. But now they are two different species, because, as a perfect example of the BSC, the genetic drift between the (now) two species became so significant that genuine reproductive isolation was complete.

This is perhaps the best known example of what has been called a “ring species” — “Perhaps” indeed. That honor probably goes to the greenish warbler, as we will see on the next page. Certainly this example and the greenish warbler are together the best known and most pointed-to among the putative “ring species” examples. The point here is that we are not looking at “edge cases” that scientists can respond to by saying, “Well, those are not even good examples of the phenomenon! We have much better examples than those.” No, this and the greenish warbler are the paradigm and most oft-cited examples of true “ring species” and clear-cut, dramatic cases of “evolution in action.” So, we will focus on these two examples, and the points we make will apply even more strongly to the “edge cases” that are not such clear-cut examples.

Now, let us closely example what is happening

This example shares the same critical five points as does the greenish warbler (and all other putative “ring species”), so we will list the critical points here and then refer to them by number:

1) There must be a “starting species” that is geographically static. It has not “yet” migrated into “new territory,” which would constitute territory it did not yet occupy. So, in this example, at some point in time you “start” with Northern Ensatina salamanders, and South of them there are exactly zero Ensatina salamanders.

2) That “one species” must then start to “migrate into new territory” that it did not previously occupy. The population of Ensatina salamanders (at a later point in time from the “start” in point (1) above) grows and expands to occupy territory not previously occupied.

3) The migration must have a particular direction. It won’t do to claim that there are simply Ensatina salamanders all over California, as that would make establishing the critical “starting point” impossible! In the case of the Ensatina salamander, that direction is supposedly South (coupled with both East and West around California’s Central Valley).

4) A substantial, “impassible,” geographical boundary must divide the migration into two “branches,” where what is still “the same species” begins to occupy geographically isolated ranges, isolated by the boundary. The geographical isolation must genuinely separate the two “branches” of “the species.” This is the role played by California’s Central Valley in the salamander example. And there must be no geographic isolation within the “branches” (this ensures gene flow and “adaptation” in each branch.

5) The boundary must have an “end” at some distance from the starting point, so that the “diverging species” can be kept geographically isolated from each other but then ultimately “brought together” again at the “end” of the migration around the boundary. Only by comparing the species at both ends of the boundary can it be determined what the genetic result of the “migration” actually was (whether it was “enough” to produce a speciation event).

6) The geographic isolation during “migration” must produce genuine and persistent genetic isolation during the “adaptation” that supposedly occurred during the “migration.” In this case, as this video states, the two “end species” cannot interbreed.

Can any of these five points be sustained by the evidence?

Well, the well-known biology site, actionbioscience, tries to sustain point (1) and (2) this way:

Stebbins thought that this situation arose when an ancestral population of salamanders, in northern California, expanded southward along two fronts, one down the Sierra Nevada mountains, and the other down the coastal mountains. The two groups gradually became different as they moved south. When they met again in southern California, the two expanding fronts were so different that they rarely interbred, and were therefore different species. More recently, a team of researchers led by David Wake has examined genetic relationships among salamander populations using DNA sequences and other molecular traits, and the genetic evidence has supported Stebbins’ hypothesis. The geographical variation, when combined with the inferred history revealed by the molecular traits, allows us to envision the small steps by which a single ancestral species in the north gave rise through evolutionary divergence to two species in southern California.

So, David Wake is cited as the genetic researcher providing the “genetic relationships” evidence that in 2002 prompted actionbioscience to post this article.

However, in 2010, Jerry Coyne authored a book entitled: Why Evolution is True. In that book Coyne quotes and cites Wake and summarizes:

The problem, as David Wake now admits, is that these salamanders never comprised a continuous ‘ring,’ but were separated geographically on and off over millions of years, so it’s entirely possible that the reproductive isolation did not occur through the gradual attenuation of gene flow with distance.

Wait! Wait! David Wake is the expert on the Ensatina salamander “migration” based upon his genetic research. What can this mean?

Jerry Coyne himself, on his website, states that “there are no ring species” and explains why Wake has been incorrect on these crucial points. Note that Coyne is an evolutionist. Coyne is simply being intellectually honest about how things really work and that the whole “ring species” idea has so far proved to be unsustainable. He writes:

There used to be several examples of “ring species” that were staples of evolution textbooks, the most famous being the salamander Ensatina eschscholtzii in California. This species was first worked on by Robert Stebbins but later and most intensively by David Wake of the University of California at Berkeley and his colleagues.  It was a classic example supposedly demonstrating all the principles I described above….

The ring closed when the ranges encountered each other in southern California, where the subspecies E. eschsholtzii eschscholtzii encountered the long-diverged subspecies E. e. klauberii. These two did not interbreed in nature, and so behaved as different species. Genetic studies demonstrated a long divergence between these, attesting to the “move around the ring” scenario, but also to a lesser divergence between adjacent populations….

This complex, then, was long regarded as the paradigm of ring species, and was (and is still in places) taught as an example of this form of speciation with gene flow.

Except it’s wrong. That is, it’s not a ring species in the classical sense. Why not? Because genetic studies, done by both Dick Highton at Maryland and then by Wake and his colleagues themselves (references below) also showed that in places around the ring there were sharp genetic breaks, suggesting not a process of continuous gene flow over the 5-10 million years it took to close the ring, but sporadic geographic breaks in the ring, so that the salamanders could differentiate without pesky gene flow from adjacent populations. Some adjacent populations showed very sharp genetic differentiation, implying geographic isolation in the past (Continuous gene flow would not produce such “breaks”.) Finally, geologic work has shown that it is very unlikely that there were two unbroken forest corridors for those millions of years required to produce a ring.

Well, that’s a bummer, but it still shows how geographic isolation by distance can promote reproductive isolation and speciation. Other putative cases of ring species, including gulls in the genus Larus encircling the Arctic, also fell victim to genetic studies, showing that it was very unlikely that they were ever a continuous ring that was geographically uninterrupted.

Now, keep in mind that Coyne is not claiming that evolution has not occurred in the Ensatina salamander population! He is only claiming (and citing Wake as agreeing) that points (1) through (4) of “ring speciation” have not been demonstrated and that likely (3) and almost certainly (4) are untrue.

So, already we see the claims of this video falling apart. But things get even worse for it.

If (1) through (4) are not established, and (4) is almost certainly untrue, then the whole notion of a “ring” goes out the window, and with it the ability to demonstrate that the “initial” population “evolved” into one or both of the Southern “forms” of the salamander. Take away the “ring” and its associated “genetic flow” down the “branches,” and you are left with a big, spread-out population of salamanders, and that without any ability to “map” the “flow” of “evolution” down the “branches” of the population. There is no demonstration of “process” over time, and there is only the remaining speculation (that Coyne and Wake continue to cling to) that the two “branches” did have different environments that did produce genetic differences sufficient to cause a speciation event. Only now, such scientists don’t have “flow” or “process” to bolster their speculations. Again, all they have is a big pile of salamanders occupying geographically diverse environments. These salamanders are “genetically similar,” but the researchers can no longer demonstrate that “one kind” became “another kind.” Perhaps all of the salamander “kinds” have always been spread out there more or less as they now are, without any “process” relating them in evolutionarily relevant ways.

Now, even worse for the initial hope of “ring species” force indicated in the video, it turns out (as with all putative ring species) that the “end forms” actually do interbreed; they are not “reproductively isolated” as was initially thought.

As Irwin noted in 2001 on page 232 (this realization has been around a long time, although sites and videos still claim what is not true), there has been “hybridization” between the “end species” in the Ensatina salamanders. This is a technical term that means that enough interbreeding is taking place that the genes of one population can be found in observable quantities in another population. Contrast that with interbreeding without hybridization, in which case some interbreeding is observed but without observable genetic flow between the populations (which means that the interbreeding is the exception and happens infrequently). For hybridization to occur (as Irwin notes), the interbreeding must be frequent enough that genetic flow between the populations can be observed.

Summary

The Ensatina salamander has been widely cited as one of the two best examples of ring species in existence. Websites and videos continue to claim all of the power of ring speciation for this species and the green warbler (the other biggie). Lay evolutionists are downright derisive of creationists on the basis of this “overwhelming evidence” of “evolution in action.” Yet, none of the “power” is demonstrated, and most of it has lately been outright falsified (often by the very researchers who first claimed to demonstrate the power).

Points (1) through (4) are based upon speculation and genetic research that has since been entirely revisited with different results. Point (5) is irrelevant in the absence of the first four, as there is no reason to think in terms of an “ending population” when there is no demonstration of a starting point or migration.

Worse for points (1) through (5), the whole point to a purported “ring species” is that there is demonstrable genetic flow between the populations in each “branch,” such that it cannot be said that any point along each branch has become a “new species.” So, there is in principle no demonstration of natural selection to produce new species all along the entire length of the “branches.” The hope of the “ring species” model is that the “new species” emerges at the “end points” of the branches. However….

Point (6) is flatly false, as the “end populations” can in fact interbreed and do so frequently enough that hybridization has occurred.

So, this “amazingly compelling” case demonstrates nothing about evolution at all. The likes of Coyne and Wake can continue to believe all they want that they are learning something about evolution by following genetic flow on the “branches,” even if the whole is not demonstrating a “ring species” at all. But the unbiased mind reviews the evidence (and how it has developed over time) and sees that the Ensatina salamander population does not clear the BSC bar at any point along the “branches” nor even at the “end points” where the BSC speciation was supposed to have been demonstrated.