Speciation marches on...

[River]

Evolution in action!

Darwin’s finches may be the best-known example of evolution by natural selection, yet a new study suggests that one species of this famous group of birds may be reaching an "evolutionary dead end." According to a paper in PLoS ONE this week, the mangrove finch—one of the rarest birds in the world—is undergoing a speciation event that could reduce it to two populations with dangerously small numbers.

There are only about 100 mangrove finches in the world, and they are all confined to Isabela, one of the Galapagos islands. Only two populations survive: one group of about 80 birds on the island’s west coast, and a tiny population of about 20 on the island’s eastern side. The two populations are separated by more than 40 miles of lava desert and volcanic terrain, and the authors estimate that they have been isolated from each other for more than 100 years.

The authors decided to test whether this isolation has caused enough divergence between the two populations that they are unlikely to interbreed. They recorded the songs of 20 male mangrove finches on the western population, and the songs of the only 2 males they could locate in the eastern population. They found significant differences between the two groups in song duration, syllable rate, and peak frequency.

Moreover, when the eastern songs were played to finches on the west coast (and vice versa), the birds responded much more strongly to songs from their own side of the island. Male birds increased their territorial behavior and female birds approached the loudspeaker at a much higher rate when a local song was played than when the other population’s song was played. The responses to the other population's songs were low for males and nearly nonexistent for females (although the sample size for female responses was merely 5 finches).

These results suggest that birds from opposite sides of the island might not recognize each other by song and, since song is a major part of the courtship ritual in mangrove finches, they would likely show little or no interest in breeding with each other. Once this type of reproductive isolation occurs, the two populations can be considered separate species.

In addition to the song divergence, the authors show evidence of both morphological and genetic differences between the two populations. Birds on the eastern side of Isabela have a dark stripe on their breasts that western birds lack, and the authors found they had seven completely unique alleles when a panel of 16 variable DNA regions was genotyped. If speciation is occurring—or already has occurred—in mangrove finches, they are likely to face extinction. With minute population sizes and no interbreeding, it is very likely that one of Darwin’s famed finches will go the way of the dodo.

It's sad to lose a species, but, on the other hand, it's incredibly cool to be able to make these observations.

[yovargas]

Damn that's cool.

[Dave_LF]

Shouldn't that be "Genetic drift and/or sexual selection march on..."

[River]

Noted. Also noted that I should not open topics before being properly caffeinated.

[Dave_LF]

Almost one and you're not properly caffinated yet. You poor individual.

[River]

I started the topic before 9 am. But I'm still not properly caffeinated.

[Dave_LF]

Of course. And I spelled caffeinated wrong too. I don't have an excuse, though...

[Frelga]

Isn't that one of the "arguments" used against the theory of evolution, that no one has ever seen this sort of thing in action?

* brews a nice cuppa for River *

[Primula Baggins]

Some evolution opponents say this kind of thing is "microevolution," the existence of which doesn't prove that evolution itself happens.




Edited for snarkiness

[yovargas]

That's inaccurate and a bit unfair, Prim. The distinction made between the two is more like the difference between modifications to an existing trait (eg. a red bird evolving dark streaks) vs appearance of brand new ones (eg. a red bird evolving, I dunno, more eyes or sumfin). I do think the attempt to make this distinction is highly problematic but it is a more meaningful distinction than what you're making it out to be.

(Your post sounded kinda snarky which didn't seem helpful; if snarkdom wasn't intended then my apologies.)

[Primula Baggins]

That was a good catch, yov. I'm having computer troubles that are causing me to lose my typical sunny happy-baby-bunny-rabbit outlook on life. Not to mention the fearsome swearing that's frightening the dog.

<trouts self>

That said (and edited), I do maintain that some find the flexibility of that definition pretty useful. If there's easily available data, it's too trivial and everyday to provide any support for a theory; if data is hard or impossible to come by, that proves the theory false. I don't mean to be snarky here at all. I'm pointing out what I see as a flaw in some antievolutionary arguments—put forth by people who are honestly trying to use the tools of science to make their case.

[yovargas]

I don't disagree. I think many who are earnestly making that distinction (a distinction that's at least potentially interesting to ponder, imo) unwittingly end up doing some odd rationalization-dances.

[Primula Baggins]

Thanks, yov.

It's the difficult-to-accept fact that theories stand, not because they're easy to prove, but because so far no one's been able to disprove them. That's not how people generally think in their daily lives; we want to see tangible proof of things that matter. Absence of disproof is kind of abstract and out there, and we're trained by life experience (with, say, teenagers coming in late) to distrust complicated explanations.

[MithLuin]

It would also be unfair to claim that only those who are attempting to disprove or discount or disregard evolution use the distinction between 'microevolution' and 'macroevolution' - you can find those terms in standard biology textbooks (and I'm not referring to texts written by creationists).

Microevolution is, perforce, much more observable. Scientists are more comfortable tracing the origin of an extra stripe than, say, how an eyeball developed in the first place. It's a little harder to see the progression from eyespots to eyeballs that actually work.

This is a really cool article, though. I can't say I will be heartbroken if the mangrove finch (or do they get two different names now?) becomes extinct. But understanding how isolation of tiny populations can be dangerous is important, so actually watching the demise (or potential rebound?) of this bird will be rather informative.

[River]

Among biologists, microevolution applies to everything short of a speciation event. Once you get into the divergence of species, that's macroevolution. When the two populations are no longer capable of producing viable offspring, things have moved past small changes that might occur either because there's no new blood in the gene pool or the environment requires a slightly different trait. Even if the two populations have only subtle differences in appearance, if they can't make babies, that suggests that the genetic differences are quite far apart. If someone is trying to write what's happening in the Galapagos off as microevolution (and it doesn't look like anyone is), they're either being intellectually dishonest or they don't understand the term.

[anthriel]

I guess I'm unique, because I haven't the tiniest problem believing in micro and macro evolutions, AND in creationism. I truly do believe there was and is a creator (I know that officially lowers my IQ in many of your books, but there you go), and I don't understand why anyone has trouble following the obvious similarities between species, and the logical associations that come with those observations. Obviously things are different, but closely related, and perhaps had common origins. I think of evolution as a tool, used by the creator.

People seem to think if evolution is acknowledged, we must not have a creator. Or if one believes in a creator, then we can't have evolution. I see it like a chef and his spatula. Acknowledging the spatula hardly negates the chef. And believing there is a chef doesn't mean one has to ignore the fact of the spatula.

And no amount of ignoring the spatula is going to lead people to consider a possible chef. If you are one who does not believe there was a creator, then that's what you believe, and evolution is the whole answer for you. That's cool. Works for me. I just have no issues with either.

But anyway... this is a really neat story, River. Thank you for posting it!

[Frelga]

(I know that officially lowers my IQ in many of your books, but there you go)

Anthy! You are doing it again. It pains me, it really does, that you imagine us putting you down in such way. Or any way.

Anyway, I really don't have a problem with it, either. The way I see it, even assuming the Bible is actually literally God-given, it was God-given to a bunch of refugee slaves in the middle of the desert. It was the giving of the Law. It does not seem reasonable to expect the Lord to start with a lecture of astrophysics, genetics and similar. It wasn't the point, and it would go way over their heads in any case.

[yovargas]

The final moment of this vid kills me:

http://www.youtube.com/watch?v=L640vc_X ... r_embedded

[Voronwë the Faithful]

(I know that officially lowers my IQ in many of your books, but there you go)

Anthy! You are doing it again. It pains me, it really does, that you imagine us putting you down in such way. Or any way.

I don't want to osgiliate this thread too much, but Anthy is not the only person who has felt that way at this site. I myself have seen comments that I could easily understand making people feel that way. So please don't imply that it is an irrational reaction, because it is not.

[River]

Guys, as the thread starter, I'm getting a mite uncomfy with the direction this is headed. I didn't start this thread to disprove the existence of a god - science can't even go there and many scientists, including ones who study things like cosmology and evolution, are religious and don't have issues reconciling their faith with their empiricism (Morgan Freeman covered this very elegantly in one of his Through the Wormhole episodes; I urge anyone interested to go find it as it is extremely well done). I just wanted to highlight one of the most interesting scientific observations I have come across in a long time. To be able to catch a speciation event within a period of recorded human history...that's huge. That's amazing. We're so very very lucky.

It also deals a strong blow to those who would dismiss evolutionary theory, but there's no need to be snarky about that. That's mean. Nor should there really be a need to fail to acknowledge what the finding means. That's dishonest.

But, all that aside, I wonder what this finding suggests in the larger scene of things. How many other species have, in the past, diverged without ever really getting off the ground? Which is more common? A lineage branching into success or a lineage branching into failure? The fossil record might help, but the thing about fossils is they only form under the right conditions and so if a species lives and dies out where fossilization is somewhere near impossible you won't see it in the record.