Transplanted Lizards Evolve New Traits in Just 36 Years?

Science Daily reports on a new study in which a species of lizards, transplanted to a new island, evolved a number of new traits in just 36 years. As is often the case with Science Daily, I’m a little skeptical of the reporting. If the transplanted lizards experienced morphological changes, how could they be genetically “identical” to the source population? And no matter how rare these “cecal valve” structures are in lizards, the fact that they are known in other lizards should at least suggest the alternative hypothesis that they are an environmental reaction rather than a genetic change (though it could also be a very simple and common mutation that only takes hold in certain environments).

In any case, rapid evolutionary change in response to a new environment is actually nothing new. Many previous studies have transplanted species into a new environment, and then observed morphological changes (the unit of measure here is charmingly called a “Darwin“) happening that are orders of magnitude faster than the fastest changes observed in the fossil record.

Findings like these are part of why the incredulity of most creationists about the power of evolutionary change is hard to square with the known realities of biology. If anything, one of the big mysteries in evolution is not how large changes can possibly happen quickly (or happen at all), but rather just the opposite: why change seems to have happened so slowly in the past compared to the potential for speedy change that we observe in the present.

Advertisements

13 Responses to Transplanted Lizards Evolve New Traits in Just 36 Years?

  1. Nimravid says:

    They only sequenced a bit of the genome, so there may be other changes. Additionally a lot of changes are tweaked by gene regulation without much genetic change occurring.

    I read about this article too and posted in on my blog a while ago. My question was whether they’d surveyed other islands in the area to make sure there wasn’t an older population with the same traits that happened to invade their test island. I’m sure that they did, since that would be an amateur mistake. The paper itself was only a couple pages so hopefully when they do a longer writeup we’ll get more detail.

  2. Glazius says:

    March 25, 2008 this was published in the Proceedings of the National Academy of Sciences, under the title “Rapid large-scale evolutionary divergence in morphology and performance associated with exploitation of a different dietary resource”. If you have a way of getting article reprints you can check this out yourself.

    To trace it genetically, they didn’t sequence the lizard genome, they matched the mitochondrial DNA, which doesn’t have nearly as much cause to rapidly change. The population of lizards matched the originals much more closely than it did any lizard species from a neighboring island.(If you did read the original article, it’s supplementary figure 5, which is a link in the PDF.)

  3. elfinugget says:

    I’m with Nimravid – gene expression and regulation seems much more likely – I’m sure it’s a conserved sequence in the genome common to many species of lizard.

    Granted, it may lead to further changes if the population is left separate for a good twenty-thousand years, but . . . in the meantime. . . . they see this kind of divergence in plants all the time. (Plants just have, in general, a much longer genome)

  4. Perhaps apropos of nothing…

    I am well out of my depth here – I have not been in a science class in a decade, and it isn’t part of my field or passion…

    But could an analogy be drawn between this lizard population and the Soviet-era siberian experiment with domestic foxes? In that case the manipualation was to selectively breed the most docile to the most docile… After about 10 generations of doing just that, the foxes the produced had dropped ears, wildly varying coat patterns and colors and began to… get this… bark!

    I am not all that skeptical about the possibility of a lizard population adapting in a short amount of time… How many generations exactly does a 36 year period allow for?

    Another question that comes to mind – that may not be relevent, but I just happened to think of it – is there a possibility of any cross-breeding having occured with a different type of lizard that may have existed on that island? Just a thought.

    All very interesting!

  5. Glazius says:

    is there a possibility of any cross-breeding having occured with a different type of lizard that may have existed on that island? Just a thought.

    Genetic testing was done with mitochondrial DNA, not chromosomal DNA. mDNA is much more highly conserved, though it’s only inherited matrilineally.

    It’s within the realm of possibility that interbreeding occurred only male-to-female and then the other lizard species was overrun, but that would be extremely remote and biologically unprecedented.

  6. JimD says:

    asimplesinner Quote:
    “Another question that comes to mind – that may not be relevent, but I just happened to think of it – is there a possibility of any cross-breeding having occured with a different type of lizard that may have existed on that island? Just a thought.”

    But the lizard is still a lizard and the dog is still a canine though a different breed or flavor. Science has yet to prove one species can change to another without intelligent manipulation of the animals DNA.

  7. Glazius says:

    Science has yet to prove one species can change to another without intelligent manipulation of the animals DNA.

    Ah, so Schilthuizen’s survey of Lake Malawi and documentation of new cichlid species arising in lake offshoots that weren’t there 100 years ago (in this book) is just a tissue of lies, then?

    The two separate Hawaiian butterfly species adapted to feed from banana flowers are just so much fairy petals, since there weren’t any bananas on Hawaii 1000 years ago?

    The monkey-flowers (genus Mimulus) adapted to high copper concentrations aren’t actually growing in the tailings of California copper mines, since there weren’t any California copper mines before the 1850’s?

    Speciation happens slowly but it’s been documented. Also documented are cases of incipient speciation – the so-called “ring species” of salamanders, mice, migratory birds, etc, where each subspecies can only breed with one or two others, meaning all it takes is for one link in the ring to snap (through extinction or evolution to lock off one of its breeding partners) and suddenly one species becomes two.

    Thanks for playing, please enjoy this edition of our home game!

  8. Glazius says:

    Science has yet to prove one species can change to another without intelligent manipulation of the animals DNA.

    Ah, so Schilthuizen’s survey of Lake Malawi and documentation of new cichlid species arising in lake offshoots that weren’t there 100 years ago (in “Frogs, Flies, and Dandelions: Speciation”) is just a tissue of lies, then?

    The two separate Hawaiian butterfly species adapted to feed from banana flowers are just so much fairy petals, since there weren’t any bananas on Hawaii 1000 years ago?

    The monkey-flowers (genus Mimulus) adapted to high copper concentrations aren’t actually growing in the tailings of California copper mines, since there weren’t any California copper mines before the 1850’s?

    Speciation happens slowly but it’s been documented. Also documented are cases of incipient speciation – the so-called “ring species” of salamanders, mice, migratory birds, etc, where each subspecies can only breed with one or two others, meaning all it takes is for one link in the ring to snap (through extinction or evolution to lock off one of its breeding partners) and suddenly one species becomes two.

    Thanks for playing, please enjoy this edition of our home game!

  9. Glazius says:

    Science has yet to prove one species can change to another without intelligent manipulation of the animals DNA.

    Ah, so Schilthuizen’s survey of Lake Malawi and documentation of new cichlid species arising in lake offshoots that weren’t there 100 years ago (in “Frogs, Flies, and Dandelions: Speciation”) is just a tissue of lies, then?

    The two separate Hawaiian butterfly species adapted to feed from banana flowers are just so much fairy petals, since there weren’t any bananas on Hawaii 1000 years ago?

    The monkey-flowers (genus Mimulus) adapted to high copper concentrations aren’t actually growing in the tailings of California copper mines, since there weren’t any California copper mines before the 1850’s?

    Speciation happens slowly but it’s been documented. Also documented are cases of incipient speciation – the so-called “ring species” of salamanders, mice, migratory birds, etc, where each subspecies can only breed with one or two others, meaning all it takes is for one link in the ring to snap (through extinction or evolution to lock off one of its breeding partners) and suddenly one species becomes two.

  10. Glazius – thanks for the clarification! Again, havne’t been in a science class in a decade, if I ever knew that, I had long forgotten.

    This is all very fascinating.

  11. Bad says:

    JimD Says: But the lizard is still a lizard and the dog is still a canine though a different breed or flavor. Science has yet to prove one species can change to another without intelligent manipulation of the animals DNA.

    I sometimes wonder if people are putting me on when they make claims like this. I’ve explained this over and over so many times on this blog that I start to get sick of it.

    Once again: if you think of speciation as a process by which a species transforms into a different sort of thing: a new thing classed on the same level as its forbears, then you are quite missing the point, and its no wonder your mistaken view of evolution stands in contrast to reality.

    Evolution, however, is descent with modification: new groups nested within old groups, not leaping laterally.

    Yes: the ever diversifying descendants of the original dogs are indeed “just” a different breed or flavor. But that’s the case all throughout all evolutionary history. Human being are simply a breed of ape, which is a breed of primate, which is a breed of mammal, and so on.

    Defining what a “species” is isn’t easy: and in fact, it’s a problem precisely for the reasons we would expect if evolution is true. But perhaps the simplest to understand definition concerns whether some group can breed with a different group of the same ancestry. Creationists seem to see this as some sort of magical barrier. But in reality, these species barriers (which happen for all sorts of different reasons) are nothing more than the effects of the very sorts of variations that most creationists already admit to.

    Abalone, for instance, have a neat “lock/key” system for their broadcast reproduction methods: only some protein codes in abalone sperm will work on other protein keys in abalone eggs. The but the necessary exactness of the match is somewhat fuzzy, and mutation is constantly fudging both the lock codes and the key codes, and the result is often rapid speciation do to some now isolated portion of ablones ending up with locks that only work in specific keys, both budded off from the original set of compatible combinations. From there on out, these different species become reproductively isolated from each other: the new “breeds” that arise in one cannot help shape the other. And so the lines diverge over time.

    And that’s all there really is to it.

  12. oceallaigh says:

    Bad wrote:

    why change seems to have happened so slowly in the past compared to the potential for speedy change that we observe in the present.

    My take: most of the “rapid speciation” events that we observe in the present day are of populations with a high capacity for variation (relatively non-stringent DNA replication) and relatively low selection pressure allowing most of those variants to survive and compete.

    Most of what we see in the fossil record are long-lived species subjected to high selection pressure (“stay where and what you are, or you’re dead”) and successful under this type of pressure.

    There are points in the evolutionary history of many domains of life where a whole bunch of lineages appear to have arisen almost simultaneously; for example, the ancestors of most of the lineages of multicellular animals appeared in a “brief” window just before and during the Cambrian period; most land plant lineages appeared in a “brief” window around the Silurian period. It is difficult to trace the history of these lineages during these “evolutionary nodes”. It may be that these were times when species were evolving under lax selection pressures, analogous to those now observed in these lizards and the other examples Glazius mentioned. Most of those species did not last long enough to be captured in fossils. We see only those of their descendants that survived the imposition of tight selection pressures later on.

  13. Hey, cool tips. Perhaps I’ll buy a bottle of beer to that man from that forum who told me to visit your blog :)

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: