Home » extinction, News » Rapid evolution of asexual species … toward extinction

Rapid evolution of asexual species … toward extinction

water flea/Indiana University

Researchers studying the water flea, which features both sexual and asexual genotypes (the asexual ones reproduce when females simply lay unfertilized eggs that hatch, a process known as parthenogenesis) found:

Ground-breaking new research from a team of evolutionary biologists at Indiana University shows for the first time how asexual lineages of a species are doomed not necessarily from a long, slow accumulation of new mutations, but rather from fast-paced gene conversion processes that simply unmask pre-existing deleterious recessive mutations.

In another remarkable finding from the genome-wide survey for asexual markers, the team was also able to determine the age of the entire asexual radiation for D. pulex. Just a few years ago biologists were guessing that asexual daphnia lineages could be millions of years old, and most recent estimates put it between 1,000 years and 172,000 years. But new calculations for the molecular evolutionary rates of the two chromosomes implicated in asexuality date the establishment and spread of the asexual lineage to just 1,250 years ago. Some current asexual lineages, in fact, were only decades old, younger than Lynch himself.

“A pond of asexual daphnia may go extinct quite rapidly owing to these deleterious-gene-exposing processes, but the small chromosomal regions responsible for asexuality survive by jumping to new sexual populations where they again transform the local individuals to asexuality by repeated backcrossing,” Lynch said. “Soon after such a transformation, the processes of gene conversion and deletion restarts, thereby again exposing resident pre-existing mutations leading to another local extinction event. As far as the sexual populations are concerned, asexuality is infectious, spreading across vast geographic distances while undergoing no recombination.”

Perhaps further study will show that the spread of asexuality is a common cause of extinction of susceptible species.

  • Delicious
  • Facebook
  • Reddit
  • StumbleUpon
  • Twitter
  • RSS Feed

10 Responses to Rapid evolution of asexual species … toward extinction

  1. Ha!

    Evidence Darwinism doesn’t work as advertised:

    Natural Selection is daily and hourly scrutinising, throughout the world, the slightest variations; rejecting those that are bad, preserving and adding up all that are good.

    C.DARWIN sixth edition Origin of Species — Ch#4 Natural Selection

    In this case the bad just keep accumulating till it kills off a lineage. The lineage doesn’t march inevitably toward improvement but extinction.

    The same is true for sexually reproducing species, but maybe slower in some cases.

    If the fittest were the parents, then the fittest have died, just as I predicted.

    http://www.uncommondescent.com.....e-fittest/

    But these simple truths are ignored by evolutionary biologists. Instead tenure and reputations are conferred to those determined to perpetuate theoretically and empirically falsified ideas like Darwinian evolution.

  2. I don’t understand how this information forms an argument for or against evolution. Obviously we have a lot of evidence, even controlled lab experiments, of asexually-reproducing organisms improving their fitness.

  3. Well, that’s not what this study showed about asexual water fleas.

  4. I don’t understand how this information forms an argument for or against evolution. Obviously we have a lot of evidence, even controlled lab experiments, of asexually-reproducing organisms improving their fitness.

    Improvement in fitness can lead to extinction because “fitness” is so poorly defined as to mean loss of function and such narrow specialization that a population becomes at risk due to environmental changes. Those lab experiments perpetuate the illusion that reproductive success means the population is necessarily better adapted to future adversity. At best it shows selection can in some cases slow decline, but there are cases where selection is known to ensure persistence of malfunction (like sickle cell anemia or anti-biotic resistance through loss of function).

    If strong selection for a single trait results in elimination of other useful traits, this is a bad situation, and “fitness” improvement is only in the eye of the beholder.

    The problem with evolutionary “proofs” is that it is rooted in cherry picking. The evidence of extinction and decline versus evolutionary advance toward complexity is abundant. See:

    http://www.uncommondescent.com.....darwinism/

  5. Improvement in fitness can lead to extinction because “fitness” is so poorly defined as to mean loss of function and such narrow specialization that a population becomes at risk due to environmental changes.

    “Fitness” is a really simple math identity, usually we say it’s the number of surviving organisms after selection, divided by the number before — relative fitness is used more, and that’s just a count of an organism’s surviving children relative to its competitors.

    That fit individuals thrive in one environment (a big lake) and die in a very different one (a tiny puddle) is really not a surprise. If a dog fell and drowned in the ocean, we would’t say that it’s loss of the trait for gills was a maladaptation or a “loss.”

    Those lab experiments perpetuate the illusion that reproductive success means the population is necessarily better adapted to future adversity.

    I think you might be confused and think that fitness somehow relates to some sort of teleological desirability. It’s really just a question of how many kids survive, there’s no way to predict “future adversity” or to say that a particular trait will “come in handy” or “be a ticking time bomb.” That would require making value judgements. Lab experiments do not prove that populations are better adapted to future adversity, nor does anyone claim so — when Lenski’s E. Coli eat citrate, nobody’s saying that they’re better for it, or that they’re a more perfect E. Coli, nor does evolutionary theory require this.

  6. Well, that’s not what this study showed about asexual water fleas.

    I know. In light of that I don’t see why it got posted here…

  7. 7
    TheisticEvolutionist

    More evidence for saltational evolution. Good stuff.

  8. I find it incredibly ironic that this website is using Michael Lynch’s work as some sort of evidence against evolution.

    Whoever wrote this must have never even heard of i>The Origins of Genome Architecture let alone read any of his other writings….

  9. Isn’t it interesting that there are 3 different interpretations of the results of this study?

    And all three seem to be greatly influenced by the worldview of the interpreter!

    Science itself can tell us very little when it comes to the unobservable unrepeatable untestable distant past.

    Even tho this experiment was done in the present, there is still dispute on how to interpret the findings!

Leave a Reply