Friday, July 11, 2014

Proof that Boys Better Behave Because It Looks Like Evolution Is Playing On The Girl's Team!

No Sex Needed: All-Female Lizard Species Cross Their Chromosomes to Make Babies

These southwestern lizards' asexual reproduction is no longer a secret

asexual lizard
Since the 1960s scientists have known that some species of whiptail lizards need a male even less than a fish needs a bicycle. These all-lady lizard species (of the Aspidoscelis genus) from Mexico and the U.S. Southwest manage to produce well-bred offspring without the aid of male fertilization.

But how do they—and the other 70 species of vertebrates that propagate this way—do it without the genetic monotony and disease vulnerability that often results from asexual reproduction? "It has remained unclear" and "has been the topic of much speculation," report a team of researchers who aimed to answer just that question. Their results were published online February 21 in the journal Nature. (Scientific American is part of Nature Publishing Group.)

These lizards and other "parthenogenetic species are genetically isolated," explains Peter Baumann, an associate investigator at the Stowers Institute for Medical Research in Kansas City, Mo., and co-author of the study. Species as diverse as Komodo dragons and hammerhead sharks do it asexually if necessary, but some species, like these little lizards, don't have a choice. "They can't exchange genetic material, and this loss of genetic exchange is a major disadvantage to them in a changing environment," he says. Unless an animal can recombine the DNA they already have, they will produce an offspring with an identical set of chromosomes, in which any genetic weakness, such as disease susceptibility or physical mutation, would have no chance to be overridden by outside genetic material from a mate.

The new research by Baumann and his team reveal that these lizards maintain genetic richness by starting the reproductive process with twice the number of chromosomes as their sexually reproducing cousins. These celibate species resulted from the hybridization of different sexual species, a process that instills the parthenogenetic lizards with a great amount of genetic diversity at the outset. And the researchers found that these species could maintain the diversity by never pairing their homologous chromosomes (as sexual species do by taking one set of chromosomes from each parent) but rather by combining their sister chromosomes instead. "Recombination between pairs of sister chromosomes maintains heterozygosity" throughout the chromosome, noted the authors of the study, which was led by Aracely Lutes, a postdoctoral researcher in Baumann's lab.

This discovery, which had until now been unconfirmed in the reptile world, means that "these lizards have a way of distinguishing sister from homologous chromosomes," Baumann says. How do they do it? That's something the group is now investigating.

Another big unknown is precisely how the lizards end up with double the amount of chromosomes in the first place. Baumann suspects that it could happen over two rounds of replication or if two sex cells combine forces before the division process starts.

Although asexual reproduction might seem like a bore—and one that can have questionable genetic outcomes unless done right—it has its benefits, too, Baumann notes. "You're greatly increasing the chances of populating a new habitat if it only takes one individual," he says, citing the example of the brahminy blind snake (Ramphotyphlops braminus), another parthenogenetic species. "If she has a way of reproducing without the help of a male, that's an extreme advantage." Indeed it is—the brahminy has already colonized six continents.



  1. Oh, lordy. The author is seriously irritating (to me!); claiming several long discarded dogmas are current thinking- and I'm sure he knows better. There are zillions of asexual higher organism; my very favorite being dandelions. Flowers? yep; color, fragrance, nectar, bees - but NO SEX involved in the genes of the seeds. They seem to be successful, yes? Like; globally. So pretty obviously the old thing about "if there's no sex they can't adapt" is bullshit, and has been for a very long time. There are, I'll guarantee, thousands of different ways. Tetraploids (double diploid chromosomes) are old hat; I've got tetraploid frogs in my pond. My fave is the all female salamanders that live across the Mississippi from me; they are TRIPLOIDS; which are very rare, since you can't divide 3 by 2. They're sexual parasites on the parent diploid species; they have to mate with a male diploid; but no DNA exchange happens; they just copy the mom's DNA. Far weirder and likely more interesting than all female Tetraploids.

    We're at a place in Science where a huge amount of past research and knowledge is basically forgotten, and not very accessible. It's a really big problem-

  2. Just checking back to see if you'd responded to my rant yet; and what do I see? "If she has a way of reproducing without the help of a male, that's an extreme advantage."
    Argh. Bullshit. This guy is seriously undereducated. He's the blind man with a firm grip on the elephant's tail; unaware of the rest of the elephant; and arrogant about it. There's more to gender differentiation than just gamete formation. It's very common across many taxa for males and females - and juveniles - to utilize different sub-niches; in other words, they do not compete; and that means the species actually has access to more resources than if they were all identical. Among other things! :-)

    Actually, this is a major quarrel in the Biology world; the Field workers scorn the ignorance and narrow understanding of the Lab workers, who think the Field workers don't understand the vast power of new technology. Why would you need to know anything about the outdoors when you can dissect all the genes involved? Guess which side I'm on? :-)

    Lol. On my trip recently one of my hosts kind of blurted out "you're much less cranky in person than I was lead to believe!" :-) I thought that was pretty funny. I guess I AM cranky about science. Goddammit- it's really really important it be done right- and so very many times it is not. And it's usually just pure laziness.

  3. Um, ah...not really my area of expertise. I...appreciate your wide knowledge base... sorry about the war between lab and field workers.

    Should we talk about fashion?


  4. lol. Nah, you won't escape my cranks there! I think fashion is part of anthropology, as you do, if I recall! Anyway- I enjoy my rants. :-) I knew this was a repost, of course, and I understand why you would find it fascinating; I do too. But. It's a hot button for me when the "science writer" involved in these stories just takes them at face value, and doesn't even google "parthenogenesis in vertebrates"; and read the Wikipedia stuff. Which is excellent, incidentally; I just looked at it; and learned a new word! Which I love!

    Kleptogenesis is a sexually parasitic form of reproduction in unisexual organisms, that is often associated with species that are also capable of gynogenetic reproduction.[8] In this reproductive mode unisexual females mate with sympatric males of related species, and genetic material in the paternal line recombines with the maternal DNA and thus is passed on. This mode of reproduction can be seen in numerous, though not all, species of unisexual salamander, particularly salamanders in the genus Ambystoma,[3] and is implicated in the exceptional genetic diversity that exists in those animals.[7]"

    Same phenomenon I was telling you about, but I didn't know they'd called it Kleptogenesis! Is that a fabulous word or what?? Plus, this says some of the male DNA does get into the new individual; which they didn't know when I was studying (and TA'ing) Herps.

    Thank you so much! :-) See! It's all good.

    1. Ha! Latest info is; my salamanders do, and don't.

      Another truth; more often than not, in Biology and Ecology, the answer to "Does this happen or does that happen?" - the answer is "yes."

      All of the above.

    2. This comment has been removed by the author.

    3. "Anyway- I enjoy my rants. :-) "

      In particular, I enjoy my rants HERE - because you - tend to understand them, and me. :-)

    4. There are more things in heaven and earth, Horatio,
      Than are dreamt of in your philosophy.
      - Hamlet (1.5.167-8), Hamlet to Horatio

      rant on! :)

    5. Seriously, I can't wait to hurl "You kleptogenesis bred moron!" at someone who deserves it. And leer at their baffled fury. :-)

      Hey, it's late here.