Hybridization and parthenogenesis in whiptail lizards

by Greg Mayer

Not much in the way of culinary pleasures here. (Although Jerry’s piece on the Inquisition killed my appetite, anyway). Reader Pete Moulton asked for some references on hybridization and parthenogenesis in whiptail lizards (Cnemidophorus [or Aspidoscelis] and related teiid lizards), in particular C. (A.) uniparens.

Desert grassland whiptail, by Davepape from Wikipedia.

A. uniparens is a triploid unisexual. It resulted from a cross of two bisexual species (A. inornata [mother] and A. burti [father]), which produced a diploid unisexual, which then backcrossed to inornata to produce the triploid uniparens. The unisexuals reproduce clonally, i.e. offspring are exact genetic copies of their mothers, except for new mutations. Courtship and ‘pseudocopulation’ between parthenogenetic females promotes reproduction. The situation is summarized nicely by Cole et al. (2010):

The natural origin of diploid parthenogenesis in whiptail lizards has been through interspecific hybridization. Genomes of the parthenogens indicate that they originated in one generation, as the lizards clone the F1 hybrid state. In addition, hybridization between diploid parthenogens and males of bisexual species has resulted in triploid parthenogenetic clones in nature. Consequently, the genus Aspidoscelis contains numerous gonochoristic (= bisexual) species and numerous unisexual species whose closest relatives are bisexual, and from whom they originated through instantaneous sympatric speciation and an abrupt and dramatic switch in reproductive biology.

The selection of papers below includes both classics and recent papers, with a preference towards ones where online full text was available (see pdf links below). These papers are all about whiptails of the family Teiidae. Laurie Vitt and Jana Caldwell, in their fine text Herpetology (Academic Press 2009), record about 50 species of  parthenogenetic lizards (adding in a few they missed) in eight families (including the whiptails), and one species of parthenogenetic snake.

Wright, J.W. and C.H. Lowe. 1968. Weeds, polyploids, parthenogenesis, and the geographical and ecological distribution of all-female species of Cnemidophorus. Copeia 1968: 128-138. no pdf (A classic on unisexual ecology.)

Parker, E.D. and R.K. Selander. 1976. The organization of genetic diversity in the parthenogenetic lizard Cnemidophorus tesselatus. Genetics 84:791-805. pdf (A classic on unisexual genetics.)

Crews, D. and K.T. Fitzgerald. 1980. “Sexual” behavior in parthenogenetic lizards (Cnemidophorus). Proceedings of the National Academy of Science USA 77: 499-502. pdf (A classic on unisexual behavior.)

Reeder, T.W., H.C. Dessauer, and C.J. Cole. 2002. Phylogenetic relationships of whiptail lizards of the genus Cnemidophorus (Squamata, Teiidae) : a test of monophyly, reevaluation of karyotypic evolution, and review of hybrid origins. American Museum Novitates 3365:1-62. pdf (In this paper, the genus Aspidoscelis is resurrected for part of the genus Cnemidophorus; because there is such a huge literature under the name Cnemidophorus prior to 2002, both names must be used when searching the literature. The part on hybrid origin begins on page 25.)

Cole, C.J., L.M. Hardy, H.C. Dessauer, H.L. Taylor, and C.R. Townsend. 2010. Laboratory hybridization among North American whiptail lizards, including Aspidoscelis inornata arizonae × A. tigris marmorata (Squamata: Teiidae), ancestors of unisexual clones in nature. American Museum Novitates 3698:1-43. pdf

The American Museum of Natural History’s Digital Library has pdf’s of all the Museum’s publications, and it has been a center for studies of parthenogenetic lizards. More papers can be found by going to the Digital Library site and searching on ‘Cnemidophorus’, ‘Aspidoscelis’, and ‘parthenogenesis’.

UPDATE. The numbers of parthenogenetic species of lizards and snakes compiled by Vitt and Caldwell and given above refers only to obligately (or nearly so) parthenogenetic species, not facultatively parthenogenetic ones (like Komodo dragons, boa constrictors, and some other snakes; they have a separate discussion of the facultative species in their book).


  1. Pete Moulton
    Posted November 19, 2010 at 1:17 am | Permalink

    Thanks, Greg. This is exactly what I was hoping for. I’m not a herpetologist, just a nature photographer who wants to know as much as possible about his subjects (of which lizards constitute a significant fraction). Looks like this list will be keeping me busy for awhile.

  2. Posted November 19, 2010 at 4:27 am | Permalink

    Thanks also from a mom with a 10-year-old who loves lizards:)) The English was a little over his head, but I did my best to explain parthogenesis… (we use Japanese/English at home, so this post had lots of big words for him;-)

    There was just recently an article about a snake that had reproduced parthogenetically–same species as the one you referred to in the post, or a heretofore non-parthogenetically reproducing species, hence all the fuss?

    • Dominic
      Posted November 19, 2010 at 5:09 am | Permalink

      Was it this story?
      The males did not father the young snakes, but the presence of males seems to have been a trigger of some type for the female to produce them.

      Here is the abstract from Biology Letters

      • Posted November 19, 2010 at 8:04 pm | Permalink

        Yes, it was! Thanks so much–BBC. Of course. (Sorry–I suffer from Mommy Alzheimer’s…)
        That snake was *gorgeous*–one of the most beautiful I’ve ever seen.

        • Torbjörn Larsson, OM
          Posted November 20, 2010 at 4:50 pm | Permalink

          Mommy Alzheimer’s isn’t serious until you forget your kids on a constant basis…

          • Posted November 20, 2010 at 9:25 pm | Permalink

            There are days I do forget them…but it’s on purpose ;-))

        • Torbjörn Larsson, OM
          Posted November 20, 2010 at 4:51 pm | Permalink

          [And no, it never happened to me. I’ve seen it, though.]

    • whyevolutionistrue
      Posted November 19, 2010 at 6:47 am | Permalink

      The snake reported reproducing parthenogenetically recently was a boa constrictor (Boa constrictor), which had not previously been known to reproduce that way. The one that has been known for a while to be parthenogenetic is Typhlops (or Ramphotyphlops) braminus (or bramina), which is a very small, burrowing, worm-like snake, widely distributed in tropical areas. Its wide distribution comes mostly via human introduction: being parthenogenetic, a single introduced individual can start a population. It is thought to have been shipped round the world hidden in the soil of flower pots. (The scientific name variation comes from a change in generic assignment, and a debate over the gender of the word ‘-ops’.)


      • Posted November 19, 2010 at 8:15 pm | Permalink

        Thank you! It seemed, according to my faulty memory, that it was a small snake that normally reproduces parthogenetically. Aha–looking at the article again, it *was* a boa constrictor, and she was surrounded by several males, so it seemed odd that she would reproduce parthogenetically. And yet she did. Why does it seem somehow normal for a very small snake to reproduce that way, but not normal for a large snake?

        Do all snakes have the ability to reproduce parthogenetically, just most of them don’t? Does that say anything about the evolution of sex itself?

      • Dominic
        Posted November 19, 2010 at 7:58 am | Permalink

        The Typhlops is so tiny I am astonished that birds do not gobble them all up. Has anyone who follows this blog seen them in SE Asia or anywhere else? I suppose it only takes one import to found a new population.

        • Sven DiMilo
          Posted November 19, 2010 at 1:00 pm | Permalink

          I’ve found them in Honolulu.

  3. Dominic
    Posted November 19, 2010 at 4:40 am | Permalink

    Perfect! I remember years ago cutting a bit out of a paper about whip tailed lizards & I was going to ask you about them with reference to yesterday’s post.

    We must not forget that other example of parthenogenesis – the BVM (angelic choirs ah-ah ahhhh!) – was Mary a hybrid? Perhaps Benedict XVI could illuminate with Roman Catholic biology!

    • Posted November 19, 2010 at 6:40 am | Permalink

      But the offspring are exact genetic copies of the mother. And Mary gave birth to–wait a minute! Jesus was a girl?!;-))

      • Dominic
        Posted November 19, 2010 at 7:51 am | Permalink

        Of course she was!

        I did a Yuletide card with that theme some years ago – Gabriel on a cloud with a phone “What do you mean, ‘It’s a girl!’? Get me the Holy Spirit!”…

        • Posted November 19, 2010 at 9:33 pm | Permalink

          (OT, but you were kind enough to admire my spiders the other day, Mr. Dominic–thank you:)) If you’re interested, this week’s Field Notes is also on the topic of spiders, but a different genus. It does have photos of the Jorougumo from before, though, since I remembered to take a ruler out with me on my last walk so I could measure.)

        • Posted November 19, 2010 at 8:05 pm | Permalink

          (sniggering… ;-))

      • Achrachno
        Posted November 19, 2010 at 8:16 am | Permalink

        Since virgin births happen in vertebrates non-miraculously, maybe the report that Jesus was not a clone of his mom was the “miracle.”

        Either that or we need to start worshiping Cnemidophorus.

        For some reason Xians never like these ideas when I float them by.

        But, they like my main idea about Jesus (total myth) even less. Perhaps they should take the best of what they can get and be grateful.

        • Dominic
          Posted November 19, 2010 at 12:43 pm | Permalink

          You are right. There is about as much solid evidence for Jebu joy of man’s desiring as there is for King Arthur. I know which one I prefer!

          • Posted November 19, 2010 at 8:07 pm | Permalink

            “I am Arthur! King of the Britons, and…”

            ” ‘oo are the Britons?”

4 Trackbacks/Pingbacks

  1. […] lobsters, goldfish, cats–  reproduce sexually. But a few of our favorite organisms– whiptail lizards prominent among them– reproduce asexually. Cnemidophorus inornatus (sexual ancestor), C. […]

  2. […] Why Evolution is True: Hybridization and parthenogenesis in whiptail lizards. […]

  3. […] Although these Whiptails don’t need to have sex to have babies, they still do anyway. The lady Whiptails engage in “pseudocopulation” – simulated sex. Research suggests that this act encourages fertility. […]

  4. […] And from an evolutionary point of view, an aversion to same-sex mating seems to make a certain amount of sense: such mating doesn’t produce offspring. But it turns out that evolution is more complicated than that. For some species, homosexual mating is not a preference or orientation for a portion of the population; it’s obligatory. For example, New Mexico whiptail lizard reproduces parthenogenetically; the species has only females, and they are all virgins. Nonetheless, even though their eggs are not fertilized, females still have go through the motions of mating, with another female, in order to produce eggs. (Incidentally, this unusual mating system seems to be a result of the hybridization between two other lizard species.) […]


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