Dawkins on Drosophila (my 4,000th post!)

August 8, 2012 • 4:00 am

I don’t think I’ve ever heard Richard talk publicly about my favorite group of animals—Drosophila, of course—but this newly posted  three-minute clip, about the Hawaiian Drosophila, is music to my ears. YouTube describes the filming:

During Richard Dawkins’ 2009 American tour, we visited Judy Diamond’s “Explore Evolution” exhibit at the University of Nebraska State Museum in Lincoln. This exhibit has now been replicated in six museums around the country. While visiting we filmed a collection of short unrehearsed and unscripted videos—just inspired by the “Explore Evolution” exhibit.

The Drosophila of Hawaii, though not as well known as the finches of the Galapagos or even the honeycreepers of Hawaii, are one of the best studied “adaptive radiations” in animals. As Richard notes, much of the “adaptation” involves sexual selection, which produces spectacular courtship displays and morphological ornaments and colors in males.  As I note in WEIT, the Hawaiian islands contain nearly half of the world’s 1500-odd species of Drosophila—I use the term warily since it looks as if the genus Drosophila is paraphyletic: i.e., contains species of flies that are more closely related to other groups than to species in the genus—even though the Hawaiian islands make up only 0.004% of the Earth’s land surface.

Here’s a famous species: Drosophila heteroneura, which lives—or “lived,” since it may be almost extinct now—on the “big island” of Hawaii.  Compared to females, males have much elongated heads and eyes. They’ve presumably evolved this via male-male competition for females. Males battle for territories, and do so by literally going head to head, butting each other and pushing each other back and forth. Presumably the males with larger heads win the territories and the females—and get to leave offspring. That is one of the two forms of sexual selection: “male/male competition.” The other is “female choice”, in which females choose whether to mate with a single displaying male, though in some cases the two classes may not be distinct since females can  choose to mate with a male who has a territory or wins a battle.

34 thoughts on “Dawkins on Drosophila (my 4,000th post!)

    1. I wondered that too, but when I re-read the post I noticed this:

      “As I note in WEIT, the Hawaiian islands contain nearly half of the world’s 1500-odd species of Drosophila.”

  1. Question from non-biologist: Is it the case that the many genetics experiments are done on just one or a few species of Drosophila? Are they bred for uniformity, maybe clones?

    1. Think of the practicalities of running your own breeding colony for the lab. You’d have as few species as you can get away with, because you’d need to house them separately (well ; OK, you could probably get away with keeping a rodent species in the same room as a fly species, but not two rodent species. It’s not best practice, and it makes management of the colony more hassle for the pourers of water, fillers of food hoppers and the shovellers of the excrement. Been there ; shovelled that.). Closely-related species you’d have to take considerable care to keep separate. Distinct strains of the same species would be even worse ; you’d probably have to cage them individually (if you could ; some species are too social) and use different cage styles for each strain. So … it’s off to the equipment catalogues and get out the cheque book.
      Most colony animals (and therefore most experimental animals) are highly inbred. That’s partly deliberate – it reduces variation in your animals, so the effects of your experimental treatments are less masked – but it’s also the sheer practicalities of running the colony : when you need 50 Guinea pigs next month for the 3rd year Zoology class, you get breeding with the animals you’ve got to hand ; you don’t buy in more.
      “Deeply inbred” is not the same degree of genetic similarity as “cloned”. But it’s an awful lot cheaper.
      There are, I believe, cloned strains of lab animals ; but they’re expensive, and your technician staff are going to have to take great care to not get them mixed up with the general colony. And you purchase agreement may explicitly ban you breeding from them.
      There are a lot of things that you can do with lab animals. But you’ve got to look at the practicalities of running your colony, the costs. And of course, the ethics.

  2. Ha, I had forgotten about the correlation between the phylogenetic tree and the island chain geology.

    [Yes, I’m encountering creationists on a science blog … again. The pests of the web.]

  3. Terrific video. I wish this very special exhibit would be on the road again and stopping in the museum in my hometown.

  4. Congratulations! This is a great 4000th post. I enjoy and appreciate your site daily.
    D. A. Langworthy

  5. Very cool post. Not only are Drosophila biologically facinating, there are often really gorgeous and very photogenic! Last week on Deas Island I was photographing some pale orange specimens with bright red eyes. Too bad they are so small…if they were the size of parrots everyone would want them as pets! LOL!


  6. Drosophila – Ode to a Fruit Fly

    Drosophila Melagaster, you sexy little fly.
    Your universe is in a bottle; you never saw the sky.
    You never had the chance to fly, free as God made you.
    Your firmament was made of glass, all you ever knew.

    A slice of apple or an orange would have been your wish.
    A ripe banana is your heaven in a little dish.
    Instead you existed under glass just for me to see,
    to reproduce and be bred by a human deity.

    I watched you copulate, lay eggs to my delight;
    I watched as your larva pupated in plain sight;
    I watched your offspring hatch and spread their tiny wings;
    I etherized your whole brood and examined the little things.

    With a little brush, I selected a few mutations,
    and then bred them once again to make some new creations.
    Playing God sure felt good for some unholy reason.
    Creating little mutants was supernatural treason.

    What I did in genetics lab with deliberate resolution
    happens all the time in nature, its called evolution.
    But there are those of little wit that still cannot conceive
    that what we did together should really be believed.

    I finished my genetics course and passed the final tests.
    I never could have done it without my fruit fly pests.
    Playing God is bad enough; some think it a holy crime.
    But, it was fun proving evolution by my design.

  7. Excellent post. Richard Dawkins shares with David Attenborough a way of imparting the information that I could listen to all day. A good one for your 4000th!

    1. Good question. I’m not even sure that any radiation produced by sexual selection could be called an “adaptive radiation” (as I did above), since it’s dicey whether sexual selection involves “adapting” (I suppose it could be seen as males adapting to females). If you mean radiations caused by drift rather than selection, I don’t know of any, since drift is such a slow and improbable cause of speciation (see my book with Allen Orr on that). I hasten to add, lest I incur your wrath, that drift is a powerful cause of MOLECULAR evolution.

      1. How long do typical speciations (reproductive isolation) take? We know that modern humans and Neanderthals didn’t speciate after several hundred thousand years.

        Is this typical? Don’t most speciation events take such a long time that drift, including founder effect, could easily be involved?

        Is speciation more rapid in animals than in plants, fungi, and protozoa because of sexual selection in animals? I don’t think courtship displays play a big role in the speciation of mushrooms.

        If one doesn’t know for certain whether a given radiation is due to drift or adaptation is it still standard practice to refer to “adaptive radiation”?

      2. How about this combination of drift and selection? Some mildly deleterious mutations are fixed during a founder-effect bottleneck. As the population expands, selection favors “fixes”, often at different sites. This process could be repeated if the population undergoes subsequent fluctuations through additional bottlenecks. In separate isolates, both the deleterious mutations and the fixes are distinct and the cumulative differences eventually make the make the two genotypes incompatible in a hybrid.

  8. Brings back fond memories of a great sabbatical spent with Hamp Carson(and Ken Kaneshiro). We used this wonderful model system to look at evolved changes in patterns of gene regulation.

  9. In the Dawkin’s video he shows a mating dance. Is that large, yellowish, worm-like thing sticking out of the back, and resting on the midsection, of the one fly it’s penis?

    1. No, that’s basically the whole abdomen. In that species, the male curves his abdomen forward over his own head and waves it at the female. There was speculation that he might be presenting a pheromone, but I don’t know about current thinking on that possibility.

      1. I was wondering if he waves it like that to make himself seem vulnerable to attack by other males, as if to say “I fear nothing!” (Presumably if another male did approach he would put it down PDQ.)

  10. On the photo of the two flies facing off: When they make contact, do they actually bump EYES? Or is the head curved just enough to keep the eyes out of the way?

    Their markings are cool, too. Alternating black and yellow patterns seem to indicate “I’m scary and dangerous” regardless of the size or type of animal.

  11. I find it particularly impressive that this was done unscripted and unrehearsed. Probably some editing, de-umming, etc, but it’s still an impressive piece of work.

  12. Jerry, your love of Drosophila has somehow escaped me.

    I keep D. melanogaster and D. hydei in my cupboards, trying to culture them. Bit mine have the fate of being eaten by my 3 Lygodactylus williamsi.

    Still, I do find them quite interesting on their own.


Leave a Reply