Monday, March 26, 2012

If you want to learn about evolution with lizards, you have to go to where the wild lizards live. Join us as The Lizard Project goes to the islands later this week!


Do you ever wonder how scientists learn about evolution? 
Follow us this week as Dan, Tim, Andrew and I will head down to the Guana Tolomato Matanzas National Estuarine Research Reserve and Tomoka State Park in Florida to continue an exciting experiment we began last year.  We are really glad to have you follow along as we do science and we are looking forward to answering your questions on line.  Let me tell you a bit about what we will be doing down there on our islands.  You can also follow on twitter @mr_reedy (#lizardproject) or on youngzine.com 

What questions are you trying to answer with your experiment?
All science starts with a question and the big question we are asking, “Why is there a 50/50 sex ratio in so many animal populations?” If you really think about it, this doesn’t necessarily make the most sense for an animal population.  Since a population can often grow faster with many females and few males, why is it that we so often find males and females in almost equal numbers?



When thinking about this we also wondered, “If the sex ratio, became really biased towards one sex or the other, how quickly would natural selection push things back to 50/50?

And,” In a world that is mostly female, would males have a better chance of surviving and reproducing? What about in a world that is mostly male?

What are your hypotheses?
The leading theory on the 50/50 sex ratio is that when the ratio gets out of balance, natural selection pushes it back towards 50/50.  For example when there are many male lizards all fighting for territory in the trees, you have a better chance of surviving if you are a female.  Therefore in a world with more males, a balance will quickly be restored as many males die before reproducing and many females survive to adulthood.  This is our general hypothesis.

We also think that in situations with biased sex ratios, natural selection will favor traits differently. We think that on an island with many males and few females,  the biggest males will be more likely to survive.  However, we think that on an island with few males and many females, the smallest males will have a better chance of survival and reproduction, because it will be easy for nearly all males to find a territory and mate. In this case, the large body size may be a waste of energy and be more noticeable to predators.

How are you testing these ideas?
With an experiment of course! Many people wrongly think that questions about evolution can’t be tested in the wild because evolution is a slow process.  However, evolution can be seen in the wild and measured if we look carefully. 

Since our question is big, so is our lab. Instead of testing animals in laboratory cages, we use entire islands as our animal enclosures for the experiments!

To test our hypotheses, we set up 9 experimental islands that did not have brown anole lizards living on them. On five of the islands we released a 66% male population and on the other four islands we released a 66% female population.  Before we introduced these populations to the islands, we took DNA samples and careful measurements from each of our founder lizards.  Now we will be able to check each year to see which individual lizards were most and least successful at producing baby lizards.  We will also continue to measure the future generations to see how natural selection is working to shape the evolution of these populations on the different islands.  We may be able to see evolution in action…but first we have to catch, measure, and take DNA samples from nearly every lizard on our nine islands.  We are going to be busy!

29 comments:

  1. Mackenzie HuffmanMarch 29, 2012 at 7:40 AM

    How are you collecting the DNA from the lizards?

    ReplyDelete
  2. How is gender determined?

    ReplyDelete
  3. How are you going to find all of the lizards on the islands for the 2nd, 3rd, etc. generations? You said that you needed to take DNA samples from nearly every lizard, but how are you going to find them all? Is it even important to find most of the lizards, or is using a few a good representation of the majority?

    ReplyDelete
  4. Mr. Reedy,
    I think this experiment sounds great! I was wondering though if you wanted predators in your experiment? It seems like keeping the lizards on an island would bring up many outside factors such as predators. How are you keeping these variables controlled? Is keeping predators in or out of the islands a constant variable? I can not wait to see the results, it should be very interesting.

    Sincerely,
    Marcy Withrow

    ReplyDelete
  5. How are you going to find all the same lizards you took DNA from? Will the experiment be affected by the elements in the wild? What if the reason they are not reproducing is because of the elements in the wild?

    ReplyDelete
  6. How does the lizard population always find its way back to 50/50? in gender? How are lizards gender determined?

    ReplyDelete
  7. Are you worried at all about the lizards maybe, fighting each other and dying off? Could that ruin your experiment if that would happen?

    ReplyDelete
  8. Are there any other animals on the island? Not even having to be predators, just other animals!

    ReplyDelete
  9. How would you keep all of the generations of these lizards separate in your experiment? Would the different generations even make a difference in this experiment or is it just testing the overall population of these lizards?

    ReplyDelete
  10. what if you can't find any of the lizards what will you do with your research then... what if all the lizards die from being on a island that they don't really live on....

    ReplyDelete
  11. Wow! Great comments/questions here. Let me answer.

    Mackenzie- We take a tiny tail clipping from each lizard for DNA. It only hurts them a little bit and it grows back. They actually are frequently missing tails from predators or fighting with other lizards.

    Sidney- These lizards have their sex determined with sex
    chromosomes, similar to humans.

    Lauren- We will work as hard as possible to catch every last lizard on the islands (or come as close as possible. There will be video coming soon showing how we catch them. It is important to come as close as we can to catching 100% of them even though we know we may miss a few.

    ReplyDelete
  12. Marcy- Great question. You are thinking like a scientist! These islands are wild, in fact we see many birds each day and saw a black rat snake as well- both anole predators. We know the environments on all the islands are not the same- that is why we have multiple islands. If we find the same results on the islands with the same treatment (sex ratio), we have strong evidence the sex ratio, and not other factors like predation, are driving the patterns we observe.

    Sami- We spend are spending several weeks of 12 hours days doing nothing but searching for lizards. This thorough searching will hopefully result in us finding nearly all of the previously marked lizards that are still alive. We are very interested in what elements in the lizards environment influence their survival and reproduction. Many other experiments have focused on particular elements of the wild, and how they influence survival and reproduction. Our experiment particularly looks at how the sex ratio influences this.

    Tyler-These anoles have gender determined by sex chromosomes. Sex ratio theory predicts the less common sex should be more valuable, and therefor should have higher fitness. So if the sex ratio is female biased, any males have a huge advantage, and should increase in number over several generations.

    Chase- We expect the lizards will be fighting each other (competition), and this is one of the coolest parts of our experiment. We aren't worried about it, but want to study it!

    Jaycee- The islands are very diverse! We see crabs, birds, insects, spiders, snakes, other lizard species, deer. Today we saw something none of us have seen before swimming to the island, a legless lizard. Check out the video coming soon.

    Stephanie- Each individual animal is marked, so we know whether it was a founder individual, or second generation. The DNA tests will also confirm these marking methods. We are interested in which generation the lizards came from, because we want to know who the successful parents are.

    Catelynn- Good question, and that is a concern of ours. Things like hurricanes could wipe the whole population out. But, its day three, and it looks like this isn't a problem, as we are catching lizards on all the islands, and some islands are really crawling with them!

    ReplyDelete
  13. Do you think the presence of other animal species on the island will affect the results of your experiment in any way?

    ReplyDelete
    Replies
    1. It most certainly will, the big question is how. Since these islands are wild, they do have predator and competitor species on the islands. We are watching closely to see if there are differences between the islands, but we did choose them partly because they are very similar to each other.

      Delete
  14. Javier p.

    Mr. reedy thanks for the skype talk with the class, a question i had was that what actual size do they grow up to be? also are the lizards more active when the climate is nice or are they active when it is rainy or cloudy as well?

    - the talk was good we had fun watching you and Dan trying to catch the lizards, i was good to see it in action and the way u guys handle running after them.

    ReplyDelete
    Replies
    1. The large male lizard might grow up to be around 65mm long from snout to vent (not counting the tail). A large female will be around 40mm.

      They are definitely more active when it is sunny. They are cold blooded (ectothermic) so they rely on the sun to warm up. When they are cold they hide and don't come out from their hiding spots. Yesterday it was sunny and we caught 76 lizards. Today it was cloudy and rainy and we caught 6.

      Delete
  15. Ray

    Thanks for the skype talk Mr. Reedy! It was pretty exciting to see scientest at work. It seems like a lot of fun and I would actually consider doing work like that, which is why I applied for TREE.

    Is there a certion diverse habitat for individual lizards differing by color, sex, size, etc.?

    ReplyDelete
    Replies
    1. That is a great evolution question. How do the differences in traits, effect habitat use? This is something we don't know the answer to, but are working to find out. This is why we record the location of every lizard that we capture and measure their traits.

      Delete
  16. Xitlaly: I think this project looked fun when you skyped us at the point when you were trying to catch the lizard on the dead palm tree. My question is what will they be eating on that island? Does the island have the same type of food they usually have in their normal habitat? When the lizards have babies and you try to catch them will you leave them on that island to test them as well?

    ReplyDelete
    Replies
    1. They love to each small arthropods like spiders and beetles. We posted a picture of a lizard eating a spider. Check it out.

      Yes, I would say that the islands have similar insects to the mainland.

      Yes, we will capture, but release all babies to let the experiment continue through many generations.

      Delete
  17. Jessica C: Hey Mr.Reedy thanks for the skype talk we really enjoyed watching you and Tim on action :) One question I had was does climate effect lizard behavior? If so does it affect the population rate? Also, does the climate affect how big the lizards grow during time?

    -Again thanks for the talk and we'll be seeing you soon :)
    Have fun!

    ReplyDelete
    Replies
    1. Climate definitely effects behavior, see my reply to Javi above.

      It probably also effects population growth and lizard growth, but since all of the islands in our study experience the same climate, it should not effect our experiments.

      Delete
  18. Brea Lembke 3 whiteMarch 30, 2012 at 9:56 AM

    How are the animals equal in Gender? How do the Females put the gender scale back on track (How do they make it 50/50 again)?

    ReplyDelete
    Replies
    1. Well we don't quite know the answer to this question. There may be differences in survival that pull the sex ratio back to 50/50, but there also might be more too it.

      There is strong evidence that females mate with multiple males and then store the sperm. Research shows that females use the sperm from large males to make their sons and sperm from small males to make their daughters. Nobody yet knows how they do this or if they can influence the sex ratio.

      Delete
  19. If the islands become male or female dominant what would happen to the ratio between them and have you seen signs of the islands being male or female dominant. How would it go back to balance if it did go out of control? -Francisco Quezada

    ReplyDelete
    Replies
    1. We really aren't sure yet if the sex ratios have returned to normal yet. The data from this trip will give us the answer.

      Delete
  20. i wish i was able to go out there and see how the whole technique works, the lizards look cool and it seems awesome working with them. -Dessiray Treviso

    ReplyDelete
    Replies
    1. We wish we could take kids out on these kinds of trips too! Maybe someday in the future we will have donations that will make this a real possibility!

      Delete
  21. Your site is a gorgeous resource to get useful info! Will you be mind if I reblog one of your blog articles on my private blog?

    ReplyDelete