Nature Podcast

This is a transcript of the 18th September edition of the weekly Nature Podcast. Audio files for the current show and archive episodes can be accessed from the Nature Podcast index page (http://www.nature.com/nature/podcast), which also contains details on how to subscribe to the Nature Podcast for FREE, and has troubleshooting top-tips. Send us your feedback to podcast@nature.com.

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Kerri Smith: Coming up first, catch your ecosystem.

John A. Arnone III: We went through the trouble of extracting these very, very large pieces of soil down to almost 2 meters and we had to containerize them and then we had to ship them on large trucks, 2000 miles from the Oklahoma prairie to our research facility in Nevada.

Kerri Smith: We discover what a 4-year study of mini ecosystems can reveal about the effects of warming.

Adam Rutherford: And we get right to the bottom of an evolutionary mystery.

Andreas Hejnol: When animals increased in body size, this made sorting food and waste through a single opening inefficiently. So they needed to evolve an anus.

Adam Rutherford: This is the Nature Podcast. I'm Adam Rutherford.

Kerri Smith: And I'm Kerri Smith.

Kerri Smith: We kick off this week with those containers of soil. Ecosystems are big, complicated, and inherently rather unpredictable. And while this makes them interesting to study, it also poses a problem for scientists who like to control the experiments they do. So when a team of researchers wanted to study the effects of warmer than normal years on ecosystems, they didn't go to the ecosystem, they brought the ecosystem to them. Study author Jay Arnone explained to me what the team were aiming to find out with the aid of their portable plants. Nature 455, 383–386 (18 September 2008)

John A. Arnone III: We knew the terrestrial biosphere was an important player in modulating CO2 in the atmosphere and the question was we know a lot about what was occurring within a year. What that ecological driving variables were within a year, but we didn't know about how the behaviour or the response to climate within a given year might carry over to years that follow and subsequently the real hitch was that we needed to be able to create you know realistic environment, essentially several years of identical climate which you can't get in nature.

Kerri Smith: And so how did you manage to get over that problem then. You couldn't go to the forests, so...

John A. Arnone III: Right so...

Kerri Smith: I gather that you brought the forest to you.

John A. Arnone III: Well, we didn't bring a forest, we brought a native grassland to us. We tried to keep things as natural or as close to nature as possible. So we went through the great trouble of extracting these very, very large pieces of soil down to almost 2 meters. We extracted 12 of these units and we had to containerize them and we had to ship them on large trucks, 2000 miles from the Oklahoma prairie to our research facility in Nevada and we basically imposed on this realistic piece of ecosystem, climate that was repeatable and then we perturbed the climate in our treatment chambers for one year to simulate an extreme year and then we turned temperatures back down at the end of that year and basically monitored all ecosystem processes that we know from past experience are involved in controlling the exchange of carbon dioxide from the ecosystem to the atmosphere and from the atmosphere to the ecosystem.

Kerri Smith: What was the effect of the warmer temperatures that you subjected some of them to?

John A. Arnone III: What we found was that in the warm year, we measured a decrease in that ecosystem productivity which is basically a net amount of carbon that either moves into or out of an ecosystem within a year and this was mainly due to a decrease in that primary productivity which is the carbon uptake side of the equation and not to an increase in the CO2 emissions from organisms that are living in the soil. The interesting thing we found was in the second year after we turned the temperatures back down to normal, we found that we still didn't get a complete recovery in the net ecosystem productivity and the reason that occurred was because of a lagged effect of the warming, a one year lagged effect on the respiration that's attributed to the organisms that breakdown carbon in the soil. Basically, the warmed ecosystems were slowed in one year. So even if they recover completely, in the following year they still would be behind the ecosystems that have been receiving the warm treatment.

Kerri Smith: So it's not necessarily, sort of, a positive feedback thing. It's not that every year after this warm year, the ecosystem is less able to, sort of, absorb this carbon.

John A. Arnone III: Well, we only treated one year, so we don't know for sure how this might perpetuate if we had more than one warm year in a row or years that, you know, say every five years we have an extreme year, we don't know what the response would be after a second or third warm year, but what our data do show is that, after one extremely warm year, we see this effect and it's more or less a warning to us that we can't just, kind of, look at the productivity of an ecosystem and would be able to infer about its carbon sequestration potentials, strictly.

Kerri Smith: And what might the implications of your results be for obviously, we're pretty sure that human activities causing the global warming right now. So what are the implications of your results?

John A. Arnone III: What I think we can take away from this experiment is that we haven't really even began to scratch the surface in knowing and understanding how the ecosystems of the world will respond to global change. We are continually surprised about the way in which ecosystems respond. They respond in ways that some of which we understand and we can believe and others that we have to puzzle about. And so I guess what I would say is, not only do we have to be concerned that the increased frequency and intensity of anomalously warm years, as they increase in the future, they may actually be causing a sustained decrease in the ability of ecosystems to store carbon.

Kerri Smith: Jay Arnone there of the Desert Research Institutes in Nevada. Coming up later in the show, columnist David Goldstein drops by to tell us what to look forward to in the third instalment of our special US election podcasts.

Adam Rutherford: But for the rest of the show, it's a truly tangled bank of evolution. In a minute Natasha Gilbert finds out how teeth evolved, but first we are looking forward. Earlier in the summer, a highly select gang of researchers met up in Altenberg in Austria to try to plot the future of evolutionary theory. Science writer, John Whitfield was lucky enough to be invited and he has joined us in the studio. Hi John. Published online 17 September 2008 Nature 455, 281–284 (2008)

John Whitfield: Hello.

Adam Rutherford: So John, we've heard of the Modern Synthesis which was the marrying of Darwinian natural selection with the newly emerging field of genetics as a mechanism for evolution that happened in the first half of the 20th century. I understand that one of the themes of the meeting was the post-Modern Synthesis, so what's that all about.

John Whitfield: It means different things to different people. To some people, it means filling in the gaps in the Modern Synthesis. So for example, the Modern Synthesis is really, is very mathematical; how it represents a gene and how it represents approaches such as Natural Selection is all in the forms of equations and since that happened we've discovered DNA, we've discovered how cells work, we have discovered a lot about development and things. So partly it's putting biological reality into things that have been black boxes up until now, so that's what some people mean by an extended synthesis. On the other hand, you've got people who are more radical in wanting to change how we understand how Natural Selection works, for example, and how things like legs and wings and feathers or evolutionary novelties emerge.

Adam Rutherford: So, what are the big issues facing evolutionary biology right now. We're coming up to Darwin's 200th birthday, what are the big questions that still need to be answered?

John Whitfield: Well, the Modern Synthesis has been very successful at dealing with evolutionary change within populations, so it's very good explaining things like the spread of antibiotic resistance in bacteria for example. What it's not so good at and what it never tried to do was to tackle things that a lot of those of us outside the discipline would believe as were the big questions of evolution. So why did the fish go on to the land, why and where did wings come from, why are there chromosomes, why are there big animals and small animals. All these questions and all the patterns that you see in the fossil record, that are striking examples of evolution, that's something that the maths of the Modern Synthesis which looks at the change of gene frequencies within populations has never really tackled and that's something the synthesis extenders hope to be able to get grips with.

Adam Rutherford: Okay, tell us a little bit about the meeting itself. Who was there? I understand it was quite small and it was in a small Austrian town.

John Whitfield: That's right. It was held in the family mansion of the Lorenz family, Konrad Lorenz, the famous animal behaviour researcher. That is now the home of the Konrad Lorenz Institute and that was where the meeting was held. There were 16 people there from around the world, a mixture of biologists and philosophers of biology.

Adam Rutherford: That's a very small and potentially elitist group of people. How is it that the information, the discussions in this conference, are going to be disseminated to the evolutionary biologists of the world?

John Whitfield: Well, these people, the idea wasn't to come up with an extended synthesis that could then be announced in a fanfare and would be adopted. Everyone involved in this acknowledges that things are at a very early stage and people aren't expecting to have all the things wrapped up very quickly. The Modern Synthesis took several decades to come together and it will probably take at least the same amount of time for us to have a revisioning of evolutionary theory on the same scale.

Adam Rutherford: Okay, so finally you say it's a preliminary meeting, can you give us an idea over the big experiments in evolutionary biology that need to be performed in the next few years?

John Whitfield: One of the big things that people in all aspects of the discipline are concerned with is the origin of the animals, of multi-cellular animals. You probably know that we see all the groups that we see today appear in the Cambrian explosion; it looks instantaneous almost in the fossil record about 550-560 million years ago. People at Altenberg again and elsewhere are wondering how that transition happened and how all that diversity was generated so quickly and that's something that you can see in the fossil record. We can also use genes and particularly the genes of development to see how those body plans might have been laid down at that time and so that's a really exciting area full of puzzles still about what happened and in what order and the different forces involved. All these different approaches are bringing themselves to bear on at the moment.

Adam Rutherford: Okay, thanks John. His feature on the Woodstock of Evolution can be found in the magazine this week and online at http://www.nature.com/news. Just click on the features tab.

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Adam Rutherford: We've got the unlikely combination of the teeth and the anus coming up in just a few minutes. Happily it's not in the same piece of research, but first Kerri has more on Science in the race for the White House.

Kerri Smith: So this week sees the third of our special podcasts on Science and Technology issues in their run ups the US presidential election. Innovation is our third topic. David Goldstein, the host of that discussion has joined me. Hi David.

David Goldstein: Hi Kerri.

Kerri Smith: Is innovation a priority for the candidates?

David Goldstein: It's in a kind of a generic way. It's not clear how much they're focused on it, when you get to specifics and on some aspects of it one candidate is more specific, on other aspects the other is and it hasn't necessarily cohered into a complete innovation policy focus yet.

Kerri Smith: Should they be bothered or what did your guests think of that?

David Goldstein: Absolutely, I think all three of the guests felt that the US were still a leader and may be still the leader in Innovation in Science and Technology, certainly can see the pack creeping up on it and that US really needs a focus on innovation now, if it's going to stay ahead in the years to come and that was the theme from all three of the guests.

Kerri Smith: So here's what Bill Bates of the council on competitiveness had to say about that.

William Bates: The United States is still, you know to coin the phrase, number one in our economics strength. But everybody else has noticed what worked so well for the United States and they are catching up and they are making tremendous investments and in countries like China and India they've got a population that dwarfs ours. So everything is amplified. We can't assume anything. We can't assume what has worked in the past is going to work in the future. So we've got to run a little bit faster. We have to make the investments too.

Kerri Smith: So as you said then David, the stances of the candidates have been somewhat generic on this, if enthusiastic alongside. What did the panellists feel the next president ought to be doing, sort of, concretely to encourage or maintain innovation and competitiveness.

David Goldstein: I think there were several areas that came up increased spending on research, particularly basic science research, additional efforts to help companies work with companies to do later stage research, improved education policy, tax policy that particularly creates incentives for research and development and some discussion of immigration policy, particularly making sure that students who come here can actually stay here and so those are some of the areas that we discussed.

Kerri Smith: So in terms of the man power then aside of these things, money is all there well, but you have got to have the people doing the work, what areas of the education process were the guests most worried about?

David Goldstein: Really the entire pipeline as it's called from the Kindergarten through graduate school and there was also a sense that the government needed to do things including may be some symbolic things or just rhetorical things to get students to send the message that students need to be more interested in math and science, that this is the key to the nation's future, but also to improve instruction at elementary, secondary, and higher education levels and they had some specifics to talk about in those areas.

Kerri Smith: All right David, thank you very much.

David Goldstein: Thanks.

Kerri Smith: And for more information on all of those special podcasts and the print coverage, go to http://www.nature.com/news/specials.

Adam Rutherford: Once again that full length discussion is available free as a separate podcast. It will arrive automatically if you've subscribed through iTunes or you can find it online at http://www.nature.com/nature/podcast. We are sticking with the evolutionary theme in our final two segments this week. First up, knashers with Natasha Gilbert.

Natasha Gilbert: Teeth are a key innovation for animals allowing them to adapt and survive in different environments, but their evolutionary origins are still a matter of debate. Scientists have thought that teeth developed from the ectoderm, a collection of cells in the embryo that give rise to tissues covering the body such as skin and hair, but a team from Charles University in Prague have now shown that teeth can also be derived from the endoderm from which an organ such as the gut develop. They made their discovering by adopting a technique called fate-mapping that is used to show how a cell or tissue develops. I spoke to Robert Cerny the lead researcher and he explains that the evidence could answer the question of whether teeth evolved just once. Nature advance online publication (14 September 2008)

Robert Cerny: So basically we are able to show that oral teeth of vertebrates can be derived from both ectoderm as well as from endoderm which are germ layers.

Natasha Gilbert: So, can you tell us a little bit more about what you found and how this overturns the existing theory.

Robert Cerny: Mostly people are claiming that oral teeth which are developing in the mouth cavity can develop only from the ectoderm and this is some evolution connotations, because people are thinking that the teeth evolved as a superficial skin denticles which during the course of evolution moved into the oral cavity and therefore from embryological point of view, teeth are developing in the ectoderm only and we are using Mexican Axolotl the salamander and we had been using some fate-mapping techniques and we have been able to show that the oral teeth can be derived from both ectoderm and endoderm and we believe that it has some strong connotations for both developmental as well as evolutionary theories in the field.

Natasha Gilbert: So this is the first, sort of, evidence is it that shows that teeth have evolved from both the ectoderm and the endoderm.

Robert Cerny: Yes, the problem is of course that if you're not using precise fate-mapping, you are unable to say anything about this germ layer contribution, because ectoderm and endoderm, these two germ layers are very difficult to distinguish during later phases of development. And interestingly enough, what was a great surprise for us that these relationships, where various precise border between ectoderm and endoderm are not known even for very famous modern animals like chick, mouse, or zebra fish for example.

Natasha Gilbert: But with your technique, will you be able to look at that now?

Robert Cerny: It is very difficult to say so. Our technique I would say is pretty specific for salamanders. So they would need to use different kind of fate-mapping approaches to solve that in order to contribute into this question, I would say.

Natasha Gilbert: Why is it important that you have discovered that teeth can come from both the ectoderm and the endoderm?

Robert Cerny: Yeah, it is quite an interesting question. So from one point of view, it shows nicely that this is not just a feature of Urodeles or salamanders, but that this kind of development can be seen in many more animals and therefore that based on embryological derivation we cannot claim something about evolution derivation of these or about evolutionary origin of these.

Natasha Gilbert: So what's your next step? What are you going to look at next?

Robert Cerny: Yes of course, we are going to compare gene expressions between these ectodermal and endodermal teeth and the great advantage of our animal is that because we can really precisely say which teeth are derived from the ectoderm and which are derived from the endoderm, so we are going to compare gene expressions on these two kind of teeth in order to say if both kinds of teeth are using the same molecular machinery for their development and we hope that this will somehow deeply contribute into the question of whether all teeth developed just once.

Kerri Smith: Robert Cerny talking to Natasha. And at the other end Geoff Brumfiel reports on the origins of the anus. What a bum deal.

Geoff Brumfiel: Now I've got to be honest. I have not put a lot of thought into the origin of the anus. But evolutionary biologists have and they've come up with a theory about it. They believe that the anus and the mouth started out as one and over time separated into a front and a rear hole. But it turns out that theory is probably wrong. Andreas Hejnol of the University of Hawaii has been doing some genetic tests on acoel, simple flatworms with only a mouth, and other bilaterian animals with mouths and anuses. His work promises to turn the theory of the anuses origins on its head. Try not to giggle, here's Andreas. Nature advance online publication (17 September 2008)

Andreas Hejnol: There have been old hypothesis about how the mouth and the anus of bilaterians, these are these animals which have left and right side of the body like us humans but also flies, how these two openings have been evolved. And there always has been the hypothesis that they evolved simultaneously from one opening during the embryogenesis; but I have looked at the old literature and found that there is no animal today which develops in this direction, so there must be a different solution for evolving this.

Geoff Brumfiel: You were looking at this flatworm and I understand you, sort of, did some genetic work, looking at the genes expressed in the mouth and the anus, is that right?

Andreas Hejnol: Yeah, so we looked at genes which are expressed in the bilaterian mouth in this flatworm and we found that these genes are expressed in this mouth but furthermore we were surprised by the finding that in the posterior end we found genes which are expressed in the anus and this was pretty surprising and I thought, so what does it mean when you have a worm which has no anus but in this posterior tip of this animal there are genes expressed which are expressed in some bilaterian hindguts. So I looked a little bit more carefully at the anatomy of the acoel flatworm and found that there is indeed an opening which is not the anus, it is the male gonopore gonoduct where the sperm is released in which these genes are expressed.

Geoff Brumfiel: So, you're saying basically that the anus evolved from sexual organs?

Andreas Hejnol: Yes, through a connection of the gut to this duct and if you think about many animals have indeed a so called cloaca where you have a connection of a duct, where the gametes are released and the digestive system.

Geoff Brumfiel: What would be the advantage of hooking the two up together, why would animals do that.

Andreas Hejnol: So we have to think as our ancestors to be a very small worm, which lives probably between the sand grains in the ocean, but when animal lineages increased in body size like we for example and they elongated as well, their body. And this increased energetic needs and the long blind gut would have made sorting food and wastes through a single opening inefficient, so they needed to evolve an anus.

Geoff Brumfiel: You're saying that the anus is just something you need, if you get above a certain size, you've got to have it?

Andreas Hejnol: Right, yep.

Geoff Brumfiel: Do you find that you're the butt of a bunch of jokes from other researchers for your line of work?

Andreas Hejnol: Not yet. They only say that, when I give the presentation they say that they've never heard a presentation in which so often the word anus is used, but this might be the same for this interview.

Geoff Brumfiel: Yeah, no I don't think we will get the word anus on the podcast as much before or after. So what comes next for you Andreas?

Andreas Hejnol: Of course I continue to look at these worms and now I am investigating the nervous system and this would also give us an interesting insight in to brain evolution and nerve cord evolution and so then there will be less anus but more nerves.

Kerri Smith: That was the University of Hawaii's Andreas Hejnol. That's all from us this week. Tune in next time when we will have X-rays, fish fingers and a round up of the Science at stake in the race for the White House. I'm Kerri Smith.

Adam Rutherford: And I'm Adam Rutherford. No more bum jokes next week, we promise.

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