Why are some animals larger than others? Often the simplest questions are the most difficult to answer. This didn’t stop Mehdi Khadraoui, whose interest in the evolution of body size took him on a search for a delicate wren with brilliant purple plumage, found only in the crocodile-infested Australian tropics. This was his fourth MEME semester, jointly supervised by Anne Peters from Monash University in Melbourne, Australia, and Wolfgang Forstmeier at the Max Planck Institute for Ornithology in Munich. Over a century ago, German anatomist Carl Bergmann observed that, on average, smaller animals were more common close to the warm tropics, whereas large animals tend to be found at higher latitudes. This makes sense: larger animals have an increased ratio of surface area to volume and are, in principle, better equipped to deal with seasonal changes in temperature. This came to be known as Bergmann’s rule. But does this “rule” hold up in light of modern evidence, and if so, what does it mean for the evolution of animals in a rapidly warming climate? Using over a decade’s worth of pedigree data from a population of purple-crowned fairywrens, Mehdi was able to ask a range of fundamental questions about the evolution of body size. Did nature or nurture better explain size differences? Are these differences associated with a warming climate, as Bergmann’s rule predicts? How does cooperative breeding, where offspring are raised by non-parental helpers, influence the evolution of body size? Mehdi pursued his interest in cooperative breeding as a PhD student at the University of Würzburg, where he is determining the proximate and ultimate mechanisms of sociality in fungus-farming wood-boring weevils. In this episode, Mehdi is interviewed by Henry North, who was in his final MEME semester at the University of Cambridge at the time of writing. Written by Henry North
Since recording, Mehdi has decided to switch careers from his announced PhD to pursue his passion for science communication and outreach. Follow Mehdi on twitter here!
If you are interested in Mehdi's project look up the Associate Professor Anne Peter's lab in Monash University. Mehdi also is a very talented artist - check out his website called Brush Tale! Subscribe and listen to MEME Stream on soundcloud! Follow us on twitter! This episode is brought to you by:
Mehdi and a purple-crowned fairywren (left), a purple-crowned fairywren (middle) and Mehdi in the field in Australia (right).
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Just like Beyoncé and JAY-Z, evolution also has its own power couples. This time it passionflower plant (Passiflora) and the sword-billed hummingbird (Ensifera ensifera). They are a classic example of coevolution, or where two or more species influence the evolution of the other. In this case, the 10cm nectar-tubes long nectar tubes of the passionflower and the extremely 11cm long bill of the sword-billed hummingbird are thought to have co-evolved under mutualism. For the hummingbird, the passionflower and its long-tube are beneficial, as it means only the sword-billed hummingbirds have access to its nectar. While for the passionflower, having an exclusive pollination mechanism means that it’s seeds are dispersed to mainly passionflower plants.
In this episode, we talk to Daniel Souto about his MEME project looking at how these mutualisms evolved and under which conditions. Daniel analysed the DNA of 43 long and short-tubed passionflower species to pinpoint when they evolved. It was found that the long-tubed passionflower species evolved at roughly the same time as the sword-billed hummingbirds – suggesting that co-evolution did occur. But by looking at all the passionflower species, it was found that the specialisation of having a long-tube was not permanent. Indeed, there were thought to be times throughout evolution were the sword-billed hummingbirds dropped in number, influencing some passionflower species to rapidly evolve shorter tubes that could be pollinated by bats and shorter billed birds. Read more about the findings in Daniel's project in the paper! See more examples of coevolution here! Check out the great biodiversity and competition of hummingbird's in this Planet Earth II clip .
Daniel's MEME project was supervised by Professor Susanne Renner, a professor at Ludwig Maximilian University
You can follow Daniel on twitter Daniel is now studying a PhD at the University of South Bohemia in České Budějovice. Czech republic. Subscribe and listen to MEME Stream on soundcloud! Follow us on twitter! This episode is brought to you by:
Cloud forests in the Andes by Green88 (left), Daniel in the field (middle), sword-billed hummingbird feeding on a long-tubed passionflower by Andy Morffew (right).
What do you do with a spare genome?
If you thought only plants could do crazy things with their genomes, then you’re in for a surprise. Sturgeons are a group of the most ancient bony fish that from the outside, seemed to have changed very little since they hung out among the dinosaurs over 200 million years ago. However, their genetics tells a different story. Jelena’s research in Montpellier showed that at least three times during their evolutionary history, different lineages of these fish have doubled all their chromosomes going from diploidy (two copies of each chromosome) to tetraploidy (four copies of each chromosome). Such events are mostly known to happen in plants, but the sturgeons have proven that animals can do it too. But once you got this “spare” genome, what do you do with it? Some of these extra chromosomes started to develop their own unique functions, differentiating them from the other copies. This process is called “functional diploidization." This is where the genetic material of a tetraploid species degenerates to become functionally diploid but maintains twice as many different chromosomes. Jelena studied several genetic markers in 10 species of sturgeon to find out how many of them would show traces of this process and how often the transition from diploidy to tetraploidy may have occurred in the evolutionary history of sturgeons. In this episode, she will tell us about her findings and share some of her insights on how to embrace the unexpected on the journey of scientific discovery. Written by Hilde Schneemann Read more about Jelena's findings in her published paper here! You can watch this simple video explaining more about chromosome linkage and polyploidy here . According to the IUCN, Sturgeon's are thought to be more critically endangered than any other group of species. To find out more about what is being done for their conservation check out the Sturgeon Specialist Group. You can watch this National Geographic video on the state of sturgeons in China.
Read more about Jelena's work on her twitter .
Since recording Jelena has started a postdoc at the GEOMAR Helmholtz Centre. Jelena's MEME project was conducted at the University of Montpellier II, at ISEM (Montpellier Institute of Evolutionary Sciences), in the Fish Evolution group, supervised by CNRS research director Dr Patrick Berrebi. Subscribe and listen to MEME Stream on soundcloud! Follow us on twitter! This episode is brought to you by:
Photo of Jelena during her Sturgeon MEME project (left). Picture of sturgeon by Andrey Nekrasov / WWF (middle). Jelena and Hilde after the interview (right).
Episode Five: Islands, herbariums, ancient DNA and the evolutionary history of a plant pathogen3/16/2019 The impacts of plant pathogens have long plagued agriculture history. With the use of modern genomics, it has become possible to study the genetics of pathogen emergence, evolution and spread. In this episode of the MEME Stream, Merve Öztoprak interviewed past MEME Clara Groot about her work on the plant pathogen Xanthomonas citri. This pathogen is well known for causing citrus bacterial canker which produces lesions on citric plants and has caused a massive reduction in citrus crops worldwide. By using herbarium samples Clara was able to analyze ancient plant DNA sequences from infected herbarium citric plants. This led her to conduct phylogenetic analyses to model its evolution and movement across the world. Clara also tells us about her wonderful time on the island of Réunion where she conducted her MEME project. Watch this video by Cambridge University on ancient DNA in herbarium plants. Read about how recent study on ancient DNA in corn has recently lead to findings about the origins of its domestication.
Follow Clara on twitter and read her wonderful new blog ' The Gene Time Machine'.
Her project was conducted with Professor Adrien Rieux at CIRAD in Réunion Read about Clara's other mini MEME thesis project here! Subscribe and listen to MEME Stream on soundcloud! Follow us on twitter! This episode is brought to you by:
Photo of Clara and her herbarium samples (left). Photo Clara took during her time in Réunion (middle). Example of citrus bacterial canker on a fruit (right) by APHIS photographer R. Anson Eaglin
Some hungry geese walk into the warming arctic tundra. This might sound like the start to a weird joke, but, it also was the start of Chelsea Little’s amazing MEME project! The question of evolutionary resilience, in animals and plants, is becoming increasingly a concern in light of climate change. One ecosystem of interest is the arctic tundra. Chelsea talked to us about her project investigating how the arctic tundra vegetation community recovered from years of intense herbivory in the context of our warming world. She did this by trekking (well she took two buses and a helicopter) all the way out to Longyearbyen, Svalbard. Here she collected data on plots of tundra that, over a long term experiment, have been subjected to varying levels of grazing by geese as well as, different temperatures controlled by Open Top Chambers (like mini temperature controlled greenhouses!). Chelsea measured how the plots differed in the structure and composition of tundra and growth and the plants reproduction output. It was thought that because tundra plants have been under strong selective pressure for their harsh environmental conditions that their response to warming temperature and grazing may differ from plants in temperate regions. Chelsea found that the tundra plants are resilient to current warming - but their underlying ecosystem process was changing in response to rising temperatures. These findings are important to understand and predict the functional changes that will happen to the tundra with the on-going effects of climate change. Written by Kate Garland. To learn more about evolutionary resilience to climate change watch thisgreat video by TED Ed. Check out the International Tundra Experiment ITEX to see what scientists are doing to better understand the impacts of climate change on tundra and alpine vegetation.
Read more about Chelsea’s tundra study here !
Chelsea’s tundra data has also been used in recent global tundra studies, including this recent paper in Nature! Her project was supervised by with Dr. Juha Alatalo and co-supervised by Elisabeth Cooper. You can follow Chelsea on Twitter, Researchgate and her website. Here current lab is the Altermatt lab. Chelsea is also the coordinator for an online group of runners and bikers in ecology and evolution. Subscribe and listen to MEME Stream on soundcloud! Follow us on twitter! This episode is brought to you by:
Photo of the arctic tundra by Chelsea (left). Chelsea while in Svalbard(middle). Barnacle geese feasting on the tundra, photo by Steve Garbie.
How do you get your genes in the next generation?
Fertilize your neighbours by making the best pollen! (in case you happen to be a member of Arabis alpina, commonly known as the Alpine rock-cress). Alternatively, you could be a strong and independent Arabis alpine - who don't need no pollen and fixes reproduction all by herself. Both self-fertilization and outcrossing occurs in Arabis alpina, but the latter strategy poses a greater challenge on the plant’s pollen to compete with that of other plants. This is what Juanita Gutiérrez-Valencia could detect even at the gene-level, where she observed that self-fertilizing plants had accumulated more debilitating mutations in their pollen-making genes than their outcrossing relatives, which rely more heavily on the excellent quality of their pollen. Juanita is a MEME graduate who is now working on her PhD at Stockholm University. She was interviewed in this episode by Hilde Schneemann who is doing an external project at Cambridge University at the time of recording.
Written by Hilde Schneemann IMPORTANT NOTE from Juanita - "At some point during the interview I misused the term Darwinian Selection -- also known as positive selection. Darwinian selection leads to the spread of an allele with beneficial effects on its carrier. If you remember in the interview, we were measuring purifying or negative selection, by which variants with deleterious effects are removed from the population. Therefore, the usage of Darwinian Selection is wrong in this context.”
You can follow Juanita for updates about her scientific journey on Research Gate.
Juanita did her Arabis project and is now doing her PhD with the Slotte lab, check them out out here ! Juanita also mentioned her other MEME projects with Professor Guillaume Chomicki and Professor Susanne Renner. Subscribe and listen to MEME Stream on soundcloud! Follow us on twitter! This episode is brought to you by:
Juanita enjoying the sun and flowers in Stockholm (left). A naturalist drawing of Arabis alpina subsp. alpina, by E.H.L. Krause (middle). Hilde and Juanita after their interview (right).
What is the tempo of evolution?
Do new species arise continuously over time or in sudden bursts? These scenarios were termed “phyletic gradualism” and “punctuated equilibria,” respectively, by the famous evolutionary biologists Stephen Jay Gould and Niles Eldridge. They emphasised the importance of the latter in macroevolutionary patterns of biodiversity. This caused substantial controversy in the field, with some peers referring to punctuated equilibria as “evolution by jerks.” Gould suggested his opponents’ enthusiasm for phyletic gradualism was “evolution by creeps.” Raphaël Scherrer is neither a creep nor a jerk. He is a MEME graduate currently undertaking his PhD at the Groningen Institute for Evolutionary Life Science. His final project during the MEME programme was undertaken at Uppsala University, where he studied the tempo of diversification of colour patterns in birds-of-paradise. In this episode, Raphaël is interviewed by Henry North, who was in his third semester of the MEME programme at Harvard University at the time of recording. Discover the pretty accident that is the birds-of-paradise in the wonderful video by Planet Earth - BBC. To see what the first naturalist thought birds-of-paradise looked like, read this fantastic essay titled "Fallen Angels: Birds-of-paradise in Early Modern Europe" by the Public Domain Review. Written by Henry North You can follow Raphaël on LinkedIn. Right now he is doing a PhD under two labs (he proclaims himself a hybrid): the Etienne lab for theoretical evolutionary and community ecology, and the Van Doorn lab for evolutionary systems biology. Feel free to send him an email to ask for his poster too! You can also check look up the supervisors he worked with on the birds-of-paradise project: Professor Melanie Monroe and Professor Jochen Wolf. Subscribe and listen to MEME Stream on soundcloud! Follow us on twitter! This episode is brought to you by:
The Le Nebuleux bird-of-paradise by Robert Havell, 1835 (left). Henry and Raphaël after the interview at the Congress of Evolutionary Biology (middle). Raphaël during his project on the birds-of-paradise.
The “creation” of new and distinct species in the course of evolution is an ongoing and dynamic process. Distinguishing new species solely on morphological features (i.e. the form or appearance of an organism) is a challenging endeavour, but with new molecular tools characterizing populations and species becomes much more reliable. Population and speciation genetic studies help to protect new species and their fragile populations as well as conserve their unique genetic innovations. To understand more about the process of speciation check out this great explanation by the University of California, Berkeley.
In Episode One of the MEME Stream, we talk to the past MEME student Daniel Méndez Aranda (cohort 2013-2015). During his final semester of the MEME Programme, Daniel studied the population and speciation genetics of Moroccan Spiny-footed lizards (Acanthodactylus erythrurus) and managed to provide genetic evidence for at least two new sub-species. Daniel carried out this research withProfessor Pierre-André CROCHET Crochet at the CNRS Center of Functional Ecology and Evolution, in Montpellier, France. The work is being prepared for publication so be sure to follow Daniel on Twitter to get updates! Right now, Daniel is a 3rd year PhD student at the Max Plank Institute for Ornithology in Professor Maude Baldwin’s lab. Daniel is interviewed by Merve Öztoprak, who is in her 3rd semester of the MEME programme doing an external project at the Australian National University at the time of recording. During this interview, Merve and Daniel will discuss the importance of genetics for conservation, science ethics, life as a MEME and how the MEME programme has impacted and prepared Daniel for a scientific career. Written by Merve Öztoprak
Check out Daniel's Twitter here!
Subscribe and listen to MEME Stream on soundcloud! Follow us on twitter! This episode is brought to you by:
Daniel during the time of his project in Montpellier climbing Pic Saint Loup (left). The study specimen the Moroccan Spiny-Footed Lizard (middle). Merve and Daniel after their interview in Montpellier (right).
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About the MEME StreamA podcast following MEME students past and present on their adaptive walks of life as they embark on a career in evolutionary biology. The MEME is a unique masters program that enables upcoming evolutionary biologists from all over the globe to study and research in Europe. These podcasts will travel all over Europe and the world, leaping, as Richard Dawkins says, from brain to brain, MEME to MEME, telling tales of our scientific ventures and research projects. ArchivesCategories |