Living at the edge, range expansion is a losing battle with mutations

Environments can vary substantially in habitat quality, local population abundance, or carrying capacity. Under some climate change scenarios, new, higher quality habitats become available along the margin of a species’ range (e.g. higher latitudes or altitudes) (Thomas et al 2001). These new habitats may be able to support larger population sizes. Factors of demography, evolution, and qualities of the abiotic and biotic communities all interact to determine where a species is found and may influence the ability of a species to expand its range. New research is building genetically explicit models in order to understand how the interplay of these different factors influence evolutionary changes,

Wordle of Peischl et al 2013

The authors of a recent study focus on how the interaction of the demographic process of range expansion changes the way that natural selection favors beneficial and deleterious mutations (Peischl et al 2013). Using both computer simulations as well as mathematical approximations, the authors find that at the range margins, individuals carry a substantial load of deleterious mutations.

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Environmental change influences the pathway to the evolution of antibiotic resistance

Observed changes in (a) global average surface temperature; (b) global average sea level from tide gauge (blue) and satellite (red) data; and (c) Northern Hemisphere snow cover for March-April. All differences are relative to corresponding averages for the period 1961-1990. (IPCC 2007)

Observed environmental changes. All differences are relative to corresponding averages for the period 1961-1990. (IPCC 2007)

How will populations respond rapidly changing environmental conditions? We’ve all seen the imagery of the polar bears surrounded by thawing ice sheets, but this isn’t just a problem of the environmentally concerned. The rate of environmental change may be dramatic and making economically relevant impacts on our everyday lives. It seems obvious to scientists that global change is occurring (IPCC 2007). How do organisms respond, not just on an ecological basis, but also in an evolutionary sense? Microbe based experiments can help us understand the evolutionary processes that come into play in rapidly changing environments.

A recent paper (Lindsey et al., 2013) does just this…

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A unifying perspective on pathogen specificity

Linking microevolutionary processes to macroevolutionary patterns

I have always been interested coevolutionary interactions, particularly host-parasite interactions. I have often wondered if the local patterns of interaction between host and parasite (e.g. local adaptation) can scale up and lead to patterns of host specificity. Having a thorough understanding of these selective forces may help us better understand the conditions for disease emergence and perhaps disease virulence evolution.

WORDLE_Antonovics_etal_2013

Population genetics is concerned with the processes that generate evolutionary change within species and populations. A major question in evolutionary biology is whether these same processes ultimately generate patterns of diversity at higher organizational levels. While interactions between species such as hosts and their parasites (or plants and pollinators, herbivores and plants) have long been implicated as a means of generating patterns of diversification (Ehrlich and Raven, 1964,Thompson, 1994, 2005), the process by which microevolutionary forces generate macroevolutionary patterns is not well understood for coevolutionary systems.

Highly specific interactions between pairs of species can result in population level patterns. Both theoretical and empirical studies show that genetic specificity combined with specific gene flow patterns lead to parasites tracking of local host populations (Dybdahl and Storfer, 2003,Gandon et al., 1996,Gandon and Michalakis, 2002,Kaltz and Shykoff, 1998). In a mutualism between plant and pollinator, the seeming match between the length of a flower corolla and bill may be the result of strong selective pressure. Although we have many good examples of the processes that work at the population level, we have little evidence as to how those processes generate patterns of diversity among interacting species (Thompson, 2005). At the macroevolutionary scale, the processes leading to the observed patterns of host specificity have remained unclear.

The authors of a recent perspective piece in Evolution have addressed this exact issue by asking:

“Can microevolutionary adaptive processes acting at the within-species level explain macroevolutionary patterns across host and pathogen taxa?” (Antonovics et al., 2013)

What processes can explain why most pathogens cannot infect all encountered hosts ?

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Friday Coffee Break: snail coauthors, rejection letters, Swiss cheese plants, and more

coffee_at_origin_roasting_IMG_0172-784070Every Friday at Nothing in Biology Makes Sense! our contributors pass around links to new scientific results, or science-y news, or videos of adorable wildlife, that they’re most likely to bring up while waiting in line for a latte.

Which Coauthor are you? Sadly during the winter due to snowboarding constraints CJ thinks she is the snail.

Are you looking for an academic job like Jeremy (@JBYoder) and Devin (@devindrown)? Be sure to check out the rejection letters here when you are feeling glum.

More mammal news from Sarah (@sarahmhird) this week: The news on NIH research Chimps being retired and moved to sanctuaries made her pretty happy.

Via Amy: Cornell Launches Archive of 150,000 Bird Calls and Animal Sounds, with recordings going back to 1929.

The Swiss Cheese plant, one of CJ’s favorite tropical plants, is in the news. Can you have only one favorite tropical plant…laughable? Why not check what Christopher Muir has to say over at the American Naturalist or the BBC.

Mutts digest carbs?!?! Oh yeah, that makes perfect sense to Sarah (@sarahmhird). Why not check out what researchers propose as a pathway from wild wolf ancestors to domesticated dogs.

Did your office succumb to the seasonal flu this year? CDC reports had some scary outlooks this winter. Fear not, researchers have ended the moratorium on influenza H5N1 research have resumed work on these important strains.

Friend of the blog Chris Smith is recruiting “citizen scientists” for Joshua tree work. Hear what he has to say over at KNPR.

Friday Coffee Break, barnacle sex, crab lice, and chimps

credit ilovecoffeebook.com

credit ilovecoffeebook.com

Every Friday at Nothing in Biology Makes Sense! our contributors pass around links to new scientific results, or science-y news, or videos of adorable wildlife, that they’re most likely to bring up while waiting in line for a latte.

Amy was learning about Synesthesia this week over at the Neurocritic Blog. Do you taste shapes or hear in colors?

Noah (@NM_Reid) must be getting tired of winter and read up on Brazilian bikini waxes making crab lice an endangered species. Tom Houslay (@tomhouslay) asks via Twitter if we need protected areas or migration corridors setup. The Bug Girl (@bug_girl) has a different point of view that you should check out.

CJ says, who doesn’t love barnacle sex? Check out the lasted news that shocked scientists, well not CJ, over at Science NOW.

Do you have a diet of milk, meat, blood? Jeremy (@JBYoder) suggests you take a look at the Empirical Zeal blog to learn how the Maasai of Kenya can consume over 200% of the daily cholesterol intake yet remain relatively healthy.

How did they get here? A new study in PNAS shows ‘gene flow’ from India to Australia 4000 years ago. See the digested report here.

Sarah (@sarahmhird) is about fairness and chimps this week. Chimps may have a sense of fairness similar to humans. If you’re curious for yourself, on the BBC lab site, you can find out how your sense of “fair” relates to others with a morality test. The Lab UK site also has other tests and your results are used for scientific research.

Late breaking addition from CJ: Being Married Helps [MALE] Professors Get seo companies Ahead.

Averting the Approaching Apocalypse

This post is a guest contribution by Dr. Levi Morran, NIH postdoctoral fellow at Indiana University. Levi studies the role that both coevolutionary relationships and mating systems play in shaping evolutionary trajectories. His research using experimental coevolution to test the Red Queen hypothesis recently appeared in Science and was featured on NPR and the BBC.

electron micrograph of the aerobic soil bacterium Pseudomonas fluorescens(photo credit http://bacmap.wishartlab.com/organisms/500)

Electron micrograph of the aerobic soil bacterium Pseudomonas fluorescens
(credit BacMap)

I’ll begin by acknowledging that the title of this entry is probably a bit more dramatic than it needs to be. Nonetheless it’s pretty catchy isn’t it?

Given that the human population seems to have survived that whole 2012 Mayan calendar thing without incident, I know several of my friends (I won’t name names, but you know I love you) that would immediately think about zombies upon reading this title.  However, I am not particularly concerned about the extinction of the human race at the hands of zombies. For one thing, I need more evidence (or in fact any evidence whatsoever) before I buy the whole “zombies will rise up and end us all” fear. Further, Max Brooks (son of Mel Brooks) has given us a hilarious and potentially mildly effective guide to surviving the zombie apocalypse. Ultimately I am far more concerned about bacteria. To avoid inducing mass panic, I’m not talking about a terrified level of concern here, but certainly concerned enough to give it some thought.

Why bacteria? Well, the human population is currently in an evolutionary arms race with many of the bacterial species that infect us.  We continue to hurl scores of antibiotics at bacterial infections, imposing very strong natural selection, with little regard for the evolution of antibiotic resistance in those bacterial populations. Using current strategies in medicine, we are forced to administer greater doses of drugs or develop novel antibiotics to combat infections as the bacteria evolve greater levels of resistance (Levy and Marshall 2004, Martinez et al. 2007). This is a vicious cycle. I believe it is time to develop new strategies of managing our pathogens and treating infections. Thankfully there are many people that agree and are conducting ground-breaking research in this area, like Andrew Read’s group at Penn State University.

A paper by Quan-Guo Zhang and Angus Buckling (2012) takes an experimental evolution approach to begin addressing this issue empirically. In search of a different strategy for curbing the evolution of antibiotic resistance in their experimental populations of the bacterial species Pseudomons flourences, Zhang and Buckling treated their bacterial populations with either antibiotics, a bacteriophage or “phage” (a virus that attacks bacteria), or a combination of the antibiotic and phage. Zhang and Buckling predicted that the combination treatment might be more effective than either antibiotics or phage alone because the combination treatments should better reduce bacterial population sizes and limit their response to selection (Alisky et al. 1998, Chanishvili 2001, Comeau 2007). Additionally, bacterial mutations that confer resistance to antibiotics generally do not also confer resistance to phage, so evolution of resistance to the combination treatments would likely require at least two mutations, and thus require more time to evolve resistance than the other treatments (Chanishvili 2001, Kutateladze 2010). Continue reading

Friday Coffee Break, more news than a Giant Squid

Asian Palm Civet  (Wikimedia Commons)

Asian Palm Civet (Wikimedia Commons)

Every Friday at Nothing in Biology Makes Sense! our contributors pass around links to new scientific results, or science-y news, or videos of adorable wildlife, that they’re most likely to bring up while waiting in line for a latte.

Just about everyone here found the news from the Discovery Channel about the video footage of the giant squid facinating.  If you haven’t seen it yet, check out the clip at the bottom, it is just so bad ass looking. CJ recommends the blog Species New to Science for some additional background.

Following up on Sarah’s awesome post on Women in Science, why not check out how folks at the Eigenfactor Project compiled raw data on gender bias in publications and made a beautiful visualization. Devin (@devindrown) thinks it is particularly cool how the authors figured out how to sex the authors in the large corpus that is JSTOR. Be sure to read the methods for the details.

Sarah (@sarahmhird) points out this excellent blog post form Dr. Bik on the Postdoc life which follows up on the fallout from the Forbes story about Professors having least stressful job.

Via Jeremy (@JBYoder) see how conservationists are using the DNA inside fly guts to census biodiversity from Ed Yong (@edyong209) over at the Not Exactly Rocket Science section of Phenomena.

THE most unbelievable title and figure Sarah’s (@sarahmhird) ever seen. Check out this apt named publication in PLoS Neglected Tropical Diseases. Curse words are not just for when you experiment goes awry anymore.

Apparently nothing is absolute anymore. A study in published in Nature cooled quantum gas below absolute zero. Amy didn’t know that it was possible, did you?  Don’t lag behind the times. Check it out now. (You can get the story over at Scientific American as well.)

CJ is all about visual animals today and the Tardigrade is no exception. Check out this one because his face is so darn cute.

Via Amy: A study in Europe finds that choosing your child’s name poorly may make him/her dumber and lonelier.  If you’re thinking about procreating, this might be topically relevant for you.

When extreme violence can’t be explained, is genetic analysis warranted? You can read the Nature editorial here.

Amy highlights this exciting news: JSTOR begins offering free yet limited access to its online academic seo company library. Very helpful for when you are outside your institution, or lack access generally.

Did you know this existed, 2012 in Science? Now you do thanks to Sarah (@sarahmhird).

And now, what you’ve been waiting for, the Giant Squid!

Friday Coffee Break, a new year begins

Every Friday at Nothing in Biology Makes Sense! our contributors pass around links to new scientific results, or science-y news, or videos of adorable wildlife, that they’re most likely to bring up while waiting in line for a latte.

Aeropress and mug

credit: Rik Panganiban

Massive open online courses (MOOCs) have caught Devin’s eye (@devindrown). This January the Santa Fe Institute is offering an Introduction to Complex Systems Science. You don’t need a science or math background.

Things to think about for New Year’s Resolutions related to health.  It’s the little things that matter says Jonathan (‪@Bonovox1984)

Why not check out what Carl Zimmer on the Loom blog writes about sex differences in spatial abilities over at National Geographic’s Phenomena. Sarah  (@sarahmhird) feared this article (Of Men, Navigation, and Zits) was going to be drawn into evolutionary psychology BS but thankfully, Zimmer is smarter than that.

Via Jeremy (@JBYoderWhy not see what makes humans so restless and learn about human migration.This looked like it was going to go into deep adaptationist territory, then all of a sudden actual population geneticists started showing up.

Noah (@NM_Reid) recommends this story on how the tree frog is redefining conventional wisdom about evolution over at the Smithsonian Magazine. He also thought this article on the a biological field station in the Amazon is worth checking out.

They say scariest of the deep sea, but Sarah (@sarahmhird) says coolest monsters, take a look over at the seo companies Smithsonian and decide for yourself.

More than just a metaphor, Wright’s Adaptive Landscape provides inspiration

Review of The Adaptive Landscape in Evolutionary Biology edited by Erik Svensson and Ryan Calsbeek

adaptive_landscape_book_coverHave you ever wished you could go back in time to be present at a particular historical event? The 1932 International Congress of Genetics sounds perfect, right? There R. A. Fisher, J. B. S. Haldane, and Sewall Wright all presented papers of their recent research. If you’re a student of population genetics, you probably recognize these names as some of the founders of the field. At this meeting, Wright was asked to condense some of his more technical mathematical framework into a form that was more widely accessible to the audience of biologists. The result was his conceptualization of the Adaptive Landscape where an analogy is made between the fitness of an individual or population and the varied topographic landscape (pictured on the cover of the book). Wright used this metaphor to describe aspects evolutionary dynamics of populations.

The editors of a recent book, The Adaptive Landscape in Evolutionary Biology, gathered together contributions from evolutionary biologists, ecologists, and philosophers to demonstrate the impact that the Adaptive Landscape has had on the field of biology. This book embraces an 80 year old metaphor created by one of the founders of the modern synthesis to explore the breadth and depth of research generated in evolutionary biology. Unlike a recent book addressing aspects of the modern synthesis, Evolution: The Extendend Synthesis (Pigliucci and Müller, 2010) which called for a revolution, Svensson and Calsbeek have assembled authors that explore the innovations and contributions that build upon the fundamental ideas of population genetics and seek to grow the field. Early in this book, Pigliucci asks about the utility of the Adaptive Landscape metaphors, even titling his chapter with the question, “what are they good for?” I think the rest of the book provides a more than sufficient answer to his question.

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When mummies attack! Why specificity matters for coevolution

Evolutionary change by means of Natural Selection needs a couple of things in order to happen: heritability and variation in fitness. That is, offspring need to resemble their parents at least a little (heritability) and individuals need to differ in their survival and offspring production (fitness). WORDLE Rouchet Vorburger 2012We’ll worry about heritability in another post, but variation is something that seems like it might be hard to maintain. Some forms of Natural Selection will reduce variation as more fit individuals become frequent and all the different kinds of less fit individuals are eliminated from the population. However, there is a force, common in nature, which may maintain variation, parasites.

Interactions between hosts and parasites can generate strong selective pressures on each player, especially if your life depends on infecting a host. Often, biologists make an analogy to an arms race where players are developing bigger and better defenses or weapons. Antagonistic interactions may also generate negative frequency dependence where a rare host type is favored because the parasites are adapted to a common type. You can learn more by checking out CJ’s post on the Red Queen Hypothesis or Jeremy’s post on a different coevolutionary puzzle. A key component for maintaining variation via negative frequency dependent selection is specificity. There must variation in the interaction among different host genotypes and parasite genotypes. This is sometimes referred to as a GxG interaction. If parasites can infect all the hosts, there is no specificity. Specificity allows different hosts to be favored over time depending on the composition of the parasite population.

Theoreticians love to use different models of interactions between hosts and parasites, but without empirical evidence, there seems little point. In a recent paper by Rouchet and Vorburger (2012), the authors looked for evidence of just the kind of genetic specificity would result in the maintenance of genetic variation.

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