The Nature of Natural History: Kelowna CSEE 2013

Every few years a group of ecologists or evolutionary biologists experiences existential angst about the decline of natural history knowledge. This angst is wholly justified when many biologists no longer take the time to experience how the organisms they study actually live in nature. At best (and this is better than most), many biologists run off to the field for a day, stop at a bridge over a stream or along a forest trail, quickly collect their samples, and then run back to the lab to extract the DNA, run PCRs, and genotype their critters. Organism reduced to molecules. And yet we can’t possible hope to understand how organisms have evolved and how they fit into the polity of nature without careful observation and experimentation IN NATURE. After all, genotypes do not directly experience selection, nor do genotypes have ecological effects: instead it is phenotypes that experience selection and that have effects. And these phenotypes evolve and have effects through interactions with the environment that usually cannot be discerned without careful observation and study.

A five minute walk from the conference center.

This year, the Canadian Society for Ecology and Evolution held their annual meeting – organized by Jason Pither – in Kelowna, British Columbia. The overall theme was Range Margins in a Rapidly Changing World and I was in a symposium organized by Root Gorelick and Kevin Judge on – you guessed it – natural history. My own talk was about the role of photography as a way to bring readers and listeners a bit of a feel for the natural history of the systems under study. I told two stories through data and pictures. One story was about the interaction between bears and salmon and how the former drive evolu-tion in the latter.  The second story was about how humans are altering the evolution of Darwin’s finches in Galapagos.  I ended my talk by pointing out that, yes, photography was expensive but that anyone could set themselves up well from scratch for only about $3,000. The talk after me was about the role of illustration (as opposed to photography) toward the same goal. Lyn Baldwin pointed out that – in contrast to cameras – you can set yourself up well for illustration with a pencil costing less than a dollar. I don’t think that is really fair though as some pencils cost considerably more than a dollar.

The stories I told through data and photos.

The Natural History symposium was fascinating and yielded many curious tidbits about organisms that reminded me of the game I play with my kids at dinner “what did I learn that was new today.” (I did a similar post a few years ago based on a symposium in Leuven.) If I were home today, here is what I would tell my kids:

1. Many cactuses have a large and extravagant cephalium which – according to Root Gorelick – has no function and could well be maladaptive. Of course, I would then tell my impressionable kids that, no, Darwin was not wrong, instead Root must be, but that, yes, biologists still have no clear explanation of what benefit the cephalium brings.
2. Jumping spiders, those charismatic midgets with forward facing eyes that leap on their prey, have crazy mating colors and displays. I will also tell my kids how Wayne Maddison, when he was a kid in Ontario, discovered that two species found on sand dunes have incredibly different strategies for building their “nests.” Wayne told the audience that he feared that he would go to his grave before he published this observation and so I here pledge that, should this be so, my kids (one of whom loves spiders) will take up the study and published it (without mentioning Wayne of course).
3. Feather mites are tiny (often microscopic) mites that cling to the feathers of birds. Heather Proctor explained how these mites show an incredible diversity of forms - even on the same birds – and have a number of crazy features. Males apparently grapple with each other for access to females by trying to throw each other off the feather – just like tiny sumo wrestlers on a tight-rope. And some groups show handed-ness, with the individuals on one wing of the bird showing a different body coiling pattern than individuals on the other wing of the bird.
4. Like a number of other insects, male Mormon crickets give nuptial gifts to females – in this case, little “cheese balls” that the female munches on while the male mates with them. Cheese balls appear to be quite costly for the males to produce and they are an important part of the diet for females. This leads to so-called “sex role reversal,” where males become the limiting sex during mating and females compete intensely for males. When asked during the question period whether he had ever tasted these cheese balls, Darryl Gwynne admitted proudly that he had and that they weren’t actually that bad.
5. Hump-winged grig males, like Mormon crickets, provide a nuptial gift for females but not a yummy cheese ball. Rather, they offer up their wings for the females to munch on while mating. Kevin Judge showed an amazing video of grigs mating, with the female on the back of the male munching vigorously away at the male’s wings (and seemingly trying to get at other male parts too), while the male simultaneously tried to keep her wandering mouth under control with his legs while crimping her abdomen with a structure that looked like a small staple remover (and at least once it removed part of the female’s abdomen).

That is just a small selection of natural history tidbits from the symposium – my apologies for any inaccuracies which I am sure the above hyperlinks can clear up. After sitting through this great symposium, I happened to see Sally Otto, who had some binoculars around her neck. “Have you been bird watching” I cleverly asked, and she proceeded to tell me about a nearby lake with nesting Avocets and many other great birds. How could I not take my own advice, and that of everyone in the symposium? So I ran off to take some photos of the natural history of Kelowna. Amazing stuff. In just a few walks, I saw 45 different bird species, including one – the Pygmy Nuthatch – that I don’t think I have seen before. The conditions were great and I was able to get some good photos, which I show below (many more are here).

So that is it for CSEE 2013 – now I am off to Vancouver Island for field work on stickleback. After that, it is time to get geared up for CSEE 2014, which we are hosting in Montreal. It will be the first ever joint meeting of CSEE, the Canadian Society of Zoologists (CSZ), and the Society of Canadian Limnologists (SCL). The meeting title is “GENOMES TO/AUX BIOMES” and it is supported equally by the three societies and by four Montreal Universities (McGill, UQAM, Condordia, and Universite de Montreal) – we hope to see you there. Montreal has some natural history too!

Breeding Avocets.

The omnipresent chipmunk

A robber fly (thanks for the ID Bob).

Common Flicker - the red-shafted flavor.

The ever-cute California Quail

A Wilson's Phalarope takes flight.

Life after death: When does your phenotype expire?

Throughout an organisms’ life, the expression of genes, regulated by the biotic and abiotic environment, gives rise to traits that determine how fast it can run or how tall it can grow. Many traits also affect species interactions; for example, are you fast enough to outrun predators? Do you look tasty to herbivores? Most traits (e.g., running speed) cease to be important once an organism dies, but some traits linger and have “afterlife” effects on the environment. A prominent example of afterlife effects can be found in decomposing plant material, which is a crucial part of nutrient cycling. Microbes and fungi are critical to many stages of nutrient cycling, such as the mineralization of organic matter and the nitrification of NH4+, which plants cannot use, to NO3-, which is usable by plants. However, microbes and fungi can be “picky eaters” in a sense, as they prefer substrates with labile simple sugars instead of defensive molecules such as lignin. Simple sugars have carbon and nitrogen supplies that are easily accessible, while larger, more complex molecules require degradation by energetically-costly enzymes. Therefore, genetic and environmental influences on the chemical composition of plant material can persist after a plant sheds its leaves and affect how quickly its nutrients are cycled.

Afterlife effects aren't a new concept; exposure to herbivores and ozone has been shown to indirectly affect decomposition by altering leaf chemistry. However, we recently documented a new type of afterlife effect by showing that genotypic variation in a focal plant’s neighbors could affect the chemical composition of the focal plants litter. Although we don’t have the mechanism completely nailed down, it appears that focal-plant biomass allocation (putting carbon into roots vs. rhizomes vs. stems, and so on) is affected by neighbor-plant genotypic variation, and that shifts in focal-plant biomass allocation are correlated with focal-plant litter quality (specifically, lignin:N). This type of afterlife effect can also be considered an indirect genetic effect (technically, an interspecific indirect genetic effect because the neighboring plants belonged to different species), through which the expression of genes in one individual affects the phenotype of a different, heterospecific individual.

Solidago altissima, one of the study's focal species, along the TN-NC border.

We (Jen Schweitzer, Joe Bailey, and me) were curious whether genetically­-based afterlife effects were unique. Do they have consequences that, for example, ozone-driven afterlife effects would not? Ultimately, we started to think about ecosystem processes (productivity, nutrient cycling, among many others) and the basic drivers of these processes. We argue that ecosystem processes are the “gene-less products of genetic interactions”, meaning that the plant, animal, and microbial traits that interact to create ecosystem processes all have a genetic basis, although the expression of that genetic basis may change depending on how an organism’s genes interact with the biotic and abiotic environment. So, you may ask – “What does this mean?” We’d argue that the “ecosystem processes are gene-less products” perspective allows us to put ecosystems in an evolutionary framework. We can then ask questions like: How might nitrogen cycling or plant productivity change as natural selection acts on the genes that are the most basic drivers of these processes?

If you’re interested in the research behind this post, head to http://www.plosone.org/article/related/info%3Adoi%2F10.1371%2Fjournal.pone.0053718.

More Galapágos Adventures

This year I joined Team Pinzon for the first (and hopefully not the last) time – and so it is time to do my first Galápagos post on this blog. Previous expeditions (sadly, without me) have done a number of posts about our work, including Suskewiet as a new statistical method for comparing beak size and shape, a five day re-cap of a field season that included posts on blood sucking maggots, people sleeping on the job, and adventures in 3-D. It's hard to beat that, though I suppose I should mention parasites to skew Joost's statistics about them. Actually, this year we worked closely with another team from the University of Utah who are studying the ecological effects of the blood sucking maggot, Philornis downsi. Thus, I'm allowed to mention parasites in this post.  Cha-ching!

The Galápagos islands have much to offer in terms of data, but the first thing that one notices in the Galápagos are the unique animals and environment. These experiences figured heavily in my own blog on the adventures of field work in Galápagos – and I would like to recap just a few of them here.

I'll start off with a time series going from nest building to fledging. One of the best parts of being in the field for an extended period is that you get to follow ‘mother nature’ doing her thing. In this case, I got to watch the entire process of finches raising their babies, over the span of one month. It starts with nest building...

Many of the birds on the island make their nests in cacti, acacia trees, and other prickly plants. The finches make a spherical nest, and you can often find them gathering materials for their nests. I wonder how much beak shape and size affects nest building. We know it affects everything from foraging abilities to singing... perhaps it affects nests?

It's kind of like buying a home. Once you've got a home (and a partner), you can raise a family, starting with the juveniles...

Part of the project is to look at assortative mating – the extent to which finches mate with other finches that have beaks that are similar in shape to their own. There are two ways to do this. One is to band as many birds as possible, and then do focal observations on nests you find and figure out which finches are paired. The other way is to find a nest, and then try to sample the birds you find at the nest. Due to lack of time, we’re going with the second method for now. The coolest thing about this is finding nestlings in the bird nests!

Finch nestlings

Mockingbird nestlings and parent(s)

Finally, the juveniles are ready to leave the nest! Once the nestlings have developed their feathers to be able to fly, they become fledglings and can fly and leave the nest, but they are still dependent on their parents for food. Finches build their nests at all heights, and this particular fledgling was quite curious before it took off from the nest.

Finch fledgling

Some juvenile anis were grooming each other and generally behaving as siblings often do:

Our work is done on the island of Santa Cruz, where the Charles Darwin Research Station is located. There are several other volcanic islands in the Galápagos, a few of which I had the opportunity to visit. One spot I visited is Sierra Negra, on the island of Isabela. Sierra Negra is a caldera where the volcano collapsed onto itself after an eruption, similar to the famous Ngorongoro crater in Tanzania.

 On the rim of Sierra Negra

Bartolome Island is one of the younger islands in the archipelago, and offers a beautiful view. We spotted a juvenile Galapagos hawk there:

Two other famous islands are Wolf and Darwin. These islands rise up straight out of the sea, and you are not allowed to land and go onto the islands. However, as beautiful as the islands are above water, even more treasures lie beneath the water.... (psst, scroll down for photos of underwater critters)

To give you an idea of field work, here’s a post from my blog, talking about how we do field work on the islands:

It seemed the hobbitses did well enough yesterday morning to venture to Rohan, which is complete with an entrance gate and a statue to guard over the mist nets. 

Processing birds under the tarp

Father and son take a break from the intense morning heat

Joost checks out the GPS

The bird banding kit, which we couldn't find in Montreal (where it is normally stored). Banding an individual bird includes a unique silver band with an id number, and a unique colour band combination to identify individual birds from a distance

The statue is a Pegasus, but who says Tolkien and Greek Mythology can’t have a mash-up?

 Team Pinzon with the Pegasus

If Jacques Cousteau had lived before Charles Darwin... hmmmm. Some interesting late night discussions could have been had....

And lastly, if you made it down here, congratulations! Thank you for sharing my adventures with Team Pinzon this year, and I’ve got my fingers and toes crossed that I get to go again next year. Actually, my fingers are not crossed as I need to write some manuscripts. Hopefully, in the near future, one of those manuscripts will be on assortative mating in the medium ground finch. We know that there is a bimodal distribution of beak shape in a population of medium ground finch, and we hypothesize that assortative mating is one of the ways this bimodal distribution is maintained. However, we know there is temporal variation in their assortative mating, but we don’t know the extent or the potential sources of this temporal variation. Stay tuned for future work on this tantilizing project.

OK. My toes are cramping now. Uncrossing toes as well. Still hoping that I'm joining the team in future years...

Carnival of Evolution #59

Carnival of Evolution #59 is up!  Our contribution is Thomas Cameron's recent piece Of Mites and Men, about some fascinating experiments into harvest-induced selection.  Lots of other good stuff in there, check it out!

The theme this month is, somewhat bizarrely, Doctor Who.  It has nothing to do with evolution, but I'll leave you with a picture of Sarah Jane Smith, a companion of the 3rd and 4th Doctors, played by Elisabeth Sladen.  I watched Doctor Who more or less nonstop as a kid, and I had a terrible crush on Sarah Jane.

Genome-wide recombination patterns and their implications in threespine stickleback fish

[This post is by Marius Rösti; I am just putting it up.  -B.]

During meiosis – the characteristic cell division in sexually reproducing organisms – the mother cell that gives rise to sperm or ova has to multiply and reduce the number of chromosomes from two full sets to one. During this process, the two homologous chromosomes (one from each parent) can exchange DNA segments. This process is called meiotic recombination. In a paper just published in Molecular Ecology, we demonstrate in one of the prime model systems in evolutionary biology (threespine stickleback fish) that recombination is distributed highly heterogeneously within the genome, and highlight implications for genome evolution and its empirical investigation.

A threespine stickleback, Gasterosteus aculeatus

Heterogeneous recombination rate

Threespine stickleback (Gasterosteus aculeatus) offer a powerful model system in evolutionary biology. Some of the reasons are the well-known natural history and ecology of this fish, as well as the availability of many genetic and genomic tools. However, a detailed analysis of recombination in stickleback has been missing so far. To do this, we first reassembled and improved the stickleback’s reference genome. Based on 300 individuals and approximately 2000 genome-wide SNP markers, we find that the recombination rate is highly elevated in the chromosome peripheries relative to the chromosome centers. A similar distribution of recombination events along chromosomes has recently been found in several other taxa, including humans. We further detected a minimum of one recombination event per chromosome (but not chromosome arm) per meiosis event. These findings likely point to strong functional constraints on the rate and distribution of recombination within the genome.

Heterogeneous recombination rate drives patterns of genetic diversity and population divergence

Incorporating genome-wide sequence data from four natural stickleback populations inhabiting ecologically different lake and stream habitats, we can demonstrate clear associations between recombination rate and the magnitude of allele frequency shifts between populations, and between recombination rate and genetic diversity within populations. In these young (only a few thousand years old) populations experiencing divergent natural selection, these patterns certainly reflect genome-wide heterogeneity in the effect of selection on linked sites, which has proved hard to demonstrate convincingly in non-ecological (genetic) model systems such as Drosophila flies. This recombination-driven heterogeneity in signatures of selection has a potentially important methodological implication: ecological genome scans will detect divergence outliers more easily in low-recombination regions. Furthermore, we detected a strong association between recombination rate and GC nucleotide content. As suggested in other organisms, this pattern perhaps arises from GC-biased gene conversion, potentially reflecting a direct influence of recombination on genome evolution.

Recombination and sex chromosome evolution

As in humans, in threespine stickleback  males are the heterogametic sex: males carry an X and a Y sex chromosome, while females carry two X’s. We were able to confirm and narrow down the physical boundaries of a previously inferred small ‘pseudoautosomal’ region within the sex chromosome where recombination between the X and Y still occurs. The rest of the X chromosome does not recombine with the Y any more, but it does exhibit two regions characterized by distinct levels of differentiation between the X and the Y. Such ‘evolutionary strata’ of Y-degeneration are expected when the suppression of recombination between the X and Y occurred in discrete pulses across large chromosomal regions. This first demonstration of evolutionary strata of Y-degeneration in a fish species highlights the devastating effects of suppressed recombination during the evolution of sex chromosomes.

Paper reference

Roesti, M., Moser, D. and Berner, D. (2013). Recombination in the threespine stickleback genome—patterns and consequences. Molecular Ecology. doi: 10.1111/mec.12322

Of mites and men

[This post is by Thomas Cameron; I am just putting it up.  -B. ]


Those that observe ecological dynamics have always stated that evolution plays a role, but it is only relatively recently that there has been a fever of interest in quantifying what that role might be. It is not the case that there was ever a lack of interest; it was just generally assumed that as evolution occurs on very long timescales, it will have little influence on contemporary ecological dynamics – certainly on the timescales over which ecologists would want to make predictions. But increasingly we have come to accept that phenotypic change can occur very quickly, in only a few generations, and we have a good body of evidence showing that “rapid” or “contemporary” evolutionary change in the underlying biology of species is common. (As an aside, I wonder if it should not be called “rapid” evolution, as it has recently been pointed out to me that palaeontologists see little more phenotypic change within species in thousands of generations than ecologists see in tens of generations.)

Much of the recent interest in contemporary evolutionary change was generated by the theory of harvest-induced selection, a framework in which it is thought that high trait-selective harvesting rates lead to a change in the frequency of traits in a population, diminishing the type of animal or plant that the harvester is seeking. More recently further interest has come from the question of species responses to current rates of environmental change. And so it was with these questions in mind that a project was born. What exactly is the contribution of evolution to the way in which populations respond to their environment, and how is this influenced by high (but reasonable) harvesting rates?

Our project was to compare the adaptation of populations of soil mites, taken from the wild and placed into environments differing in the form of environmental variation caused by experimental manipulation in the variance, but not the mean, of the food they received. In a recent paper (DOI: 10.1111/ele.12107) I presented the results of one of these environmental treatments: periodically varying food. The variation of the food is not so important for this blog post, so I won’t discuss it again here. Overlaid upon this, we harvested 40% of either juvenile or adult individuals each week, with an unharvested control. This harvest rate was estimated to be close to a maximum sustainable yield, based on harvesting adults. Other important information is that these soil mites have essentially three demographic stages: eggs, juveniles and adults. They are sexually dimorphic as adults and have a generation time of approximately five weeks.

A mite.  Photo credit: Dr. Tom Cameron.

For two years we counted the numbers of the different stages of soil mites each week in each of 6 replicate population tubes per harvesting treatment (18 tubes). We combined this census of demography with a census of the life history of the mites. For the uninitiated, a life history is a way to describe the balance between how an organism invests its available resources into survival, growth or reproduction. To conduct the life history census, approximately every 15–20 weeks we took a sample of mites from two of the population tubes per treatment and reared them in a common garden for three generations (a common garden is where you rear all organisms in the same conditions, which helps to minimise any non-genetic effects of the parents’ environment on the life history of the mites). Our assumption is that if we view the life history of the mites after they have been in the common garden then any differences that remain should be mostly genetically based. Because that is an assumption, we also conducted a third census of the genetic dynamics in those two sample populations per treatment so we could estimate whether any changes we saw in the life history of the mites was “likely” to be caused by natural selection.

We have two main results. First, by placing mites from the wild into closed populations in the laboratory we created populations not suited to their new environment and the populations began to decline toward extinction. However, after only five generations this decline slowed and then reversed into a long-term increase. This dynamic occurred in all stages in each of the 18 tubes across all harvesting treatments. Our analysis of the life history found that there was a large delay in mite growth rates occurring during this period. Normally we think of a delay in growth to maturity as a negative response to poor conditions, but under the conditions the mites found themselves in compared to their wild ancestry, it was selected for. To understand why, we also looked at survival and fecundity. While survival was little changed, those mites that delayed their growth to maturity and spent a longer time in the juvenile stage could double their peak reproductive output. To confirm this pretty adaptive story that mites investing in increased individual reproductive output could rescue their population from extinction, we compared the population growth we would predict based on the life history of an average individual with the real population growth rates we observed in the population time series, and they were highly correlated. Indeed, if we do not use the changing life history trait values we observed throughout the experiment we cannot predict the recovery and long-term population size increase we saw in the experiment. Finally, we were able to show that this delay in age-to-maturity was linked to patterns of change in the genetic diversity in the populations, suggesting that natural selection was an important factor in the ecological dynamics even over just a few generations.

Harvesting had both an ecological and an eco-evolutionary effect on the population dynamics. Its eco-evolutionary effect was to prevent individuals from juvenile-harvested populations from reaching the optimal phenotype, as they could not stay in the juvenile stage too long or the populations would go extinct. Adult-harvested populations produced individuals that delayed maturity a little longer but matured larger, which we suggest is an adaptive response that increases fecundity early in adult life. These results are exactly what we would predict from current theory. Certainly the ecological effects of harvesting were strong, in that when we ceased harvesting the population dynamics of all treatments were more similar; but differences remained for many generations, especially in terms of population variation.

So our take-home message from our first result from this project is that ecology and evolution are not as separate as we have traditionally assumed. Even over a few generations we can see that evolution has a role to play in how populations respond to environmental change, whether biotic (e.g. harvesting) or abiotic (e.g. climate change).

There has been some criticism of microcosm studies of harvest-induced evolution that they produce trait change underpinned by selection far faster (i.e. 10% per generation) than the slow rates observed in the heavily exploited wild populations (1–2%). In our study, in which mites were simply enclosed in population tubes and exposed to strong density-dependent competition for food and then harvested near the maximum sustainable yield, we saw a 4% per generation response to environmental change and a 1.4% per generation change in response to harvesting. This clearly places the trait changes we saw in the “slow” category and suggests that even slow rates of harvest-induced evolution can have significant and long-term effects on population dynamics. Our results are therefore further evidence that evolutionary considerations should be taken into account in harvesting management. By this I do not necessarily mean the harvest rate, as I think ecological models can mostly deal with this; rather, I mean in terms of making realistic predictions regarding whether harvested populations will recover from overexploitation, and how long such recovery might take.

How important are these results of contemporary/rapid evolution? Well, the truth is we do not know. Many studies have concluded that rapid or contemporary evolution may have repercussions beyond population ecology, for example in ecosystem services and ecological community structure, resilience and function; but to date there are few (if any?) examples in which this has been demonstrated. For this reason, I would suggest that future studies of the role of evolution in ecological dynamics should turn toward community ecology.

CEEB 2013

Every year, the Conservation, Ecology, Evolution, and Behaviour group (CEEB) of the Department of Biology at McGill organizes a retreat for faculty and graduate students. When I say retreat I mean a cocktail of science talks, workshops, trivia, lots of wine and even more fun, with a final touch of Kommando Pimperle. As usual, the event was held in the beautiful Maison Gault in Mont Saint-Hilaire. It was the first time that I was able to attend one of these, so I thought I would write a short post about it.

The retreat began with a series of ignite talks, which are basically 5 min presentations where the slides are automatically changed every 30 seconds. This is the first time that this format was used at the retreat, so it was interesting to see how different people dealt with the pressure of time and the unexpected change of slides. Ignite talks definitely have some advantages, particularly because most people are able to keep their ADD on a leash for 5 min. Moreover, you don’t have time to spare on irrelevant stuff; you go straight to the main point. But things can get awfully complicated if you are not prepared, or if your topic is too complicated. Some of the talks were really interesting, but they were so fast that I already forgot the details. However, I do remember that topics ranged from NSERC funding, Fowler’s toads, evolution of cognition, smaller and smaller R²s, ecoevolutionary dynamics, flowering time and climate change, ant evolution, among many others.

Jonathan Davies and Andrew Hendry gave a workshop on how to write research papers, and how to deal with reviewers if your paper is rejected. I really don’t know if the latter was added because it was assumed that if you did as suggested in the first part you were likely to be rejected, but I hope not. Monica Granados and Eric Pedersen gave another workshop, but this one focusing on how to make sexy plots using R and Adobe Illustrator. If you attended this workshop you were also less likely to worry about the reviewers mentioned in the first one.

I think this is some sort of water polo on chairs and without the water, bathing suits, and all of that. 

After dinner it was time for trivia, but not just any trivia, it was a CEEB trivia. Questions were related to the talks and general knowledge in Biology. I won’t go into detail here because I spent most of the time trying to get the other teams to answer wrong, rather than actually helping my team  –a good reason for which we didn’t win, sorry les tetines.

Some of the post trivia survivors

The night ended –very late– with a German game called Kommando Pimperle. I want to be honest here and say that until I started writing this blog I thought the game was Kommando Bimpula, not even google knew what I was talking about. Eventually I found out what the real name of the game was, and it turns out that it is quite popular! It is also very fun to play. Basically, there are several instructions for movements with your hands that are given by the person leading the game, but they can not be performed by the rest unless the word kommando is given before. It gets even trickier! The person leading can also trick you by combining different movements and throw the kommando word wherever s/he likes. And to make it even worse, it is all in German! I was also usually the first person to lose…

This is a video of Kommando Pimperle at a cafeteria in a German university.

All in all, my first CEEB was a great experience! I got to know (in 5 min) what a lot of the people in the department are doing, and got to talk about science in a more informal environment. It is a good way to interact with your peers and establish future collaborations. It could also be the first step to learning German! Kommando Pimperle…

Evolutionary Rescue, Pappy Van Winkle, and Next-Level Smokin-Hot Secret Sauce

Many years ago, when Mike Kinnison and I were office mates in Seattle, we started a list of “words we should use more often.” These were usually esoteric English words that we had encountered in some publication and decided were just too cool to be used so infrequently. I can’t remember all of the words but consanguineous was certainly one of them. I did use consanguineous in at least one paper but, sadly, it did not precipitate a particularly far-reaching or long-lasting meme. But what if I had tried harder? What if I had insisted that my fellow graduate students use the word in their papers – or bribed them to do so? What if I had used it in all of my own papers? What if I had extorted (or bribed) each visiting seminar speaker to use it in their talks? This is precisely the experiment currently being conducted by the Jen Schweitzer and Joe Bailey labs at the University of Tennessee.

While visiting UT for a seminar last week, I met with Joe and Jen’s students. At the end of our meeting, the students casually mentioned that they had come up with a series of phrases that should be introduced into the scientific lexicon – and they pointed out that I could help their cause by using the phrases in my seminar later that day. I immediately thought back to consanguineous and its ignominious continuance in anonymity. Maybe I here had a new chance to save some cool lost word or phrase from the dustbin of academia. I would be glad to help, I told them, what are the phrases? They pointed to the chalkboard behind me, where I read:

“Next level shit”

“Smokin’ hot right now”

“There ain’t no secret sauce”

Hmmm – not quite what I was expecting and perhaps not so deserving as consanguineous but, then again, who am I to quash enthusiasm and ambition. The meme does not stop here. After presenting some genetic data in my talk, I pointed out that the particular genetic markers (microsatellites) I used were rather old school, and that what we really needed to answer the question was some “next level shit.” I then pointed out that what is “smoking hot right now” (actually I had forgotten the phrase and needed some prompting) is RAD-tag based SNP discovery – for which I conveniently had some results in my next slide. Two phrases down, one to go: the hardest one. I struggled to think of an appropriate use for “there ain’t no secret sauce” and eventually realized, while looking at my conclusions, that this was precisely the spot.

Now, I can’t say that I will continue to use these phrases in all my talks, but I do feel I have done my part and that, should the meme not take off, I will at least have given it the "old college try.” If it does take off, I suggest that consanguineous should be next. In fact, I anticipate that all of Jen and Joe’s students will now feel obliged to use it in their talks. (It means “of the same blood” and so can be used in relation to ancestry or relatedness.)

Jen and Joe holding court in the Smokies.

During my visit, I stayed with Jen and Joe, who kept me well fed (home-made crab cakes, gumbo, and cherry pie), well beveraged (beer, wine, and – in a rare treat – a drink of 23-year-old Pappy Van Winkle’s Family Reserve Bourbon), and well entertained (Emmylou Harris, Rodney Crowell, and Richard Thompson at the historic Tennessee Theater). Joe even let me beat him at ping pong on his home court. I stayed through Saturday to see some sights in the nearby Smoky Mountains, a major biodiversity hotspot. Joe and Jen both had field courses to teach in Cade’s Cove – a mountain valley in the Smokies – and so I tagged along. Both courses – one graduate and one undergraduate – were to collect data at a series of deer exclosures. 

Deer exclosure - or Hendry enclosure?

At one site, Mark Genung and Joe showed me a dead hemlock tree and then found a hemlock sapling that was covered with an invasive scale insect. This insect has apparently decimated hemlock populations on a massive scale. This brought to mind many seemingly parallel instances: Dutch elm disease, myxomytosis in Australian rabbits, phyloxera in European grape varietals, sudden oak death, white nose syndrome in bats, tuberculosis in native Americans, the Black Death in Europe, mountain pine beetles, chestnut blight, and chytrid fungus in amphibians. In each case, an emerging disease – often (maybe always) an invasive, or at least spreading, species – decimates native populations that are not resistant.

What I find interesting about these catastrophes is that they rarely cause species extinctions – except perhaps for chytrid fungus. Instead, the massive declines are arrested short of extinction and the native species either carry on at a much lower abundance or ultimately recover. The interesting question for me is why extinction does not occur. Three possibilities come to mind. First, success of the disease may be frequency dependent, such that its impact or ability to spread greatly decreases as the host becomes rare. This makes some sense as the spread of a disease often depends on the number of nearby susceptible hosts – and so a decline in population density of hosts will decrease the chance that the remaining individuals will be infected. Second, hosts may evolve resistance – as long as genetic variation in resistance exists, then the individuals that survive and reproduce will increase the frequency of resistant genes. In fact, massive mortality events are expected to drive the fastest rates of evolution – because they can impose the strongest selection. Third, the disease may evolve to be less severe, as would befit its continued existence. I have no idea which of these effects is most important in any of the above examples, but it seems to me an important eco-evolutionary question in the context of evolutionary rescue.

Evolutionary rescue is the idea that when environmental change results in maladaptation that causes a population decline, adaptive evolution might reduce maladaptation and thereby arrest the population decline and allow recovery. Evolutionary rescue is generally thought to be most effective for organisms with short life spans, such as bacteria, viruses, or some weeds and insect pests. This makes good sense because these short-lived and numerous organisms presumably have high genetic variation and mutation rates and thus greater evolutionary potential. But it seems to me that large and long-lived organisms, such as trees, have something else going for them. In particular, high mortality can eliminate all but the few mature individuals that are most resistant, which – owing to their very high reproductive output (a birch tree can produce 15-17 million seeds per year) – have the potential to rapidly recover population size. I am not saying that bacteria and viruses don’t have the advantage in evolutionary rescue, merely that the supposed disadvantage to long-lived organisms might sometimes be partly offset by a combination of extremely strong selection and high potential reproductive output in survivors. For more about evolutionary rescue, see the recent PTRSB special issue.

A Tennessee Turkey strutting its stuff.

Well, that’s it for now. I hope to enjoy the rest of my day in the airport of some city that ends in “ville” (Tennessee has more than 50 such cities and towns – more than any other state) and some city that ends in “ark” before finally making it home to that city that ends in “real”.

In the Newark Airport, is it the Earl himself? Or maybe a descendent, perhaps basking in the glory of his ancestor - or protesting the lack of royalties.

Carnival of Evolution #58

Carnival of Evolution #58 is now up!  Although they got the name of our blog wrong, Felipe Dargent's post on mixed-species groups made it in!  A month later than it was supposed to go in, but nevertheless, it made it.  :-O  Joost Raeymaker's post on parasite-induced evolution in cichlids was supposed to be our nomination for this month, but, well, there has been a bit of confusion lately.  Perhaps it will make it into next month's Carnival.  :->  Check out Synthetic Daisies to see all the other groovy evolution-related posts up there now!

The theme this month is the future of evolution, so here's a possible future for human evolution.  Dig the threads, man.

The Hendry Lab in the year 2380.

Evolutionary consequences of indirect trophic interactions

This post is by Philipp Hirsch - I am just putting it up. (Andrew) 

When teaching ecology classes I frequently apply a method called concept-mapping. In concept-mapping assignments students are asked to connect different concepts on a sheet of paper with labeled arrows, thus outlining the interrelations among these concepts. I noticed that, if you wait long enough, every concept will be connected to every other. In addition to initially drawn solid arrows, over time, there are more and more dashed arrows drawn.  Students like to expand the assignment to include dashed arrows that indicate indirect interactions and feedbacks among concepts.

This very much reminds me of food webs. While some arrows e.g. between predator and prey are obvious (quickly drawn) there are a lot of indirect interactions between non-adjacent components in the food web (dashed lines that require a second thought). Such indirect ecological interactions are increasingly recognized as being ubiquitous and ecologically relevant. The question then becomes: What are the evolutionary consequences of indirect trophic interactions?

Lake Erken’s shoreline and all the other lakes in our survey are near-pristine except for the introduction of the zebra mussel (Photo credit: PE Hirsch).

In a recent paper we addressed this topic. We asked how indirect effects of one species that cascade through the food web can contribute to the early stages of adaptive divergence. As a model species we used perch which show a clear phenotypic divergence between littoral and pelagic forms. The magnitude of this divergence is dependent on the availability of profitable habitat-specific resources. Feeding on these resources leads to a specialization of perch morphology to resource-acquisition, mainly through phenotypic plasticity. To study how this phenotypic divergence is affected by indirect interactions we compared perch from lakes in Sweden that were either pristine or invaded by the zebra mussels.

Zebra mussels are numerous in Lake Erken and in the other studied mussel-lakes (Photo credit: PE Hirsch)

Perch do not feed on zebra mussels. Zebra mussels affect both the benthic and pelagic food base of lakes by filtering nutrients from the water column and providing a surplus of structure and nutrients on the bottom. Their filtering activity also increases water clarity. We therefore hypothesized that zebra mussels indirectly increase the phenotypic divergence between littoral and pelagic perch by increasing the habitat-specific food resources for perch.

Indeed we found higher densities of large benthic prey items in the littoral and higher densities of large zooplankton in the pelagic zone of mussel-lakes. Water clarity was also higher in lakes with zebra mussels. Finally, the magnitude of divergence between littoral and pelagic perch was higher in lakes with zebra mussels.

Phenotypic divergence between pelagic (top individuals) and littoral (individuals below) was higher in lakes with zebra mussels (Photo credit: PE Hirsch)

We suspect that indirect interactions between zebra mussels and perch could have triggered this increase in divergence. We considered two main causes of how the mussel-mediated resource changes might indirectly affect perch divergence. First, increases in littoral and pelagic resource density might allow for stronger plastic responses and therefore better adaptation of pelagic and littoral individuals to their different environments. Second, increases in water clarity and resource density might increase disruptive selection acting on morphology -although direct evidence is lacking.

The stronger plastic response in perch from lakes with zebra mussels plausibly results from the surplus of energy-rich invertebrates and zooplankton that specialized phenotypes can exploit in mussel-lakes. A higher growth rate in perch allows for a faster modulation of body shape to better fit the feeding mode. Costs of phenotypic plasticity should also be lower when profitable resources are plenty.

Perch feeding on zebra mussels on the underside of a foot bridge in one of the study lakes (Photo credit: PE Hirsch)

The possible change in disruptive selection regime in mussel-lakes is more complex and partly counter-intuitive. Most studies predict that increasing resources (as seen here in lakes with zebra mussels) should reduce disruptive selection. The puzzling question is how disruptive selection can be more pronounced in lakes with zebra mussels, given the higher resource densities. We propose that the combination of higher water clarity and higher resource density might enhances the connection between diet and morphology. Recently, we could show that if the water is clearer then resource use as well as morphology are more divergent between littoral and pelagic perch (Bartels et al. 2012). The stronger connection between diet and phenotype in mussel-lakes might then affect the selective regime i.e. the “disruptiveness” increases favouring extreme littoral and pelagic phenotypes (with more specialized diet and morphology) and disfavouring intermediate ones. However, at present this remains an educated guess and an exciting field for future research. In any case, on the concept map of the studied lakes the drawing of at least one dashed line between zebra mussels and perch is certainly warranted.

Here’s the link to our paper:

Hirsch P.E.,  Eklöv P.  and Svanbäck R. Indirect trophic interactions with an invasive species affect phenotypic divergence in a top consumer. Oecologia

http://link.springer.com/article/10.1007%2Fs00442-013-2611-1