We threw the S bomb

We resist it for the first three chapters of my thesis, but for the last one we threw the S bomb. That is right, a plain and simple sympatric speciation model. The paper recently went online at the Journal of Evolutionary Biology. In that paper we have separated three different factors that potentially contribute to sympatric speciation. The first one is assortative mating, the second one is intraspecific competition and the last one is resource distribution, not in the spatial sense, but unimodal resource distribution versus bimodal resource distribution.

We found that the most important factor was assortative mating, but other factors must also be present. Bimodal resource distribution was found to be the next most important factor. And, at last but not least, intermediate competition among phenotypes promotes sympatric speciation. To spice up the conclusions, there was no recipe to always end up in sympatric speciation, stochastic factors play also an important role.

The paper already received a lot of press Science Daily, Science 360, etc. What grabbed my attention is coverage from Uncommon Descent, where they highlight in bright red change they made in a quotation, to reverse the conclusion of the paper in the favor of a weird argument.

Do not let the 17Mo file size deter you from downloading are reading this paper. Next time when they ask me for a high resolution figure, I will be more careful, I promise.

In search of eco-evolutionary dynamics: Norman, Oklahoma

After the bioGENESIS meeting in New York, I was off to Norman, Oklahoma, for the annual meeting of the Society for the Study of Evolution. Arriving with Joel Cracraft, we were greeted by 103 degree temperatures and high winds. (After a walk, Spencer Barrett likened it to being in a blow drier.) I went almost immediately to the reception at the wonderful Sam Nobel Museum of Natural History on the University of Oklahoma Campus. The reception was, as usual, a great place to meet up with old friends and combatants, and to make new ones; all the while arguing about various aspects of evolution and science (the cool field work, those damn reviewers of that last MS, the rarity of jobs and grants, etc.) It was bit harder than at past meetings to get too worked up on these topics because the university, city, or state authorities had seemingly dictated that each participant was allowed exactly two drinks. We had a nice little card that they would stamp each time we got a drink. Great, I thought, looking at the card, two free drinks! Finishing those quickly, I went to buy some more – no dice. You simply couldn’t buy more drinks. So off I went in search of someone who wasn’t drinking in hopes that they hadn’t yet given up their tickets. Beside the world’s largest dinosaur skull, I found Xavier Thibert-Plante, and was then able to get back in the beer line.

I will get to some science and nature later but first a few more notes on the puzzling approach to alcohol consumption in Oklahoma. At the barbeque the following night, we were allowed THREE beer and, perhaps to make sure we didn’t have four, several uniformed policemen were circling the tables. And very serious they were – although one had a beer glass filled with something that looked remarkably like beer. Afterwards we went to a bar in town and found out that it is illegal to serve beer over 3.2% alcohol on outdoor patios – because this is public space. Fortunately (or not), Bud, Coors, Corona and the like produce special beers with the alcohol content euphemistically labelled as “Not more than 3.2% alchohol.” Either 3.2% is imperceptible or the words “not more than” had considerable import.

A few nights later, I was about to head from the conference centre hotel to the university dorms (where I was staying) when I passed by Howard Rundle: “How about a whisky at the bar” he asks. Well, I am a sucker for any conversation that starts with those four words. Over the next 15 minutes, Howard, Jeff McKinnon, Jenny Boughman, and a few other folks cleaned the hotel out of all single malts not called Glenlivet or Glenfiddich. At one point, someone asked the bar tender if he had Laphroaig or Lagavulin, to which he responded “I have no idea what you are saying.” You get the idea. Paradoxically, however, we were never once asked for ID at any venue and no one else mentioned having been ID’d. Perhaps anyone can drink in Oklahoma, as long as they only have two drinks below 3.2% alchohol. All of a sudden it was nearing midnight and I realized in a flash that it was father’s day and I hadn’t called my Dad. Lacking a cell phone (I lost it a year ago and haven’t bothered to replace it), I was rescued by the loan of a phone from Mike Whitlock. Not having a cell phone in a world of cell phone users is a great way to make a lot of free calls.

The science at the meeting was the usual mix of a wide variety of topics on all things evolution. There was an eco-evo symposium, called “reciprocity between ecology and evolution,” organized by David Reznick. But I didn’t spend much time there as I had seen similar talks by most of the speakers quite recently. It did seem like a great introduction for folks who don’t normally think about the topic. Sadly, I saw few other talks on eco-evolutionary dynamics, with some key exceptions being Ron Bassar on guppies and Matt Walsh on zooplankton and alewife. (Expect posts on this blog from them soon as I made it clear that I would personally ensure neither of them would get academic positions until they did a post.) The sessions that I enjoyed most were those related to ecological speciation in all sorts of critters. The sessions or talks that I enjoyed the least were those that sought to find the “gene for this” or the “gene for that” – boring stuff for the most part (although not always of course). The introduction to a talk shouldn’t motivate the question of interest as “we wanted to find the gene for ....” For me, the scientific questions of greatest interest don’t rely on what the name of the gene is, although I will admit that finding a set of genes influencing adaptation or speciation does then allow some interesting analyses.

On the last day, I took a walk in the area around the conference center. In very short order, I found and photographed a nesting Killdeer (on a small island in the parking lot beside a car), a Jay (it hit me on the head from behind while I was walking), a nesting Mockingbird (it hit me on the head while I was looking at its nest), nesting Redwing Blackbirds (nearly hit me on the head), and the symbol of the meeting the Scissor-tailed Flycatcher (spectacular stuff). Then I was off to the airport for a flight that never left owing to thunder storms in Chicago. I spent the night put up in a hotel by the airline and had a few glasses of beer and discussion about the genetics of adaptive radiation with Rees Kassen. (It’s a many small world after all!!!) Then it was up at 4:15 am for the trip home. Here’s hoping the next adventure in the search for eco-evolutionary dynamics will have just as much science and wildlife but more beer and whisky.

EVOsystem Services in the Big Apple.

For the past three days, I have been in New York City at the American Museum of Natural History for the annual meeting of the DIVERSITAS core project bioGENESIS (thanks to Joel Cracraft for hosting). The goal of bioGENESIS is to promote the incorporation of evolutionary biology into biodiversity science. Every year, evolutionary biologists of many stripes gather in some exotic locale (Paris, Brazil, Bali, NYC) to discuss how the goals of the project can be advanced and to make steps in that direction. More importantly, we drink large amounts of fine wine and argue, argue, argue about all things biodiversity and evolution.

At each meeting, a major topic of discussion is how biodiversity science seems to have lost the biodiversity – and, for that matter, the science. Instead, it seems to be all about ecosystem services, which does not recognize the value of biodiversity per se and makes policy makers think that all that matters is that we have (for example) pollinators and clean water right now. What is forgotten is that all of these services are provided through the evolution of different species from a common ancestor, and so all ecosystem services are really EVOsystem services. (If you like or dislike the term all credit or discredit should be directed to Dan Faith, who seems to have a knack/fault for such terms or acronyms – PD anyone?). Moreover, evosystem services are so much more because they recognize that biodiversity has current or potential future values to humans that we don’t know about yet and can’t yet envision. And, of course, conserving biodiversity is important in its own right – even if there isn’t any clear human benefit now or in the future.

So what are some evosystem services that biodiversity has provided over the past few days. How about wine? Would you like it if all we had to drink was Merlot? Thank Evolution for Cabernet Sauvignon, Carmenere, Pinot Noir, Malbec, and Block 7 versus Block 28 Zinfandel. All of this is the product of genetic diversity arising through evolution in the recent past. And maybe in a few years we will have something new variety or strain; I propose “Petit Donoghue” – one can only imagine it will be accessible. And what about all those different dogs I have seen straining the leashes of those frenetic dog walkers of New York. All of this – the diversity of dog skull anatomy is as great as the entire Carnivora (work by Abby Drake) – was the product of evolution over the recent past. Now there is clearly an evosystem service that doesn’t filter water or pollinate crop plants yet is nevertheless an important part of our modern cultural landscape. I suppose dogs in general might perform an important role fertilizing Central Park but presumably this task could be accomplished just fine – maybe better – by only one breed, or just wolves for that matter.

Biodiversity produced by evolution: 2000 wines at Nice Matin, the site of our dinner on Tuesday Night.

And this is indeed the problem with ecosystem services as the primary justification for biodiversity in a policy arena – it doesn’t necessarily require biodiversity per se. That is, if all we were interested in is a particular set of ecosystem services, perhaps we could just figure out those species we need for those services and then stop – Great Danes for everyone. But this ignores the possibility the Pomeranians and Weiner Dogs interact with the environment in different ways – ways that have consequences for current and future ecosystem function – even if we can’t see it now.

Further reading:
Faith, D.P., S. Magallón, A.P. Hendry, E. Conti, T. Yahara, and M.J. Donoghue. 2010. Evosystem services: an evolutionary perspective on the links between biodiversity and human well-being. Current Opinion in Environmental Sustainability 2:66-74.

Hendry, A.P., L.G. Lohmann, E. Conti, J. Cracraft, K.A. Crandall, D.P. Faith, C. Häuser, C.A. Joly, K. Kogure, A. Larigauderie, S. Magallón, C. Moritz, S. Tillier, R. Zardoya, A.-H. Prieur-Richard, B.A. Walther, T. Yahara, and M.J. Donoghue. 2010. Evolutionary biology in biodiversity science, conservation, and policy: a call to action. Evolution 64:1517–1528.

Conferences, meme-sex and some science for good measure...

This post was co-authored by Kiyoko and Ben (equal contributors). Photos are merely eye-candy.

This blog is generally about eco-evolutionary dynamics, especially involving contemporary evolution (rapid microevolution, if you will). Recently, the Sixth Annual Congress of the Canadian Society for Ecology and Evolution (CSEE) was held in Banff, Alberta. Given the theme of this blog, we thought we’d present some musings on the eco-evolutionary dynamics of grad students and conferences.

            A key component of eco-evolutionary dynamics is genetics, genes being the primary way that organisms transmit biological information to future generations. Grad students, however, aren’t passing on genes (well, maybe they are, but not in public), but memes. We’re transmitting ideas and beliefs to each other. During talks, at lunches and dinners, and even during coffee breaks, the primary activity that defines a conference is the passing of information. This information can range from tips for surviving grad school, to a new statistical method for data analysis, to gossip about who just got rejected from Science (and, more juicy still, why). Students are sometimes still looking for ideas for a Masters or PhD, profs are looking for new lab members, and governmental organizations are on the prowl as well. CSEE was particularly conducive to the lateral transfer of memes, with fabulously catered coffee breaks spread out on different floors, as well as breakfasts and lunches for all attendees in one common area. The local pubs of Banff also proved an excellent place for ‘meme-sex’; everybody knows that the exchange of heritable information goes more smoothly after a beer or two.  Microbrews speed microevolution!

            Camouflage and mimicry play a major part in these eco-evolutionary dynamics, as we consciously seek to blend into our academic surroundings so that we don't get picked off by predators (with those pesky un-answerable questions!).  At the same time, though, we want to have sparkly new ideas that others like, and that attract collaborators to us.  Thus, we are torn between natural selection for crypsis and sexual selection for conspicuousness, tossed about wildly by the unpredictable vagaries of a spatiotemporal mosaic of selection. Such opposing selective forces are perhaps best negotiated via phenotypic plasticity, although many graduate students find other bet-hedging strategies. A lot of our traits are inherited from our advisors, with some variation, giving the process a distinctly Darwinian demeanour.  However, our advisors choose us and we choose our advisors so it is perhaps also a little Lamarckian: traits that our advisors have found useful during their careers tend to be encouraged in their offspring. For instance, Andrew likes to stick his neck out to reach tasty leaves. Perhaps he will turn into a giraffe by the time we finish our theses.

            Conferences like CSEE are where graduate students go to have meme-sex. And CSEE was HOT! We promiscuously mixed our ideas together, allowing them to recombine freely, and we dreamt up new, wild and wonderful concepts that we will now pursue alone in our basement offices.  Some graduate students have actual sex at conferences, and some of those end up married as a result; but probably many more have "meme-sex" and end up in lifelong collaborations as a result. Please, don’t confuse your model organism with your offspring. Just remember the top three differences: (1) granting agencies are unlikely to fund the development of your children; (2) Drosophila do not wear diapers; and (3) naming your children and becoming emotionally attached to them – even anthropomorphizing them! – is generally encouraged.

            So what kind of meme-sex happened? As an example, let’s see what happened to Kiyoko’s project, which looks at spatiotemporal variation in selection using the Trindadian guppies (now you get the above references, right?). She got great feedback on her talk on spatiotemporal variation in colour patterns in guppies, including ideas on possible sources and drivers of this variation. Other lateral meme transfer came from posters and talks on topics ranging from opsin genes to visual perception based on cone sensitivities to potential physiological costs of producing colour pigments. She got to bounce ideas for future experiments off of other folks, and even sniffed out a few potential collaborations for the future.

So where does that leave us? Nowhere really, except to go back to our office dwellings and cultivate these new memes we’ve absorbed. We will evolve and grow and differentiate, and by the next conference, we’ll have a new batch of memes prepared, ready to be, uh, sprayed indiscriminately at our colleagues. Well, sometimes analogies can be taken too far; we apologize for that last mental image. Next year’s congress has been unofficially dubbed Evo-palooza, as it will be a joint conference including CSEE, SSE, ASN, SSB, and ESEB! That will be an incredibly stimulating conference. Don’t forget a condom!

P. S. We saw a bear!

Eco-evolutionary Trophic Dynamics and the Loss of Top Predators

Humanity is at odds with the world’s top predators. Ecologists have long recognized the importance of top predators for the functioning of food webs. Decades of work have revealed that top predator removal can impact the biomass of primary producers. This is because, as top predators decline, prey populations increase, initiating trophic cascades. Traditional trophic cascades are mediated by the demographic and behavioral responses of prey populations. But predator removal may also have important effects on prey evolution. When predators are present and prey density is low, natural selection may favor prey traits that are important for predator escape ability. However, when predators are eliminated and prey density increases, natural selection may shift, now favoring traits that are important for competitive ability. This shift in natural selection may modify important trophic interactions.

Mike Kinnison, Ben Wasserman and I investigated the impact of predator loss on the evolution and ecology of prey. We took advantage of a historical introduction experiment involving Trinidadian guppies. In 1976, John Endler introduced about 200 guppies from a site with the top fish predator Crenicichla to a site lacking predators. Much is known about how this introduced guppy population has evolved in terms of color patterns and life history traits. However, little is known about how trophic morphology and feeding rates have changed in response to predator loss. We hypothesized that the absence of Crenicichla would lead to increased guppy density and heightened intraspecific competition. Due to trade-offs between gathering resources and avoiding predators, we predicted that the population released from predation would display heightened feeding rates compared to the high-predation source population.

Our results confirmed this prediction. The introduced population and a nearby natural low-predation population both displayed greater guppy densities and higher individual level consumption rates than the high predation source population. In addition, morphometric analysis revealed that both head and body shape have evolved to facilitate heightened resource acquisition. Results from prior experiments in mesocosms suggest that heightened feeding rates in low-predation guppy populations may cause them to have stronger top-down effects on algal biomass compared to high-predation populations.

Traditionally, the loss of top predators has been considered from a strictly ecological point of view. Our results suggest that predator loss may drive prey evolution, which itself may have important ecological effects – in this case, amplifying the strength of trophic cascades. If our results reflect a common response of prey populations to the loss of top predators, then a full assessment of the ecological impacts of top predator removal must carefully consider the effects of prey evolution.

This study recently appeared in PLoS ONE: http://dx.plos.org/10.1371/journal.pone.0018879.

Suskewiet! Finchy parallelisms between intended selection by domestication and unintended alterations of the strength of natural selection.

The dutch word in this title probably needs translation. “Suskewiet“ is an onomatopoeia (=a sound-imitating word) imitating the last part of the song of the male chaffinch (Fringilla coelebs), a small passerine bird in the finch family Fringillidae. Sorry, this is not entirely correct. “Suskewiet” only refers to the last part of the song as it is performed in Flanders, Belgium. Indeed, the chaffinch occurs all over Europe, parts of Asia, and North Africa, and there is considerable geographical variation in song. So “suskewiet” belongs to the repertoire of the birds’ Flemish dialect.

The male of the chaffinch.

Why would one need a specific word to talk about the last part of the song of Flemish chaffinches? This is a long story – but the picture below tells it all:

A “vinkenzetting”, or finch championship, in Flanders (Belgium).

Silence please! Here you see an important folkloristic competition going on, called “vinkenzetting” (finch championship) . Each of the boxes contains a male finch, and the championship is all about which finch makes this precise “suskewiet” sound most often. The men and women in the picture are holding a pole and a piece of chalk, to keep track of the number of suskewiet’s. The birds can hear each other, and their territorial nature makes them sing “suskewiet” as much as possible. The best finches sing more than 600 times per hour! The owner of the best finch wins a symbolic price, and the finch becomes more valuable. The tradition goes back to the Middle Ages (first mentioning of a finch game in 1595), and, despite or thanks to its weirdness, still persists. People practicising the game are called “vinkeniers” (“finchers”). They used to have a pretty bad reputation for illegal practises such as blinding the birds (up to the 1900’s it was thought that blind birds sing more) and depleting the wild finch population with rude catching techniques (up to the 1970’s). Luckily, the finchers are now organised in an official federation (http://www.avibo.be/home.php), controlling the games with strict regulations, using domesticated birds only.

Just like farmers who know how to breed cattle, finchers have an impressive knowledge about how to breed finches (including the inheritance of interesting traits such as song and colour). I’m not sure how much of the variation in song is heritable, but breeders do select fathers based on song quality. However, it is possible to teach a male bird the right song exposing them to “teacher birds” or audiorecords. Interestingly, a bird not singing the Flemish “suskewiet” is called a “francophone”, making a supposedly less elegant “suskeweiih” noise. Talking about Belgium (and Quebec), this sounds a bit politically incorrect. However, birds have a right wing and a left wing, so they are probably politically neutral.

Returning from the Galapagos field expedition 2011, it came to my mind that male Darwin’s finches use neither “suskewiet” nor “suskeweiih” in their songs. This is no surprise, as Darwin’s finches and the chaffinch are not related. Their songs are actually very different, even though they have similar beaks.

Darwin probably would not be surprised to read that people are weird enough to domesticate finches (such as chaffinch and zebra finch), applying his theory of selection by domestication. He also wouldn’t be surprised to read that Darwin’s finches have become iconic for his theory on natural selection. But he might be surprised to read that humans can alter the strength of natural selection in Darwin’s finches. During previous expeditions, the Hendry lab has been investigating this possibility in the seed-eating medium ground finch (Geospiza fortis) from Santa Cruz island, by comparing the morphology of a population living at Academy Bay, a human-impacted site, with a population living at El Garrapatero, a natural site. G. fortis birds from Academy Bay had smaller beak size than birds from El Garrapatero. This probably implies that the presence of humans has caused a shift in the finches’ resource distribution by the introduction of human food (such as bread, rice and potato chips) or new plant species into the environment, creating a selective advantage for finches with smaller beaks.

Chaffinches in captivity and Darwin’s finches in the wild thus seem to have in common that humans can influence which finches are going to contribute to the next generation. In the first case we talk about intended selection by domestication, in the second case about unintended alteration of the strength of natural selection. Is it exaggerated to describe the latter as “unintended domestication”?

So far, indications that humans might influence the evolution of Darwin’s finches have only been observed in a single species. However, as scientists we don’t want to rely on a single significant P-value - just as a fincher is not satisfied with a single “suskewiet”. During the 2010 and 2011 expeditions, we measured five additional species at the human-impacted and the natural site study site: the small ground finch (Geospiza fuliginosa), the large ground finch (Geospiza magnirostris), the cactus finch (Geospiza scandens), the vegetarian finch (Platyspiza crassirostris), and the small treefinch (Camarhynchus parvulus). So, let’s have a look at the potential human impact on the beak morphology of these species. P-values are not very suitable here - as finchers wouldn’t understand them. Luckily , “suskewiet” sounds like a significant result (P < 0.05), whereas “suskeweiih” sounds perfect for an non-significant result (P > 0.05) – and finchers do understand it. This opens opportunities for a new “suskewiet vs. suskeweiih”-based school in statistics. Here I show how it works, testing for differences in beak length, beak depth and beak width, respectively, in of each of the investigated species.

The small ground finch – “Suskeweiih, suskeweiih, suskeweiih!”.

Oops, bad start. We hear three times “suskeweiih”, as none of the three beak dimensions differs significantly between the population at the human-impacted site and the natural site. Actually, small ground finches seemed to have larger beaks at El Garrapatero in 2010, but this difference disappeared in 2011. But let’s go on, maybe we are more lucky with the next bird.

The vegetarian finch – “Suskeweiih, suskewiet, suskewiet!”.

That’s a nicer song! Beak width and beak depth differ significantly between the sites, beak length does not. Beaks were larger at El Garrapatero, and this was consistent across years.

The large ground finch – “Suskeweiih, suskeweiih, suskeweiih!”.

Awtsch, another bad song – this must be a francophone finch. No differences between the sites at all. I will have to sell this bird to another fincher.

The cactus finch – “Suskewiet, suskeweiih, suskeweiih!”.

This song is a bit silent, but still elegant. There is a marginally significant difference for beak length, which was larger at El Garrapatero in both years. The other beak dimensions don’t differ.

The small treefinch – “Suskeweiih, suskewiet, suskewiet!”.

Ha! Exactly the same song as the vegetarian finch. Beak width and beak depth differ significantly between the sites, beak length does not. Beaks were larger at El Garrapatero, and this was consistent across years.

So far so good. Now lets listen to the birds when they sing all together. It sounds harmonious because all suskewiet’s are generated by significantly larger beaks at El Garrapatero than at Academy Bay. So, the human-altered environment of Academy Bay seems to affect the bird species in the same way as observed previously for the medium ground finch. This makes sense, because the diets of these bird species partially overlap. A human-induced shift towards smaller and softer food items might thus select for smaller beaks in multiple bird species.

After the game finchers don’t go home early. They go to the local bar to talk about the championship and their finches, and to share their experiences or secrets. Science might benefit from this, so I might go there and ask them for advice. I'll probably start drinking to forget my disappointment in the ground finches, because both the large and the small one did not sing very well. In contrast, my cactus finch, small tree finch and vegetarian finch did a great job. This is changing my perspective. Small ground finches in particular are really keen on human food. Perhaps it does not affect the direction of selection in this species, because its natural diet might already be rather similar to the human food they can find. In contrast, I expected that cactus finches (feeding on cactus flowers), vegetarian finches (feeding on fruits) and small tree finches (mostly feeding on insects) would not bother about the introduction of novel food items by humans, and that their beak morphology would be conserved. However, my state-of-the-art “suskewiet vs. suskeweiih”-based statistical analyses suggested the opposite.

It is about time to bring back my finches to the aviary. It is worrying how rice, bread and potato chips might alter the live of a finch in the wild. In this sense there is sadness in all of the above songs. Let’s see how this is going to affect finch championships in the future.

Joost

Eco-Evolutionary Effects on Population Recovery Following Catastrophe

As a new PhD student I had read many of the classic studies confirming the role of natural selection in generating adaptive divergence between guppies that coexist with fish predators (high-predation populations) and those that did no (low-predation populations), and I was very excited to experience this system firsthand as I started my dissertation research. However, when I arrived in Trinidad for my first full field season, I was horrified to discover that my study organism was nowhere to be found. Intense and prolonged flooding resulted in near complete decimation of the guppy populations inhabiting the high-predation (downstream) sections of many of the famous guppy rivers in Trinidad. The "millions fish" (a local Trinidadian name for the guppy), seemed like quite a misnomer after it took us the better part of a week to catch a couple dozen guppies from our focal study stream (the Marianne River). This was problematic for me because I had intended to study how geneflow from low-predation populations constrained adaptation of high-predation guppies (of which there now were almost none). After the initial panic subsided, this situation inspired my advisor (Michael Kinnison) and me to think about eco-evolutionary dynamics. How would contemporary evolution (in the form of selection against migrants) influence recovery of the high-predation populations? Would reproduction by the few remaining high-predation guppies (which were locally adapted) drive recovery, or, would the low-predation immigrant guppies make a significant demographic contribution despite lacking many of the anti-predator characteristics of high-predation guppies? In the March 2011 special issue of Evolutionary Applications ("In the light of evolution: interdisciplinary challenges in food, health, and the environment"), myself and several co-authors describe research where we attempt to answer some of these questions.

Intense flooding decimated high-predation guppy populations (notice the scourning on the bank of the Marianne River) and negated my dissertation research proposal.

Metapopulation theory provided some basis for anticipating an important role for contemporary evolution in this circumstance. One important concept within metapopulation ecology is the population rescue effect, where immigration from nearby populations prevents the extinction of a local population subjected to a catastrophic disturbance or chronically harsh environmental conditions. Of course, the ability of migrants to contribute to population growth depends on their ability to survive and reproduce; if the phenotypes of migrants are poorly-suited to local conditions, then any population rescue will be mitigated by selection against migrants. Several studies have attempted to model these eco-evolutionary dynamics and have found that migration can variously facilitate or prevent extinction, depending on (among other things) the fitness and number of migrants. Few studies have actually quantified these eco-evolutionary dynamics in the wild, which is unfortunate because many conservation and restoration programs rely on supplemental stocking from captive populations or natural recolonization from nearby populations (in either case we might expect migrants to have lower fitness than residents).

To assess the eco-evolutionary consequences of selection against migrants we performed an experimental introduction of both high- and low-predation guppies (each individually marked) into a focal high-predation site (where local high-predation guppies had been completely wiped-out). Consistent with our expectations, we found that both male and female low-predation guppies had very poor survival compared to high-predation guppies. We surveyed this experimental population for approximately 3 months which allowed us to sample the offspring of the original experimental fish introduced into our site, and (using population genetic assignment tests) quantify the demographic contribution of each ecotype. We found a large difference in the demographic contribution of each ecotype to population recovery. Compared to a population model based on purely “ecological” expectations (assuming no fitness differences between ecotypes), the demographic cost of selection against migrants was very high (around 45% in two different years). We describe these eco-evolutionary dynamics as “cryptic” because they resulted from a fleeting environment perturbation, and caused no net phenotypic change in the local population. Nonetheless, the consequences of eco-evolutionary interactions in this system were profound for population recovery. Such “cryptic” dynamics suggest that eco-evolutionary interactions may be quite common in nature and generally relevant to conservation and restoration efforts.