Monday, April 28, 2014

In view of the Mallard: on ecological fitting and non-fitting

Collecting things (coins, stamps, music, guitars, cars) is the nature of humans (and Bowerbirds), and I am not immune to it. My single-malt Whisky collection is up around 50 different bottles, although it is different from most collections in that it suffers constant turnover. One particular type of collecting – I am sure there is an official name for it that I don’t know – occurs when traveling: one purchases the same item with only a minor change (usually the name of the place) everywhere one goes. How about that cupboard full of otherwise identical Starbuck’s mugs from London, New York, San Francisco, and a host of other cities? And you simply must get that new one I heard of – from Greenland! A collection of this sort tells the visitor to your house that I went to all these cool places and I want you to know it but I don’t have to tell you because you can see it in front of you. In essence, you are collecting and displaying places rather than things.

Stockholm – prime Mallard habitat, but then where isn’t?
I found a particularly puzzling version of this phenomenon in the back recesses of an out-of-the-way cupboard when we moved into our new house some years ago. It was in several big Mason jars and closer examination revealed hundreds of matchbooks, each with a different restaurant or hotel imprinted on it. These are the kinds of collections that detectives in Hollywood movies use to track down the whereabouts of some otherwise cryptic serial killer. I have to confess, however, that I haven’t spent much time reading the actual business names on the matchbooks, and their presence in the jars has steadily dwindled to a fraction of its former exuberance. (It is a lot easier to just go back to the jar than it is to remember where I put those damn matches I got out yesterday.)

I don’t suffer from this habit of collecting while traveling – except for pictures of wildlife. The trouble with wildlife pictures in the above context is that they aren’t of the same thing with some small indication that they come from a different place (like those Starbuck's mugs). They instead show huge turnover from place to place. Just a few days ago, however, I was in Stockholm walking around in the beautiful spring weather and trying to find wildlife to photograph when I saw a Mallard.

The Stockholm Mallard that started it all.
Everywhere I travel I see Mallards and I rarely take a picture as they are so boring and ubiquitous. In fact, I only take a picture of a Mallard when they are the only thing to take a picture of; and when taking the picture, I always think to myself: Why the hell am I taking a picture of this Mallard? I will never do anything with the photo anyway! But then it struck me: Mallards can be my match books, my Starbuck’s mugs, my t-shirts, my hats. I can take pictures of Mallards everywhere I go – well over half the world, anyway.

The current distribution of Mallards. They were introduced to Australia and New Zealand and presumably will eventually cover the globe.
In my dotage, I can display all my Mallard pictures in one of those picture frames designed for multiple small pictures – or maybe one of those electronic picture displays that sits on the table and cycles through photos. Right then and there, Mallards became a key goal of my future trips. Everywhere I go, I will be asking my surprised hosts: Can you please take me somewhere where I can see a Mallard? Now, no matter how urban, no matter how short the trip, I can have a good reason to bring my camera and take a walk looking for birds – a bird, that is.

The Stockholm Mallard again – or, wait, maybe it’s a different one.
By now you are probably thinking that the joke is on me, because Mallards look the same everywhere. What would be the point of taking a picture of them in each place – and surely nothing would come of displaying them? Or perhaps you are thinking that this is a type of place-collecting for which it is easy to cheat. You actually have to go to London to get a London Starbuck’s cup (or someone has to go for you) and a cup you buy in New York can’t be mistaken for one you bought in Stockholm. With Mallards, however, I could take a hundred photos of the same bird outside my house in Montreal, label each as coming from a different country and no one would know the difference. Or I could take the same Mallard (or maybe just a Mallard model) to every city and take a picture in front of ineffable landmarks (the Eiffel Tower, Times Square, the Sydney Opera House, and so on). It would be like that gnome that traveled the world in one my favorite movies, Amelie.

An Amsterdam Mallard fitting into a new frosty habitat.
Mulling over these thoughts in the bright sunshine, staring at a Mallard who was steadfastly ignoring my existence, brought me all the way back to 2001 when I was giving a job interview at the University of Pennsylvania. One of the first faculty members I met with after my talk was Dan Janzen. I didn’t know much of his work at the time but I did know he was famous, and so I resolved to pay attention – I was angling for a job after all. Remarkably he seemed not to have gotten the point of my talk as I imagined an astute naturalist would have done. My talk had been about rapid adaptive evolution (in only 14 generations) of trait differences between introduced salmon populations. How cool is that? Even Science thought it was cool enough to publish – something that hasn’t happened for me again in the subsequent 14 years. But all Dan wanted to talk about was how I should be more interested in why many organisms look the same in different places. Coyotes are pretty much the same from northern Alaska to Panama, Great Blue Herons from Alaska to Galapagos, Great White sharks from Newfoundland to Cape Town, and so on. Hmm, I said, hoping to seem intelligent.

A Montreal Mallard. At least I think that is where this was taken, as I didn’t think to label it – who would bother? It was only a Mallard.
Perhaps he could tell I was unconvinced, or perhaps he just wanted to increase his citations, because he then handed me a paper he had written. It was a short opinion piece (sort of a blog post, before blogs existed) about “ecological fitting,” in which he explained the phenomenon and gave its name. In essence, organisms find ways to retain their existing way of life in a new environment, which reduces selection on them and allows/requires them to stay much the same. (Gene flow is another reason why organisms might be very similar across large ranges, an idea pushed most recently by Doug Futuyma in his hypothesis of “ephemeral divergence.”)

Another Stockholm Mallard – this one looks a bit different for some reason.
I hadn’t thought too much about ecological fitting in the 13 years between then and now, but it all came back in a rush staring at the damn Mallard and thinking about the implications of my new world-wide photo-collecting quest. Surely Mallards were the best example of ecological fitting in existence – they look and act bloody well the same across their huge distribution. Why might this be so? Without bothering to read any literature that might exist on the topic (this is a blog, after all), I will speculate that ecological fitting will be most common for organisms that have key habitat needs that are similar everywhere (Mallards need shallow water – found worldwide) and diets that are independent of particular prey species (Mallards eat aquatic plants of many sorts – at least I imagine they do). The same is true of Great Blue Herons (they eat any type of small fish) and coyotes (they pretty much eat anything) and great white sharks and so on.

Some Mallards in California – or maybe Edmonton. I can't remember.
Then, for just a moment, I thought about it from the Mallard’s perspective looking back at me. What would a well-traveled Mallard with a camera (maybe a GoPro with unlimited batteries strapped to its head) experience in an effort to collect photographs of humans, which are also distributed worldwide? I am pretty sure he wouldn’t come up with the idea of ecological fitting (even if he weren’t a duck) because humans are hugely variable from place to place, most obviously in color and stature. In fact, this effect was staring me in the face: Swedes are HUGE. When I travel to the tropics of South America, I am nearly always the tallest person in a crowd – except for the occasional person from higher latitudes – but when in Sweden, I am average or a bit below. This non-constancy of humans (in comparison to Mallards anyway) was quite literally staring me in the face. Still mulling this over in my head as the duck swam off (to be replaced by another that looked pretty much the same), I realized that I had already explored this non-constancy in my own research. 

Some Kelowna (British Columbia) Mallards. (Yes, I realize it is a female, but you know what the male looks like.)
I used to live across a small canal from a biking/walking path. In the summers, I would sit outside in the warm sun and play with the kids or read a book or mow the lawn or whatever. In doing so, I would be in view of a constant stream of humans walking by on the path in front of me – and they seemed immensely variable. This apparent variation got me to wondering: are humans more variable than other organisms, as they seemed in that moment? To answer the question, I recruited a Master’s student , Ann McKellar. We (when I say “I” I mean “we” and when I say “we” I mean “she”) collated data from hundreds of human populations and hundreds of animal species for a trait that would be comparable among all of them – height/length. Analysis of these data showed that, contrary to my naive expectation from the lawn in my backyard, and more in line with the view of the Mallard, humans were about as variable among populations as were other animals (for example, they follow “Bergmann’s Rule” of being larger at higher latitudes – Swedes vs. Ecuadorians) but they were much less variable within populations than were other animals. We suggested in the paper that humans are the antithesis of “ecological fitting” (although we didn’t use that term) in that selection seems to have favored particular forms in particular places.

Some New Orleans Mallards. I realize the photo is crappy but I had to crop this out of the corner of a photo I took of a much cooler bird. No one ever intentionally takes pictures of Mallards when cooler birds are around.
Of course, everything is now changing. Humans from all over the world are migrating to all other places in the world (my neighbours are from Germany, Norway, Sweden, France, Italy, and even New Caledonia) and doing quite well in their new habitats – buffered by our technological solutions that make climate similar within houses from Ecuador to Alaska. Eventually, due to such migration, we might imagine that humans will be quite similar among locations but quite variable within them. This isn’t ecological fitting in the classic sense because humans won’t look the same everywhere, instead they will look different WITHIN everywhere. So we will need some new term (gotta love coining terms in blogs – "squib traits,” anyone? – where it has no real consequence for the literature) – perhaps “ecological ignorance,” although maybe that can have too many meanings. I am sure readers of this blog can come up with other, better, suggestions.

Some Laval (Quebec) Mallards in a snow storm. (They look like normal Mallards when the snow clears.)
In the meantime, I intend to continue my nascent photo collection of the World’s Mallards. So, if I happen to visit you in the years to come, please scope out a good Mallard sanctuary for me. I will bring my camera – and a Mallard model in case you can’t find me a real one.

More Mallards on the way.

Dan Janzen's paper: On Ecological Fitting

Doug Futuyma's paper on ephemeral divergence: Evolutionary Constraint and Ecological Consequences

Our paper on How Humans Differ from Other Animals in their Levels of Morphological Variation.


Mallards photographed since this post was first published:

New Orleans, LA, USA, Dec. 2014
Saskatoon, SK, Canada, May 2015

Napa, CA, USA, Dec. 2015
Sanssouci Park, Potsdam, Germany, June 2016.
Lago Maggiore, southern Switzerland, June 2016.


  1. Interesing post and funny to read. I have a few things to think about though. Remember that mallards are native just in the Palaearctic and being introduced in the Nearctic and Australia. So there was maybe not enough time to evolve morphological (sexual) character traits in mate choice. Within their native range Mallards are migrating. I know from a bird ringed at a park in a bigger german city (I guess it was Hamburg but anyway) that was shot in Russia. This (relatively recent spread of the range combined with high mobility) makes the Mallard different to the examples stated by Dan Janzen. By the way, you'll find nearly the same pattern in any other Duck species in its native range (but note the slight divergences occurring in sister species becoming isolated for much longer times such as Nearctic/Palearctic Teals, Shovelers or Wigeons).

    In humans (that were not that mobile as birds exept of the most recent centuries) geographically differences in morphological traits are more likely a result of a kind of allele surfing of adaptive genes during humans expansion out of africa (as you said: it's a blog and I'm not very well into the literature of human adaptations during expansion). This makes humans and mallards difficult to compare because of differences in the underlying biogeographical histories. Why not comparing humans with, say, Yellow Wagtails (Ödeen & Björklund 2003 MolEcol) or Nearctic Juncos (Milá et al. 2007 PRSB) those are really good examples of geographic distinctions in geographical space likely as a result of postglacial spread.
    Maybe evolution of sexual traits are evolving slower than your really nice example from cods which are rather selected by the environmental conditions and some sort of interspecific interactions leading to a rapid nice shift or something like that. Female Mallards mate choice on the visual traits in males might be in comparison more conservative and "old fashioned" (remember, among all other animal examples, ducks are very sexual dimorphic and sexual selection on morphology plays consequently just an minor (no) role).

    1. Sorry, delete cod and replace by salmon :)