Friday, February 11, 2011

Over-reviewed?

EP: Please submit original research articles for your presentations, not review papers.

Student X: What is a review paper?

EP: It is a summary of prior studies.

Student X: Why should we not pick them?

EP: Because they are summaries. The data are in the original studies – that is what I want you to focus on.

Student X: Submits review paper.

I have now had this conversation, and this result, more than once. So, why are my students picking reviews? And what does this have to do with eco-evolutionary dynamics when my class is on marine global change?

When considering these questions, I had a thought – maybe my students are picking reviews because there are so many out there. Perhaps a student choosing a paper at random has a relatively high likelihood of picking a review.

This reminded me of a question posed at the recent QCBS working group – is eco-evolutionary dynamics “over-reviewed?” This question stemmed from a recent flurry of reviews on the topic and the brief proposal that our working group supply yet another (we opted against). So I thought… if selecting at random, is an undergraduate student taking a course on eco-evolutionary dynamics more or less likely to select a review paper compared to a student taking a course on marine global change?

I did a bit of searching on Web of Science, and it turns out that reviews make up a larger proportion of papers on the topic of eco-evolutionary dynamics than on the topic of marine global change. For example, searches on “eco-evolutionary dynamics,” “niche construction,” “community genetics,” and “contemporary evolution” all independently yielded about 25% review papers (if papers categorized as “editorial material” are combined with papers categorized as “reviews”). Searches for common topics in marine global change, such as “coral bleaching,” “ocean acidification,” and “arctic warming” all independently yielded around 10% reviews.

So, it is unlikely my students are selecting at random. They are actively picking reviews – perhaps because reviews often present a more straightforward message than original research articles. And if the topic of my class was eco-evolutionary dynamics, they might be picking even more reviews. Of course, my quick-and-dirty analysis is admittedly imperfect. Many early research papers we would now consider to be eco-evolutionary dynamics, do not use one of the key words I searched. Nonetheless, 25% is a surprisingly high proportion.

So, is eco-evolutionary dynamics over-reviewed? Perhaps I will delve more deeply into that question next time. I have to get cracking on a paper on “the eco-evolutionary dynamics of marine global change.” It promises to be one heck of a review!

Eco-evolutionary dynamics in salmon


Empirical support for eco-evolutionary dynamics has emerged from several fish systems and a recent paper published in Heredity presents the case for diverse and strong effects in Pacific salmon (Carlson et al. 2011, Heredity 106(3): xxx-xxx). Several aspects of salmon biology make them amenable to the study of eco-evolutionary dynamics: they are philopatric (return to their natal sites to breed), anadromous (migrate between freshwater breeding and marine feeding grounds), and semelparous (die at the end of their first breeding season). Consequently, discrete populations can be subject to local selection pressures during their breeding season, presumably driving divergence in traits that can influence ecological processes. And such effects seem likely given their large adult body size and dense breeding populations that can change many features of the stream environment.

Building on earlier research that revealed the importance of water level and bears as sources of natural selection acting on breeding salmon, Carlson and colleagues (2011) explored the consequences of phenotypic change due to selection within a generation on salmon population dynamics, community interactions, and ecosystem processes. Despite a rash of recent studies documenting eco-evolutionary dynamics, little attention has been paid to the importance of this aspect of selection on ecological dynamics. Carlson and colleagues (2011) show how selection on body size simplifies age structure and strengthens cohort effects, which then alters population dynamics. They suggest two possibilities for how selection on salmon body size might then influence community interactions, namely through possible effects on bear energy stores (smaller salmon are less energetically rewarding, which might require increased foraging effort by bears) and aquatic insect community dynamics (smaller salmon dig shallower nests, which might differentially influence benthic invertebrates). Finally, the authors calculate the relative importance of selection (phenotypic shifts due size-dependent mortality) versus ecology (size-independent mortality) in determining the flux of salmon biomass across habitats. They report that selection can alter fluxes between habitats by up to 11% due to interannual variation in water level and up to 9% due to interannual variation in selection due to bears. The resulting combined effects of selection within a generation may have large cumulative effects on ecosystem processes. The authors speculate on such effects by comparing body size among nearby populations of salmon.

The authors thus conclude that phenotypic change within a generation due to selection influences ecological dynamics, and so should be considered within a complete eco-evolutionary framework. They also show that salmon are likely to be a good place to study eco-evolutionary dynamics.

Stephanie Carlson (Assistant Professor in the Department of Environmental Science, Policy, and Management, University of California, Berkeley)

Carlson, SM, Quinn, TP, and Hendry, AP. (2011). Eco-evolutionary dynamics in Pacific salmon. Heredity 106(3): xxx-xxx.

(http://www.nature.com/hdy/journal/vaop/ncurrent/pdf/hdy2010163a.pdf)

Saturday, February 5, 2011

What did I learn today? Lessons from Leuven.

Andrew Hendry aghast at the apparent co-evolution of Belgian beers and glasses.

Every night at dinner, my family plays a game of “what did you learn that was new today.” Each of us has to come up with some new bit of knowledge, usually science-related, that emerged during the day. Often Aspen (7 years old) tells us about some new animal from a BBC video that we watched the night before. Usually Cedar (4 years old) tells us about how chameleons turn red when they are mad. She tells us this nearly every night and so it isn’t exactly new, but it is cool enough that we don’t mind. And then it comes to Heather or I. Sometimes we struggle to remember something new that we learned, which either means we knew a lot already or we didn’t pay much attention that day. This struggle has made me increasingly take mental notes of things that I learned on any given day to then relate to the family that night.

These past few days the task would have been easy. I have been attending a symposium on Eco-evolutionary dynamics, held at K.U. Leuven, Belgium. A host of talks from Belgians plus some visitors, as well as discussions in various restaurants and bars, has yielded a variety of cool new findings – new to me at least. For instance, I learned that only a few months of evolution in warm temperatures by previously cold-adapted Daphnia can make them perform as well – or better – in warm temperatures than Daphnia that had evolved in warm temperatures for centuries. I learned that the population size of southern elephant seals was probably upwards of one million individuals only a century ago. I learned that unrelated armoured catfish species, which have poison glands that deter consumption by predators, converge on similar color patterns in the same locations, presumably because this provides a more effective warning to predators (Mullerian mimicry). I learned that cuckoos, which lay their eggs in the nests of other birds, showed increasing convergence of egg shell color toward that of their host species (because the host would be less likely to reject the eggs) over the 20 years that a monk sampled nests in the early 20th century. I learned that wolf spiders in Galapagos have independently evolved similar species in similar habitats on different islands. And so on and so on. Too bad I can’t spread these observations out and use them over a few weeks of family dinners.
But it wasn’t only science. I also learned that Belgian bars keep a specific glass for each of the dozens of Belgian beers they serve. It seems that each brewery has promoted – and provided – a signature glass that (presumably) best suits that beer. I am sceptical. Are they really trying to convince us that the co-evolution of beer and glass is so perfect that every brewery has discovered the best glass shape for their specific beer – and that this shape is different for each beer? Or would Westmalle Dubbel taste just as good – or better – in a Rochefort glass as in a Westmalle Dubbel glass? I doubt that the matching of beer to glass is really that critical. Maybe it is instead like sexual selection: the match tastes no better than a non-match but the chooser (us) thinks a match is somehow sexier than a non-match. So, with that in mind, my goal tonight is to buy four different beers, pour each into the four glasses corresponding to those beers, and then subject myself, Joost Raeymaekers, and Katja Rasanen to a blind 16-glass taste test. Here’s hoping we make it through the night.