Who the #$%* is Robert Whittaker?

As I was flipping through the September issue of Ecology, I came across something rather interesting. There were two articles that addressed the importance of using multiple approaches to answer research questions. Ironically, both articles were written to address criticism from a man named Robert Whittaker. This man has his strong opinions about using multiple approaches in science.  After reading both Whittaker’s criticism and the author’s responses, I really started to dislike this Whittaker character. Not only is he not a fan of multiple approaches, he discounts hundreds of studies several times throughout both papers, and the basis for his arguments are weak to say the least. Who the #$%* is this guy?

What if a random herd of cows eats my entire project?

I don't want to look like this next September.

I feel like a huge hypocrite right now. I have spent countless hours researching, reading and blogging about natural experiments and droning on and on about how important and valuable they are. Now, as it seems, my M.Sc. research project is going to be a massive manipulation study. As much as I and my supervisor don’t like manipulation studies it seems like it has to be done. It’s the obvious next step following my undergrad thesis.

This whole situation has brought me to thinking about why I don’t like manipulation studies and experimental set-ups to begin with. The truth is I don’t hate them. In fact, most of the popular and innovative science of both the past and today has come from these manipulations. So why am I so hesitant to design and implement a vegetation manipulation study? I think it’s mostly fear. I am afraid that things just won’t work out.

Watch out trees, it's a twister!

The other night I watched the movie Twister. I have always hated that movie—it scares the crap out of me. Today I came across a study in the September issue of the Journal of Plant Ecology about just that—tornadoes! So in the spirit of the now almost 15 year old film twister here is a great, natural study about how tornadoes affect re-sprouting and special heterogeneity in the Cross Timbers ecotone.

The transition zones between different ecosystems are known as ecotones. The most studied ecotones are ones that involve transitions between woody and non-woody vegetation. You would find these in alpine tree lines, coastal dunes and grasslands. Ecotones can be caused my both abiotic and biotic factors for example maintenance of positive carbon balance and competition, respectively. Myster and Malahy designed a study that was focused on the Cross Timbers ecotone in Oklahoma—the boundary between the eastern deciduous forest and the Great Plains grasslands.

Spare me some land or just go organic!

In my third year of Undergrad I took a course on the global struggle for food and food security and have since been really interested in organic vs. Conventional farming. We studied that topic alone for about 6 lectures and even had guest lectures from some local organic farmers. When I saw a study that compared organic farming and land sparing with respect to optimal yields and butterflies I couldn’t resist blogging about it. I mean, come on, who doesn’t love butterflies. And ... it’s a natural field study to boot!

As biology students I am sure we all know about the advantages and disadvantages to organic and conventional farming. Organic farming often yields fewer products but is generally better for the environment and uses no fertilizers or pesticides. Conventional farming uses large amounts of these pesticides but has yields that can realistically address the global struggle for food--something organic farming cannot do.

There actually is some value in reading what's on your coffee table

It seems surprising to me that as you glance over the current issues of the most popular science journals, very little is done about plants in general, let alone plant ecology. Of course, I look through the Journal of Plant Ecology and that’s all it is. But, very few of those experiments are natural experiments. There is such a heavy focus on manipulations and complex experimental designs the natural experiments seem to get lost in them.

For about 8 months, there have been three issues of Bioscience sitting on the coffee table in our lab. I was feeling very “blog-uninspired” today and thought –what the heck, I might as well flip through these and see if there is anything I could use. The first article I came across had to do with Biodiversity losses and ecosystem function in freshwaters. My first thought was- nope and I turned the page. But what I found right in the middle of this article was a beautiful chart that outlined my whole entire idea for starting a blog about natural experiments. Needless to say I read this paper, and have some interesting things to report!

Wtf! That is so NOT fitness!

For several weeks now I have been doing in depth literature searches on different topics. Today I began my literature search on plant body size and fitness, and I’m having some issues with how people define “fitness”. Let’s look at how some common sources define fitness. In fact, let’s do a simple google search for “define: fitness”- take a look below. The image is a bit small so google this yourself and follow along with my red marks.

Figure 1: Google search for "define:fitness"

It’s getting hot in here... let’s compensate!

Natural experiments are great because they tell us what is happening in real life. We aren’t manipulating anything to see what could, should or would have been there. This experiment done by Doak and Morris is a long-term natural experiment that without manipulations tells us what is there, what was there, and what might be there in the future. 

It seems that most climate change researchers today agree that as the Earth’s climate warms that species will shift their ranges to compensate for that warming. Typically they will move either towards the poles or to higher elevations. However, as Doak and Morris note in their paper, anywhere from one half to one quarter of species show no net range shift in response to climate change. So, why do some species move to cooler areas and why do some species stay? I doubt the species that stay are investing in A/C and fans to keep them cool...so why is this happening? 

For real guys, bigger isn't always better

In my previous post I alluded to a study that framed a potential answer to the question: Why are there so many small plants? Well, here is that study-its results are fascinating.

As I mentioned before, traditionally people assume that bigger is better in terms of plant competition. I also mentioned that the majority of plants are small. So, if the majority of plants are small, how come most plants aren’t big if that is considered to be so advantageous? 
 

It is known that bigger plants generally produce more viable offspring- and this makes sense, right? They usually have more flowers and thus more fruits and more seeds. They are also less sensitive to some of the physical constraints of the environment. So, in the “traditional plant competition theory boxing ring” round 1 goes to the big guys. Let’s think about this though. We have a few big guys with a lot of offspring. But we have way more small guys than big guys. So does the collective offspring of the small guys trump the big ones? Round 2 here we come.

Jesse Chambers conducted a natural field experiment to test this idea. She sampled natural populations of 21 herbaceous angiosperm plant species throughout the Kingston area. Each population was harvested at reproductive maturity by placing a 1x1m plot in the area of highest density-it was assumed this would be where crowding was the most intense.  Within the 1x1m plot, reproductive plants were harvested, bagged, dried and weighed. Plant size frequency distributions were created by dividing the range of individual plant sizes for each population sample into 10 equal deciles of plant size. Relative reproductive output per size decile was calculated as the relative total mass per decile relative to the grand mass total for the entire population. Estimated reproductive output was generated under the assumption that total seed production is proportional to plant mass. 

Figure 1: Size and fecundity relationships for Cardamine parviflora

Here is what Jesse found- it’s pretty cool, but expected. All species had size distributions that were strongly right-skewed. The number of seeds per plant was counted for the entire population of the species Cardamine parviflora and it was found that the mean seed mass did not differ between the 10 largest and smallest plants and fecundity was directly proportional to plant size (See Figure 1). This confirmed the estimate of relative reproductive output. 

Here’s the kicker: For each of the 21 herbaceous study species, the vast majority of the offspring production within the population was contributed by the three, four, or five smallest deciles of plant size. And in 7 of those species the majority was from the 2 smallest deciles of plant size distribution. 

Wait so the smallest plants are collectively producing the most offspring in crowded vegetation? Yeah! They are!

So what does this all mean then? Well, as it says in Chambers and Aarssen “A renowned chemical evolutionist, Leslie Orgel is credited with saying, “Evolution is cleverer than you are””. It seems, well, it seemed intuitive that larger plants would have the ability to produce large and highly fecund offspring, a huge component of plant fitness and that this made bigger better. Chamber’s study is interesting in that is opens the eyes of plant ecologists to a new potentially important component of plant fitness- that being the ability to produce offspring that will survive AND reproduce before death despite having to live as small, suppressed weaklings. This is evidence for the concept of plants having reproductive economy. Reproductive economy is a product of natural selection in plants as a result of the inability of most plants to escape being small as a result of crowding. 

So, bigger isn’t necessarily better. Natural selection does favour large plant size, just not most of the time. Most of the time, plant communities and populations are crowded where most plants are relatively the same, suppressed size. 

I think it’s a knock-out. Round 2 goes to the small plants!





Source: Chamber, J and Aarssen, L.W. 2008. Offspring for the next generation: most are produced by small plants within herbaceous populations. Evolutionary Ecology. 23:737-751.

Consider this.

Consider this:

 According to traditional plant competition theory, bigger is better. Plants with a large body size are better at capturing resources and space from their neighbours and they have a clear advantage in the race towards the canopy. The bigger plant would be a better competitor and would likely have a higher fitness.

The above ideas have been part of the underlying focus of much of the research done in the Aarssen lab to date. But what makes that so interesting? Why do we care? 

Consider this:

Plant size distribution is right-skewed at virtually all scales. This means that the majority of plants have a relatively small plant body size. 

Wait...so it’s generally accepted in the literature that bigger is better. But if bigger really was better...why then are there so many small plants? 

Consider this yourself. Post some comments with potential explanations for this paradox. 

My next post will discuss a beautiful, natural experiment done in the Aarssen lab, which provides a mind-blowing potential explanation for this paradox.

Precision, Generality and Realism

It is nearing the end of the second week of classes and I am in the process of designing a project for my M.Sc. thesis. A couple of days ago I met with my supervisor to discuss some potential ideas for my project. It is not uncommon for him to rant about all sorts of different ideas; however, this time something he said really sparked a fire in me. He pointed out that my B.Sc.H thesis was a natural experiment that involved no set-up or manipulations of any kind and that he really appreciates the beauty of these “realist” experiments- an experiment where you simply go out and record or collect exactly what you see. This inspired me to do a literature review of this idea of natural experiments and I came across a very interesting paper in which Richard Levins addresses different types of biological studies.

In 1966, Levins wrote a paper titled Strategy of Model Building in Population Biology published in American Scientist. He explained that it is ideal to work with mathematical models in biology that maximize three things: 1) Generality, 2) Realism and 3) Precision, but that it is never possible to maximize these three things simultaneously.

Levins suggests that there is a trade-off between these three ideals and that three strategies have evolved to deal with this problem. For example, one could sacrifice generality to realism and precision. The focus of an experiment could be on the behaviour of an organism within very small parameters that would yield real and precise results but would tell us very little about the organism’s behaviour in general. Scientists could also sacrifice realism to generality and precision in which general equations and models can be developed that yield precise results but are extremely unrealistic. Finally one can sacrifice precision to realism and generality which rely on flexible models that assume wide variance in different functions.

Different scientists prefer different methods and each way has its merit. In my blog, I will discuss current studies in ecology that sacrifice generality or precision for realism and why I believe this approach is the most valuable.

Source: Levins, Richard. 1966. The Strategy of Model Building in Population Biology. American Scientist 54(4): 421-431.