Evidence for the existence of three primary strategies in plants and its relevance to ecological and evolutionary theory

JP Grime. The American Naturalist 111(982): 1169-1194. Evidence for the existence of three primary strategies in plants and its relevance to ecological and evolutionary theory

I find your lack of competitive ability disturbing. Grime's CSR triangle (main), with his estimates of where trees (top-left) and annual herbs (top-right) might lie within it.    Taken from figures 2 and 3 from Grime (1977).

I find your lack of competitive ability disturbing. Grime’s CSR triangle (main), with his estimates of where trees (top-left) and annual herbs (top-right) might lie within it. Taken from figures 2 and 3 from Grime (1977).

Will Pearse

Will Pearse

I’m a zoologist who somehow keeps looking at plants, and this paper is probably the best demonstration of how plant and animal ecologists really do seem to think differently (in my mind, at least). Grime has a section about animals and fungi at the end, but all of this is clearly written by a plant person – and is all the better for that.

There’s a growing feeling in plant trait ecology that plant traits can be grouped together along some economic spectrum (reflecting pay-back of nutritional investment), be that of leaves or wood. Recently, Peter Reich has argued that all of these can be considered as part of the same system, where plants are either fast-adapted or slow-adapted. I don’t want to point out connections between these ideas and Grime’s CSR strategies, but instead draw attention to how plant functional trait studies have somewhat lost their way. Grime makes it quite clear that position along each of his spectra depends on plant traits, but that there’s no one-to-one matching of trait onto CSR strategy. I feel as thought his general message has been lost among papers pointing out how different species have different adaptation to drought, and how SLA or xylem diameter has changed, as if those particular traits defined those species’ niche dimensions. Convergence means that there are many ways to skin a cat, and there are many ways to be ruderal – individual traits that we have decided to measure do not define species.

I fee Grime implies that there’s very little difference between being in a nutrient-poor or stressful environment based on the species around you or because the environment is inherently that way. He argues an area can be nutrient-poor because all of your neighbours have soaked up all the nutrients and won’t let go. If (as he argues) some species have evolved to maximise nutrient retention, not rate of absorption, this becomes doubly important. I’m constantly referring to abiotic and biotic drivers, and on second thought there’s really very little reason to distinguish between them if they have the same effect – shade is shade, no matter what the cause.

At times I felt like Grime was implying that much of plant traits come from the environment they’re exposed to – I’m not sure things are always as plastic as some would believe, but I certainly agree plants can change. Most importantly, we shouldn’t be teleological in assuming that observed shifts in species’ traits reflect the thing we’re interested in – what may seem like an adaptation to drought may just be a consequence of altered nutrient turnover rates, and without some kind of breeding experiment I don’t think we could ever disentangle the two.

Lynsey McInnes

Lynsey McInnes

I let Will pick the paper this week, forgetting that he was trying to teach himself about plants. He might be a zoologist learning about plants now and again, but I’m just a bad mathematician/pattern seeker masquerading as a biologist. I found this paper tough going, mostly because I haven’t really thought all that much about the ins and outs of actual individual plants making it in their stressful /disturbed/competitive environments. So, I learnt a lot while reading this and would certainly recommend the paper to budding ecologists interested in a framework for classifying their different plant species based on how they might do in different environments.

Once I got to the end of the paper, I realised it, in fact, did fit into my pattern seeking world view (Grime was trying to squeeze plants into a triangle with three distinct lifestyles at its vertices, after all). But only if you are willing to really work for your patterns. Counting species is easy, but disentangling how many of each kind of species is already one step harder. Especially when, of course, the three strategies form a triangle rather than three distinct boxes.

I am typing as I think here, but I just wonder how macroecology, and its resulting insights, would change if we stopped counting species and really tried to count function. Sure, there have been macroecological studies of functional diversity, genetic diversity, body size, but all still very much tied to species counts. I wonder if we will ever let go of the notion of a species as this magic unit. But perhaps it is a magic unit and function/type/etc. still ultimately harks back to species.

I really don’t know if broad-scale analyses need finer divisions than species counts, but, as Will states above, macro people obsess over the relative importance of biotic and abiotic drivers of diversity patterns and thinking in terms of Grime’s classification, or some other similarly nuanced one,might actually help us spend work out what the biotic drivers might be or rather how they might work.

Ok, this is a real ramble now. In short, I appreciated all that I learnt in this paper and it underlined that we macro people have to get more smart in what we measure if we really mean it when we say we want to know how diversity is ‘generated & maintained’ (& turns over).


About will.pearse
Ecology / evolutionary biologist

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