Macroecology: Does it ignore or can it encourage further ecological syntheses based on spatially local experimental manipulations?

Macroecology: Does it ignore or can it encourage further ecological syntheses based on spatially local experimental manipulations?

"Macroecology... is not a fruitful path for thoe of us seeking to understand how ecosystems are sutrcutred and function" - Paine (2010). Image from

Macroecology… is not a fruitful path for those of us seeking to understand how ecosystems are structured and function” – Paine (2010). Image from

Will Pearse

Will Pearse

This paper made  a real impression on me; I also think it wins the ‘most polite knock-down of a field’ award, in that the first two paragraphs make it clear he doesn’t like the field but somehow he does it so politely I want to read on.

Paine is right; marine ecosystems are different, and since they’re the largest part of our planet we shouldn’t be so terrestrially-focused. I feel that much of what a terrestrial ecologist means by ‘history’ is really ‘dispersal limitation’; at evolutionary timescales vicariance and/or distance leads to speciation where we wouldn’t otherwise expect it, and in ecology it leads to species with identical environmental tolerances not co-existing. Thus when Paine identifies marine ecosystems as having huge dispersal distances (particularly in the larval stages), he’s essentially pointing us towards how terrestrial and marine ecologists are always going to view history differently. If everything truly can be everywhere, then historical contingency is a very different thing in water.

Paine is also right when he says that a species list is no end-goal for a field. Yet, for all the importance of local-scale contingency (Paine did invent the keystone species concept!), it’s worth remembering that species distribution models (SDMs) do actually work (some/most of the time). That’s not to say that they always work – trophic cascades and other biotic interactions are always mentioned but seldom modelled in SDMs – but if everything can be everywhere in water, can that change how they should be modelled? Can trophic cascades be captured by understanding the environmental conditions that enable those keystone species to survive there?

I think Paine is missing an important trick when he discusses comparative experiments. He wants comparative experiments on taxonomically similar species to identify underlying rules, and macroecology is the search for those same principles that determine a system’s rules of engagement. We study the species pool because, particularly on land, that determines what smaller-scale communities look like; maybe fundamental differences in dispersal mean the kind of macroecology Paine discusses is more appropriate for terrestrial systems. I’m always harping on about the importance of changing the phylogenetic, spatial, and temporal scales at which we examine an assemblage to help us better understand ecology. Perhaps terrestrial ecology has shifted too far in favour of laptop-jockeys like me who re-analyse datasets, and maybe we do need more local-scale experiments where we can test ecological mechanisms. Yet if broad brush-strokes without detail will never help us understand mechanism, detailed work without a context will never help us predict.

Lynsey McInnes

Lynsey McInnes

This paper is great. I think my fellow commuters were perplexed by what I was reading that was making me smile so much. As a macroecologist, I’d never heard of this man Paine until this paper came out in Am Nat a couple of years ago. But Paine is no macroecologist, so perhaps that’s OK. In fact, he is a vocal marine microecologist (I think) and is attempting in this address to argue the dual points that ‘micro’ ecology has a lot of insights to give that are impossible from macroecological techniques (fair enough, really) and then a slightly weirder, this might be my fault because I know more about terrestrial than marine systems, but not really that much about either, that macroecology is better suited to terrestrial than marine systems?

Well, we picked a nothing if not provocative paper to relaunch PEGE with.

Paine’s address is packed with home truths about macroecological approaches, but regularly (at least to me) jumps off the deep end into ridiculous. Macroecology (‘the study of relationships between organisms and their environment at large spatial scales to characterise and explain statistical patterns of abundance, distribution and diversity’) is often berated for being overly concerned with documenting pattern without a thought to processing generating patterns, and I think this criticism does stand true. However, there is a. plenty of work that tries much harder to understand process and b. more fundamentally (and this is where my opinion differs from Paine’s) I think there are processes operating at these broad scales that are of interest to identify and understand (a factor that probably contributes to so many people attempting to document the patterns these processes produce).

I’d argue that an across scales approach is the most valuable. Are local scale happenings relevant to emergent broader scale patterns? Are they divergent? How do ecological responses at one trophic level affect others? How do responses on evolutionary timescales affect things? What governs turnover through time and across space? What allows invasion from one site into another? And so on. Sure, documenting yet another latitudinal diversity gradient, or an exception to it, doesn’t get us much further in any endeavour, but a comparative analysis of food web structure across continents does.

I am not sure I followed Paine’s terrestrial vs. marine arguments, but I think the crux of it might have been that ‘local’ or ‘micro’ in marine systems is already way broader than in terrestrial systems where people can more easily summarise whatever they wish in 100km grid cells (oh the horror) and go to town with their pattern documentation. I would argue that both systems have interesting and important ‘micro’ and ‘macro’ ecology and that perhaps the easier route to deeper understanding of ecology or ecological responses comes from an objective comparison of the two (like here and here).

Lastly, Paine laments the ‘niche craze era.’ What a great phrase. And so true. I, and many others, jumped on the – somewhat specialised – niche conservatism bandwagon and went a little crazy. We documented crude patterns using deficient taxonomies and didn’t get very far in working out what drives change in some dimensions’ of a species niche and not others. This was perhaps because we didn’t know what a niche was or how to quantify as we embarked on this endeavour or perhaps because we didn’t care. No doubt about it, understanding species’ roles in ecosystems is more vital than quantifying variation along some orthogonalised niche axis, but once robust methods are devised (and I don’t think they have been yet) to quantify ‘role’ (and I mean on a ‘micro’ or ‘macro’ scale), I imagine they will simply be some axis of the (again not properly defined yet) elusive niche. I see these advances as an exciting challenge for the pretty near future than a reason for contention.

I recommend this paper to all brands of ecologist. It helped me realise I did still find macroecology and the insights it seeks to identify interesting and important, while feeling chasistised that macroecologists can sometimes, in fact often, be lax in defining relevant and appropriate research goals.

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