Who says macroecology doesn’t have any processes? Thoughts on #BESMacro

I attended the BES Macroecology meeting in Oxford last Thursday and Friday. It was a great meeting. Check out  a storify of the conference tweets for details. I suppose it says something about me, but everytime I get >24 hours of all macroecology, I get reflective on trends I see. As I noted last year, macroecology is in a self-aware and self-reflective adolesence. And this was evident again this year. A great deal of the conversation was on topics like “what is macroecology?”, “is macroecology working?”, “should we move past pattern to to process?”. and “how does macroecology relate to conservation and the public/policy dialogue?”. For those of you who hang around macroecology, these seem like perennial conversations. There was a great conversation with many enlightening thoughts shared on all of these topics.What follows are my own thoughts on the state of macroecology (as observed in the non-self-reflective science talks in the conference and building on the self-reflective thoughts others shared).

The first thought has been sneaking up on me for a while but really came home to me this conference: macroecology is going through serious mission creep. Maybe you have to have called yourself a macroecologist circa 1995-2000 to see this. Brown & Maurer’s seminal 1989 paper that was one of the launching points for macroecology set the agenda as “Our goal is to understand the assembly of continental biotas in terms of how the physical space and nutritional resources of large areas are divided among diverse species.” Brown’s 1995 book on macroecology pretty clearly identifies species abundance, body size, and range size, the distributions of those three variables across species, and the relationship between those three variables as macroecology. Rosenzweig’s 1995 book “Species Diversity across Space and Time” pretty clearly adds species richness including the species area relationship and the latitudinal diversity gradient (sorry Rob W. – you’re right but I am lazy*). Gaston & Blackburn’s 2001 book on macroecology keeps exactly the combined scope of Brown & Rosenzweig. Note that there is nothing really that is spatially explicit and aside from some of Rosenzweig’s book and the LDG in Gaston & Blackburn there is very little incorporation of the environment. I think you could count on the fingers of one hand the number of maps across all three books. But at this macroecology conference, I saw gobs of macroevolution, conservation-inspired analyses, climate change, thermal tolerance, and more generally species-environmental fit analyses, and more. It was great. I applaud all of it. we should and need to go to all these places. And I saw a lot of highly spatially explicit drawings (aka cool  maps!). But we most definitely are in the midst of mission creep on macroecology.  This is all a good thing. But its not surprising we’re a little confused what exactly is macroecology right now .Macroecology is not our advisers’ version anymore.

My second thought is everybody is making the connection between macroecology and conservation. Unlike the last thought which snuck up on me, it has seemed glaringly obvious that macroecology is a (the?) pivotal science for conservation efforts. It seems like a lot of other people are thinking the same thing. In my randomly assigned discussion group 2 of the 8 or so people self identified as conservation biologists who just came to a macroecology conference. The rest of us (including macroevolutionists and others) all are thinking about conservation biology. This is a very good thing.

The last thing I want to touch on is the relationship of macroecology to process. This has long been a sore point for macroecologists as we repeatedly apologetically acknowledge that we are better at patterns than process and publish calls to move on to process about once a year. I was pleased to see this embarrassment diminishing and several people made a robust defense of the importance of patterns even without process (a role as the lone looney I’ve been asked to fill out on speakers panels more than once in the past, so I was glad to see others jumping in). It seems we’re finally getting over this hang up. Ironically, one reason we may be getting over this hangup is I think we’re actually starting to get a serious handle on processes in macroecology. They’re not necessarily what we all were trained to think of as processes (e.g. equilibrium focused differential equations of population processes). Mark Vellend has upset the apple cart in community ecology with his 2010 paper and book forthcoming this month by pointing out that community ecology really only has four processes: drfit, selection, dispersal and speciation (which closely parallel the big 4 of evolution). It is at this level, that I think macroecology has really found its legs with identifying a core set of processes, not surprisingly overlapping with those of community eology.

To wit, I would suggest that the following list of processes is comprehensive for macroecology:

  1. Dispersal (colonization and spatial spread)
  2. Trait evolution (possibly on a phylogeny)
  3. Environmental fit of a species/traits (this is sometimes phenomenological and sometimes goes down to detailed physiology)
  4. Speciation (modelled mostly as a rate – not at a detailed level of speciation processes)
  5. Stochasticity (amenable to sampling and central-limit type analyses)
  6. Local & global extinction

Energy capture and allocation might go in there somewhere as well. Some (actually all) of these processes could be unpacked into the core processes of evolution or population or community ecology, but that would be an unfortunate mistake (just as Mark didn’t unpack speciation into its evolution level processes like reproductive isolation and sexual selection). These processes are right-sized for the macro scale and are the level at which macroecologists think about things. This is why we are finally getting traction on processes – we’re picking our own. I heard references to these proceses over and over during the 1.5 days of science talks at BES Macroecology. And I saw many instances of people pulling several of these processes into simulation models and showing how they explain and fit empirical data. Processes have arrived to macroecology!

Although I followed the twitter feed on the conference, I am curious what others who are attended are thinking after a few days of distance and reflection. What are your big picture thoughts that don’t fit in 140 characters? Do you feel the same way about processes that I do?

*Rob Whittaker made an elegant rant about how we’ll never make progress on the global variation of richness if we continue ot insist on only looking at it as a pattern vs. latitude.

24 thoughts on “Who says macroecology doesn’t have any processes? Thoughts on #BESMacro

  1. Some really interesting thoughts here Brian! They got me thinking too – especially your list of macroecological processes. Sorry about the long-winded stream of consciousness that follows.

    Imagine if you could remotely scan the entirety of life on Earth.

    You would log a set of individual organisms (animals, plants, other; some easier to delineate than others). They all need resources to survive and reproduce. Energy, nutrients, water. They all live somewhere. They all have traits. They all belong to a species (some easier to delineate than others).

    This is a snapshot. You can do this every second of the last 4 billion years and the picture will never be the same twice, because individuals are being born, dying, moving. This leads in turn to species being born and dying, colonising or de-colonising.

    This is all against a background of an environment that determines which traits are needed – ultimately, who survives and reproduces, and who doesn’t. The key elements of the environment may be abiotic or biotic. It is also constantly changing, which may or may not drive change in traits. Different processes act over different scales and have different consequences for different populations.

    You can quantify this biodiversity in a number of ways. Abundance, range size, biomass, number of species, turnover. You can graph this, and map it. We can plot the changes in species present and their traits in part using a phylogeny. How you do it depends on whether you are interested in variation in space, or time, or across species, or across populations, or some combination, or something else altogether. The scale you do it at depends on which processes you think matter most – although those processes may have consequences beyond your scale of interest. It also depends on what you can do, which changes all the time too (maps and phylogenies were much harder to do 20 years ago). We cannot yet scan the Earth.

    But the fundamental processes are the same across evolution, ecology, macroecology. Birth, death, movements in between. We slice up how we study the world depending on exactly what our questions of interest are. Macroecologists are interested in how the fundamental processes translate into the broad scale (space and/or time) distributions of organisms. Increasingly we can ask questions at those scales, so we do. They are relevant scales because many of the processes that drive the fundamental processes – and perhaps especially variation the abiotic environment – operate at them.

    In summary, I guess I could just have written that I agree with your point that “these processes could be unpacked into the core processes of evolution or population…ecology”. The above thought experiment leads me to your list (though ordered differently). It also leads me to one view of what it is that makes process difficult for macroecologists: ultimately those core processes come down to what happens to individual organisms. But that really shouldn’t (and doesn’t) matter so much to us because we’re not trying to study properties at those scales. We’re trying to produce gas laws while judging ourselves on our ability to predict the motion of molecules. We shouldn’t be beating ourselves up over what are really other fields’ metrics of success. We should be happy to be doing what we are, because it’s really interesting, and useful!

    • Hi Tim – thanks for sharing these thoughts. I agree with pretty much everything. I especially liked your last few summary sentences.

      You put your finger on the core issue – how do we link macroecology to individual birth death events. It is in many ways an impossible task. And yet out of the strong MacArthur & Wilson tradition for 50 years that was the only valid approach to ecology. As a result, for a long time I was comfortable with saying we don’t need processes because I thought the population definition of processes was untenable at macroecological scales.

      I still am comfortable with pattern without process process. But I think I am also increasingly comfortable with more summary processes (e.g. colonization rate) without needing to unpack it to more individual/population processes (dispersal kernel). Or species fit to environment instead of. birth rate as a function of temperature. These processes are in some level overlapping with the MacArthur & Wilson population processes as you very poetically highlight. But in an important way they are perceived and measured and used at a different level/scale. And I think that is critical – we cannot and should not feel the need to drop down from these more aggregate/summary processes to the classic population-level approaches and machinery even if they are overlapping in nature. In short, as you say, we can and should our own metrics of success (i.e. what processes count as valid explanations).

  2. Hi Brian; I am surprised you did not mention the METABOLIC THEORY OF ECOLOGY as a big mechanistic part of macroecology. What role did it play in the conference ?
    ric charnov

    • Hi Ric – fair enough. I certainly see it in my mind as part of macroecology. And it probably isn’t really addressed by my list of processes (although I did have a note about needing to fit energy in somewhere). To be honest, it did not seem to me to feature largely in the #BESMacro conference (although it was buried as a way of parameterizing some of the simulation models).

  3. Sounds great, I wish I could have been there (Oxford’s only an hour down the road) but my diary was just too full at the end of last week😦 Are you still in the UK or have you gone home now?

    A couple of thoughts:

    1. If macroecology is currently suffering or enjoying (depending on your point of view) Mission creep, is it creeping into areas normally associated with biogeography? It sort of sounds it from your description; in which case are we in danger of re-running debates about when is it macroecology versus biogeography, which will do no one any favours.

    2. Rob W.’s rant sounds great and I agree – there’s a hell of a lot of diversity outside of the tropics!

    3. Re: “several people made a robust defense of the importance of patterns even without process” – absolutely – I’ve long maintained that we know much less about the patterns than we
    believe we do, especially as they relate to the diversity and biogeography (or is it macroecology?!) of species interactions.

  4. It’s been fun hearing about the science emerging from the BES Macroecology meeting.

    I have to admit that my ‘old school’ view of macroecology is different from the one you articulate. Maybe I imprinted more on a Jim Brown late 90s-early 2000s view of macroecology (his Santa Fe Institute years), which focused not so much on spatial patterns but on understanding the statistical patterns that emerge from lots of particles – maybe those particles are individuals of a species or different species. From that point of view, macroecology is not so much a specific set of questions, but an approach or tool for asking questions – in which case I view the “mission creep” as up figuring out more and more questions that can be addressed through this lens.

    And I would definitely put energy capture and allocation on the list of processes, but then I am a Jim Brown progeny, so that is a predictable response🙂

    • Hi Morgan; without energy capture and allocation, and the avoidance of death ( for a while, anyway), its not ecology, not really about living things. Brian Maurer, when we were both in Utah[ early 90s?], sent me a letter with enclosures pointing out that the consumption of energy showed a big ~ 0.75 allometry for various taxa; and that optimal foraging was not particularly relevant here! You can imagine how receptive I was to this, but the mere fact that 25+ years later I recall the event testifies to his + influence.

    • Hi Morgan – I agree with what your saying about the old school version not being very spatial (the latitudinal diversity gradient being the one exception for some but I agree not for Jim). I think I was probably just unclear in my writing.

      • Hi Brian. Thanks for the clarification! To be clear, I think a lot of people really do believe that macroecology is the study of really large spatial scales (I run into the comment a lot). I think this confusion about macroecology being only spatial emerged because a lot of the early work was spatial. But that was a data availability/data management constraint on what questions could be asked (BBS gives you large N across space, and back in the 90s temporal dynamics were not in vogue).

      • If I were to take another sweeping generalization about North American vs European macroecology (again sweeping enough to annoy everybody) I think you could say NA are more concerned about patterns across species and Europeans are more concerned about patterns across space. And you & I are on the same page I think that we need more attention to patterns across time.

      • This conversation has me confused – in what way was “old school” macroecology not about large spatial scales? The 1989 Brown and Maurer paper was called “Macroecology: The Division of Food and Space Among Species on Continents”. Am I missing something here?

      • Hi Jeff – if you look at say Jim Brown’s book or Gaston & Blackburn (or Lawton’s papers) there is a lot of emphasis on species abundance distributions, body size distributions, range size distributions, correlations between abundance and range size (or abundance and occupancy), etc. The spatial scale of some of this was vague or not necessarily large. Although certainly species ranges and Brown’s emphasis on continental assemblages was implicitly large scale. But there was a lot of discussion of how body size distributions were flat at local scales, local SADs, abundancy-occupancy correlations were mostly local etc too.

        This is why at the journal GLobal Ecology and Biogeography we remain agnostic to all these flavors and just say large in at least one of taxonomic, spatial or temporal scale. But this definition too implies including things that most people don’t yet think of as macroecology.

        See the conversation of “what is macroecology” is never far from the surface🙂

      • Sure, that’s what “macroecology” means now (though it’s unclear to me how the large temporal scales dimension differs from what has always been called “historical ecology”). But I’ve always thought of the “old school” definition as dealing with small spatial scales only in as much as they informed what was happening at larger scales.

        In any case, someone needs to revise the Wikipedia entry:

        “Macroecology is the subfield of ecology that deals with the study of relationships between organisms and their environment at large spatial scales”

      • The issue is not whether old school macroecology was conducted on large-spatial scales. It’s if that was the focus of macroecology (i.e. macroecology was *only* the study of ecological patterns at large spatial scales). My argument is that the spatial scale component was a by product of needing lots of data to see patterns, not the focus. Biogeography was already a venerable field and landscape ecology was already established. What distinguished macroecology is the focus on statistical patterns that emerge from having “lots of particles” as Jim would put it. An easy way to get lost of “particles” was from spatial data like the BBS.

  5. Thanks Brian. I’m also bit surprised that MTE didn’t play a larger role in the discussion. I agree with Morgan and Ric (surprise!), that the rules of energy capture and allocation would seem to be baked in to Macroecology, especially as they link maps of water and temperature (which as RW would agree, don’t just track latitude) to what we are trying to predict. The third leg of the abiotic stool, biogeochemistry, also has a continental geography. I am throwing my bets in with a Macroecology that asks “Given the distribution of energy, water, and elements (and their temporal variance), how can the rules governing how we build organisms predict their distribution and abundance?”.

    Many of your mechanisms focus on predicting species distributions. What fraction of the talks this year focused on predicting abundance/density of individuals (not just the abundance of individual populations,or their distribution among species, but the total number of individuals of a given clade in an area)? A focus on patterns of taxon richness by the conference, which MTE is not good at, might help explain its rarity.

    • I think its interesting your definition of macroecology (which I like) is almost all about spatial variation across the globe which was pretty rare in the early macroecology days. The thing I miss in your explanation (and maybe its just me missing it) is the comparative approach across species (e.g. why are abundant species large-ranged).

      It is an interesting point I hadn’t thought of, but I think it is fair to say with a few notable exceptions, not much of the conference was about abundance.

      • I think one way that our approaches diverge is on the primacy of the species vs the individual as the focus of research. Which is why I find posts like your’s enlightening.

        The questions I find most interesting, that lie more on the periphery of Macroecology as is (or at least in one of its quadrants) address “How do the properties of a taxocene vary geographically?” and my preferred tool to answering the question combines maps of the abiotic environment and physiological ecology/MTE.

        In that sense, I am *very* much interested in how and why the answer varies across clades of ca. equal age (e.g., collembola vs oribatids), but also the same clade and its constituent parts (ants, the subfamilies of ants, the genera of ants…). One reason that fascinates is you have to “bin” individuals some way, and I’m curious how binning rules affect our answers.

        And I particularly like to focus on abundance, as its something invertebrate ecologists can often measure rather accurately, and it is a variable that links Odum and MacArthur schools.

      • So if I follow you’re interested in the taxonomic variation in the structure of spatial variation. That is a sophisticated question in comparison to purely taxonomic variation (ignoring space) or spatial variation (ignoring taxa).

        I do think many macroecologists, including most of those descending on Biddeford ME next week for the Gordon Conference on unifying ecology across scales do secretly believe that we will find more answers at the level of individual behavior and physiology (=functional ecology?) than populations. I thought this for a long time. I have to say at this moment my personal pendulum is swinging back towards a bit more population.

        I agree abundance is a very important variable that often is overlooked. Especially with niche models we’ve completely shifted focus to distribution instead of abundance, which is unfortunate.

  6. In the spirit of being a process lumper, could you make the argument that energy use and allocation fits under species traits/fit with the environment? From my perspective, you care about traits/env. fit because of the improved ability of an individual/species to extract resources and/or allocate to fitness relative to other species it competes with.

    I have wondered if different emphases have developed between North American and European macroecology?

    • I definitely think different emphases have developed between NA and European macroecology. Many more maps and much fewer general principles (and equations) at European meetings if I were to try to make a sweeping generalization that would annoy everybody.

      Yes – in my mind I sort of vaguely saw energy under fit to the environment although it is clearly a different sort of environment than temperature – distinguishing ambient conditions from resources is probably necessary.

  7. Very interesting post and comments. Wish I could dive in, but being on holiday with a 5 year old means only brief snatched opportunities to look in on the blog. So just a couple of questions for Brian:

    1. Is macroecology’s mission creep entirely a good thing? I get the sense Morgan thinks it’s a bad thing. Perhaps leading to an ill-defined subdiscipline lacking conceptual coherence? I’m reminded a bit of our old discussion of whether “synthesis ecology” is a discipline (https://dynamicecology.wordpress.com/2012/04/20/is-synthesis-ecology-a-distinct-scientific-discipline/). And also a bit of my old post on whether some ecological concepts are too general, subsuming so much stuff as to be empty, like a theory of “growth” that covers everything that can be said to grow (organisms, populations, economies, egos, the universe…; https://dynamicecology.wordpress.com/2011/05/12/are-some-general-ecological-concepts-too-general-revisiting-an-oikos-classic/). If macroecology is about “any bit of ecology that’s ‘big’ in some sense or other”, well, is that a discipline? And if not, is there any practical cost to that lack of coherence? What, if anything, is bad about a bunch of people doing unrelated ‘big’ stuff, but labeling all of it as “macroecology”?

    2. Can you talk a bit more about the conservation angle in macroecology? What are the key concrete ways you see macroecological analyses feeding into practical conservation?

    • 1) – its awkward for sure. This is why self-definition has been a topic at every macroecology conference for a while. I do think macroecology is going from here’s the 5 things we study to a viewpoint or perspective or approach to the world that can be applied to very many things. I personally don’t think that’s bad. I assume (without evidence) that this is something all fields go through as they expand and grow up. But it has its downsides for sure.

      2) for starters nothing in conservation plays out at the scale of replicated manipulated experiments (1 m plots, 40 x 40 m plots for trees etc). Conservation is practiced at the scales of landscape ecology and macroecology. Secondly only one other group (population biologists) cares as much about abundance as we do, and no other group cares about distribution of species as much as we do. Those are core fodder for macroecology. As for concrete ways. Nearly all the models of species loss under global change are macroecological (Pimm & Ashton’s species are curve, various applications of niche models & climate change). I personally think they’re oversimplistic and wrong but the solution is more macroecology. The macroecological approach linking traits to extinction (or threatened risk) is very useful given how little we know about most species on the planet. A growth area right now is taking a macroecological approach to assessing trends in diversity and populations (across many many populations) through time and the factors influencing those trends. That is the very essence of what conservation and treaties like the convention on biodiversity are targeted at.

      • Sorry I’m coming to this late: I have just a brief comment on the mission creep on this side of the pond. With the UK Macroecology group, we’ve taken the view that anyone interested in attending and speaking at a macroecology conference is doing macroecology (unlike the GRC, where the scope is well-defined). For many folks, I think this really means “inspired by macroecological principles”. Maybe the breadth reflects a lack other suitable outlets (there is no BES-sponsored community ecology group, for example, and the conservation group is very applied), or maybe our meetings are more fun.

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