Charting Our Progress: Evolving Thoughts on Population Dynamics

By: Sarah Solomon

I have always been fascinated by the natural world – by the species that I encounter on a daily basis, and by those that exist on faraway lands. In thinking of how complicated and diverse human population dynamics can be, I’ve always sought to understand how other species’ populations are regulated. Why do some species go extinct, and what prevents others from meeting this same fate?

With ever-increasing human activity around the globe, some species are actually beginning to flourish beyond their natural ranges. From Asian carp to Dog-strangling Vine, the increased abundance and distribution of native and introduced species can be detrimental to the survival of others.

Louis Charles Birch, 1918-2009
University of Sydney

In the early 1940s, Australian insect ecologist Louis Charles Birch began to study how certain species of Dacinae fruit flies were becoming pests as a result of the expansion of cultivated fruit crops. Birch and his supervisor (and would-be lifelong colleague) Herbert Andrewartha were fascinated by the relationship of evolution to ecology, with a particular interest in how evolution can be charted in dynamic species of insects.

At the time of Birch and Andrewartha’s original research on the five most abundant species of fruit flies in eastern Australia, there was a prevailing hypothesis suggesting that all animal populations were self-regulating. This meant that populations of animals would increase under favourable conditions, and that eventually the population would grow so crowded that the birth rate would drop and the death rate would increase – hence the notion of self-regulation. It was believed that once a population reached a low enough density, the pressures on it would decrease and the population would be spared from extinction. Now in a laboratory setting, there was compelling evidence to support this hypothesis, but Birch had a different idea.

What actually happens to populations in nature? Why don’t they become extinct? How might we regulate populations of species that have extended beyond their natural ranges? Birch was part of a generation that started to wonder about these notions as they related to changes in natural environments due to human activities. He decided to look both within and outside of different fruit fly species in order to explore how external factors affect species density and changes in distribution.

In particular, D. tryoni had become a pest to fruit crops spanning the eastern coastal portion of Australia, with a significant increase in its range, adapting to cooler southern temperatures. He was also interested in charting this change – are species actively adapting to environmental changes, and are these changes observable? As it turns out, D. tryoni was even hybridizing with D. neohumeralis – another endemic fruit fly species of eastern Australia – to produce a population of flies with a 15 percent higher survival rate of immature eggs than D. tryoni. And all of this as a result of cultivating more fruit crops across the country!

Thus it seems that Birch was on to something – as it turns out, something very important indeed. It is unclear whether Birch could have anticipated just how much of an impact human activity would have on the environment, and in turn, just how much this change would affect species population dynamics. Today, conservation is at the forefront of science and policy, and the notion of studying the effects of abiotic factors on species population dynamics is imperative.

With scientists like Birch paving the way for thinking beyond the “self-regulating” hypothesis, research groups like that of Australian ecologist Euan Ritchie are committed to producing population models that can help inform conservation policies, and protect at-risk species from extinction.

In a 2009 study, Ritchie and colleagues uncovered how competition between the antilopine wallaroo and its wide-spreading counterpart, the Eastern grey kangaroo, is a threat to the survival of the former species. They also found that habitat – especially changes to landscape and the introduction of cattle ranching – contributed greatly to the viability of these species, and that of the common wallaroo (http://www.ncbi.nlm.nih.gov/pubmed/19175695). This type of modeling research is commonplace in the field of ecology today, as the notion of abiotic factors playing a significant role in species' survival is a widely accepted school of thought. With the growing impacts of climate change becoming more and more evident each day, it seems we have come a long way from the era when Birch’s ideas were considered a minority view.

More than fifty years later, the need to produce sound science with which to inform conservation policy is critical. Since Birch’s kick-start to understanding population dynamics, significant advancements have been made in genetics, and in the technologies for analyzing genetic diversity. Such techniques are helping to further highlight the types of genetic adaptations that Birch started to chart in the 1950s, producing fascinating insights into how populations are disappearing, appearing and adapting to external changes.

Overall, have we made all that much progress since Birch?

I would like to think that in many ways we have, but we still have yet to bridge the gap that exists between sound science and policy enforcement. It seems that despite strides being made on the scientific forefront, useful data are often not used or are discounted by policy decision-makers to suit the goals of various stakeholders. Research, like that of Birch and Andrewartha, and more currently Ritchie and colleagues, has major implications for conservation issues, and particularly for the growing concerns of harmful invasive species (see The Genetics of Colonizing Species).

Share your views, and leave a comment below!

References:

Baker, H. G., and Stebbins, G. L. (1965). The genetics of colonizing species: proceedings. Academic Press Inc.

Ritchie, E. G., Martin, J. K., Johnson, C. N., and Fox, B. J. (2009). Separating the    influences of environment and species interactions on patterns of distribution and abundance: competition between large herbivores. Journal of Animal Ecology, 78,    724-731. doi: 10.1111/j.1365-2656.2008.01520.x

50 years of applying theory to ecological problems: where are we now?

Fifty years ago, the seminal volume ‘The Genetics of Colonizing Species’ edited by Herbert G. Baker and G. Ledyard Stebbins was published, and it marked a new phase for the nascent sciences of ecology and evolutionary biology –namely applying theories and concepts to understanding applied issues. Despite the name, this book was not really about genetics, though there were several excellent genetics chapters, what it was really about was the collective flexing of the post-modern synthesis intellectual muscles. Let’s back up for a minute.

The modern synthesis, largely overlooked and forgotten by modern course syllabi, is the single most important event in ecology and evolution since the publication of Darwin’s Origin of the Species. Darwin’s concepts of evolution stand as dogma today, but after publishing his book, Darwin and others recognized that he lacked a crucial mechanism –how organismal characteristics were passed on from parent to offspring. He assumed that whatever the mechanisms, offspring varied in small ways from parents and that there was continuous variation across a population.

For more than 30 years, from about 1900-1930, evolution via natural selection was thought disproven. With the rediscovery of Mendel’s garden pea breeding experiments in 1900, many influential biologists of the day believed that genetic variation was discontinuous in ‘either-or’ states and that abrupt changes typified the appearance of new forms. Famously, this thinking lead to the belief that ‘hopeful monsters’ were produced with some becoming new species instantaneously. This model of speciation was referred to ‘saltationism’

Of course there were heretics, most notably the statisticians who worked with continuous variation (e.g., Karl Pearson, and Ronald Fisher) who refuted the claims made by saltationists in the 1920s. Some notable geneticists changed their position on saltationism because their experiments and observations provided evidence that natural selection was important (most notably T.H. Morgan). However, it wasn't until WWII that the war was won. A group of scientists working on disparate phenomena published a series of books from 1937-1950 that showed how genetics was completely compatible with Darwinian natural selection and could explain a wide variety of observations from populations to biogeography to paleontology. These ‘architects’ and their books were: Theodosius Dobzhansky (Genetics and the Origin of Species); Ernst Mayr (Systematics and the Origin of Species); E. B. Ford (Mendelism and Evolution); George Gaylord Simpson (Tempo and Mode in Evolution); and G. Ledyard Stebbins (Variation and Evolution in Plants). With this, they unified biology and thus the modern synthesis was born.

Now back to the edited volume. Which such a powerful theory, it made sense that there should be a theoretical underpinning to applied ecological problems. The book grew out of a symposium held in Asilomar, California Feb. 12-16, 1964[1], organized by C. H.Waddington, who originally saw an opportunity to bring together thinkers on population genetics. But the book became so much more. According to Baker and Stebbins:

“…the symposium … had as its object the bringing together of geneticists, ecologists, taxonomists and scientists working in some of the more applied phases of ecology –such as wildlife conservation, weed control, and biological control of insect pests.”

Thus the goal was really about modern science and the ability to inform ecological management. The invitees include a few of the ‘architects’ (Dobzhansky, Mayr, and Stebbins) and their academic or intellectual progeny, which includes many of the most important thinkers in ecology and evolution in the 1960s and 70s (Wilson, Lewontin, Sakai, Birch, Harper, etc.).

Given the importance of the Genetics of Colonizing Species in establishing the role that theory might play for applied ecology, it is important to reflect on two important questions: 1) How much have our basic theories advanced in the last 50 years; and perhaps more importantly, 2) has theory provided key insights to solving applied problems?

This book is the fodder for a graduate seminar course I am teaching, and these two questions are the focus of our comparing the chapters to modern papers. Over the next couple of months, students in this course will be contributing blog posts that examine the relationship between the classic chapters and modern work, and they will muse on these two questions. Hopefully by the end of this ongoing dialogue, we will have a better feeling of whether basic theory has advanced our ability to solve applied problems.

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[1] See 50^th anniversary symposium

Ecological progress, what are we doing right?

A post from Charles Krebs' blog called "Ten limitations on progress in ecology" popped up a number of times on social media last week. Krebs is a established population ecologist who has been working in the field for a long time, and he suggests some important problems leading to a lack of progress in ecology. These concerns range from lack of jobs and funding for ecologists, to the fracturing of ecology into poorly integrated subfields. Krebs' post is a continuation of the ongoing conversation about limitations and problems in ecology, which has been up for discussion for decades. And as such, I agree with many of the points being made. But it reminded me of something I have been thinking about for a while, which is that it seems much more rare to see ecology’s successes listed. For many ecologists, it is probably easier to come up with the problems and weaknesses, but I think that's more of a cognitive bias than a sign that ecology is inescapably flawed. And that’s unfortunate: recognizing our successes and advances also helps us improve ecology. So what is there to praise about ecology, and what successes we can build on?

Despite Krebs’ concerns about lack of jobs for ecologists, it is worth celebrating how much ecology has grown in numbers and recognition as a discipline. The first ESA annual meeting in 1914 had 307 attendees, recent years’ attendance is somewhere between 3000-4000 ecologists. Ecology is also increasingly diverse. Ecology and Evolutionary Biology departments are now common in big universities, and sometimes replacing Botany and/or Zoology programs. On a more general level, the idea of “ecology” has increasing recognition by the public. Popular press coverage of issues such as biological invasions, honeybee colony collapses, wolves in Yellowstone, and climate change, have at least made the work of ecologists slightly more apparent.

Long-term ecological research is probably more common and more feasible now than it has ever been. There are long-term fragmentation, biodiversity and ecosystem function studies, grants directed at LTER, and a dedicated institute (the National Ecological Observatory Network (NEON)) funded by the NSF for longterm ecological data collection. (Of course, not all long term research sites have had an easy go of things – see the Experimental Lakes Area in Canada).

Another really positive development is that academic publishing is becoming more inclusive – not only are there more reputable open access publishing options for ecologists, the culture is changing to one where data is available online for broad access, rather than privately controlled. Top journals are reinforcing this trend by requiring that data be published in conjunction with publications.

Multi-disciplinary collaboration is more common than ever, both because ecology naturally overlaps with geochemistry, mathematics, physics, physiology, and others, and also because funding agencies are rewarding promising collaborations. For example, I recently saw a talk where dispersal was considered in the context of wind patterns based on meteorological models. It felt like this sort of mechanistic approach provided a much fuller understanding of dispersal than the usual kernel-based model.

Further, though subdisciplines of ecology have at times lost connection with the core knowledge of ecology, some subfields have taken paths that are worth emulating, integrating multiple areas of knowledge, while still making novel contributions to ecology in general. For example, disease ecology is multidisciplinary, integrating ecology, fieldwork, epidemiological models and medicine with reasonable success.

Finally, more than ever, the complexity of ecology is being equalled by available methods. More than ever, the math, the models, the technology, and the computing resources available are sufficient. If you look at papers from ecology’s earliest years, statistics and models were restricted to simple regressions or ANOVAs and differential equations that could be solved by hand. Though there is uncertainty associated with even the most complex model, our ability to model ecological processes is higher than ever. Technology allows us to observe changes in alleles, to reconstruct phylogenetic trees, and to count species too small to even see. If used carefully and with understanding, we have the tools to make and continue making huge advances.

Maybe there are other (better) positive advances that I’ve overlooked, but it seems that – despite claims to the contrary – there are many reasons to think that ecology is a growing, thriving discipline. Not perfect, but successfully growing with the technological, political, and environmental realities.

Ecology may be successfully growing, but it's true that the timing is rough...

What can the future of ecology learn from the past?

Ecology has been under pressure to mature and progress as a discipline several times in its short life, always in response to looming environmental threats and the perception that ecological knowledge could be of great value. This happened notably in the 1960s, when the call for ecology to be better applicable occurred in relation to the publication of Silent Spring and fears about nuclear power and the Manhattan Project. Voices in academia, government, and the public called for ecology to become a “Big Science”, and focus on bigger scales (the ecosystem) and questions. And yet, “[Silent Spring] brought ecology as a word and concept to the public…A study committee, prodded by the publication of the book, reported to the ESA that their science was not ready to take on the responsibility being given to it.”

Arguably ecology has grown a lot since then: there have been advances in statistical approaches, spatial and temporal considerations, mechanistic understanding of multiple processes, in the number and type of systems and species studied, and the applications being considered. But it is once again facing a call (one that frankly has been ongoing for a number of years) to quickly progress as a science. The Anthropocene has proven an age of extinctions, human-mediated environmental changes, and threats to species and ecosystems from warming, habitat loss and fragmentation, extinctions, and invasions abound. Never has (applied) ecology appeared more relevant as a discipline to the general public and government. This is reflected in the increasing inclusion of buzzwords like “climate change”, “restoration”, “ecosystem services”, “biodiversity hotspot”, or “invasion” as keys to successful self-justification. Also similar to the 1960s is the feeling that ecology is not ready or able to meet the demand. Worse, that the time ecology has to respond is more limited than ever.

This first point--that ecology isn’t ready--is repeated in Georgina Mace’s (the outgoing president of the British Ecological Society) must-read editorial in Nature. The globe is in trouble, from climate change, disease, overpopulation, loss of habitat and biodiversity and Mace argues that ecology is incapable in its current form of responding to the need. She suggests that unless ecology evolves, it will fail as a discipline. Despite the growth of ecology that followed the 1960s, it is still a 'small' discipline: collaborations are mostly intra-disciplinary, data has been privately controlled, and the tendency remains to specialize on a particular system or organism of interest. However, this 'small' approach provides very little insight into the big problems of today - particularly understanding and predicting how the effects of global change on ecosystems and multispecies assemblages. To Mace, the solution, the undeniable necessity, is for ecology to get bigger. In particular, collaborations need to be broader and larger, with data sharing and availability (“big data”) the default. Ecological models and experiments/observations should be scaled up so that we can understand ecosystem effects and identify general trends across species or systems. In this new 'big' ecology, “[g]oals would be shaped by scientists, policy-makers and users of the resulting science, rather than by recent publishing trends”. Making research more interdisciplinary and including end-product users would allow the most important questions to receive the attention they deserve.

The difficulty with the looming environmental crises and the pressure on ecology to grow, is that the important decisions to be made have to be made rapidly and perhaps without complete information. Often scientific progress is afforded the time for slow progression and self-correction. After all, change is costly and risky, it requires reinvesting effort and funding, and may or may not pay off, and so science (including ecology) is often conservative. For example, a conservative mind would note that Mace’s suggestions are not without uncertainty and risk. Big data, for example, is acknowledged to have its strengths and its weaknesses, it may or may not be the cure-all it is touted as. Regardless of the amounts of data, good questions need to be asked and data, no matter how high quality, may not be appropriate for some questions. Context is often so important in ecology that attempts to combine data for meta-analysis may be questionable. Long running arguments within ecology reflect the fear that making ecological research more useful for applications and interdisciplinary questions may come at the expense of basic research and theory. It seems then that ecology is in an even worse scenario than Mace suggests, since not only must ecology change in order to respond to need, but it also must predict with incomplete information which future path will be most effective.

So ecological science is at an important junction with choices to make about future directions, limits on the information with which to make those choices, little time to make them, and much pressure to make them correctly. Perhaps we can take some comfort from the fact that ecology has been here before, though. There are some lessons we can draw from ecology’s last identity crisis, both the successes and failures. The last round resulted in ecology gaining legitimacy as a science and being integrated into policy and governance (the EPA, environmental assessments, etc). It appears, particularly in some countries, that ecology is more difficult to sell to policy and government today, but at the very least ecology has established a toehold it can take advantage of. Ecology also tried to focus on bigger scales in the 1960s--the concept of the 'ecosystem' resulted from that time--but the criticism was that the new ideas about ecosystems and evolutionary ecology weren't well integrated into ecological applications, and so their effect wasn't as broad as it could have been. Concepts like ecosystem services and function today integrate ecosystem science into applied outputs, and the cautionary tale is the value of balancing theoretical and applied development. It also seems that ecology must first consider what its duty as a science is to society (Mace’s assumption being that we have a great duty to be of value), since that is the key determinate of what path we decide to take. Then, we can hopefully consider what have we done right in recent years, what have we done wrong, and then decide where to go from here.

Page from "Silent Spring", Rachel Carson.

#esa2013 What ESA tells us about where ecology is going

The annual ESA meeting functions in a lot of different ways. There are the obvious: the sharing of ideas and work, the discovery of new ideas, methods or sources of inspiration, networking and job finding, social reunions. But it also functions as a kind of report on the state of the field (and that's not even considering sessions meant to explicitly do this, like the panel “Conversations on the Future of Ecology”). The topics and methods presented say a lot about what ideas and methods are timeless, what is trendy, and over many meetings, where ecology appears to be going. If you go to enough ESAs, you are participating in a longitudinal study of ecology (or at least your subfield).

I went to my first ESA five years ago in Albuquerque, NM. One of the things that struck me was that there were two Community Assembly and Neutral Theory sessions and many talks in those focused on tests of neutral theory, particularly looking at species abundance distributions (SADs) and various iterations of neutral models. There are usually still one to two sessions called Community Assembly and Neutral Theory, but five years later, I don't think I saw a single talk that looked at SADs for evidence of neutral theory (and only one or two talks that were named to explicitly include neutral theory). Instead, the concept first introduced by Hubbell has morphed from "neutral theory" in to something slightly more general, designated "neutral dynamics". This gets used in a lot of ways – most precisely, neutral dynamics are in the spirit of neutral theory, suggesting that population demographic rates are similar, allowing long-term co-occurrence. Sometimes this is cited with reference to equalizing fitness effects in a Chessonian framework, where similarity in fitnesses prevents exclusion despite overlap in species niches. But it also seemed to get used in a default sort of way, as the explanation for why niche differences between species weren't discovered by a study, or else "neutral" was used interchangeably with "stochastic". In any case, the pattern appeared to be a move from highly specialized and precisely defined usage of the term, to broader incorporation of the concept that had suddenly acquired several, often less precisely defined meanings. Instead of being the central focus of a few specialized talks, neutrality was commonly invoked as a minor theme or explanation in many more talks. It is not what I expected, but its continuing usage suggests that neutrality has developed a life of its own.

Other topics similarly seem to have taken on separate lives from their initial application; even over the short time I've been attending ESA. For example, sessions focused on simple applications of ecophylogenetics methods (overdispersion, clustering, using different systems) were relatively common 3-4 years ago, while there wasn't a single contributed session specifically named for phylogenetics this year. There was however many sessions in which phylogenetic work formed the backbone of talks that were about broader questions, including in the "Evolution, Biodiversity, and Ecosystem Function" session and the “Coexistence of Closest Relatives: Synthesis of Ecological and Evolutionary Perspectives”. In the best case scenarios, it seems like even over-hyped approaches may be used with more nuance in time, as people recognize what information these methods can and cannot provide.

Sometimes it did seem that there is a lag between when critiques of certain methods or ideas are expressed and when they actually get incorporated into research. I could be wrong, but it seems this is most common where the research is focused on particular study systems or species, and methodology may be driven more by precedent in the literature and criticisms may take longer to infiltrate (since they aren’t the main focus of the work anyways). And unfortunately, the topics and sessions which appear to be timeless are those on human-related applications (restoration, climate change, invasion). Those pressures are sadly unchanging.

*The great thing to do would be map out changes in keyword frequency over the ESAs that have archived programs. Unfortunately, I don’t have the time/motivation.

Reinventing the ecological wheel – why do we do it?

Are those who do not learn from (ecological) history are doomed to repeat it?

A pervasive view within ecology is that discovery tends to be inefficient and that ideas reappear as vogue pursuits again and again. For example, the ecological implications of niche partitioning re-emerges as an important topic in ecology every decade or so. Niche partitioning was well represented in ecological literature of the 1960s and 1970s, which focused theoretical and experimental attention on how communities were structured through resource partitioning. It would be fair to say that the evolutionary causes and the ecological consequences of communities structured by niche differences were one of the most important concepts in community ecology during that time. Fast-forward 30 years, and biodiversity and ecosystem functioning (BEF) research slowly  has come to the conclusion that niche partitioning to explains the apparent relationship between species diversity and ecosystem functioning. Some of the findings in the BEF literature could be criticized as simply being rediscoveries of classical theory and experimental evidence already in existence. How does one interpret these cycles? Are they a failure of ecological progress or evidence of the constancy of ecological mechanisms?

Ecology is such a young science that this process of rediscovery seems particularly surprising. Most of the fundamental theory in ecology arose during this early period: from the 1920s (Lotka, Volterra), 1930s (Gause) to 1960s (Wilson, MacArthur, May, Lawton, etc). There are several reasons why this was the foundational period for ecological theory – the science was undeveloped, so there was a void that needed filling. Ecologists in those years were often been trained in other disciplines that emphasized mathematical and scientific rigor, so the theory that developed was in the best scientific tradition, with analytically resolved equations meant to describe the behaviour of populations and communities. Most of the paradigms we operate in today owe much to this period, including an inordinate focus on predator-prey, competitive interactions, and plant communities, and the use of Lotka-Volterra and consumer-resource models. So when ecologists reinvent the wheel, is this foundation of knowledge to blame, is it flawed or incomplete? Or does ecology fail in education and practice in maintaining contact with the knowledge base that already exists? (Spoiler alert – the answer is going to be both).

Modern ecologists face the unenviable task of prioritizing and decoding an exponentially growing body of literature. Ecologists in the 1960s could realistically read all the literature pertaining to community ecology during their PhD studies –something that is impossible today with an exponentially growing literature. Classic papers can be harder to access than new ones: old papers are less likely to be accessible online, and when they are, the quality of the documents is often poor. The style and accessibility of some of these papers is also difficult for readers used to the succinct and direct writing more common today. The cumulative effect of all of this is that we read very little older literature and instead find papers that are cited by our peers.

True, some fields may have grown or started apart from a base of theory that would have been useful during their development. But it would also be unfair to ignore the fact that ecology’s foundation is full of cracks. Certain interactions are much better explored than others. Models of two species interactions fill in for complex ecosystems. Lotka-Volterra and related consumer-resource models make a number of potentially unrealistic assumptions, and parameter space has often been incompletely explored. We seem to lack a hierarchical framework or synthesis of what we do know (although a few people have tried (Vellend 2010)). When models are explored in-depth, as Peter Abrams has done in many papers, we discover the complexity and possible futility of ecological research: anything can result from complex dynamics. The cynic then, would argue that models can predict anything (or worse, nothing). This is unfair, since most modelling papers test hypotheses by manipulating a single parameter associated with a likely mechanism, but it hints at the limits that current theory exhibits.

So the bleakest view of would be this: the body of knowledge that makes up ecology is inadequate and poorly structured. There is little in the way of synthesis, and though we know many, many mechanisms that can occur, we have less understanding of those that are likely to occur. Developing areas of ecology often have a tenuous connection to the existing body of knowledge, and if they eventually connect with and contribute to the central body, it is through an inefficient, repetitive process. For example a number of papers have remarked that invasion biology has dissociated itself from mainstream ecology, reinventing basic mechanisms. The most optimistic view, is that when we discover similar mechanisms multiple times, we gain increasing evidence for their importance. Further, each cycle of rediscovery reinforces that there are a finite number of mechanisms that structure ecological communities (maybe just a handful). When we use the same sets of mechanisms to explain new patterns or processes, in some ways it is a relief to realize that new findings fit logically with existing knowledge. For example niche partitioning has long been used to explain co-occurrence, but with a new focus on ecosystem functioning, it has leant itself as an efficacious explanation. But the question remains, how much of what we do is inefficient and repetitive, and how much is advancing our basic understanding of the world?

By Caroline Tucker & Marc Cadotte

Charles Darwin, founder of evolution AND ecology

Perhaps a good alternative title should be: “Why we need a second modern synthesis”

Darwin is rightfully seen (or vilified in some quarters) as the founder of modern evolutionary biology. He gave the naturalists of that era an observable and testable mechanism explaining species change and for understanding the similarities and differences among species. As we celebrate Darwin’s 200th birthday and the 150th anniversary of the publication of the Origin of the Species, it seemed right to think about Darwin’s contributions beyond just evolutionary change, namely ecological patterns and processes.

I’ve read Origin probably half a dozen times now and as an ecologist, I am always amazed by the depth and breadth of Darwin’s insights. Every time I read it, there are passages that directly relate to what I happen to be thinking about or working on at the time, which leads me to the conclusion that he thought a lot about what scientists would come to call ecology. Though the word “ecology” wouldn’t be invented for another seven years (by Ernst Haeckel in 1866) and the first ecology text book didn’t appear until 1895 (by Eugenius Warming, and which includes interesting Lamarckian invocations in the last chapter), Darwin thought and wrote about ecology extensively.

In the Origin (1st edition), Darwin makes predictions about ecological patterns. On page 109, he states, “a … larger number of the very common and much diffused or dominant species will be found on the side of larger genera”. That is community dominance likely relays on inherited traits linked to species success. This certainly sounds like the result of some recent, interesting papers (e.g., Strauss et al.*).

Almost the whole discussion in the Struggle for Existence chapter is about ecological interactions and the severity of negative interactions, which stems from the fact that populations, if unchecked, will increase exponentially (i.e., page 116). We all know from work by ecologists such as Connell and Huston that those negative, deterministic interactions can be overridden by non-equilibrium processes, especially disturbances. Here again Darwin’s observations lead him to this conclusion; “If turf which has long been mown …be let to grow, the more vigorous plants gradually kill the less vigorous” and he observes that diversity in a plot goes from 20 species to 11 when the disturbance is removed.

Further, we often think of Darwin’s view of the environment as a selective pressure (e.g., fur thickness), but he also saw the environment as a determinant of species interactions. Lush places support a lot of species and the control of populations is due to competitive interactions, whereas in harsh places, populations are controlled by “injurious action” of the environment (e.g., page 121). Thus there is a shift from biotic to abiotic controls on ecological processes.

I think that we have collectively forgotten that evolution directly informs our expectations and predictions of ecological patterns and processes. While ecological geneticists drove much of the modern synthesis in the mid 1900’s by incorporating ecology (namely selection) into evolutionary processes, the reverse, bringing evolution into ecology is only now really starting to happen. Lets hope this second modern synthesis completes Darwin’s vision.

Ecology's romantic period

As an ecologist of the 21st century, I often think about the early ecologists from the period between 1900 and 1920 (Clements, Forbes, Warming, Spalding, Grinnell, etc.) and wonder what it was like for them to do their science. Being a scientist today usually means being a technophile. Amazing advances are made through technology, from new and larger genomes to running mind-bogglingly complex computer simulations with a scale and scope that would have been simply incomprehensible a generation ago. We also have a vast foundation of ideas, theories, hypotheses and observations that drive our current quest for knowledge.

Ecologists of 1900 did not have access to our level of technology, they did not have this huge foundation of knowledge informing their science. In fact the totality of human knowledge of the ecological world, from Aristotle to Darwin to Haeckel to Warming, could fit on a single bookcase. And for this I envy them. Every observation was something new and exciting. Hypotheses created to explain observations were novel and creative. I may be romantic, but the idea of a wide open frontier of ideas seems so exciting to me.

Being an ecologist today means competing in a crowded market of ideas. Much of our creative work involves revising and fine-tuning existing hypotheses or finding new technological and computation methods to better test existing hypotheses. Sometimes it feels like the scientist who yells the loudest in this crowded market will be heard. And so I wonder, would it be worth giving up the technological advances to simply stick your head in a hole and describe a brave new world.

P.S. I love both the photos of Frederic Clements shown here. The first is of him near Santa Barbara, CA were he would spend his winter months researching plant communities. The second is of him (head in hole) and his wife Edith, also an ecologist, apparently studying below ground interactions among plants.