“Life is a train of moods like a string of beads, and, as we pass through them, they prove to be many-colored lenses which paint the world their own hue, and each shows only what lies in its focus.” Ralph Waldo Emerson, Experience, 1844.
The concept of looking at nature through multiple lenses to see different things is not new and has been long recognized. As always, the devil is in the details. Recent developments in analytical tools and the embracement of an integrative metapopulation concept and the newly emergent field of functional biogeography, are allowing exciting new insights to be made by population ecologists that have direct bearing on our understanding of the effects of environmental change on biodiversity patterns.
The metapopulation concept posits that isolated populations of organisms are connected through dynamics of dispersal and extinction. Across a landscape, areas of suitable habitat occur, which at one point in time may or may not host a viable population of a particular species. I study this concept with terrestrial plants, and have asked what environmental conditions determine suitable habitat for metapopulations.
Much of the foundational work in this topic was conducted on butterfly populations in meadows across otherwise forested habitat. Regardless of study organism, embracement of this concept has been enough to make population ecologists realize that studying single populations may give only a limited view on generalities of ecology and evolution. Indeed, taking this concept on board, has led population ecologists to want to predict in which areas of suitable habitat across the landscape a new population may establish.
“There’s no getting away from field work!”
There are obvious conservation and management implications that result from being able to predict the geographical distribution of a species, whether an invasive exotic spreading across the globe, or an endangered organism. Unfortunately, just knowing where a species or a group of species may occur across the landscape is not enough. Individuals in some populations may have low fitness and their populations may be barely hanging on. For some species such as potential island colonizers, it has been proposed that limited ability to colonize vacant habitat patches may be due to the occurrence of closely related species occupying a similar niche.
Important ‘missing pieces’ from a full understanding of the metapopulation puzzle have been through inclusion of population growth rate estimates and incorporation of species evolutionary relationships (i.e., their phylogenic ancestry). Population ecologists have been toiling away making fitness estimates of their species of interest in the field. Systematists, on the other hand, have been grinding it out in the lab to generate the molecular data necessary to construct phylogenetic trees to help classify their species.
Community ecologists studying multispecies assemblages, as a third-dimensional angle to this question, have been working with geographers to develop species distribution models. It is only recently that the analytical tools have emerged that allow these groups of scientists to collaborate and address questions of common interest about metapopulations.For example, Cory Merow and colleagues have recently shown how Bayesian models can be used to propagate uncertainty estimates in the application of integral projection models (IPMs) to forecast growth rates as part of predictive demographic distribution models (transition matrix models could also be used). In other words, species geographic distribution predictions can be improved by accounting for population-level fitness estimates.
In another study, Oluwatobi Oke and colleagues have shown how phylogenetic relationships among 66 co-occurring species in populations across a metapopulation structured landscape of Canadian barrens can improve understanding of species distribution patterns. The basis for Oke et al.’s phylogenetic patterns among their species was the large angiosperm supertree based upon nucleotide sequence data of three genes from over 500 species.
The basis for all of the work described above are precise and accurate estimates of individual fitness and population growth rates. There’s no getting away from field work! Methods for carrying out the field work component of these studies, to allow the use of modern statistical methods including Bayesian analysis, IPMs, and transition matrix models, have to be planned and carried out with care. We have come a long way in the last decade in enabling population studies to scale up to address fundamental questions at higher levels of the ecological hierarchy.
The field of population demography is moving fast. For example, the recent launch of the COMPADRE Plant Matrix Database, with accurate demographic information for over 500 plant species in their natural settings worldwide, will make addressing these scale-related types of comparative evolutionary and ecological questions even more tractable in the future.
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By Frank S. Gilliam
It is likely that most ecologists have their own stories regarding the annual meetings of the Ecological Society of America (ESA), the world’s largest organization of professional ecologists. Some revere it, whereas others may criticize it. There is, however, truth in numbers—growth in attendance has been seemingly exponential since my first meeting in the early 1980’s. So, it is without debate that the annual ESA meeting remains an integral part of the professional life of many ecologists throughout the world.
This year’s ESA meeting will take place in Sacramento, CA. Image credit: Public Domain via Wikimedia Commons.
My first ESA meeting was at the Pennsylvania State University (note: we were small enough to meet on college campuses then) in 1982 while still a Ph.D. student at Duke University working with Norm Christensen on herb-layer dynamics of pine forests of the southeastern United States. I was understandably wide-eyed at seeing the actual human forms of ecologists walking around, giving talks, drinking beer—all of whom had only been names on papers and books I had read as I was writing my dissertation. Despite logistical errors regarding my talk (the projectionist insisted on placing my slides in the tray, rather than allowing me to do so; then promptly put them in backwards), my first ESA was an unmitigated success, allowing me to meet folks who would become lifelong friends and colleagues. Small surprise that I not only attended the next year, but have attended all meetings since then, save two—1991, when I could not afford to travel to Hawaii, and 2012, when my son was entering the United States Naval Academy.
Although I still recall high points of virtually all meetings through the years, the ones that stand out the most for me are those when I collaborated to organize symposia. There have been three of these: 1993 (University of Wisconsin—Madison), 1998 (Baltimore, Maryland), and 2006 (Savannah, Georgia). Although they were of somewhat contrasting themes, I took the same approach to all of them—I always thought that topics/presentations worthy of an ESA meeting were also worthy of some type of formal publication, whether in a peer-reviewed journal or a book.
My old Duke office mate/best friend/collaborator, Mark Roberts, and I organized a symposium on the effects of disturbance on plant diversity of forests for the 1993 meeting. Highly successful at the meeting, with very high attendance and vigorous question/answer periods following each talk, this symposium resulted in the publication of a Special Feature in Ecological Applications in 1995.
Mark and I used that first symposium as a kind of template for the one which was part of the 1998 meeting, well into the period where the number of attendees had outgrown college campuses, relegating ESA to convention centers. The 1998 symposium was on the ecology of herbaceous layer communities of contrasting forests of eastern North America. We had assembled what we felt was a very good group, including the late Fakhri Bazzaz, who was actually the first person I had contacted prior to writing the proposal for the Program Committee, also very successful in terms of attendance and questions. We were also pleased with our efforts on this topic following the symposium.
For the 2006 meeting, another friend and colleague of mine, Bill Platt, and I organized a symposium on the ecology of longleaf pine ecosystems. This experience was especially rewarding in that it was so closely connected with both the meeting theme of that Savannah (Uplands to Lowlands: Coastal Processes in a Time of Global Change), and the meeting’s geographic location in the main region of natural longleaf pine—the Coastal Plain of the southeastern United States. We published these talks in a Special Feature in Applied Vegetation Science.
Oh, there was another high point for me—one not related to symposia. It was with great pride that I accepted the nomination to become the Program Chair for the 2010 Annual Meeting of ESA in Pittsburgh, PA. I chose the following for the scientific theme: Global Warming: the Legacy of Our Past, the Challenge for Our Future. At a time when eastern US venues were not nearly as popular for attendance as were western ones, attendance at this meeting was surprisingly high. I was especially pleased to be able to thank the Society publicly and collectively when I addressed them at the beginning of the meeting.
Since my arrival in 1990 here at Marshall University—a public school small state (West Virginia ranks 38th among the 50 United States) and with limited direct access to colleagues doing similar research—annual ESA meetings have provided me a lifeline, if you will, connecting me with ecologists, especially biogeochemists and vegetation scientists, from throughout North America and, indeed, the world. Most of my contributions to the field of ecology, including peer-reviewed publications, book chapters, and books, have been products of this event that has not only become an annual summer tradition of mine, but also has been invaluable to my career as a plant ecologist.
It’s 2014, folks—see you in Sacramento!
Frank S. Gilliam is a professor of biological sciences, teaching courses in ecology and plant ecology, at Marshall University. He is also the editor of the second edition of The Herbaceous Layer in Forests of Eastern North America.
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