This symposium was presented at the 1995 Annual Meeting of the Ecological Society of America, held in Snowbird, Utah.
WHAT CAN THEORETICAL ECOLOGY DO FOR APPLIED ECOLOGY?
Organized by: Alan Hastings, University of California, Davis, CA, 95616. (919)-752-8116. firstname.lastname@example.org
THURSDAY 3 AUGUST, 1995, 8:00 a.m.-12:00 p.m.
There have been several symposia, including the one leading to the book "Perspectives in Theoretical Ecology", that have focussed on the interface between theory and experiment in ecology. The role of theory in Applied Ecology per se has not been covered nearly as well. Yet, theory has a special role to play in applied ecology, where in essence prediction becomes an essential part of the process.
Both the scope and limitations of prediction in Applied Ecology, as guided by theory, will be covered in the symposium. Speakers will range from very general (Levin) to those covering principles (e.g., my talk) to specific case studies (e.g., Turchin). The goal will be to show both the current state of the art in using theory in Applied Ecology, as well as to show possibilities for the future.
One major stated goal of the Theoretical Ecology Section is to demonstrate to the wider membership of ESA the role and importance of theoretical ecology. The symposium proposed here has been designed with this in mind -- the topics are likely to attract many members of ESA who do not consider themselves theoreticians. As a further step towards dissemination, papers from the symposium will likely be used to create a feature in Ecological Applications.
8:00 Hastings Introductory Remarks
8:15 Turchin Theoretical ecology and the management of the southern pine beetle.
8:45 Botsford Population dynamics and fisheries
9:15 Lande Genetic, demographic, and economic factors in extinction.
10:00 Hastings Can ecological theory really predict the rate of spread of an invader?
10:30 Kareiva Can ecological theory help us evaluate the invasiveness of genetically engineered organisms?
11:00 Turner Biodiversity in time and space: application of landscape theories
11:30 Levin Towards a theory of applied ecology
1. Turchin, Peter. Dept. of Ecology and Evolutionary Bio logy, University of Connecticut, Storrs, CT 06269-3042. THEORETICAL ECOLOGY AND MANAGEMENT OF THE SOUTHERN PINE BEETLE.
The southern pine beetle (SPB) is the most destructive insect pest of southern conifers. Its economic impact is measured in hundreds of millions of dollars, and it is a significant factor in ecosystem dynamics and in management of endangered species, such as the red-cockaded woodpecker. Yet, ecological mechanisms responsible for outbreaks of this destructive insect are poorly understood. Theoretical ecology provides the necessary (but underutilized) framework for answering this question. For example, until recently it was believed that SPB outbreaks were driven by exogenous, probably climatic variables. A time-series analysis of historical outbreak data, however, implicated some endogenous factor acting in delayed density-dependent manner. This result motivated an ongoing experiment testing the effect of natural enemies on SPB populations. Another application of ecological theory is a current investigation of area-wide effects of various SPB suppression tactics. This project blends together model development, using the diffusion framework, with empirical estimation of model parameters, and experimental testing of model predictions in the field.
I explore relationships between population dynamics in theoretical ecology and the appropriate area of potential application in fisheries, population modeling for management. Fishery managers realized early on that they needed to develop a general understanding of the way in which fish populations respond to harvest, rather than treating each case as completely unique. This theory developed in government agencies rather than academia, and it differs from ecological theory in being more empirically based and, of necessity, more frequently tested. Review of the development of fishery theory in the context of parallel developments in theoretical ecology shows several interesting interactions: (1) cases in which concepts from theoretical ecology were benefically applied to practical fishery problems, (2) instances in which theoretical constructs developed to meet the demands of fishery management presaged and influenced theoretical ecology, and (3) misguided attempts to apply supposedly general concepts from theoretical ecology to fishery problems. Future interactions between theoretical population dynamics and fishery management hold promise for both.
Current understanding of different factors affecting the risk of population extinction is incorrect and incomplete in many respects. Genetic factors include inbreeding depression, the maintenance of genetic variance for adaptation to changing environments, and fixation of new deleterious mutations. Demographic factors include Allee effects, edge effects, demographic and environmental stochasticity, random catastrophes, and metapopulation dynamics. Economic factors include habitat destruction and fragmentation, and overharvesting caused by economic discounting of future profits. Understanding the relative importance of, and interactions among, different factors affecting extinction risk can help to maximize the effectiveness of conservation efforts based on limited resources.
One of the most important issues in conservation biology and other areas of applied ecology is the invasion and spread of introduced species. Attempts to prepare for the consequences of or control invasions will require predictions of rates of spread. There is a well developed theory, tracing back to Skellam and Fisher on the rate of spread of invading organisms. More recently, this theory has been shown to provide a reasonable fit to the rate of spread of organisms ranging from plants to insects to mammals. Yet, the theory for rate of spread has almost always been used (and tested) in a retrospective fashion by fitting all the previous data. Here, I will assess the utility of the theory for the rate of spread by testing the theory in a prosepctive manner by examining predictions of the rate of spread of invading organisms based on data collected during the initial phases of an invasion, or on life history measurements. The theory of invasions will be shown to have limitations, and ways of determining whether the initial predictions of rates of spread are accurate will be provided.
Regulatory agencies seem to accept staggeringly primitive ecological theory in the form of "life history syndromes" when evaluating the risks of genetically engineered organisms. Although the current level of "risk assessment" thus seems totally unacceptable, it is hard to find better approaches. Among the possibilities we examine are: explicit fitting of Lotka-Volterra models to experimental data for genetically engineered microbes, small-scale experimental evaluations of population growth rates for transgenic crops, and invasion models that meld heterogeneous environments and a possible role for monitoring. While the issue of risk assessment for genetically engineered organisms is frustrating, addressing the issue may at least push us towards making much needed advances in our theories concerning ecological invasions and mechanisms for species coexistence.
Biotic diversity is dynamic through time and appears different depending upon the scale of investigation. This leads to confusion about the nature of diversity, the mechanisms which create and maintain diversity and appropriate analytical methods. Theoretical developments within landscape ecology may clarify these issues. Quantitative assessments of diversity depend upon the grain and extent of observations and upon the number of samples. Comparison of diversity assessments requires and explicit accounting of these factors. Theoretical considerations suggest that research should be conducted at multiple scales, both to enhance intercomparisons between sites and to elucidate the mechanisms regulating diversity within a site. Novel modeling approaches may prove valuable as a tool for testing hypotheses about mechanisms which can generate and maintain patterns of biotic diversity. Spatially-explicit, rule-based simulations allow investigation of how local interactions lead to broad-scale spatial patterns and long-term dynamics. We present a review of current work in landscape theory and suggest application of this body of theory to biodiversity research.
The challenge of applied ecology is to learn from experiences, and to derive principles that allow one to extrapolate from case studies and to develop approaches that recognize thuniqueness of particular situations, ye permit one to go beyond treating each new situation and each new system de novo. A bridge must be found between the indiscriminate abstraction of much ecological theory, and the site specificity of individual applications. Challenges and successes will be discussed.
Alan R. Johnson
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