Search

The Sky Island Restoration Collaborative (SIRC) is a growing partnership between government agencies, nonprofit organizations, and private landowners in southeast Arizona, the United States, and northern Sonora, Mexico. Starting in 2014 as an experiment to cultivate restoration efforts by connecting people across vocations and nations, SIRC has evolved over 5 years into a flourishing landscape-restoration initiative. The group is founded on the concept of developing a restoration economy, where ecological and socioeconomic benefits are interconnected and complimentary. The variety of ideas, people, field sites, administration, and organizations promote learning and increase project success through iterative adaptive management, transparency, and sharing. The collaborative seeks to make restoration self-sustaining and improve quality of life for citizens living along the US-Mexico border. Research and experiments are developed between scientists and practitioners to test hypotheses, qualify procedures, and quantify impacts on shared projects. Simultaneously, partners encourage and facilitate connecting more people to the landscape—via volunteerism, internships, training, and mentoring. Through this history, SIRC’s evolution is pioneering the integration of community and ecological restoration to protect biodiversity in the Madrean Archipelago Ecoregion. This editorial introduces SIRC as a unique opportunity for scientists and practitioners looking to engage in binational partnerships and segues into this special journal issue we have assembled that relates new findings in the field of restoration ecology.

Supplemental material, sj-pdf-1-asw-10.1177_11786221211009478 for Editorial: Combining the Science and Practice of Restoration Ecology—Case studies of a Grassroots Binational Restoration Collaborative in the Madrean Archipelago Ecoregion (2014-2019) by Laura M Norman, H Ronald Pulliam, Michele M Girard, Steve M Buckley, Louise Misztal, David Seibert, Carianne Campbell, James B Callegary, Deborah J Tosline, Natalie R Wilson, David Hodges, Jeffrey A Conn and A Valer Austin-Clark in Air, Soil and Water Research

Watershed studies are often onerous due to a lack of data available to portray baseline conditions with which to compare results of monitoring environmental effects. A paired-watershed approach is often adopted to simulate baseline conditions in an adjacent watershed that can be comparable but assumes there is a quantifiable relationship between the control and treated watersheds. Finding suitably matched pairs that can most accurately depict similar responses is challenging and attributes are rarely quantified. In southeastern Arizona, United States, researchers are investigating the effectiveness of watershed restoration techniques employed by land managers. We selected Smith Canyon to develop a rigorous and quantitatively defensible paired-watershed experimental design. The Smith Canyon watershed consists of 91 structurally similar sub-basins that have a defined basin-like structure and flow channel, allowing for consideration as replicate units. We developed a statistical approach to group sub-basins based on similar structural, biophysical, and hydrologic traits. Our geospatial database consisted of 35 environmental variables, which we reduced to 12 through a correlation analysis. We identified three primary collections of paired sub-basins within the larger watershed. These clusters are being used to inform studies actively being employed in the watershed. Overall, we propose a hierarchical clustering protocol for justification of watershed pairing experiments.

Within habitats the overlap of food—size utilization of five sympatric finch species is almost 100% despite considerable differences in culmen lengths. It is suggested that the differences in bill size reflect differences in the proportion of large seeds in the set of habitats in which each species feeds and does not function to reduce competition within habitats. Although seed production was sufficient to maintain the finch populations through winter, the finches did eat at least 40% of the available seeds. Of the five finch species commonly present at least three seem to be limited by their winter food supply. The diversity of finches in the yield was not significantly correlated with either food abundance or food diversity. See full-text article at JSTOR

Summary Why some herbaceous plant species refrain from sprouting in some years is a longstanding puzzle in plant ecology. When vegetatively ‘dormant’, the plant lives as a rootstock, but does not produce or maintain photosynthetic tissue. During this time, energy may be remobilized from resource reserves or acquired from mycorrhizal fungi, although the mechanisms are still poorly understood. If vegetative dormancy is adaptive, it may be in response to a harsh environment, to life-history costs, or as a bet-hedge against unpredictable environmental variability. We tested whether vegetative dormancy is adaptive via game theoretical analysis of deterministic and stochastic ahistorical and historical life-history models parameterized with long-term census data for two long-lived plants, Anemone americana and Cypripedium parviflorum. The ahistorical deterministic model provided a test of the hypothesis that dormancy is adaptive in response to a generally harsh environment and/or short-term life-history costs, while the historical model tested whether long-term costs drove the evolution of dormancy. The stochastic ahistorical model provided a test of whether dormancy is a bet-hedging trait. We found that vegetative dormancy is an adaptive consequence of life-history costs of growth to survival and that these costs may be operating under a variable but generally harsh environment. Such costs led to sprouting and survival probabilities that generally increased with size in adults but never reached unity and decreased with size in juveniles. Historical deterministic models particularly predicted observed sprouting frequencies, while deterministic ahistorical and stochastic models did not, suggesting although the environment is likely stressful and fluctuates between harsh and mild states, short-term costs and temporal stochasticity alone do not explain observed sprouting frequencies. Synthesis. Life-history costs can drive the evolution of seemingly paradoxical traits. In particular, growth can lead to survival costs that may become significant in future years. These costs may be incurred via the use of stored reserves that, once used, cannot be used in the next several years. Such costs are the currency favouring the evolutionary maintenance of vegetative dormancy in two distantly related perennial plant species and may account for dormancy throughout the plant kingdom.

Summary 1. Mismatches between species distributions and habitat suitability are predicted by niche theory and have important implications for forecasting how species may respond to environmental changes. Quantifying these mismatches is challenging, however, due to the high dimensionality of species niches and the large spatial and temporal variability in population dynamics. 2. Here, we explore how probabilistic assessments of habitat suitability based on demographic models may be used to better bridge niche theory and population dynamics. We use integral projection models (IPMs) to predict population growth rates for a terrestrial orchid in response to environmental variables. By parameterizing these IPMs with hierarchical models, we develop a spatially variable measure of a species’ demographic niche, which can then be compared against its distribution to test ideas about what factors control a species’ distribution. 3. We found that demographic suitability of sites was not well correlated with the orchid’s distribution at local scales, with many absences from microsites of high predicted suitability and occurrences in sites with low predicted suitability. However, at the population scale, abundance was positively correlated with demographic suitability of the sites. These results are consistent with dispersal limitation and source–sink dynamics at small scales but stronger distribution-suitability matching at larger landscape scales. 4. Synthesis. The relationships between species distributions and demographic performance underlie basic niche theory and have important implications for predicting responses to a changing environment. The complexities of these relationships will require approaches that can encapsulate what we know in probabilistic terms and allow for spatially varying niche relationships.

Models of Mobile Animal Populations (MAP models) simulate long-term land use changes, population trends and patterns of biological diversity on landscapes of 103-105 ha. MAP models can incorporate information about past land-use patterns and management practices and can project future patterns based on management plans. We illustrate this approach with an example of how implementation of a U.S. Forest Service management plan at the Savannah River Site in South Carolina, U.S.A., might influence population trends of Bachman's Sparrow Aimophila aestivalis, a relatively rare and declining species in southeastern pine forests. In this case, a management plan, largely designed to improve conditions for an endangered species, Red-cockaded Woodpecker Picoides borealis, may have a negative impact, at least in the short term, on another species of management concern, Bachman's Sparrow. In a parallel processing version of the MAP models, a single landscape that would ordinarily be too large or detailed to be simulated on a single computer is subdivided into a number of smaller landscapes, and each landscape is simulated in parallel, either on a single multi-tasking machine or on a group of networked machines. With this approach we are attempting to determine just how large a landscape must be before the dynamics of a population within it are more or less independent of factors beyond the landscape boundaries.

Abiotic and biotic processes operate at multiple spatial and temporal scales to shape many ecological processes, including species distributions and demography. Current debate about the relative roles of niche-based and stochastic processes in shaping species distributions and community composition reflects, in part, the challenge of understanding how these processes interact across scales. Traditional statistical models that ignore autocorrelation and spatial hierarchies can result in misidentification of important ecological covariates. Here, we demonstrate the utility of a hierarchical modeling framework for testing hypotheses about the importance of abiotic factors at different spatial scales and local spatial autocorrelation for shaping species distributions and abundances. For the two orchid species studied, understory light availability and soil moisture helped to explain patterns of presence and abundance at a microsite scale (

By combining a spatially explicit, individual-based population simulation model with a geo- graphic information system, we have simulated the potential effects of a US. Forest Service managementplan on the population dynamics of Bachman's Sparrow (Aimophila aestivalis) at the Savannah River Site, a US. Department of Energy facility in South Carolina Although the Forest Service's management plan explicitly sets management goals for many species, most of the prescribed management strategy deals with the endan- geredRed-cockaded Woodpecker (Picoides borealis) because of legal requirements. We explored how a species (the sparrow) that is not the target of specific management strategies but that shares some habitat require- ments with the woodpecker, would fare under the management plan. We found that the major components of the proposed management plan may allow the sparrow population to reach and exceed the minimum management goal set for this species, but only after a substantial initial decline in sparrow numbers and a prolonged transition period. In the model, the sparrow population dynamics were most sensitive to demo- graphic variables such as adult and juvenile survivorship and to landscape variables such as the suitability of young clearcuts and mature pine stands. Using various assumptions about habitat suitability, we esti- mated that the 50-year probability of population extinction is at least 5% or may be much higher ifjuvenile survivorship is low. We believe, however, that modest changes in the managementplan mightgreatly increase the sparrow population and presumably decrease the probability of extinction. Our results suggest that

Isolation effects on species richness of woody plants were investigated in a system of islands that were created by the filling of the Clarks Hill Reservoir, Georgia. This reservoir was built between 1946–1954. Some islands were logged and cleared of woody plants prior to the filling of the reservoir and others were not logged. The presence of logged versus unlogged islands in the same system allowed us to test whether and how geographical isolation interacts with island history and species-specific dispersal properties in determining patterns of among-island variation in species number. Thirty-six years after the islands were created, logged islands had significantly fewer species of woody plants than unlogged ones. On logged islands, total number of woody species was negatively correlated with distance to the closest mainland (r=−0.95). On unlogged islands, variation in species number was very low (CV=4.9%) and was not correlated with distance to the mainland. These results indicate that the studied system as a whole has not yet reached equilibrium. However, the mean number of species on unlogged islands was very close to the intercept of the regression obtained for logged islands, suggesting that islands close to the mainland have already reached their equilibrium species richness. This conclusion is consistent with predictions of island biogeography theory. When species representing different dispersal properties were analyzed separately, statistically significant distance effects were obtained for bird-dispersed species (r=0.88) and for species with no adaptations to bird or wind dispersal (r=0.81). Wind-dispersed species did not show a decrease in species number with increasing isolation, but their relative frequency was positively and significantly correlated with distance to the mainland (r=0.94). Historical factors, as well as differences among species in dispersal properties, are important in explaining patterns of among-island variation in species number.

occurred in the past several tens of millions of years. Furthermore, it appears that we ourselves are the primary causal agents for this change. Yet we are in profound ignorance of the details of what is happening and what impact the changes might have on the quality of life for us and for future generations. Given this degree of scientific uncertainty, it is little wonder that we are unable to fully agree among ourselves about what to do, if anything. We all clearly have a stake in the outcome of the debate about how we approach questions of biological diversity. We all share some of the responsibility. However, the US Department of the Interior (DOI), as custodian of 22% of all US lands, has a special responsibility. Therefore, it is perhaps not surprising that the Secretary of the Interior, Bruce Babbitt, on assuming office, asked the question: How can science be better organized in the Department of the Interior? The result was the birth of the National Biological Survey (NBS) in November 1993.1

ECOLECON is a spatially-explicit, object-oriented computer simulation model that simulates animal population dynamics and economic yield from timber harvests based on forest landscape structure and timber management schemes. The model has been parameterized to simulate the population dynamics and extinction probability of Bachman's Sparrow (Aimophila aestivalis), a species of management concern in southeastern pine forests. Simulations with ECOLECON have shown that forest landscape structure and management options such as rotation lengths influence both population sizes of the sparrows and economic returns from timber harvests. Sparrow population size and economic income were often maximized by different management strategies. For example, land expectation value reached a maximum when a rotation length was 20 years; however, whenever harvest rotation length was shorter than 80 years, sparrow population size had a negative linear relationship with rotation lengths. As the amount of mature pine habitat increased, sparrow population size increased, but annual net income decreased. Fragmentation of landscapes with only a small amount of mature habitat caused lower population sizes, but fragmentation of landscapes with a large amount of mature habitat resulted in a larger population size. Differences in placement of the mature habitat within the landscapes resulted in large differences in population size. Larger stand sizes produced higher economic revenues, but the effect of stand size on population size was confounded by the amount of mature habitat. Simulation models such as ECOLECON provide a potentially powerful tool for balancing wildlife population needs and economic revenues through designing and managing forested landscapes.

Island biogeography theory attempts to explain and predict among-island variation in species richness. However, two islands with the same number of species may still differ from each other considerably in their species composition. In this study the authors test the hypothesis that among-island variation in species composition is predictable and can be related to the corresponding differences in distance to the mainland. They focus on woody plants inhabiting islands in the Clarks Hill Lake, a reservoir completed in 1954 on the Savannah River, between Georgia and South Carolina, US. Two groups of islands were sampled: islands that were logged prior to the filling of the reservoir and islands that were not logged. Each island was surveyed for the presence of all tree and shrub species, and its distance from the mainland was determined. In both groups of islands, the degree to which two islands are similar in their species composition was negatively and significantly correlated with distance to the mainland only on logged islands. The authors conclude that geographic isolation may affect species composition on islands, and that such an effect may occur even in the absence of a corresponding effect on species richness. 22 refs., 2 figs., 2 tabs.

The conventional ecological approach to predation provides a limited frame- work for understanding perceptual and tactical mechanisms of search and detection and their dynamical consequences. In contrast, models developed to guide naval search op- erations are "spatiotemporal dynamic interaction models," analogous to those developed in plant population ecology. Our application of these models to foraging sparrows indicates that perceptual and tactical constraints play a critical role in the allocation of search effort across habitat patches, in the choice of tactics within patches, and in the predation dynamics that emerge over time. Sparrows search where prey are most detectable rather than where they are most abundant, and they tune search tactics to perceptual operating conditions. The approach describes and predicts details of search and detection, cumulative harvest rates, and selectivities more accurately than the conventional search-efficiency approach.

*Department of Wildlife Ecology and Conservation, Newins-Ziegler 303, Box 110430, University of Florida, Gainesville, FL 32611 U.S.A., email conbio@gnv.ifas.ufl.edu tDepartment of Zoology, University of Washington, Seattle, WA 98195, U.S.A. t Center for Biodiversity Research, University of Nevada, Reno, NV 98557, U.S.A. ? Department of Fishery and Wildlife Biology, Colorado State University, Fort Collins, CO 80523, U.S.A. **Institute of Ecology, University of Georgia, Athens, GA 30602, U.S.A. ttBoard of Environmental Studies, University of California, Santa Cruz, CA 95064, U.S.A. t Department of Botany, University of Wisconsin, Madison, WI 53706, U.S.A.

Among the greatest challenges facing society is the need to more fully understand the complex ecological processes that maintain our human life support system and to integrate knowledge about these processes into management and policy decisions. As the report of the Ecological Society of America Committee on the Scientific Basis of Ecosystem Management indicates, the incorporation of good science into management decisions at a landscape to regional level is an essential component of ecosystem management. There is much we do not know about ecosystem functions, primarily because ecological interactions are very complex, and we have only recently begun to ask questions about multiple, interacting components. As ecologists, perhaps imbued with physics envy, we often seek neat, clean answers to specific hypotheses and may be frustrated by the more variable, less predictable results of research on ecosystems. Both of us have worked extensively in the relatively "simple" ecosystems of the Sonoran Desert. The reputation of deserts as hostile, dangerous habitats is unwarranted and obfuscates the real advantage of working in a habitat where the parts are relatively discrete and easy to identify, count, weigh, measure, and manipulate. We both investigated the complex interactions among several desert-adapted taxa (ants, birds, mammals) and the seeds they consumed. The diets and foraging behavior of these granivores were complicated, but, with persistence, could be investigated, modeled, and even predicted. However, our realization that ants not only consume seeds but also disperse them and that rodents and birds not only compete with ants for seeds, but also prey on the insects, pointed out to us that these systems are much more complex than simple consumer/ resource relationships. The asymmetries of mutualism, competition, and concurrent predation muddied the waters that had once appeared clear to us. Ecologists everywhere now encounter similar complications such as third-order interactions, cascading trophic effects, and nonlinear relationships. In addition to being generally complex, ecosystems are often in nonequilibrium states, such that no particular endpoint may be obvious or predictable. Consequently, resources managers seeking a stable outcome for their units may encounter difficulties and frustrations with attempting to apply specific management regimes. This circumstance makes understanding the processes involved a key factor in attempting to comprehend and manage systems. Ecological interactions such as those mentioned above are further complicated by the need to understand relationships on spatial scales that extend beyond the boundaries of individual study plots and temporal scales that extend beyond the life-span of a typical grant or the tenure of a graduate student, and in some cases, beyond the career of individual scientists. Furthermore, we are subject to what sociologists call the "last pioneer syndrome" -each generation accepts the world as it is when they arrive, including the built environment, but is intolerant of any substantial changes during its life-span. Hence, dissatisfaction or disgust with environmental degradation tend not to be cumulative between generations such that long term changes in environmental quality and functioning may go unnoticed or unappreciated. These difficulties notwithstanding, it is clear that we must move forward with attempts to understand the basic ecological processes that drive our biosphere. Ecosystem studies have been conducted for decades, but the momentum for this approach, especially as it pertains to resource management, has recently been building. The burgeoning of talks, meetings, committees, and reports on the topic probably indicates a growing awareness of the need for embedding many ecological questions in the appropriate ecosystem context. The true catalyst, however, may be the recognition that no one research unit (bureau, department, university, etc.) has the resources to accomplish the goals of ecosystem research and management, and that cooperation, collaboration, and efficiencies are in order. The National Biological Service (NBS) was spawned from a realization that biological research within the Department of Interior would benefit from integration. Many studies being conducted by DOI biologists overlapped geographically or topically, but only a few fit together as parts of broader questions. Furthermore, studies were often restricted to specific geographic or political boundaries, precluding analyses at national, regional, or even landscape scales. With its mandate to integrate the previously isolated research components of the Department of Interior and to address regional issues in a holistic fashion, the NBS I Manuscript received 16 November 1995. 2 For reprints of this Forum, see footnote 1, page 692.

To understand the impact of our science on the practice of conservation, ecologists and other environmental scientists need to realize that the information we provide is ultimately used, or ignored, by people with a variety of backgrounds and perspectives. I am pleased that this volume, and the conference from which it was derived, incorporates the views and opinions not just of scientists, but also of conservation practitioners. Conservation practitioners include both people who make regulations and laws and practicing land and natural resource managers in the private and in the public arenas.

The abundance and distribution of natural populations can be strongly influenced by the types and arrangement of habitat patches within a landscape. The impact of landscape changes on population dynamics is difficult to study using conventional population models and field techniques. Spatially explicit simulation models provide a powerful method for modelling landscape and population changes at large spatial scales and may prove useful as a management tool for mobile animal populations. As an example of this approach, we present a model designed to elucidate the effects of landscape—level variation in habitat dispersion on the size and extinction probability of avian populations in a region managed for timber production. In the model, habitat suitability and availability within the landscape change annually as a function of timber harvest and management strategies. The model incorporates life history characteristics of Bachman's Sparrow (Aimophila aestivalis), a species of management concern in the southeastern United States, and the landscape characteristics of the Savannah River Site, South Carolina, an area managed for timber production where the sparrow is relatively common. Life history characteristics used in the model include dispersal, survivorship, and reproductive success information reported for Bachman's Sparrow at this site or elsewhere in its range. Results of the simulations suggest that variation in demographic variables affects population size more than variation in dispersal ability. Changes in adult and juvenile survivorship have especially large impacts on the probability of population extinction. The presence of habitat types that serve as permanent sources of dispersers increases the total population size in the landscape, and lowers the probability of extinction. Results of models such as BACHMAP can suggest modifications to current management plans that would increase the probability of population persistence for species of special concern in managed landscapes.

A report by Dobson et al . ( p. 550 ) in this week's issue of Science brings together data from many sources on the distribution of endemic plants and animals in the United States and identifies three “hot spots” that contain a particularly high number of endangered species. Hawaii, California, and Florida contain concentrations of endangered organisms. In their Perspective, Pulliam and Interior Secretary Babbitt describe how these data can be profitably used in improving the fate of endangered species and making policy decisions.

The Distinguished Service Citation recognizes long and distinguished service to the ESA, to the larger scientific community, and to the larger purpose of ecology in the public welfare. The winner of the 2002 Distinguished Service Award is H. Ronald Pulliam, Regents Professor of Ecology at the University of Georgia. Professor Pulliam is unique in fulfilling completely all three criteria for this award: he has contributed long, distinguished service to our Society, to the larger scientific community, and has made highly significant contributions toward the application of ecology to the public welfare. This is in addition to being a first-class, internationally known scientist whose ideas have contributed substantively to current research in behavioral ecology. Ron Pulliam has served as ESA’s Vice President and President. He helped to initiate the Issues in Ecology series that has encouraged ecologists to relate their research to public policy issues. He played a key role in developing the Sustainable Biosphere Initiative, which greatly raised the profile of ESA, and the field of ecology, in global environmental issues. Both of these efforts continue as major ESA activities. In 1994, Ron bravely stepped outside the walls of academia, taking a leave of absence from the University of Georgia to serve as the Director of the National Biological Survey. He subsequently served as Science Advisor to the Secretary of the Interior. While in Washington, he made major institutional changes that strengthened the role of ecological science within the Interior Department, and he continues to serve as an advisor on national environmental policy. He also has served on a wide range of boards for major environmental councils and organizations that have played an important role in bringing good ecological science into the arena of public policy. He currently is on the Board of Directors of the Committee for the National Institute for the Environment; the National Research Council’s Commission on the Environment, Geosciences, and Resources; the Board of Directors of the Defenders of Wildlife; and the Science Advisory Board for the David and Lucille Packard Foundation. For his service to the Society, to the scientific community, and to the purpose of ecology in the public welfare, ESA is delighted to award the Distinguished Service Award to Ron Pulliam.

Data on the seed profitabilities (mass of seed ingested per unit time) of captive emberizine sparrows and cardueline finches were used to interpret the underlying factors promoting differences in their ecologies. Sparrows consume seeds that are approx- imately an order of magnitude smaller in size that those consumed by finches of similar body mass. Because sparrows consume such small seeds and because finches are much more efficient at handling large seeds, sparrows need to encounter seeds at rates that are one to two orders of magnitude greater than that required by finches. As a result, sparrows have to spend much more time foraging than do finches, and sparrows are not able to go for as long periods of time searching for new food patches as are finches. Consequently, sparrows are relatively sedentary and restricted to areas of dense seed concentrations, whereas finches are extremely vagile and move over very large geographic areas in search of new patches of food. Furthermore, resource partitioning is more pronounced among finches. Small and large finch species eat very different seed sizes, whereas the diets of small and large sparrows overlap greatly. in the Fringillidae. In this paper, we discuss some dra- matic differences in the foraging ecology of the two groups that occur despite their superficially similar ap- pearances.

Animal and plant populations often occupy a variety of local areas and may experience different local birth and death rates in different areas. When this occurs, reproductive surpluses from productive source habitats may maintain populations in sink habitats, where local reproductive success fails to keep pace with local mortality. For animals with active habitat selection, an equilibrium with both source and sink habitats occupied can be both ecologically and evolutionarily stable. If the surplus population of the source is large and the per capita deficit in the sink is small, only a small fraction of the total population will occur in areas where local reproduction is sufficient to compensate for local mortality. In this sense, the realized niche may be larger than the fundamental niche. Consequently, the particular species assemblage occupying any local study site may consist of a mixture of source and sink populations and may be as much or more influenced by the type and proximity of other habitats a...

The cultural coefficient of similarity, or probability that two individuals learn the same idea from a common ancestor, is offered as an explanation for patterns of helping behavior in human societies. A cultural-transmission model predicts that when maternal influence in offspring learning is pre-dominant, matrilineality will evolve in a culture. Other predictions about the form of matrilineal and patrilineal societies are made from the model and contrasted to a sociobiological explanation of matrilineality.

A long-term study of sparrows in an arid oak woodland in southeastern Arizona demonstrated that local population density of sparrows is independent of local seed abundance during years of moderate to high seed production. Experimental manip- ulation of the abundance and size distribution of seeds during 2 yr of moderate seed production had no discernible influence on the local abundance or diversity of sparrows. These experimental results support the hypothesis, based on previous nonexperimental observations, that sparrow populations in this habitat are locally food limited only during infrequent years of very low seed production.

At any given moment in time a plant is partitioning total growth mass into its various component parts such as leaves, roots, reproductive material, etc. The view is taken that the plant has evolved a life history strategy to control this partitioning process. This paper illustrates the utility of optimal control theory for use in determining life history strategies which maximize fitness for a given asexual plant model. The optimal control methods are first used on a model previously analyzed by Professor Dan Cohen, who used a different method. His results of a change from 100% vegetable growth to 100% reproductive growth at a fixed switching time is again obtained. This 100% switching result is shown to be more generally applicable by using a qualitatively described model. However the switching time in general is shown to be a function of both leaf mass and time remaining to the end of the growing season. The allocation to toxin production is also considered. It is shown that under this model an inequality between system parameters must be satisfied before the plant should allocate growth to toxin production. Although the particular model explored here may rarely be realistic in nature, these same methods of optimal control theory can be applied in a similar fashion to many other proposed models of plant resource allocation.

The predictions of community matrix theory do not agree with the observed patterns of coexistence of grassland and woodland sparrows. Predictions based on the random co-occurrence of species match the observed patterns about as well as do the predictions of community theory. Predictions of both the community theory model and the random co-occurrence model are improved substantially by the addition of thresholds that account for the minimum food requirements of spar- rows of different sizes. The observed patterns of species coexistence appear consistent with a model based on resource abundance and aggressive interference; however, they are also consistent with coexistence based on interspecific partitioning of seeds by size.

A complete ecosystem analysis may be possible from the point of view of optimal control theory. Such an analysis has three parts: (1) Determination of model structure (2) Determination of coefficients for a given model (3) Determination of optimal management programs for the model obtained by (1) and (2). The methods of optimal control theory are suitable for examining these three parts separately. The essential ingredients for each part is an optimization concept. Only the second and third parts are examined in detail here. For concreteness, a specific model structure for a prey-predator system is used. It is then shown that certain coefficients of this model are determined directly, given that the predator feeds in such a way as to maximize his caloric intake. By adding man's external controls to the model, the system can then be managed in a fashion to minimize some cost criterion. To illustrate this latter point, the methods of optimal control theory are used to determine a manage ment program for controlling water quality in a natural lake at minimum cost. Man's control is re presented by the application of an algacide on the phytoplankton-zooplankton (prey-predator) system in the lake. The introduction of temperature dependence as a driving force in a simple dynamical model appears to be adequate for the determination of the optimal control program.

Differences in microhabitat utilization by sparrows wintering in southeastern Arizona, USA may be sufficient to explain their coexistence. The species either forage in different mac- rohabitats or in the same habitat at different distances from tree or shrub cover. Seed size partitioning within habitats is sufficient to explain coexistence only in one case where the seed size distribution is bimodal. The species that forage in plains grassland habitat differ by foraging in concentric rings about tree or shrub cover. The behavior of each of these species appears to enhance predator avoidance and these behaviors change in a regular pattern with distance to cover both within and between species. Species foraging close to cover are social and tend to be conspicuous both in behavior and morphol- ogy. Two different strategies adapt species to avoiding predators at great distances to cover. In dense grassland, with increasing distance to shrub or tree cover, species in the genus Ammodramus are increasingly solitary and cryptic. In sparse grassland, Chestnut-collared Longspurs are social and cryptic on the ground but conspicuous in flight.

Patterns of conflict and cooperation both within and between societies may be related to the degree of cultural similarity within and between the same societies. A simple model of social learning is used to predict patterns of conflict and cooperation in hypothetical societies that differ in the roles of relatives and nonrelatives in the enculturation of children. The model is illustrated by comparing its predictions to known differences in the patterns of conflict between males inpatrilocal and matrilocal societies.

When food is abundant, sparrows are found in great variety of habitats and appear to specialize on particularly profitable types of seeds. However, during periods of food scarcity, each sparrow species occupies a very narrow range of habitats but consumes a great variety of seeds within each occupied habitat. As a result, average dietary overlap may underestimate the potential for competition for food within habitats during periods of food shortage whereas average habitat overlap overestimates the potential for competition since each species occupies a different habitat during periods of food shortage.

There is now a considerable literature on the theory of optimal diets. To my knowledge, there has been no general consideration of the problem of caloric maximization given dietary constraints as to the minimum permissible quantities of essential nutrients. It is obvious that the set of prey choices which maximizes caloric intake may or may not constitute a balanced diet for the predator. Thus, it is important to consider the problem of diet optimization with nutrient constraints.

We observed mixed groups of dark-eyed juncos (Junco hyemalis) and grey-headed juncos (Junco caniceps) at baited sites in northern Arizona during the non-breeding season. In interspecific and inter-racial conflicts, J. caniceps dorsalis was dominant to J. caniceps caniceps and to two races of dark-eyed juncos. Junco caniceps dorsalis also fed significantly faster than any of the other juncos. For both species, feeding rates were approximately the same in large and small mixed-species groups, though in larger groups, individual grey-headed juncos won conflicts at a higher rate and individual dark-eyed juncos lost conflicts at a higher rate. Also, dark-eyed juncos fed at a significantly lower rate in groups comprised mostly of grey-headed juncos than in groups of similar size but composed mostly of conspecifics. Residency times and recapture probabilities were similar for the two species, suggesting little difference in over-winter survival.

Flocking birds frequently look up or “scan” while they are feeding on the ground. High scanning rates increase the probability that the birds in a flock will see an approaching predator in time to avoid predation; however, high scanning rates also decrease the feeding rates of the scanning individuals. Since the scanning rate that maximizes the survival probability of one individual depends on how frequently other birds in the same flock are scanning, the optimal scanning behavior must be modeled as a game. We develop a realistic model of scanning behavior and use it to find two game theoretical solutions—the “co-operative” or Pareto optimum and the “selfish” or Nash optimum. The observed scanning rates do not differ significantly from the co-operative optimal scanning rate. We argue that in a game where players meet again and again such apparent co-operation may be an evolutionarily stable strategy.

The feeding ecology of the yellow—faced grassquit (Tiaris olivacea) was studied on a large island (Jamaica) and on the mainland (Costa Rica). Despite an apparent reduction in competition on Jamaica, yellow—faced grassquits are less abundant in Jamaica than in Costa Rica and are found in approximately the same number of habitats on the island and on the mainland. There seem to be no changes in the magnitude, variance, and sexual dimorphism of hill size of island grassquits which would lead to their eating more kinds of food than the mainland grassquits. However, in a series of experiments on seed—size preference, it was noted that the grassquits from Jamaica were significantly less stereotyped in their choice of seed size than were the Costa Rican grassquits. It is suggested that an increase in the variance of bill size of island grassquits occurs only in large populations and concomitant with an increase in the number of habitats occupied by the population. See full-text article at JSTOR

Using techniques of stochastic theory, I develop a new aproach to predicting optimal diets. The models developed are for a mobile predator feeding on stationary prey; however, the models can easily be extended to include mobile prey. Parameters used in the models are caloric content, time to pursue and density of each prey type, and the speed of the predator. Both clumped and random prey distribution are considered. The models predict the optimal diet of a predator faced with a variety of potential prey types. The optimal diet is predicted as the set of successive prey choices which maximizes the rate of caloric intake or, alternatively, minimizes the time required to find a food ration. Also predicted are the criteria for specialization and switching from a specialist diet to a generalist diet. The criteria for specialization and for switching are independent of the density of the alternate prey type. Also, a predator feeding so as to maximize the rate of caloric intake should take a prey on every encoun...

A study of the coexistence of sparrows in grassland and woodland habitats of the Research Ranch in southeastern Arizona supports the predictability of current community theory. For each of the habitats studied, the production of seeds and the abundance of seed-eating, winter-resident sparrows were measured. The theory correctly predicts the number of species supported in each of the habitats. In both cases for which the prediction is that only one species could be supported, the theory correctly predicts which species should be present.

Behavior that influences animal dispersion affects both the survival and reproduction of individuals and the dynamics of entire populations. In this chapter, I consider, from the perspective of individual selection, the evolution of behavior that directly influences dispersion. I present an evolutionarily stable strategy for nest site selection and discuss how nest site selection influences population dynamics and geographic range. I also discuss the evolution of resource assessment and consider its role in overwinter survival. I show that an ability to assess relative resource availability in relationship to population density may benefit individuals, though such ability, when widespread, may destabilize population dynamics, leading to population cycles, or even population extinction. I also present an idealized model of how social dominance in concert with resource assessment might stabilize population dynamics and maximize overwinter survival probability. Finally, I reconsider Wynne Edwards’s contention that social conventions play an important role in the regulation of some animal species. I argue that epideictic displays and social conventions may benefit all participants and therefore may be explained by individual selection.