Patterns of conflict and cooperation both within and between societies may be related to the degr... more 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 in patrilocal and matrilocal societies.
ECOLECON is a spatially-explicit, object-oriented computer simulation model that simulates animal... more 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 Rachman's Sparrow (Aimophila aestiualis), 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 fmgmentation 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 sta.nd 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.
Isolation effects on species richness of woody plants were investigated in a system of islands th... more 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. '~ 4o O 35
1. Mismatches between species distributions and habitat suitability are predicted by niche theory... more 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.
before the completion of the book and did not have an opportunity to see the end product. This bo... more before the completion of the book and did not have an opportunity to see the end product. This book is much needed to educate biologists about the fascinating biology and diversity of cockroaches. It is perhaps a little too technical for the general public, but anyone with a background in science is likely to comprehend most of the information here. My one criticism is that a number of recent and relevant references have been left out. Beyond that I think this book should be read by anyone interested in cockroach diversity and evolution. I especially recommend this book to graduate students so they can perhaps realize the myriad opportunities and unanswered questions that exist in the study of cockroach biology and evolution.
Models of Mobile Animal Populations (MAP models) simulate long-term land use changes, population ... more Models of Mobile Animal Populations (MAP models) simulate long-term land use changes, population trends and patterns of biological diversity on landscapcs of lo3-lo5 ha. MAP
Abiotic and biotic processes operate at multiple spatial and temporal scales to shape many ecolog... more 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 micro site scale «4 m 2), while soil organic content was important at a population scale «400 m 2). The inclusion of spatial autocorrelation is shown to alter the magnitude and certainty of estimated relationships between abundance and abiotic variables, and we suggest that such analysis be used more often to explore the relationships between species life histories and distributions. The hierarchical modeling framework is shown to have great potential for elucidating ecological relationships involving abiotic and biotic processes simultaneously at multiple scales.
occurred in the past several tens of millions of years. Furthermore, it appears that we ourselves... more 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
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Papers by H. Pulliam