Thomas W. Schoener
Other affiliations: University of Washington, Washington University in St. Louis, University of California, Berkeley ...read more
Bio: Thomas W. Schoener is an academic researcher from University of California, Davis. The author has contributed to research in topic(s): Anolis & Population. The author has an hindex of 69, co-authored 143 publication(s) receiving 29768 citation(s). Previous affiliations of Thomas W. Schoener include University of Washington & Washington University in St. Louis.
Topics: Anolis, Population, Predation, Interspecific competition, Spider
Papers published on a yearly basis
TL;DR: To conclude with a list of questions appropriate for studies of resource partitioning, questions this article has related to the theory in a preliminary way.
Abstract: To understand resource partitioning, essentially a community phenomenon, we require a holistic theory that draws upon models at the individual and population level. Yet some investigators are still content mainly to document differences between species, a procedure of only limited interest. Therefore, it may be useful to conclude with a list of questions appropriate for studies of resource partitioning, questions this article has related to the theory in a preliminary way. 1) What is the mechanism of competition? What is the relative importance of predation? Are differences likely to be caused by pressures toward reproductive isolation? 2) Are niches (utilizations) regularly spaced along a single dimension? 3) How many dimensions are important, and is there a tendency for more dimensions to be added as species number increases? 4) Is dimensional separation complementary? 5) Which dimensions are utilized, how do they rank in importance, and why? How do particular dimensions change in rank as species nuimber increases? 6) What is the relation of dimensional separation to difference in phenotypic indicators? To what extent does the functional relation of phenotype to resource characteristics constrain partitioning? 7) What is the distance between mean position of niches, what is the niche standard deviation, and what is the ratio of the two? What is the niche shape?
TL;DR: Throughout, emphasis will be placed on strategic aspects of feeding rather than on what Holling (75) has called "tactics," and possible answers to the first problem may be given to the second problem.
Abstract: Natural history is replete with observations on feeding, yet only recently have investigators begun to treat feeding as a device whose performance as measured in net energy yield/feeding time or some other units assumed commensurate with fitness-may be maximized by natural selection (44, 1 13, 135, 156, 181) . The primary task of a theory of feeding strategies is to specify for a given animal that complex of behavior and morphology best suited to gather food energy in a particular environment. The task is one, therefore, of optimization, and like all optimization problems, it may be tri sected: 1. Choosing a currency: What is to be maximized or minimized? 2. Choosing the appropriate cost-benefit functions: What is the mathematical form of the set of expressions with the currency as the dependent variable? 3. Solving for the optimum: What computational technique best finds ex trema of the cost-benefit function? In this review, most of the following section is devoted to possible answers to the first problem. Then four key aspects of feeding strategies will be considered: (a) the optimal diet, (b) the optimal foraging space, (c) the optimal foraging period, and (d) the optimal foraging-group size. For each, possible cost-benefit formulations will be discussed and compared, and predictions derived from these will be matched with data from the literature on feeding. Because the third problem is an aspect of applied mathematics, it will be mostly ignored. Throughout, emphasis will be placed on strategic aspects of feeding rather than on what Holling (75) has called "tactics."
University of California, Santa Cruz1, Duke University2, University of California, Berkeley3, University of Montana4, University of Cape Town5, University of Wisconsin-Madison6, University of Washington7, University of Florida8, Scripps Institution of Oceanography9, University of Missouri–St. Louis10, Finnmark University College11, University of Turku12, Stony Brook University13, Oregon State University14, Wageningen University and Research Centre15, University of California, Davis16, University of British Columbia17, University of Oulu18, Swedish University of Agricultural Sciences19
TL;DR: This empirical work supports long-standing theory about the role of top-down forcing in ecosystems but also highlights the unanticipated impacts of trophic cascades on processes as diverse as the dynamics of disease, wildfire, carbon sequestration, invasive species, and biogeochemical cycles.
Abstract: Until recently, large apex consumers were ubiquitous across the globe and had been for millions of years. The loss of these animals may be humankind's most pervasive influence on nature. Although such losses are widely viewed as an ethical and aesthetic problem, recent research reveals extensive cascading effects of their disappearance in marine, terrestrial, and freshwater ecosystems worldwide. This empirical work supports long-standing theory about the role of top-down forcing in ecosystems but also highlights the unanticipated impacts of trophic cascades on processes as diverse as the dynamics of disease, wildfire, carbon sequestration, invasive species, and biogeochemical cycles. These findings emphasize the urgent need for interdisciplinary research to forecast the effects of trophic downgrading on process, function, and resilience in global ecosystems.
01 Aug 1983-The American Naturalist
TL;DR: Competition was found in 90% of the studies and 76% of their species, indicating its pervasive importance in ecological systems, and the Hairston-Slobodkin-Smith hypothesis concerning variation in the importance of competition between trophic levels was strongly supported.
Abstract: The study of interspecific competition has long been one of ecology's most fashionable pursuits. Stimulated in part by a simple theory (Lotka 1932; Volterra 1926; Gause 1934; Hutchinson 1959; MacArthur and Levins 1967), ecologists gathered numerous data on the apparent ways species competitively coexist or exclude one another (reviews in Schoener 1974b, 1983). As is typical in science, most of the early data were observational, and the few experimental studies were mostly performed in the laboratory rather than in the field. Though never lacking its doubters, the belief in the natural importance of interspecific competition is now being severely questioned (review in Schoener 1982). Many of the putatively supportive observations have been challenged as being statistically indistinguishable from random contrivance. Most such attacks have been rebutted, but not without some modification of original conclusions (e.g., papers in Strong et al. 1983). New observations have been gathered for certain systems, suggesting a lack of competitively caused patterns and catalyzing the variable environment view of Wiens (1977) in which competition is seen as a temporally sporadic, often impotent, interaction. Other critics have charged that the lack of experimental field evidence for competition would preclude its acceptance regardless of the quality of observational data. Indeed, results of some of the earlier field experiments are in part responsible for competition's presently beleaguered state. Connell (1975), after reviewing the field experiments known to him through 1973, concluded that predation, rather than competition, appears to be the predominant ecological interaction and should be given "conceptual priority." Shortly afterward, Schroder and Rosenzweig (1975) showed experimentally that two species of desert rodents overlapping substantially in habitat did not appear to affect one another's abundances. This result was interpreted as contradicting a crucial assumption of competition theory, almost its linchpin: the greater the resource overlap between species, the greater the competition coefficient, a measure of the intensity of interspecific competition (relative to intraspecific competition; MacArthur and Levins 1967; review in Roughgarden 1979).
TL;DR: It is suggested that such small, non-dimorphic species are best suited for insinuation into complex faunas, whereas larger, dimorphic forms are best for the colonization of empty areas.
Abstract: The tiny island of South Bimini contains 4 species of lizards of the genus Anolis, a number surpassed only on the 4 largest islands of the Greater Antilles and on 2 very large and nearby satellite islands. These species are syntopic with respect to a two-dimensional area of the ground but divide the habitat according to perch height and perch diameter: sagrei is partly terrestrial, but occurs more often on small and large low perches; distichus prefers the trunks and large branches of medium to large trees; angusticeps inhabits small twigs, especially at great heights; and carolinensis is found mostly on leaves or on the adjacent twigs and branches. The size classes of the species are staggered in such a way that the inter- specific classes which overlap most in habitat overlap least in prey size. Similarities in prey size and prey taxa for classes of the same species are somewhat greater than those expected on the basis of habitat and morphology alone. The distribution of the species among the vegetation communities of Bimini can be explained on the basis of perch height and diameter preference. Within the same species, the larger lizards usually eat larger food, fewer items, and in sagrei more fruit; and they have a greater average range of food size per digestive tract. One species (distichus) is extremely myrmecophagous: about 75-90% of its food items are ants. In 3 of the 4 species, subadult males take more food and average smaller prey than females of the same head length. That species (distichus) which takes the smallest food item; and whose classes overlap the most in habitat preference with those of other species is least dimorphic in size between the sexes. It is suggested that such small, non- dimorphic species are best suited for insinuation into complex faunas, whereas larger, dimorphic forms are best for the colonization of empty areas. The usefulness of various measures of "overlap" and "specialization" is evaluated for this lizard association.
28 Jul 2005
TL;DR: Preface to the Princeton Landmarks in Biology Edition vii Preface xi Symbols used xiii 1.
Abstract: Preface to the Princeton Landmarks in Biology Edition vii Preface xi Symbols Used xiii 1. The Importance of Islands 3 2. Area and Number of Speicies 8 3. Further Explanations of the Area-Diversity Pattern 19 4. The Strategy of Colonization 68 5. Invasibility and the Variable Niche 94 6. Stepping Stones and Biotic Exchange 123 7. Evolutionary Changes Following Colonization 145 8. Prospect 181 Glossary 185 References 193 Index 201
TL;DR: The commonly observed high diversity of trees in tropical rain forests and corals on tropical reefs is a nonequilibrium state which, if not disturbed further, will progress toward a low-diversity equilibrium community as mentioned in this paper.
Abstract: The commonly observed high diversity of trees in tropical rain forests and corals on tropical reefs is a nonequilibrium state which, if not disturbed further, will progress toward a low-diversity equilibrium community. This may not happen if gradual changes in climate favor different species. If equilibrium is reached, a lesser degree of diversity may be sustained by niche diversification or by a compensatory mortality that favors inferior competitors. However, tropical forests and reefs are subject to severe disturbances often enough that equilibrium may never be attained.
01 Apr 1990-Canadian Journal of Zoology
TL;DR: This work has shown that predation is a major selective force in the evolution of several morphological and behavioral characteristics of animals and the importance of predation during evolutionary time has been underestimated.
Abstract: Predation has long been implicated as a major selective force in the evolution of several morphological and behavioral characteristics of animals. The importance of predation during evolutionary ti...
TL;DR: The second volume in a series on terrestrial and marine comparisons focusing on the temporal complement of the earlier spatial analysis of patchiness and pattern was published by Levin et al..
Abstract: This book is the second of two volumes in a series on terrestrial and marine comparisons, focusing on the temporal complement of the earlier spatial analysis of patchiness and pattern (Levin et al. 1993). The issue of the relationships among pattern, scale, and patchiness has been framed forcefully in John Steele’s writings of two decades (e.g., Steele 1978). There is no pattern without an observational frame. In the words of Nietzsche, “There are no facts… only interpretations.”