Abiotic Controls of Trophic Cascades in a Simple Grassland Food Chain

I experimentally examined the relative importance of a top predator in a three trophic level food chain in which the abiotic conditions were varied. Food chains consisting of plants, grasshoppers and wolf spiders were established in field cages placed over natural prairie. Grasshopper resource intake was manipulated by altering the abiotic environment (i.e., shading during peak grasshopper feeding times to reduce temperature and radiation), and thus the time they had available for feeding. Grasshoppers in control (unshaded) food chains compensated for spider predation by increased per capita survival and food consumption by those remaining. In this scenario, plant biomass was unaffected by the presence of spiders (i.e., no trophic cascade). However, when the grasshoppers were shaded for the morning hours, reducing their time available for feeding, spiders reduced grasshopper density, and the abundance of plants increased relative to when spiders were absent (i.e., a trophic cascade). This experiment showed that by simply altering the abiotic environment such that grasshopper foraging ability changed, profound differences in the impacts of top predators resulted.

[1]  J. M. Smith.  Models in Ecology , 1975 .

[2]  M. Rosenzweig.  Paradox of Enrichment: Destabilization of Exploitation Ecosystems in Ecological Time , 1971, Science.

[3]  M. Power,et al.  Effects of Fish in River Food Webs , 1990, Science.

[4]  Robert M. May,et al.  Perspectives in Ecological Theory , 1989 .

[5]  G. Polis,et al.  Food webs: integration of patterns and dynamics , 1997 .

[6]  Jonathan M Chase.  Varying Resource Abundances and Competitive Dynamics , 1996, The American Naturalist.

[7]  M. Rosenzweig.  EVOLUTION OF THE PREDATOR ISOCLINE , 1973, Evolution; international journal of organic evolution.

[8]  G. Mittelbach,et al.  Trophic Relations and Ontogenetic Niche Shifts in Aquatic Ecosystems , 1988 .

[9]  Nelson G. Hairston,et al.  Cause-Effect Relationships in Energy Flow, Trophic Structure, and Interspecific Interactions , 1993, The American Naturalist.

[10]  O. Schmitz,et al.  Resource edibility and trophic exploitation in an old-field food web. , 1994, Proceedings of the National Academy of Sciences of the United States of America.

[11]  R. L. Knight,et al.  EFFECTS OF AVIAN PREDATION ON GRASSHOPPER POPULATIONS IN NORTH DAKOTA GRASSLANDS , 1991 .

[12]  L. Slobodkin,et al.  Community Structure, Population Control, and Competition , 1960, The American Naturalist.

[13]  G. Belovsky,et al.  The role of vertebrate and invertebrate predators in a grasshopper community , 1993 .

[14]  Jonathan M. Chase,et al.  Experimental Evidence for the Included Niche , 1994, The American Naturalist.

[15]  P. L. Errington.  Factors Limiting Higher Vertebrate Populations. , 1956, Science.

[16]  Peter W. Price,et al.  Population dynamics : new approaches and synthesis , 1996 .

[17]  D. Doak,et al.  The Keystone-Species Concept in Ecology and ConservationManagement and policy must explicitly consider the complexity of interactions in natural systems , 1993 .

[18]  J. Wootton,et al.  The Nature and Consequences of Indirect Effects in Ecological Communities , 1994 .

[19]  T. White,et al.  The Inadequate Environment: Nitrogen and the Abundance of Animals , 1993 .

[20]  D. L. Angelis,et al.  STABILITY AND CONNECTANCE IN FOOD WEB MODELS , 1975 .

[21]  John Maynard Smith.  Models in ecology , 1974 .

[22]  Peter A. Abrams,et al.  The Fallacies of "Ratio‐Dependent" Predation , 1994 .

[23]  J. H. Bock,et al.  EFFECTS OF BIRD PREDATION ON GRASSHOPPER DENSITIES IN AN ARIZONA GRASSLAND , 1992 .

[24]  M. Hunter,et al.  Playing Chutes and Ladders: Heterogeneity and the Relative Roles of Bottom‐Up and Top‐Down Forces in Natural Communities , 1992, Ecology.

[25]  M. Rosenzweig.  Aspects of Biological Exploitation , 1977, The Quarterly Review of Biology.

[26]  L. Oksanen,et al.  Exploitation Ecosystems in Gradients of Primary Productivity , 1981, The American Naturalist.

[27]  M. Power,et al.  TOP-DOWN AND BOTTOM-UP FORCES IN FOOD WEBS: DO PLANTS HAVE PRIMACY? , 1992 .

[28]  Mathew A. Leibold,et al.  A Graphical Model of Keystone Predators in Food Webs: Trophic Regulation of Abundance, Incidence, and Diversity Patterns in Communities , 1996, The American Naturalist.

[29]  O. Schmitz.  Exploitation in model food chains with mechanistic consumer-resource dynamics , 1992 .

[30]  L. Oksanen.  Ecosystem Organization: Mutualism and Cybernetics or Plain Darwinian Struggle for Existence? , 1988, The American Naturalist.

[31]  S. Fretwell.  Food chain dynamics: the central theory of ecology? , 1987 .

[32]  G. Belovsky.  Generalist Herbivore Foraging and Its Role in Competitive Interactions , 1986 .

[33]  John R. Post,et al.  BOTTOM-UP AND TOP-DOWN IMPACTS ON FRESHWATER PELAGIC COMMUNITY STRUCTURE' , 1989 .

[34]  R. Paine,et al.  Food-web analysis through field measurement of per capita interaction strength , 1992, Nature.

[35]  John R. Post,et al.  Trophic Relationships in Freshwater Pelagic Ecosystems , 1986 .

[36]  L. Hurd,et al.  Arthropod Community Responses to Manipulation of a Bitrophic Predator Guild , 1990 .

[37]  Jonathan M. Chase.  Differential competitive interactions and the included niche : an experimental analysis with grasshoppers , 1996 .

[38]  G. Belovsky,et al.  SUSCEPTIBILITY TO PREDATION FOR DIFFERENT GRASSHOPPERS: AN EXPERIMENTAL STUDY' , 1990 .

[39]  Thomas W. Schoener,et al.  Food Webs From the Small to the Large: The Robert H. MacArthur Award Lecture , 1989 .

[40]  B. Menge,et al.  Community Regulation: Under What Conditions Are Bottom‐Up Factors Important on Rocky Shores? , 1992 .

[41]  A. Joern.  Variable impact of avian predation on grasshopper assemblies in sandhills grassland , 1992 .

[42]  W. Fagan,et al.  Direct and Indirect Effects of Generalist Predators on a Terrestrial Arthropod Community , 1991 .

[43]  R. Arditi,et al.  Coupling in predator-prey dynamics: Ratio-Dependence , 1989 .

[44]  Roger Arditi,et al.  Ratio-Dependent Predation: An Abstraction That Works , 1995 .

[45]  J. Moen,et al.  The Time-Scale Problem in Exploiter-Victim Models: Does the Solution Lie in Ratio-Dependent Exploitation? , 1992, The American Naturalist.

[46]  R. A. Terry,et al.  THE DIGESTIBILITY OF THE LEAVES AND STEMS OF PERENNIAL RYEGRASS, COCKSFOOT, TIMOTHY, TALL FESCUE, LUCERNE AND SAINFOIN, AS MEASURED BY AN IN VITRO PROCEDURE , 1964 .

[47]  Andrew Sih,et al.  Predation: direct and indirect impacts on aquatic communities , 1988 .

[48]  Stephen R. Carpenter,et al.  Cascading Trophic Interactions and Lake Productivity , 1985 .

[49]  R. Paine.  Food webs : linkage, interaction strength and community infrastructure , 1980 .

[50]  M. A. Leibold,et al.  Resource Edibility and the Effects of Predators and Productivity on the Outcome of Trophic Interactions , 1989, The American Naturalist.

[51]  M. Rosenzweig,et al.  Why the Prey Curve Has a Hump , 1969, The American Naturalist.

[52]  J. R. Parker.  Some effects of temperature and moisture upon melano-plus mexicanus mexicanus saussure and camnula pellucida scudder (orthoptera) , 1930 .

[53]  A. Joern.  Experimental study of avian predation on coexisting grasshopper populations (Orthoptera: Acrididae) in a sandhills grassland , 1986 .

[54]  Mark A. McPeek,et al.  Predation, Competition, and Prey Communities: A Review of Field Experiments , 1985 .

[55]  R. Macarthur,et al.  Graphical Representation and Stability Conditions of Predator-Prey Interactions , 1963, The American Naturalist.

[56]  L. Slobodkin,et al.  Regulation in Terrestrial Ecosystems, and the Implied Balance of Nature , 1967, The American Naturalist.

[57]  M. Rosenzweig,et al.  Exploitation in Three Trophic Levels , 1973, The American Naturalist.