Experimental Ecology of Food Webs - Complex Systems in Temporary Ponds - The Robert H. MacArthur Award Lecture

Aug 23, 2026

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The Robert H. MacArthur Award Lecture presents an experimental approach to understanding how food-web structure and function are regulated in temporary ponds. Temporary ponds offer discrete, controllable communities that can be replicated in containers, enabling repeatable initial conditions and large experimental arrays. Using natural observations, experimental natural history, and controlled pond experiments, the study develops and tests hypotheses on population density, fitness, priority effects, competition, predation, and uncertainty driven by hydroperiod length.

LanguageEnglish

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Pages24

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Introduction

Food webs as a central idea in ecology

Limits and assumptions in food-web construction

Ecology, 78(8), 1997, pp. 2279–2302 q 1997 by the Ecological Society of America EXPERIMENTAL ECOLOGY OF FOOD WEBS: COMPLEX SYSTEMS IN TEMPORARY PONDS THE ROBERT H. MACARTHUR AWARD LECTURE Presented 31 July 1995 Snowbird, Utah by HENRY M. WILBUR Mountain Lake Biological Station and Department of Biology –Gilmer Hall, The University of Virginia, Charlottesville, Virginia 22903-2477 USA Henry M. Wilbur MacArthur Award Recipient Abstract. A food web graphically represents the paths of nutrients and energy through the living components of an ecosystem and the context in which individuals exploit their prey and avoid their enemies. Temporary ponds are excellent arenas for the study of food webs because they are discrete communities that can be mimicked in containers that approach the realism of natural habitats. Artiﬁcial ponds permit repeatable initial conditions and sufﬁcient replication of independent experimental units in complex experiments to test hypotheses about the control of structure and function in natural communities. I used a combination of observations of natural ponds, ‘‘experimental natural history’’ of artiﬁcial ponds in my study area, and controlled experiments in an array of 144 replicate ponds to develop, then test, hypotheses about how the structures of food webs are regulated. Understanding food webs begins with population biology. Amphibians use the aquatic larval stage of their biphasic life cycle to exploit ephemeral opportunities for growth and development in temporary ponds. The regulation of population density and the ﬁtness of individuals are determined by complex interactions among competition, predation, and uncertainty in the length of the time ponds retain water. Exponential models of densitydependent recruitment relate the number of metamorphs to the input of eggs into ponds without predators. Extensions of these models include interspeciﬁc competition and pre- 2280 HENRY M. WILBUR Ecology Vol. 78, No. 8 dation. The addition of predation to these systems has three effects. (1) Predators can reduce, even eliminate, prey. There are species-speciﬁc differences among co-occurring prey in their risks of predation, and these risks change with relative body sizes of predator and prey. (2) Individuals may evoke an inducible defense that reduces their risk by either decreasing active foraging or developing morphological adaptations, such as changes in the coloration and shape of tails. These defenses may entail costs in body size and timing of metamorphosis. (3) Finally, mortality due to predators may reduce competition, thereby beneﬁting the population of the prey by permitting individuals that escape predation to grow rapidly enough to escape drying ponds. The order of arrival of species at breeding ponds has an impact on their own success as well as having a lasting impact on the success of species that arrive later. Such priority effects may result from size-speciﬁc changes in trophic connections or indirect effects between species mediated through the food web. Anurans can have strong effects on the partitioning of the ﬂow of nutrients through the phytoplankton vs. the periphyton. This effect on partitioning of production can then have strong effects on zooplankton and insects. Salamanders can play the role of keystone, or critical, predators by affecting the structure of the assemblages of zooplankton and anurans that determine much of the dynamics of nutrient ﬂows within food webs in temporary ponds. Key words: amphibian; competition; complexity; experimental design; food web; keystone species; North Carolina; predation; priority effects; temporary pond; trophic dynamics; zooplankton. INTRODUCTION Food webs are a central, if not the central, idea in ecology. They represent known, or sometimes just suspected, trophic connections among taxa in ecological communities. These connections represent the paths of energy and nutrient ﬂow through living organisms. The

FAQs

Why are temporary ponds useful for studying food webs?

They form discrete communities that can be mimicked in containers with realistic conditions, enabling repeatable initial states and sufficient replication for complex experiments.

What factors regulate population density and individual fitness in temporary ponds?

Complex interactions among competition, predation, and uncertainty in how long ponds retain water determine density-dependent recruitment and fitness outcomes.

How does predation change outcomes in these food-web systems?

Predation can reduce or eliminate prey, trigger inducible defenses with costs, and reduce competition so surviving prey can grow rapidly and potentially escape pond drying.

Aug 23, 2026

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