SREL Reprint #2765




Physiological Ecology of Amphibians in Relation to Susceptibility to Natural and Anthropogenic Factors

Christopher L. Rowe, Wiliam A. Hopkins, Christine M. Bridges

Introduction: In nature, animals must employ strategies that allow them to optimize fitness under the range of environmental conditions to which they are exposed. When conditions diverge significantly from the combinations that are necessary for optimizing fitness, population-level changes may emerge. The type of response that will occur at the level of the population will depend upon genetic phenomena responsible for phenotypic plasticity and the potential for or constraints acting against adaptation to new conditions. Genetic aspects of populations relative to adaptability of amphibians to changing environments will be discussed in Chapter 2B. Here we are concerned with characteristics of individuals that may make them susceptible to or tolerant of certain environmental changes.
The causes and consequences of population declines cannot be examined fully on the basis of only population or demographic trends because environmental agents (biological, physical, or chemical) have their direct effects on individuals, and the responses of individuals determine population dynamics via changes to survival, growth, or reproduction. Hence, an examination of processes occurring at the individual level is required so that some mechanism for population changes in response to environmental changes can be identified.
In contrast to most experimental situations, amphibians in field settings are rarely faced with a single environmental challenge. Rather, numerous chemical, physical, and biological factors may ultimately be modified when anthropogenic or natural changes to the environment occur. For example, human activities often result in chemical contamination of habitats by complex mixtures of contaminants rather than by a single type of contaminant. Terrestrial landscapes modified by human activities may present amphibians with numerous challenges simultaneously, such as changes to temperature, humidity/moisture, habitat heterogeneity, or prey base. Susceptibility to pathogens may change with the presence of other chemical or physical factors in the environment (e.g., Carey and Bryant 1995). Thus, interactions with numerous and often disparate environmental variables requires that individuals have the physiological capacities to respond to multiple challenges in order to minimize deleterious effects...

SREL Reprint #2765

Rowe, C. L., W. A. Hopkins, and C. M. Bridges. 2003. Physiological ecology of amphibians in relation to susceptibility to natural and anthropogenic factors. p. 9-57 In: G. Linder, S. Krest and D. Sparling (Eds.). Amphibian Decline: An Integrated Analysis of Multiple Stressor Effects. Society of Environmental Toxicology and Chemistry.

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