Metabolism provides a basis for using first principles of physics, chemistry, and biology to link the biology of individual organisms to the ecology of populations, communities, and ecosystems. Metabolic rate, the rate at which organisms take up, transform, and expend energy and materials, is the most fundamental biological rate. We have developed a quantitative theory for how metabolic rate varies with body size and temperature. Metabolic theory predicts how metabolic rate, by setting the rates of resource uptake from the environment and resource allocation to survival, growth, and reproduction, controls ecological processes at all levels of organization from individuals to the biosphere. Examples include: (1) life history attributes, including devel- opment rate, mortality rate, age at maturity, life span, and population growth rate; (2) population interactions, including carrying capacity, rates of competition and predation, and patterns of species diversity; and (3) ecosystem processes, including rates of biomass production and respiration and patterns of trophic dynamics. Data compiled from the ecological literature strongly support the theoretical predictions. Even- tually, metabolic theory may provide a conceptual foundation for much of ecology, just as genetic theory provides a foundation for much of evolutionary biology.

/pdf/toward-a-metabolic-theory-of-ecology-1dxmg8xr3n.pdf

Toward a metabolic theory of ecology

Current concepts of the role of interspecific interactions in communities have been shaped by a profusion of experimental studies of interspecific competition over the past few decades. Evidence for the importance of positive interactions — facilitations — in community organization and dynamics has accrued to the point where it warrants formal inclusion into community ecology theory, as it has been in evolutionary biology.

https://www.cell.com/trends/ecology-evolution/pdf/0169-5347(94)90088-4.pdf

Positive interactions in communities.

A heuristic framework for understanding and predicting the distribution and categorical abundance of species in stream communities is presented. The framework requires that species be described in terms of their functional relationships to habitat selective forces or their surrogates, which constitute "filters" occurring at hierarchical landscape scales (ranging from microhabitats to watersheds or basins). Large-scale filters are viewed as causative or mechanistic agents that constrain expression of local selective forces or biotic potential at lower scales. To join a local community, species in a regional pool must possess appropriate functional attributes (species traits) to "pass" through the nested filters. Biotic interactions are also a potential filter on local community composition, and they are invoked at the lower hierarchical levels, after species have passed through the physicochemical habitat filters. Potential landscape filters and their associated selective properties are identified, as are ...

Landscape filters and species traits: Towards mechanistic understanding and prediction in stream ecology

/pdf/playing-chutes-and-ladders-heterogeneity-and-the-relative-4z728lsnhk.pdf

Playing Chutes and Ladders: Heterogeneity and the Relative Roles of Bottom-Up and Top-Down Forces in Natural Communities

▪ Abstract Lentic freshwater habitats in temperate regions exist along a gradient from small ephemeral ponds to large permanent lakes. This environmental continuum is a useful axis for understanding how attributes of individuals ultimately generate structure at the level of the community. Community structure across the gradient is determined by both (a) physical factors, such as pond drying and winter anoxia, that limit the potential breadth of species distributions, and (b) biotic effects mediated by ecological interactions, principally predation, that determine the realized success of species. Fitness tradeoffs associated with a few critical traits of individuals often form the basis for species turnover along the gradient. Among species that inhabit temporary ponds, distributions are often constrained because traits that enhance developmental rate and competitive ability also increase susceptibility to predators. In permanent ponds, changes in the composition of major predators over the gradient limit ...

/pdf/mechanisms-creating-community-structure-across-a-freshwater-3osigazq5u.pdf

Mechanisms creating community structure across a freshwater habitat gradient

Very few ecological studies have attempted to fully test the integrative role of abiotic and biotic factors in interspecific interactions. There is little if any dispute about the value of such an approach in community ecology. However, there is great disagreement over the present direction of the field; we advocate a reemphasis of the integrative role of abiotic and biotic factors. By using literature examples and data on the role of salinity in reversing the competitive relations between fish of the genus Lucania, we have suggested a reemphasis on these interactions. This represents a blend of the traditional fields of ecology, physiology, and toxicology and could facilitate progress in community ecology. As such it could also be a significant part of the new direction sought for the field of physiological ecology. Finally, we are not arguing that abiotic parameters are necessarily more important than any of a group of multiple factors that may be involved in regulating community structure, only that th...

The Role of Abiotic Factors in Community Organization

Brook trout (Salvelinus fontinales) exposed to a low environmental pH (3.0-3.3) showed a drop in mean blood pH from 7.39 to 6.97. Trout at an environmental pH of 3.5 lost 50% of their total body sodium. Control sodium influx (72.5 micromols/100 g hours) decreased to zero between pH 3.0 and 4.9 as Na efflux increased markedly over control levels. There was no significant difference in body Na content of wild trout from three streams ranging in pH from 6.05 to 7.10. Trout survived 13.1 to 14.7 hours in a 150 mm Na solution of pH 3.5 as compared to 2.5 to 4.9 hours at 100 micrometer Na and the same pH. The inability of brook trout to live in waters of pH less than about five, seems to be related to a drop in blood pH caused by the high hydrogen ion concentration of the medium. The loss of body Na appears to be of secondary importance as a cause of death.

Effects of low environmental pH on blood pH and sodium balance of brook trout

The effects of variable hydroperiod (three levels) and initial density of amphibians (two levels) on survival, growth rate, and time to and mass at metamorphosis were studied for wood frogs (Rana sylvatica), Jefferson salamanders (Ambystoma jeffersonianum), and spotted salamanders (A. maculatum). Experiments were carried out in 260-1 mesocosms set up outdoors in a forest. These pond simulations were designed to mimic conditions that occur in palustrine temporary wetlands in central Pennsylvania. No animals reached metamorphosis in the short hydroperiod (56 days). However a greater proportion (66%) of tadpoles of R. sylvatica survived to the end of the 56-day, treatment than the 84- or 158-day treatments (29 and 14%, respectively), from which all survivors metamorphosed. In contrast, neither of the salamanders metamorphosed by 84 days; survival to metamorphosis at 158 days was 15% for A. jeffersonianum and 10% for A. maculatum. Average instantaneous growth rates for A. jeffersonianum decreased with each increase in hydroperiod. Growth of R. sylvatica was greater in the 56-day hydroperiod than in hydroperiods of 84 or 158 days. Initial amphibian density had no effect on growth or survival of any species. It appears that salamander larvae were predatory on tadpoles, since survival of R. sylvatica was negatively correlated with survival of A. jeffersonianum in 84-day treatments and with growth of A. maculatum in 158-day treatments.

Impacts of hydroperiod on growth and survival of larval amphibians in temporary ponds of Central Pennsylvania, USA

A symposium was held 8 August 1991, at the annual meeting of the Society for the Study of Amphibians and Reptiles and The Herpetologists' League in University Park, Pennsylvania. The topic, "Amphibian Declines and Habitat Acidification" was selected for its relevance to the topical issues of a precipitous drop in many amphibian populations, and possible causation by acidic atmospheric deposition. As organizers, we felt that a rigorous approach to these issues requires meticulous field documentation of population fluctuations and correlated environmental measures of pollution, along with an experimental ecotoxicological analysis of possible anthropogenic causation. Because of the potential for large-scale environmental change acting synergistically with pollution across landscapes, the experimental elucidation of cause and effect will be extremely difficult. It appears that some amphibian populations fluctuate in an episodic fashion, but there are no long-term data bases adequate to determine whether particular declines are uniequivocally due to acidic deposition from non-point sources, other anthropogenic causes, natural causes, or interactions among them. This series of papers deals with the effects of acidic waters and soils on amphibians in England and North America. It is very clear that acidic habitats of natural and polluted origin exclude certain species and cause sub-lethal and lethal effects. However, no data are at hand which show directly that anthropogenic acidification causes amphibian populations to decline. There is consid- erable interest in the development of bioindicators of habitat decline. Net loss of body sodium and the embryonic curling defect in amphibians are examples of the best of such direct bioassays in acidified aquatic and terrestrial habitats. There is a strong need for standardization of test conditions so that better comparisons can be made among results from laboratories in different geographic regions. We recommend that a number of sites be chosen for long-term (10 year minimum) study of the relation between amphibian population cycles and anthropogenic change. This research would provide data not only specifically pertinent to the issue of amphibian declines, but would also provide valuable tests of the usefulness of amphibians as general bioindicators of ecosystem decline in response to anthropogenic stress. These issues are complex and are not amenable to quick solutions. A sustained commitment is needed by researchers and funding agencies to provide long-term monitoring and rigorous experimental tests of the causes of any declines in especially sensitive biotic components of ecosystems.

A Symposium on Amphibian Declines and Habitat Acidification

mortality caused by low pH could be responsible for the absence of the two least tolerant species from acidic ponds. Hatching of embryos of R. sylvatica was not related to pond pH while mortality of embryos of A. jeffersonianum increased significantly as pond pH declined. H. andersoni also hatched in all experimental New Jersey ponds, but embryos of B. woodhousei suffered significantly higher mortality in ponds of lower pH's. Hatching success was variable at specific pond pH's, indicating significant interaction of pH with other chemical variables. In laboratory trials, tadpoles of B. woodhousei and H. andersoni grew significantly slower when exposed to low pH. This sublethal effect on body size has important implications for dynamics of amphibian populations in acidic ponds.

https://www.jstor.org/stable/pdfplus/1445003

William A. Dunson

Papers

The Role of Abiotic Factors in Community Organization

Effects of low environmental pH on blood pH and sodium balance of brook trout

Impacts of hydroperiod on growth and survival of larval amphibians in temporary ponds of Central Pennsylvania, USA

A Symposium on Amphibian Declines and Habitat Acidification

Effects of Low pH and Other Chemical Variables on the Local Distribution of Amphibians