The application of guild and tier structure and energy flow in paleoecologic analysis: An example using parautochthonous death assemblages from a variable salinity bay

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Abstract
We examine the use of paleoproduction (the net production of somatic tissue over an individual's lifetime) and paleoingestion (the energy required to sustain the animal over its life span) in habitat tier and feeding guild analysis of paleocommunities, using modern death assemblages from a variable salinity bay. Community attributes evaluated by the abundance of the constituent species differed markedly from the same attributes described by paleoproduction or paleoingestion. Examination of the guild and tier structure from the perspective of paleoproduction and paleoingestion identified significant temporal changes in environmental optimality, probably related to changes in food supply, and in the division of resources amongst small and large species. Significant downcore changes in habitat optimality occurred only for the large species in the assemblage; those potentially most affected by changes in food supply. Tier structure was less variable than guild structure because species replacement always occurred within tiers, but not always within guilds. Predator overrepresentation, defined as a larger estimated predator consumption (paleoingestion) than preserved prey paleoproduction, so common in many euhaline assemblages, occurred rarely, as is typical for most bay assemblages. The amount of prey required to support the preserved predators normally was < 20% of the available prey preserved. Ecological resilience, viewed from the perspective of animals’ life spans, may be most closely translated into paleoecological persistence because paleopersistent species are likely to be those that recolonize rapidly rather than those that maintain populations continuously over an extended period of time. Small species may be more paleopersistent than large species because the less common large species frequently stretch the limits of their habitat's resources and, thus, are more sensitive to environmental shifts that favor other species. Thus, paleoproduction and paleoingestion may be sensitive indicators of environmental change and its effects on guild and tier structure.