Taphonomic damage, taxonomic identifiability, and preservational quality: Implications for bias in paleoecological data.

摘要

A goal of paleontologists and paleoecologists has been to reconstruct communities of the past, whether through qualitative representations of the interactions of organisms in their environment, or more quantitative treatments examining how species richness and evenness, have changed over Phanerozoic time. The difficulty in reconstructing communities of the past however, is that the tremendous amount of data in the fossil record cannot be taken at face value. A variety of taphonomic processes (physical, biological, and chemical) have acted to bias the fossil record through the uneven destruction of skeletal remains over both time and space. While the dangers of incomplete preservation and their potential to bias the fossil record are well known, relatively little effort has been applied toward identifying how best to deal with a biased record. Yet the use of a biased record is critical in paleoecology as it is the only record available. Paleoecologists need to know for example, what types of comparisons can be made between assemblages of different preservational qualities and in what direction might the results be biased due to these differences.; Through a series of computer simulations I have examined the effects of preservation on commonly used diversity metrics (richness and evenness in particular). A key outcome of this work is that at realistic sample sizes, bias introduced through incomplete sampling is equivalent to much of what is introduced through non-preservation. Additionally, the preservational quality of the abundant taxa in an assemblage is recognized as being critical in understanding bias of assemblage wide diversity metrics.; The Taxonomic Identifiability Score (TIS), is introduced as a new system for classifying the preservational quality of fossil assemblages. The TIS is based on simply determining the proportion of elements which can be identified taxonomically. Included in the TIS are a set of guidelines developed through computer simulations as to the robustness of different diversity metrics in comparisons of disparate preservational quality.