Alternative approaches to the identification and reconstruction of paleoecology of Quaternary mammals
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Since the 19th century the remains of Quaternary mammals were an important source of data for reconstructing past environmental conditions. I tested two basic assumptions that underlie Quaternary vertebrate paleoecology. The first assumption is that fossils mammals can be identified reliably to species. The second assumption is that correlations established between extant mammals and environmental parameters can be used to interpret reliably the paleoenvironment from the latest Pleistocene. Incorrect specimen identifications could lead to errors in paleoecologic interpretations. I explicitly tested an alternative to the traditional approach to identification by identifying fossil shrews based on apomorphies. My results indicated that some traditional characters are useful for identification, but only complete specimens with a combination of characters can be identified to species. This indicates that previous authors who identified shrews to species did not compare them to the full diversity of species. I tested the reliability of cenograms and species-richness models as approaches for the reconstruction of environmental conditions in the past. I used faunal data from Hall’s Cave, Kerr County, Texas to construct cenograms and species-richness models and compared the results to independent paleoclimate proxies. Neither species-richness models nor cenograms agree with paleoenvironmental reconstructions based on proxy data from the Late Pleistocene and Holocene. Cenograms and species-richness models are unreliable and fraught with problems, and both approaches should be abandoned as tools for paleoecological reconstruction. To test for potential geographic bias in the identification of Quaternary fossils I developed a GIS (geographic information systems) database of Quaternary paleontological sites within Texas. I was able to show that the identification of species of fossil soricids, heteromyids, Odocoileus, and Spilogale was influenced by geography. Those fossils should be treated as generic identifications until they are re-evaluated against the full diversity of species. Utilizing GIS I also developed a method of paleoecological analysis. My analysis showed that the environmental conditions found today in Texas might not be limiting the current range of shrews. Based on the known geographic range of shrew fossils, other ecological factors besides environmental conditions are shaping the current distribution of shrews.