EVALUATING THE GEOGRAPHIC DISTRIBUTION OF QUATERNARY SHREWS: THE POTENTIAL FOR PALEOECOLOGIC INTERPRETATIONS ABOVE THE SPECIES LEVEL

The paleoecologic interpretations of fossils are shaped by the distribution of fossil-bearing sites, which are in turn affected by the underlying factors that influence site distribution. Geographic information systems (GIS) can be a powerful tool for visualizing and quantifying spatial patterns. Using GIS, I analyzed the factors that influenced the geographic location of 189 Quaternary paleontological sites from the FAUNMAP II database within Texas. Various analyses showed that site distribution was non-random and highly clustered, and that there was probable geographic bias in the identification of some Quaternary mammal fossils. Most of the fossil shrews (Soricidae) in the FAUNMAP database, whether explicitly or not, were identified using geographic assumptions to refine the identifications to species, and should be treated as generic identifications.

Given the problems with identifying shrews to species, I explored the potential for making paleoecologic interpretations based on generic level identifications. I compared the extant ranges of shrew genera in Texas to the late Quaternary fossil record, which showed that shrews occupied ranges outside of the extant range in the Pleistocene and Holocene. In order to determine if environmental conditions of the area were different than today or if the shrews evolved away from a range of climatic tolerances that are not fully realized today, I compared the present climate to the following independent paleoenvironmental proxies that exist for central Texas: pollen, C¹³ isotopes, magnetic susceptibility, speleothem, and the sedimentation record. Compared to the fossil record, it appears that the environmental conditions found today may not be limiting the current range of shrews in Texas. If environmental conditions are not the sole factor influencing the range of shrews, then it must be possible that other ecological factors besides the environmental conditions are shaping the current distribution of shrews. Understanding the significance that past climate has had on the distribution of mammals (or the lack of influence) is an important step in assessing the vulnerability of mammalian faunas to climate change.