ESTIMATING LATITUDINAL EFFECTS ON PALEODIVERSITY USING THE PALEODATABASE MIOMAP

A latitudinal gradient in species richness, whereby species richness increases with decreasing latitude, has been well-documented among extant organisms. However, the discovery of this pattern in the fossil record has been more elusive given the vagaries (e.g., incomplete record, taxonomic and sampling biases) of paleontological data. Here we use the MIOMAP database of western North American mammals to assess how mammalian paleodiversity relates to latitude. Species lists were compiled for each quarter degree of latitude and subdivision of the North American Land Mammal Ages (Arikareean through Hemphillian) for the Great Plains, the region with the most complete fossil record. All resulting species richness numbers were rarefied to account for the species-area effect and sampling biases, such as uneven sampling, preservation biases, and the varying length of time bins. Preliminary results indicate that a latitudinal species gradient does exist, although the results lack significance given the incompleteness of the paleorecord. Further accumulation of fossil data and the application of more detailed methodologies should clarify whether the paleospecies-latitude relationship is robust and how it compares to the modern one.