The Effect of Holocene Climatic Variation on Baja California Rodent Generic Diversity: Evidence from the Abrigo de los Escorpiones Fauna.
Musser, Grace M
Cope, Dana A
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Rodent diversity and abundance are significant indicators of climate structure and change in both modern and archaeological contexts. Reconstructing Holocene paleoclimate through analysis of rodent remains is especially critical in prehistoric North American archaeology as climate variation has considerable impacts on both human and non-human faunal populations. The El Niño/Southern Oscillation (ENSO) climatic phenomenon was a major cause of such climate fluctuation throughout the Holocene and continues to impact human and faunal populations worldwide. While several modern studies support positive correlations between ENSO frequency and rodent diversity, little work has focused on ENSO effects on rodent diversity over millennial time scales. The Abrigo de los Escorpiones volcanic rockshelter on the coast of Baja California provides an excellent faunal record from which to study the effects of ENSO on rodent diversity due to its large, well dated and distinctly stratified Holocene rodent assemblage that was largely accumulated due to raptor deposits. Rodent cranial elements from 10399 BP to present were identified to the genus level and diversity values were calculated for each 100-year temporal-analytic unit using the Shannon-Weaver index. Spearman’s rho correlation of Shannon-Weaver values with geologically-derived El Niño frequencies from Ecuador exhibited a positive and significant correlation. Correlation of Shannon-Weaver values with oxygen-isotope based sea surface temperature variation from the Santa Barbara Basin also showed both a positive and highly significant correlation; however, only one unit from the site was analyzed and thus further study of Abrigo de los Escorpiones rodent remains is required in order to advance knowledge of ENSO effects on generic rodent diversity.