Photo Credits:
Thomas R. Van Devender
Arizona Sonora Desert Museum
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of a full resolution TIF image
| Paleo Slide Set: Packrat Middens: Vegetation & Climate Variability in the Southwestern United States |
| Pleistocene midden from Burro Canyon, Kofa Mountains, Yuma County, Arizona | |
| Plant remains are both
abundant and well preserved in packrat
middens, such as needles (leaves) of a singleleaf piņon (Pinus monophylla,)
clearly visible in this 12,000 year-old sample from the Kofa Mountains,
200 km west of Phoenix, Arizona. Open piñon-juniper-oak woodlands
occurred at this Sonoran Desert site during the last ice
age. The preservation of plant remains in such middens is remarkable,
even at the molecular level, allowing a variety of morphological, geochemical
and genetic studies. Researchers are working to use polymerase chain reaction
(PCR) techniques to extract, amplify and sequence ancient DNA from plant
remains found in middens. Such DNA "fingerprinting" can be used to confirm
species identifications based on leaf morphology,
to identify hybrid zones, and to determine if changes in genotype frequencies
accompanied large-scale migrations during the last deglaciation. Photo Credits: Thomas R. Van Devender Arizona Sonora Desert Museum |
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