Biology ETDs

Publication Date



Shifting climates affect the composition of biological communities. If environmental conditions change sufficiently, new species can invade, leading to large-scale community turnover. Understanding how and why such shifts occur is crucial in this era of anthropogenic global change. Paleontological studies provide a valuable long-term perspective of the dynamics of community turnover. Here, we examine changes in the plant community over the past 34 thousand years in what is now the northern Mojave Desert. This time period includes the last glacial maximum as well as numerous smaller climatic fluctuations in the Holocene and the end of the Pleistocene. We quantified plant macrofossils recovered from 48 ancient Neotoma middens collected in Titus Canyon in Death Valley, California, ranging in age from 33.5 to 0.05 ka. Using this unique fossil record, we are able to document the invasion and establishment of the important desert shrub creosote (Larrea tridentata) into the northern Mojave Desert. Overall, we are able to characterize the ecosystem shift in dominant shrubs from juniper (Juniperus osteosperma) to creosote bush (Larrea tridentata). Interestingly, we find that most secondary plant species do not follow dominant shrubs. Instead, shifts in these plants most likely depend on their own physiological limits. Our results may help predict responses of desert communities to ongoing climatic fluctuations.




Paleoecology, Neotoma, Death Valley, Plant Community, Macrofossils, creosote, Larrea tridentata, juniper, climate change, Juniperus osteosperma, Mojave Desert, Pleistocene, fossil, plant

Document Type


Degree Name


Level of Degree


Department Name

UNM Biology Department

First Committee Member (Chair)

Kodric-Brown, Astrid

Second Committee Member

Natvig, Don

Third Committee Member


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Biology Commons