The Quaternary conundrum is the seeming contradiction that while climate change is a driver of extinctions, our extant biodiversity has a legacy rooted in the multiple climate shifts of the Pleistocene. Climate refugia, areas that can facilitate the persistence of species during large-scale, long-term climate change, offers a mechanism for how species survived those past climate swings. Additionally, identifying the spatial extent of climate refugia provides a focus for conservation-aimed protection and management efforts. From 2012-2016, historic drought conditions dominated the southwestern U.S., especially in southern California, offering a window to a predicted future climate norm. My research took advantage of this window to measure spatial shifts in species abundance and recruitment responses to varying levels of drought across an elevation gradient that spanned the Mojave and Sonoran Deserts, centered on Joshua Tree National Park. I focused on a suite of habitat generalists that lack the ability to move large distances to track rapid, climate-mediated changes in habitat suitability: side-blotched lizards, Uta stansburiana, western whiptails, Aspidoscelis tigris, and zebra-tailed lizards, Callisaurus draconoides.
Rather than local extinctions or long-distance movements, the three species shifted recruitment patterns, resulting in shifts in abundance, along the elevation gradient. Locations where they maintained sustainable recruitment despite severe drought included necessary attributes of in situ climate refugia. This empirical approach avoided assumptions associated with strict model-based approaches and provided mechanistic explanations for the observed distributional shifts. Conservation aimed at reducing climate change species losses should focus on: 1) identifying and protecting in situ climate refugia; 2) maintaining landscape scale connectivity to those refugia; and 3) reducing additional stressors within those refugia such as invasive species and anthropogenic habitat degradation.