Ecologists are gaining a better understanding for how global climate change may shift latitudinal and altitudinal distributions and alter life cycle timing.  What is less understood is how climate change impacts community composition dynamics within species' existing ranges.  We used a unique long-term dataset to examine the composition of a Sonoran Desert winter annual plant community over 25 years and to relate demographic vital rates and abundance patterns to species' physiology and climate. 

Results/Conclusions

During our study, the Southwestern US has become warmer and drier during the winter growing season.  The first winter rains are arriving later in the season, during December rather than October, and winter annual seeds are germinating later.  The unexpected result is that plants are germinating under colder temperatures, which is driving a shift in community composition to favor slow growing, water-use efficient species that germinate and grow well in cool temperatures.  Our study shows that detailed ecophysiological knowledge of individual species, combined with long-term demographic data, can reveal the complex and sometimes unexpected shifts in community composition in response to climate change.