Abstract
Increased temperatures can change the structure and function of aquatic communities through both biotic (productivity, competition, predation) and abiotic (nutrient cycling, disturbance) interactions. Many warming experiments have been done in permanent freshwater systems, but few in temporary systems. California vernal pools are temporary wetlands which provide habitat for many endemic and endangered species during the aquatic phase. Hydro-regime characteristics such as the duration, magnitude, frequency, and timing of inundation are important factors that influence community dynamics in these ecosystems. Here, a mesocosm experiment tested the effects of warming and inundation timing on the community composition of California vernal pools. Both factors independently affected species densities and diversity, and community composition. Total densities were higher in both warm and late treatments. Species richness and evenness did not respond to the effects of warming, which suggests that the “storage effect” played an important role in maintaining diversity in this study. Interactive effects between warming and inundation timing led to differences in the rank-order of contributing species which had an overall effect on community composition. This study suggests that endemic species populations could decline because of increased temperatures, but this process may depend on species-specific life-history strategies. Conservation efforts should work to identify the most at risk of these species, while also accounting for public health concerns that may arise due to increased mosquito abundances in vernal pools.