Warming interacts with inundation timing to influence the species composition of California vernal pool communities

Abstract

Climate change has been associated with alterations in temperature and precipitation regimes. Increased temperatures can change the structure and function of aquatic communities through both biotic and abiotic interactions. Many warming experiments have been conducted in permanent freshwater systems, but few in temporary freshwater systems that are dependent on precipitation patterns. Temporary aquatic communities are influenced by hydro-regime characteristics such as the hydroperiod length, magnitude, frequency, and timing of inundation, which may interact with temperature changes. Here, we used mesocosms to test for the effects of warming and inundation timing on the community composition of California vernal pools. California vernal pools are temporary wetlands, which provide habitat for many endemic and endangered species during the aquatic phase. Total species abundance was higher in both warm and late inundation treatments, while higher species richness levels in late treatments were due to the rapid emergence and colonization of species compared to early treatments. Heating increased the abundance of ubiquitous passive and active dispersers, including mosquitos, but decreased the abundance of vernal pool endemic passive dispersers. We also found that significant interactive effects between warming and inundation timing led to differences in community composition. These findings suggest that vernal pool endemic passive disperser species may decline due to increased temperatures and later inundation; however, the extent of such risk will likely be influenced by species-specific life-history traits such as bet-hedging strategies. Conservation efforts should work to identify the species most at risk to a changing climate.