PARENT SESSION
Oral Session #11: Aquatic Ecology: Conservation, Plankton, Invertebrates.
Presiding: C. Cooper
Monday, August 5. 8:00 AM to 11:30 AM. Palo Verde Room, Radisson.

Environmental variability in vernal pool ecosystems: Implications for the biogeography of fairy shrimp in California.

Pyke, Christopher^*,1, ¹ University of California, Santa Barbara, Santa Barbara, CA

ABSTRACT- Environmental variability is a critical component in the dynamics of ecosystems, communities, and populations. Ephemeral wetland ecosystems may be particularly sensitive to environmental variability, and they are frequently used as model ecosystems to study the response of organisms and communities to unpredictable environments. Vernal pools are one instance of ephemeral wetlands commonly found in regions with Mediterranean climate. These wetlands fill by the accumulation of rainwater, and the dynamics of their obligate organisms are dominated by the depth, duration, and frequency of inundation (hydrologic regime). In this study, I used a simulation model to describe vernal pool hydrologic regime across the ranges of fairy shrimp endemic to the Central Valley of California. The hydrologic model was driven by output from a stochastic weather generator. The generator created 150-year time series of daily weather based on historical data for meteorological stations across the range of each species. The hydrologic model independently simulated the effect of the local climate on a reference landscape parameterized for rain-fed vernal pools on claypan substrates. Pools within the reference landscape had a realistic distribution of physical properties, including pool size, depth, vegetation cover, and soil substrate drawn from large-scale field surveys. I used a Monte Carlo procedure to simulate combinations of these variables based on their relative frequency and patterns of covariation. The results describe the hydrologic variability of the entire population of vernal pools within each reference landscape. These findings provide estimates for the distribution of mean annual flood, flooding cycles per year, and fraction of years less than the minimum duration required for fairy shrimp reproduction. Results indicate strong geographic gradients in hydrologic regime and significant differences in the long-term patterns of environmental variability experienced by each fairy shrimp species.

KEY WORDS: vernal pool, hydrology, fairy shrimp, environmental variability