Complex Biotic Interactions in a California Vernal Pool Ecosystem


California vernal pools are temporary ponds that support high levels of species diversity and endemism: over 60 species are only found in California vernal pools. Since vernal pools experience an inundation and desiccation every year, species that occupy the ecosystem have adaptations to this cycle. Some are passive dispersers creating dormant cysts or seeds, which allow survival through dry stages. Others actively disperse to permanent water bodies; these tend to be predators in the ecosystem. Little is known about how these various species interact in California vernal pools. A microcosm experiment was conducted that manipulated predator and competitor density and measured the response in the passive dispersers (invertebrates, plants, and algae) and water quality (phosphorus, dissolved oxygen, conductivity, and turbidity). Thirty vernal pool microcosms were established with inundated vernal pool soil collected near Sacramento, California. The experiment was a 3 x 2 factorial design with 3 levels of predator density (none, 1, and 3 Corixidae) and 2 levels of competitor (none and 1 Gastropoda). Treatments were implemented two weeks after inundation with biweekly sampling. Few effects on measured variables were observed. A predator/competitor interaction was found with plant densities. The presence of snails had no effect, but high predator densities resulted in decreased plant density in the absence of competitors. These results suggest predators have indirect effects on vegetation that may be mediated by their effects on prey and algae. Future studies should assess the details of predator-prey and competitive interactions in this ecosystem.


Biodiversity | Population Biology


Jamie Kneitel

Lab site

California State University, Sacramento (Sac State)

Funding Acknowledgement

This material is based upon work supported by the S.D. Bechtel, Jr. Foundation and by the National Science Foundation under Grant No. 0952013. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the S.D. Bechtel, Jr. Foundation or the National Science Foundation. This project has also been made possible with support of the National Marine Sanctuary Foundation. The STAR program is administered by the Cal Poly Center for Excellence in Science and Mathematics Education (CESaME) on behalf of the California State University (CSU).

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URL: http://digitalcommons.calpoly.edu/star/297