Water webs in riparian ecosystems

Animal ecologists have often considered energy to be the underlying currency of food webs (Elton 1933, Brose et al. 2008).  However, animal physiologists have long observed that water balance is an important aspect of organismal biology and that variation in water intake and loss may influence animal behavior (Noy-Meir 1974, Hadley 1994, Davis and DeNardo 2009).  In a series of experiments, we have shown that water often drives animal foraging behavior in terrestrial dryland ecosystems (Sabo et al. 2008, McCluney and Sabo 2009).  Specifically, we have shown that free water availability determines consumption of moist food sources by both crickets and spiders.  Essentially, crickets drink freshly fallen green leaves (greenfall) and spiders drink crickets.  Thus, this food web may be better viewed as a water web, where water is the underlying currency of trophic interactions.  Subsequently, we developed a new method for tracing the water web using stable water isotopes (McCluney and Sabo 2010) and are in the process of applying this technique to the field, identifying water sources used by many different animal species across gradients of river water availability and across time.  We are also working to better understand how rates of organismal water loss interact with the availability of free water and trophic water (water trapped in food items) to influence trophic interactions.

Brose, U., R. B. Ehnes, B. C. Rall, O. Vucic-Pestic, E. L. Berlow, and S. Scheu. 2008. Foraging theory predicts predator-prey energy fluxes. Journal of Animal Ecology 77:1072-1078.

Davis, J. R. and D. F. DeNardo. 2009. Water Supplementation Affects the Behavioral and Physiological Ecology of Gila Monsters (Heloderma suspectum) in the Sonoran Desert. Physiological and Biochemical Zoology 82:739-748.

Elton, C. 1933. The ecology of animals. Methuen, London.

Hadley, N. F. 1994. Water Relations of Terrestrial Arthropods. Academic Press, San Diego.

McCluney, K. E. and J. L. Sabo. 2009. Water availability directly determines per capita consumption at two trophic levels. Ecology 90:1463-1469.

McCluney, K. E. and J. L. Sabo. 2010. Tracing water sources of terrestrial animal populations with stable isotopes: laboratory tests with crickets and spiders. PLoS ONE 5:e15696.

Noy-Meir, I. 1974. Desert Ecosystems: Higher Trophic Levels. Annual Review of Ecology and Systematics 5:195-214.

Sabo, J. L., K. E. McCluney, A. C. Keller, Y. Y. Marusenko, and C. U. Soykan. 2008. Greenfall links groundwater to aboveground food webs in desert river floodplains. Ecological Monographs 78:615-631.



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