Print PageWater is essential for life on Earth. Although there is broad correlative support for water limiting terrestrial biodiversity and productivity, there are few studies investigating the direct effect of water limitation on animal communities. Here we tested the effect of water limitation on food-web structure by manipulating the availability of free (drinking) and trophic (contained in food) water to primary and secondary consumers in multiple 625 m2 plots at three large desert floodplains. These two water sources map onto natural surface water from rivers and ground water made available to animals by plants via evapotranspiration, and mimic the direct and indirect effects of water in food webs (water limitation and control of resource supply via net primary production, respectively).
Results/Conclusions
We found that primary consumers (juvenile and adult crickets) responded to free and trophic water additions, but for juvenile crickets this effect was only observed at the driest site. Similarly, not all secondary consumers (spiders) responded to water treatments, and those that did (large spiders) only responded to free water. Further, the magnitude of the water effect was strongest at the most arid site and weakest at the least arid site. Ultimately these results suggest that water has strong bottom-up effects that limit terrestrial community structure. These results suggest that a water-web approach to community structure may be an informative tool to describe trophic dynamics.
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