Differing nutritional constraints of consumers across ecosystems.

Stoichiometric mismatches between resources and consumers may drive a number of important ecological interactions, such as predation and herbivory. Such mismatches in nitrogen (N) or phosphorus (P) content between resources and consumers have furthered our understanding of consumer behavior and growth patterns in aquatic systems. However, stoichiometric data for multiple consumers from the same community are lacking in terrestrial systems. Here, we present the results of a study designed to characterize nutritional constraints within a terrestrial arthropod community. In order to place our results in a broader context, we compared our data on resource-consumer stoichiometry to those of stream and lake ecosystems. We found that N and P varied among trophic levels, and that high N:P content of herbivores suggests that herbivores might experience strong N-limitation. However, incredibly low P-content of plant foliage leads to potential P-limitation in herbivores that is nearly as strong as potential N-limitation. Moreover, arthropod predators may also be strongly P-limited. In fact, potential nutrient limitation of terrestrial herbivores in our study is similar to nutrient limitation from streams and lakes, suggesting that similar nutritional constraints may be operating across all three study systems. Importantly, our data suggest that consumers in lakes experience a trade-off between N- and P-limitation, while terrestrial consumers experience simultaneous strengthening or weakening of N- and P-limitation. We suggest that P may be overlooked as an important limiting nutrient in terrestrial ecosystems.