High-resolution food webs based on stable nitrogen composition of amino acids
2014
Chikaraishi, Yoshito | Steffan, Shawn A. | Ogawa, Nanako O. | Ishikawa, Naoto F. | Sasaki, Yōko | Tsuchiya, Masashi | Ohkouchi, Naohiko
Food webs are known to have myriad trophic links between resource and consumer species. However, since the difficulties associated with characterizing the trophic position of organisms—particularly omnivores and higher-order consumers—have remained a major problem in food web ecology, our knowledge on the trophic structure of food webs is often obscured. To better understand the trophic linkages and energy flow in complex networks of ecosystems, analysis of the stable nitrogen isotopic composition of amino acids has been suggested as a relatively new tool to provide accurate and precise estimates of the trophic position of organisms in aquatic and terrestrial ecosystems. In the present study, we employ this method to estimate the trophic position of a total of 200 samples from 39 species in coastal marine (a stony shore) and from 38 species in terrestrial (a fruit farm) environments, in order to provide a high-resolution view of the respective communities. In the coastal marine ecosystem, we observed the trophic position (TP) for macroalgae (0.8-1.2), gastropods (1.7-2.1), echinoids (1.8-2.0), oyster (2.4), crustaceans (2.3-4.0), and various fish species (2.7-4.7). In the terrestrial ecosystem, the trophic position was quantified for plant species (0.7-1.3), herbivorous insects (1.8-2.3), paper wasps (2.8-3.3), ladybugs (2.9-3.2), ant (3.0), mantis (3.2), and hornets (3.5-4.1). Thus, based on the trophic position from the nitrogen isotopic composition of amino acids, we are able to present a highly resolved image of the trophic structure in the food web, which is critical for revealing key elements of the trophic niches while illuminating the functional diversity of animal communities in complex ecosystems.
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