The structure of a food web in a tropical rain forest in Malaysia based on carbon and nitrogen stable isotope ratios

Carbon and nitrogen stable isotope ratios (delta C-13 and delta N-15) have been used to study the structure of food webs. However, few studies have examined how a terrestrial food web can be depicted by this technique. We measured delta C-13 and delta N-15 in various consumers of four trophic groups (detritivores, herbivores. omnivores and predators), including vertebrates and invertebrates (14 orders, >= 24 families). as well as canopy and understorey leaves in a tropical rain forest in Malaysia. We found that. delta C-13 and delta N-15 of the consumers differed significantly among the trophic groups. The predators had significantly, higher delta C-13 than the herbivores, and were similar in delta C-13 to the detritivores, suggesting that most. predators examined depend largely, on below-ground food webs. delta N-15 was higher in predators than detritivores by about, 3 parts per thousand. The comparison of delta C-13 in plant materials and herbivores suggests that most. herbivores are dependent on C fixed in the canopy, layers. The vertebrates had significantly higher delta N-15 and delta C-13 than the invertebrates of the same trophic group. likely reflecting differences in the physiological processes and/or feeding habits. This study indicates that stable isotope techniques can help better Understanding of the terrestrial food webs in terms of both trophic level and the linkage of above and below-ground systems.