Trophic interactions in centipedes as indicated by fatty acid, molecular gut content and stable isotope analysis

Background/Question/Methods

For investigating trophic interactions in decomposer food webs three novel complementary approaches are increasingly used: (1) fatty acid (FA) analysis allows determining the relative contribution of prey from major energy channels to predator nutrition; (2) molecular gut content analysis allows detailed insight into the prey spectrum of predators; and (3) stable isotope analysis provides insight into the trophic structure of decomposer food webs. Combining these approaches we investigated trophic niches of two centipede species (Lithobiidae, Chilopoda), dominant invertebrate predators in forest soils.

Results/Conclusions

FA composition of the two centipede species differed significantly with differences being stronger in spruce forests compared to beech forests suggesting that trophic niches of the two species differ significantly between coniferous and beech forests. These differences were more pronounced in Lithobius mutabilis as compared to Lithobius crassipes indicating that feeding of the larger L. mutabilis is restricted in spruce stands due to the inaccessibility of prey in dense needle litter. Molecular gut content analysis suggested that feeding on collembolan prey increases with litter mass in L. crassipes whereas the opposite was true for L. mutabilis confirming that dense needle litter restricts prey accessibility in L. mutabilis. Natural variations in stable isotope signatures suggest that compared to L. mutabilis the smaller L. crassipes relies more on root derived carbon. The results indicate that trophic niches of centipede species are defined by the combined effect of habitat structure and body size and vary little with forest age and tree identity. Combining three novel techniques for delineating predator – prey interactions for the first time allowed insight into major trophic interrelationships and their driving forces in temperate forest soil food webs.