¹⁵N/¹⁴N ratios of amino acids as a tool for studying terrestrial food webs: a case study of terrestrial insects (bees, wasps, and hornets)

Abstract

Compound-specific stable isotope analysis (CSIA) of amino acids is a new method that enables estimates of trophic position for consumers in food webs. We examined the nitrogen isotopic composition (d 15 N) of amino acids of Japanese social insects (three bee, three wasp, and four hornet species) to evaluate the potential of CSIA of amino acids in studies of terrestrial food webs. For wasps, we also examined samples at different growth stages (ranging from egg to adult) to assess the effect of metamorphosis on CSIA estimates of trophic position. The d 15 N values of bulk tissues for Japanese social insects are only weakly correlated with the biologically expected trophic positions. In contrast, the trophic positions estimated from the d 15 N values of amino acids (yielding values of between 2.0 and 2.3 for bees, between 2.8 and 3.3 for wasps, and between 3.5 and 4.1 for hornets) are consistent with the biologically expected trophic positions for these insects (i.e., 2.0 for bees, 3.0 for wasps, and 3.0-4.0 for hornets). Although large variability is observed among the d 15 N values of individual amino acids (e.g., ranging from 3.0 to 14.9& for phenylalanine), no significant change is observed in the trophic position during wasp metamorphosis. Thus, the CSIA of amino acids is a powerful tool for investigating not only aquatic food webs but also terrestrial food webs with predatory insects.

Isotopic analyses suggest mammoth and plant in the diet of the oldest anatomically modern humans from far southeast Europe

“…Based on these empirical estimations 21, 55 , equations were established to calculate the trophic position (TP) in terrestrial C 3 and aquatic food webs. For C3-plant-based ecosystems: TP(C3) = [(Δ 15 N Glu-Phe  + 8.4)/7.6] + 1.…”

Microbes are trophic analogs of animals

“…Altogether, we show that microbes can be integrated with plants and animals in a food chain, thereby unifying the macro-and microbiome in studies of trophic ecology. intertrophic 15 N-discrimination within amino acids extracted from consumer taxa, focusing on two key compounds: glutamic acid and phenylalanine (17,19,20,26). For microbial organisms to be trophically equivalent to animals, their respective patterns of intertrophic 15 N-discrimination in glutamic acid and phenylalanine must mirror those of animals.…”

“…Using amino acid stable isotope fingerprinting (17)(18)(19)(20), we measure with high accuracy the trophic positions (TPs) of cultured and freeroaming organisms. In past work, this method has produced accurate TP estimates of zooplankton (18,21), fish (17), gastropods (17), amphibians (22), and insects (19,20), ranging from simple herbivores to higher-order carnivores.…”

“…Using amino acid stable isotope fingerprinting (17)(18)(19)(20), we measure with high accuracy the trophic positions (TPs) of cultured and freeroaming organisms. In past work, this method has produced accurate TP estimates of zooplankton (18,21), fish (17), gastropods (17), amphibians (22), and insects (19,20), ranging from simple herbivores to higher-order carnivores. Although the utility of isotopic fingerprinting has been demonstrated in both aquatic (17,21,23,24) and terrestrial ecosystems (19,20), there remains an unbridged knowledge gap between the macro-and microbiome.…”

Stable isotope analysis of the gladius to investigate migration and trophic patterns of the neon flying squid (Ommastrephes bartramii)

“…Especially Ruiz-Cooley et al (2013) used a novel analysis method from both bulk tissues and individual amino acids (phenylalanine and glutamic acid) in both gladii and muscle of D. gigas captured in the Northern California Current System enabling them to detail the various migration behaviors shown by this species. This method also enables estimation of the trophic level by a comparison of the ı 15 N values for glutamic acid and phenylalanine (Chikaraishi et al, 2011). The method is a powerful tool for ecological food web studies, however the requirement for specialized equipment has precluded its more generally use.…”