More than just meat: Carcass decomposition shapes trophic identities in a terrestrial vertebrate

Most food web models fail to account for the full complexity of interactions within a community, particularly where microbes are involved. Carcasses are microbe-rich resources and may represent a common nexus for the macrobiome and microbiome, effectively uniting autotrophs, consumers, predators and microbiota. We evaluated the role of carcasses as multitrophic resources and explored dietary partitioning for a sexually dimorphic obligate scavenger known for its hierarchical social system. This study was set in a well-studied community of camelids Vicugna, Lama guanicoe, pumas Puma concolor and Andean condors Vultur gryphus in the Andes. We hypothesized that condors, by feeding on trophically distinct dietary substrates within any given carcass, would have highly variable trophic position (TP) values. Furthermore, we expected that the microbial consumers within the carcass would inflate TP values in both, the carrion and the condors. Thus, we expected that the trophic heterogeneity within a carcass could facilitate sex-based dietary partitioning in condors. We used a multifaceted approach to assess the foraging of Andean condors, using regurgitated pellet and bulk isotopic analyses, and also quantified the TP of the entire community of graminoids, camelids, camelid carrion, pumas, and female and male condors employing compound-specific stable isotopes analysis of amino acids. Our analysis of condor pellets and bulk isotopes revealed non-trivial plant consumption, close to 10% of condor diet. Isotope analysis of amino acids revealed that condors had highly variable TPs (2.9 ± 0.3) compared to pumas (3.0 ± 0.0) and camelids (2.0 ± 0.1), likely representing ‘trophic omnivory’, wherein the condors consume plants (TP = 1.0 ± 0.1) and microbe-colonized carrion (2.3 ± 0.1). Female condors exhibited a TP (2.8 ± 0.2) lower than strict carnivory, suggesting that they consume more plant biomass in a carcass, while males (TP = 3.1 ± 0.3) are likely consuming more of the microbe-rich animal tissue. Our study highlights that carcasses represent a trophically heterogeneous resource and that vertebrate scavengers can feed across trophic groups within the carcass, from autotrophs to secondary consumers, and from both the macrobiome and microbiome. Thus, integration of microbes in macroecological contexts can help to resolve trophic identity, and better characterize the importance of microbes in detritivorous and omnivorous species. Read the free Plain Language Summary for this article on the Journal blog.Fil: Barceló, Gonzalo. University of Wisconsin; Estados UnidosFil: Perrig, Paula Leticia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina. University of Wisconsin; Estados UnidosFil: Dharampal, Prarthana. University of Wisconsin; Estados UnidosFil: Donadio, Emiliano. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina. Fundación Rewilding Argentina; ArgentinaFil: Steffan, Shawn A.. United States Department of Agriculture. Agriculture Research Service; Estados Unidos. University of Wisconsin; Estados UnidosFil: Pauli, Jonathan Nicholas. University of Wisconsin; Estados Unido

CSIA for Trophic position

d15N data from amino acids used for TP calculatio

Osmia pollen chemistry analysis table

Proximate nutrient chemistry analysis of natural and sterilized and natural Osmia polle

Comparing compound-specific and bulk stable nitrogen isotope trophic discrimination factors across multiple freshwater fish species and diets

Compound-specific nitrogen stable isotope analysis provides an approach for estimating animal trophic position that may overcome key issues associated with stable isotope analysis of bulk tissue. Yet compound-specific trophic discrimination factors have not been estimated for a broad range of habitats, taxa, and diets. We conducted a controlled-feeding experiment to characterize the variation in compound-specific (TDFAA) and bulk (TDFBulk) trophic discrimination factors of four freshwater fish species fed on three distinct diets. We also compared TDFAA of fish muscle and scale to evaluate the viability of scales for making food web inferences. Mean TDFBulk was 2.2±0.9‰ (±1 SD) and there were significant effects of species and diet trophic position on TDFBulk. Mean TDFAA was 6.9±0.8‰ (±1 SD). Although there was no effect of species on TDFAA, there were significant differences in TDFAA across the three diets. TDFAA from fish scales were not significantly different from those of muscle. Our study illustrates the advantages of estimating trophic position using compound-specific stable isotopes and the need for continued investigation of factors resulting in variation in TDF values.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Bluegill isotope and morphometric analysis - 12.28.2020

Dataset associated with article: Mays JR, DeWitt TJ, Dharampal P, Andrus CFT, Findlay RH (2019) Frequent habitat migration, phenotypic plasticity, and residual ecophenotypy revealed by isotope-based natal habitat inference in bluegill sunfish, Lepomis macrochirus. Evol Ecol Res 20(6): article 3235. https://evolutionary-ecology.com/abstracts/v20/3235.htm

Data from: Omnivory in bees: elevated trophic positions among all major bee families

As pollen- and nectar-foragers, bees have long been considered strictly herbivorous. Their pollen-provisions, however, are host to abundant microbial communities, which feed on the pollen before/while it is consumed by bee larvae. In the process, microbes convert pollen into a complex of plant and microbial components. Since microbes are analogous to metazoan consumers within trophic hierarchies, the pollen-eating microbes are, functionally, herbivores. When bee larvae consume a microbe-rich pollen complex, they ingest proteins from plant and microbial sources, thus should register as omnivores on the trophic “ladder.” We tested this hypothesis by examining the isotopic compositions of amino acids extracted from native bees collected in North America over multiple years. We measured bee trophic position across the six major bee families. Our findings indicate that bee trophic identity was consistently and significantly higher than that of strict herbivores, providing the first evidence that omnivory is ubiquitous among bee fauna. Such omnivory suggests that pollen-borne microbes represent an important protein source for larval bees, which introduces new questions as to the link between floral fungicide residues and bee development