Sample consistency matters — Stable isotopes (d15N and d13C) exhibit wide variation among individuals within bee species native to North America (Hymenoptera:Apidae)

Authors: TSALICKIS, ALEXANDRA - Auburn University; Campbell, Joshua; Duffy, Margaret; VACHULA, RICHARD - Auburn University

Submitted to: Journal of Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/27/2025
Publication Date: 10/6/2025
Citation: Tsalickis, A., Campbell, J.W., Duffy, M.R., Vachula, R.S. 2025. Sample consistency matters — Stable isotopes (d15N and d13C) exhibit wide variation among individuals within bee species native to North America (Hymenoptera:Apidae). Journal of Insect Science. 25(5). Article ieaf083. https://doi.org/10.1093/jisesa/ieaf083.
DOI: https://doi.org/10.1093/jisesa/ieaf083

Interpretive Summary: Stable isotopes are different forms of an element containing added neutrons but maintain the same chemical and physical properties as the most common form of the element and do not decay. In ecology, carbon and nitrogen isotopes can give insights into an organism's diet and trophic status. We examined C and N stable isotopes from different body parts in three different native bee species. Our results indicate that statistical differences among insect body parts do not signify ecological differences and, thus, an entire insect specimen does not need to be utilized for stable isotope analysis. Additionally, our data showed wide ranges of C and N isotope values for the three bee species suggesting that large sample sizes are needed to gather information on diet and trophic status of bees.

Technical Abstract: Stable isotope analysis is scarcely utilized among bee researchers. One reason for this scarcity is unclear methods when determining whether to utilize the entire insect/arthropod or certain body parts for isotope analysis and how to interpret isotope data. Here, we analyzed d15N and d13C isotopic compositions of the abdomen, head, and leg of three native bee species (Centris pallida, Melissodes bimaculata, and Bombus griseocollis). We hypothesized that the abdomen d15N and d13C values would be significantly different compared to the heads and legs because the abdomen contains metabolically active organs, but the head and leg would not exhibit differences in either d15N or d13C isotopic compositions. Overall, we found varying degrees of statistical differences among the different body parts for isotope values. However, based on the isotope values, our results indicate that statistical differences among insect body parts do not signify ecological differences. We also suggest that it is permissible to use an insect body part (e.g., single leg) rather than the whole insect body for stable isotope analysis. Finally, we suggest that when designing an experiment using stable isotope analysis, it is important to focus on using a relatively large sample size rather than targeting body parts due to wide variance observed within individuals, especially if the goal is to determine population level ecological differences.