Trophic Spectra: An Effective Method for Characterizing Structure and Function of Food Webs

Food web analysis has provided critical insights intounderstanding biodiversity patternsand ecological processes. However, it still remains challenging since current approaches are either overly detailed and unable to track changes in trophic links, or mechanistic yet rely on assumptions that are frequently violated. The trophic spectra, describing community attributes across trophic positions, provide an effective framework for indicating food webs in a relatively simplified way, with an accurate reflection of trophic interactions. Despite the proposal of this method 20 years ago, its application is limited only tofigurate description. Here, we explored the general form of trophic spectra and quantitatively linked it to food web structure and function. We tested the general form as a logistic function resulting from the energetic hypothesis by using 17 sets of fish individual data and 152 sets of food web data across various aquatic ecosystems, and achieved satisfactory fitness (R2=0.89±0.06 at the individual-based level and 0.88±0.07 at the trophic group-based level). Our method exhibited a significant and stable relationship between the parametersof trophic spectra and food webs. Specifically, the steepness (r), the inflection point (x0), the intercept after linear transformation (rx0) and the derived parameter e-k correspond to theomnivory degree, food chain length, trophic pyramid shape, and trophic transfer efficiency, respectively.Trophic spectra support integration of food web researches since its low sensitivity to trophic resolution and time scale, providing universal and comparable proxies. It can be a valuable new tool for food web research by facilitating comparisons across various ecosystem types and periods.