Bayesian hierarchical modeling of size spectra

Abstract

AbstractA fundamental pattern in ecology is that smaller organisms are more abundant than larger organisms. This pattern is known as the individual size distribution (ISD), which is the frequency of all individual body sizes in an ecosystem.The ISD is described by a power law and a major goal of size spectra analyses is to estimate the exponent of the power law, λ. However, while numerous methods have been developed to do this, they have focused almost exclusively on estimating λ from single samples.Here, we develop an extension of the truncated Pareto distribution within the probabilistic modeling language Stan. We use it to estimate multiple λs simultaneously in a hierarchical modeling approach.The most important result is the ability to examine hypotheses related to size spectra, including the assessment of fixed and random effects, within a single Bayesian generalized (non)-linear mixed model. While the example here uses size spectra, the technique can also be generalized to any data that follows a power law distribution.