Traditional ecological models ignore evolutionary considerations, assuming that phenotypic traits are fixed attributes of species. Conversely, traditional evolutionary models ignore ecological considerations; key parameters such as selection coefficients and population sizes are treated as fixed parameters rather than as emergent, dynamic outcomes of intra- and interspecific interactions. Feedbacks between ecology and evolution can drastically alter key theoretical results. For instance, interest in many ecological models centers on the conditions on model parameters that must be satisfied in order for species to coexist stably. But those model parameters typically reflect evolvable phenotypic traits, and evolution by natural selection favors traits that increase relative fitness, independent of their effects on coexistence or stability. Trait evolution might therefore make population dynamic stability and ecological coexistence either more or less likely. Similarly, maintenance of genetic variation in evolutionary models typically requires an appropriate balance of selection, mutation, drift, and migration, but ecological dynamics affecting species’ population sizes will determine whether that balance is realized. More deeply, ecology and evolution are in many cases inherently inseparable. For instance, if the stability of population dynamics (e.g., cycles vs. equilibria) depends on the genetic diversity of the population, and the genetic diversity depends on the stability of the population dynamics (e.g., because only cycles permit temporally-varying selection pressure), then neither stability nor genetic diversity can be understood in isolation. The theme of the proposed symposium is “The Interplay of Ecology and Evolution at ‘Micro’ and ‘Macro’ Scales: Empirically-Motivated Theory.” Evolutionary models can be roughly classified into models of microevolution, and models of macroevolution (speciation and extinction). Similarly, ecological models can be roughly divided into "microscale" models that focus on one or a few species at a single site, and those that focus on more species at larger spatial scales. Our symposium considers the interplay of ecology and evolution at both "micro" and "macro" scales, and an important question is how to relate micro- and macroscale processes and patterns. Considering ecology and evolution together necessarily demands somewhat complex models, creating a need for well-motivated ways to limit model complexity to a manageable level. All of our invited speakers will present empirically-motivated theory, using data from specific real-world systems to guide theory development and testing. Many of our speakers draw their inspiration from tractable model systems, allowing development of empirically-motivated theory without sacrificing generality.