Data and code for: Plant physical defenses contribute to a latitudinal gradient in resistance to insect herbivory within a widespread perennial grass

Herbivore pressure can vary across a species’ range, resulting in different defensive strategies. If herbivory is greater at lower latitudes, plants may be better defended there, potentially driving a latitudinal gradient in defense. However, relationships that manifest across the entire range of a species may be confounded by differences occurring within genetic subpopulations, which may obscure the drivers of these latitudinal gradients. To address this, we grew plants of the widespread perennial grass <i>Panicum virgatum</i><i> </i>in a common garden that included genotypes from three genetic subpopulations spanning an 18.5° latitudinal gradient. We then assessed defensive strategies of these plants by measuring two physical resistance traits—leaf mass per area (LMA) and leaf ash, a proxy for silica—and multiple measures of herbivory by caterpillars of the generalist herbivore fall armyworm (<i>Spodoptera frugiperda</i>).