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 Panicum virgatum 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 (Spodoptera frugiperda).