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>).

植食者取食压力在物种的分布区内存在空间异质性，进而驱动植物演化出多样化的防御策略。若低纬度地区的植食作用更强，则该区域植物的防御能力通常更强，进而可能形成防御性状的纬度梯度。然而，基于物种整个分布区所观测到的防御与纬度间的关联，可能会受到遗传亚种群间差异的混淆，进而掩盖这类纬度梯度形成的驱动因素。为此，本研究在同质园中种植了广布多年生草本植物柳枝稷（*Panicum virgatum*），其基因型来自覆盖18.5°纬度梯度的三个遗传亚种群。随后，本研究通过测定两项物理抗性性状——比叶重（leaf mass per area, LMA）和作为硅含量替代指标的叶片灰分——以及广食性植食者草地贪夜蛾（fall armyworm, *Spodoptera frugiperda*）幼虫的多项取食指标，评估了这些植物的防御策略。