Data from: The influence of herbivory and weather on the vital rates of two closely related cactus species

Herbivory has long been recognized as a significant driver of plant population dynamics, yet its effects along environmental gradients are unclear. Understanding how weather modulates plant–insect interactions can be particularly important for predicting the consequences of exotic insect invasions, and an explicit consideration of weather may help explain why the impact can vary greatly across space and time. We surveyed two native prickly pear cactus species (genus Opuntia) in the Florida panhandle, USA, and their specialist insect herbivores (the invasive South American cactus moth, Cactoblastis cactorum, and three native insect species) for five years across six sites. We used generalized linear mixed models to assess the impact of herbivory and weather on plant relative growth rate (RGR) and sexual reproduction, and we used Fisher's exact test to estimate the impact of herbivory on survival. Weather variables (precipitation and temperature) were consistently significant predictors of vital rate variation for both cactus species, in contrast to the limited and varied impacts of insect herbivory. Weather only significantly influenced the impact of herbivory on Opuntia humifusa fruit production. The relationships of RGR and fruit production with precipitation suggest that precipitation serves as a cue in determining the trade-off in the allocation of resources to growth or fruit production. The presence of the native bug explained vital rate variation for both cactus species, whereas the invasive moth explained variation only for O. stricta. Despite the inconsistent effect of herbivory across vital rates and cactus species, almost half of O. stricta plants declined in size, and the invasive insect negatively affected RGR and fruit production. Given that fruit production was strongly size-dependent, this suggests that O. stricta populations at the locations surveyed are transitioning to a size distribution of predominantly smaller sizes and with reduced sexual reproduction potential.

植食作用长期以来被公认为驱动植物种群动态的关键因子，但其沿环境梯度的生态效应仍不明晰。解析气象因子如何调控植物-昆虫互作，对于预测外来昆虫入侵的生态后果尤为关键；而明确纳入气象因子的考量，或有助于解释为何入侵昆虫的影响在空间与时间尺度上存在显著差异。本研究于美国佛罗里达狭长地带，针对2种本土梨果仙人掌（仙人掌属*Opuntia*）及其专性植食性昆虫（包括入侵性南美仙人掌螟*Cactoblastis cactorum*，以及3种本土昆虫物种）开展了为期5年、覆盖6个样地的野外调查。本研究采用广义线性混合模型（generalized linear mixed models），评估植食作用与气象因子对植物相对生长率（relative growth rate, RGR）及有性生殖的影响；同时采用费舍尔精确检验（Fisher's exact test），估算植食作用对植物存活率的影响。气象变量（降水量与气温）始终是两种仙人掌物种生活史关键速率变异的显著预测因子，这与昆虫植食作用影响有限且效应不一的结果形成鲜明对比。气象因子仅对*Opuntia humifusa*（铺地仙人掌）的果实生产受植食作用的调控效应存在显著影响。相对生长率与果实生产随降水量的变化关系表明，降水量可作为信号因子，调控植物在资源分配于生长还是果实生产之间的权衡策略。本土植食性蝽类的存在可解释两种仙人掌的生活史关键速率变异，而入侵性螟蛾仅对*Opuntia stricta*（直刺仙人掌）的生活史关键速率变异存在解释力。尽管植食作用对不同生活史关键速率以及不同仙人掌物种的效应存在不一致性，但近半数*Opuntia stricta*植株的个体大小出现下降，且入侵昆虫对其相对生长率与果实生产存在显著负向影响。鉴于果实生产与植株大小高度相关，本研究结果表明，在所调查样地中的*Opuntia stricta*种群正朝着以小型个体为主的体型分布格局转变，且种群有性生殖潜力有所下降。