Department of Integrative Biology, University of Texas at Austin, Austin, TX 78712, USA.
Department of Entomology, Pennsylvania State University, University Park, PA 16802, USA.
Ann Bot. 2024 Nov 13;134(5):815-826. doi: 10.1093/aob/mcae118.
Damage from insect herbivores can elicit a wide range of plant responses, including reduced or compensatory growth, altered volatile profiles, or increased production of defence compounds. Specifically, herbivory can alter floral development as plants reallocate resources towards defence and regrowth functions. For pollinator-dependent species, floral quantity and quality are critical for attracting floral visitors; thus, herbivore-induced developmental effects that alter either floral abundance or attractiveness may have critical implications for plant reproductive success. Based on past work on resource trade-offs, we hypothesize that herbivore damage-induced effects are stronger in structural floral traits that require significant resource investment (e.g. flower quantity), as plants reallocate resources towards defence and regrowth, and weaker in secondary floral traits that require less structural investment (e.g. nectar rewards).
In this study, we simulated early-season herbivore mechanical damage in the domesticated jack-o-lantern pumpkin Cucurbita pepo ssp. pepo and measured a diverse suite of floral traits over a 60-d greenhouse experiment.
We found that mechanical damage delayed the onset of male anthesis and reduced the total quantity of flowers produced. Additionally, permutational multivariate analysis of variance (PERMANOVA) indicated that mechanical damage significantly impacts overall floral volatile profile, though not output of sesquiterpenoids, a class of compounds known to recruit specialized cucumber beetle herbivores and squash bee pollinators.
We show that C. pepo spp. pepo reduces investment in male flower production following mechanical damage, and that floral volatiles do exhibit shifts in production, indicative of damage-induced trait plasticity. Such reductions in male flower production could reduce the relative attractiveness of damaged plants to foraging pollinators in this globally relevant cultivated species.
昆虫食草动物的损害会引发植物的广泛反应，包括减少或补偿性生长、改变挥发性特征，或增加防御化合物的产生。具体来说，食草动物可以改变花的发育，因为植物将资源重新分配到防御和再生功能上。对于依赖传粉者的物种来说，花的数量和质量对吸引花的访客至关重要；因此，改变花的丰度或吸引力的食草动物诱导的发育效应可能对植物的繁殖成功有重要影响。基于过去对资源权衡的研究，我们假设在需要大量资源投入的结构花特征（如花的数量）上，食草动物损害引起的效应更强，因为植物将资源重新分配到防御和再生上，而在需要较少结构投资的次生花特征（如花蜜奖励）上较弱。
在这项研究中，我们模拟了在驯化的南瓜 Cucurbita pepo ssp. pepo 中早期季节的食草动物机械损伤，并在 60 天的温室实验中测量了一系列不同的花特征。
我们发现机械损伤延迟了雄性开花的开始，并减少了产生的花朵总数。此外，多元方差分析（PERMANOVA）表明，机械损伤显著影响整体花挥发性特征，尽管不影响倍半萜的产生，倍半萜是一类已知招募专门的黄瓜甲虫食草动物和南瓜蜂传粉者的化合物。
我们表明，C. pepo spp. pepo 在受到机械损伤后减少了对雄性花生产的投资，而花的挥发性确实表现出生产的变化，表明损伤诱导的特征可塑性。这种雄性花生产的减少可能会降低受损植物对觅食传粉者的相对吸引力，而在这种具有全球相关性的栽培物种中，传粉者是很重要的。
