Proximity to canopy mediates changes in the defensive chemistry and herbivore loads of an understory tropical shrub, Piper kelleyi

Phytochemical traits are a key component of plant defense theory. Chemical ecology has been biased towards studying effects of individual metabolites even though effective plant defenses are comprised of diverse mixtures of metabolites. We tested the phytochemical landscape hypothesis, positing that trophic interactions are contingent upon their spatial location across a phytochemically diverse landscape. Specifically, intraspecific phytochemical changes associated with vertical strata in forests were hypothesized to affect herbivore communities of the neotropical shrub Piper kelleyi Tepe (Piperaceae). Using a field experiment, we found that phytochemical diversity increased with canopy height, and higher levels of phytochemical diversity located near the canopy were characterized by tradeoffs between photoactive and non-photoactive biosynthetic pathways. For understory plants closer to the ground, phytochemical diversity increased as direct light transmittance decreased, and these plan...

植物化学性状（phytochemical traits）是植物防御理论的核心组成部分。尽管有效的植物防御由多样的代谢物混合物构成，但化学生态学研究长期偏向于单个代谢物的效应探索。我们对植物化学景观假说（phytochemical landscape hypothesis）开展了检验，该假说提出营养级相互作用取决于其在植物化学多样景观中的空间位置。具体而言，我们假设森林垂直分层相关的种内植物化学变化，会影响新热带灌木凯利胡椒（Piper kelleyi Tepe，胡椒科Piperaceae）的植食动物群落。通过野外实验，我们发现植物化学多样性随冠层高度升高而增加，且冠层附近较高的植物化学多样性，表现为光活性与非光活性生物合成途径之间的权衡关系。对于贴近地面的林下植物，其植物化学多样性随直接光照透射率降低而升高，且这些植物……