Iason Glenn R, Villalba Juan J
Macaulay Institute, Craigiebuckler, Aberdeen, UK.
J Chem Ecol. 2006 Jun;32(6):1115-32. doi: 10.1007/s10886-006-9075-2. Epub 2006 May 23.
We review the evidence for behavioral avoidance of plant secondary metabolites (PSMs) and identify how, and the circumstances under which it occurs. Behavioral strategies of avoidance of PSM can only be fully understood in relation to the underlying physiological processes or constraints. There is considerable evidence that animals learn to avoid PSMs on the basis of negative postingestive effects. The extent to which this process determines foraging choices is limited by the ability of animals to experience the consequences of their behaviors and associate particular cues in foods with their specific effects in the body. The proposed learning mechanisms require that animals must at least "sample" plants that contain PSMs. They do not completely avoid PSMs, but there is evidence that they restrict their ingestion to within limits that they are physiologically able to tolerate, and that the amounts of PSM ingested result from a balance between toxicological considerations and the nutrient content of the plant material. These limits are influenced by the kinetics of PSM elimination, which underlies patterns of bite and patch selection from plant parts to landscapes. We suggest that altering spatial location of feeding (to alternative food patches or alternative foods within patches, including plant parts), and temporal distribution of feeding activity, by either cessation of feeding or by continuing to feed, but on alternative foods, can both lead to reduction of the intake and toxic effects of PSMs. We propose that the strategy of avoidance or reduction of intake of PSMs coevolved with the animal's ability to physiologically tolerate their ingestion, and that avoidance and tolerance are inversely related (the avoidance-tolerance continuum). The animals' propensity and ability to seek alternatives also vary with the dispersion of their food resources. Further work is required to test these proposals and integrate temporal and spatial aspects of foraging behavior and its nutritional consequences in relation to PSMs.
我们回顾了动物行为上避免摄入植物次生代谢产物（PSMs）的证据，并确定其发生方式及所处环境。只有结合潜在的生理过程或限制因素，才能全面理解动物避免PSMs的行为策略。有大量证据表明，动物基于负面的摄食后效应学会避免摄入PSMs。然而，这一过程在多大程度上决定觅食选择，受到动物体验其行为后果以及将食物中的特定线索与其在体内的特定效应相联系的能力的限制。所提出的学习机制要求动物至少要“品尝”含有PSMs的植物。它们并非完全避免PSMs，但有证据表明，它们会将摄入量限制在生理可耐受范围内，且摄入的PSMs量是毒理学考量与植物材料营养成分之间平衡的结果。这些限制受到PSMs消除动力学的影响，而PSMs消除动力学是从植物部分到景观的咬食和斑块选择模式的基础。我们认为，通过改变觅食的空间位置（转向替代食物斑块或斑块内的替代食物，包括植物部分）以及觅食活动的时间分布，无论是停止进食还是继续进食但选择替代食物，都可以减少PSMs的摄入量及其毒性作用。我们提出，避免或减少PSMs摄入的策略与动物生理上耐受其摄入的能力共同进化，且避免和耐受呈负相关（避免 - 耐受连续体）。动物寻找替代食物的倾向和能力也会因食物资源的分散程度而有所不同。需要进一步开展研究来验证这些提议，并将觅食行为的时间和空间方面及其与PSMs相关的营养后果整合起来。
