Harvell C D
Section of Ecology and Systematics, Cornell University, Ithaca, New York 14853.
Q Rev Biol. 1990 Sep;65(3):323-40. doi: 10.1086/416841.
Inducible defenses are responses activated through a previous encounter with a consumer or competitor that confer some degree of resistance to subsequent attacks. While the importance of inducible resistance has long been known in host-parasite interactions, it is only recently that its importance has emerged in other natural systems. Although the structural defenses produced by invertebrates to their competitors and predators are by no means the same as an immune response triggered by parasites, these responses all share the properties of (1) specificity, (2) amplification and (3) memory. This review discusses the following ecological consequences and evolutionary causes of inducible defenses: (1) Inducible defenses render historical factors important in biological interactions and can affect the probability of individual survival and growth, as well as affect population dynamics of consumers in some circumstances. (2) Although the benefits of inducible defenses are often balanced by fitness costs, including reduced growth, reproductive output and survivorship, the role of costs and benefits in the evolution of inducible defenses is by no means clear. A more integrated approach would involve a multivariate analysis of the role of natural selection on the inducible characters of interest, their norms of reaction and correlated fitness characters. (3) The disproportionate representation of inducible, morphological defenses among clonal organisms may be due to both a higher rate of origination and enhanced selection to maintain these defenses in clonal taxa. (4) Inducible defenses should be most common when reliable cues are available, attacks by biological agents are unpredictable, and the fitness gains of defenses are balanced by the costs. An integrated approach to studying inducible defenses would thus combine mechanistic estimates of costs, population-level estimates of defense effectiveness, and genetic estimates of correlations between fitness and inducible characters. This will allow us to estimate rates of evolution in these phenotypically plastic threshold characters.
诱导性防御是通过先前与消费者或竞争者的接触而激活的反应，这种反应会赋予对后续攻击一定程度的抵抗力。虽然诱导性抗性在宿主 - 寄生虫相互作用中的重要性早已为人所知，但直到最近其在其他自然系统中的重要性才显现出来。尽管无脊椎动物针对其竞争者和捕食者产生的结构防御与寄生虫引发的免疫反应截然不同，但这些反应都具有以下特性：（1）特异性，（2）放大作用，以及（3）记忆功能。本综述讨论了诱导性防御的以下生态后果和进化原因：（1）诱导性防御使历史因素在生物相互作用中变得重要，并且会影响个体生存和生长的概率，在某些情况下还会影响消费者的种群动态。（2）虽然诱导性防御的益处通常会被适应性成本所平衡，包括生长减缓、繁殖产出减少和存活率降低，但成本和益处在诱导性防御进化中的作用尚不清楚。一种更综合的方法将涉及对自然选择在感兴趣的诱导性特征、它们的反应规范和相关适应性特征方面作用的多变量分析。（3）克隆生物中诱导性形态防御的不成比例表现可能是由于起源率较高以及在克隆类群中维持这些防御的选择增强。（4）当有可靠线索可用、生物因子的攻击不可预测且防御的适应性收益与成本相平衡时，诱导性防御应该最为常见。因此，研究诱导性防御的综合方法将结合成本的机制估计、防御有效性的种群水平估计以及适应性与诱导性特征之间相关性的遗传估计。这将使我们能够估计这些表型可塑性阈值特征的进化速率。
