Collaborative Research: Plant Tolerance of Herbivory: A Test for Constraints on Adaptation

人类长期以来一直关注虫害对植物性能的影响。到目前为止，生态学家和农学家一直专注于植物对攻击的抵抗力，即植物威慑潜在敌人的能力。然而，昆虫的攻击很少是致命的，所以植物有机会用第二种方法来应对敌人的攻击，恢复和再生。在遭受攻击后生存和繁荣的能力称为容忍。与了解抗性的遗传学和生态学方面的研究进展相比，人们对植物恢复的了解很少。这种知识空白阻碍了对整个植物防御系统的理解。不仅要研究容忍本身的成本-收益结构，我们还需要理解容忍，以理解抵抗的适应价值。抵抗和宽容的相互依存源于两个方面的考虑。首先，抗性和耐受性可能是多余的--如果一株植物能够完全从攻击中恢复，那么抵抗攻击也几乎没有什么好处。第二个考虑来自最优防御理论。人们普遍假设，阻力因素代价高昂，因为用于阻力的资源不能也分配给增长。许多实验已经验证了这一假设，但结果喜忧参半。最近的模型表明，抵抗成本很难被检测出来，因为它们被容忍成本掩盖了。但由于人们对耐受性知之甚少，所以对耐受性成本也知之甚少。因此，评估这些重要的理论预测几乎没有依据。这些实验将使用野生芥菜物种Brassica campestris来寻找耐受成本，Brassica campestris是重要的油料作物油菜籽的野生祖先。将进行人工选择，以确定基因权衡是否会造成适应成本，从而限制油菜耐受落叶的能力。这项实验涉及选择每一代都经历严重损害的植物品系的表现，从未经历过损害的品系，以及同时经历两种情况的品系。选择将通过兄弟姐妹选择进行。经过几代的选择，将通过在所有危害环境中种植这些品系来衡量它们之间的耐性差异。因此，这些实验将检验关于遗传限制耐受性的几个主要假说，并将启动一项长期努力，以确定有助于植物恢复的生理性状和潜在的遗传位点。此外，通过检查两种环境下的选择反应，这些实验将提供对表型可塑性选择限制这一更一般问题的见解。

9815873WeisHumans have long been concerned about the impact of insect pests on plant performance. To date ecologists and agronomists have concentrated on plant resistance to attack, that is, the plant's ability to deter potential enemies. However, insect attack is rarely fatal and so plants have the opportunity for a second way to deal with enemy attack, to recover and regrow. The ability to survive and prosper after attack is called tolerance. Compared to the research progress in understanding the genetics and ecology of resistance, very little is known about plant recovery. This knowledge void hampers understanding of the total plant defense system. Not only is it important to study the cost-benefit structure of tolerance in it own right, we also need to understand tolerance to understand the adaptive value of resistance. The interdependence of resistance and tolerance emerges from two considerations. First, resistance and tolerance can be redundant-if a plant can completely recover from attack, there is little profit in also resisting attack. The second consideration arises from optimal defense theory. It is widely hypothesized that resistance factors are costly since resources devoted to resistance cannot also be allocated to growth. Numerous experiments have tested this hypothesis, but with mixed results. Recent models suggest that resistance costs are hard to detect because they are obscured by tolerance costs. But because little is known about tolerance, little is known about tolerance costs. Thus, there is little basis for evaluating these important theoretical predictions. These experiments will look for tolerance costs using a wild mustard species, Brassica campestris, which is the wild progenitor of canola, the important oil seed crop. Artificial selection will be perform to determine if genetic trade-offs impose a fitness cost that constrains the ability of B. campestris to tolerate defoliation. This experiment involves selecting for performance in plant lines that experience sever damage every generation, lines that never experience damage, and lines that experience both. Selection will be by sib-selection. Following several generations of selection, tolerance differences among the lines will be measured by growing them across all damage environments. These experiments, thus, will test several major hypotheses about genetic constraints on tolerance, and will initiate a long-term effort to identify the physiological traits, and the underlying genetic loci, that contribute to plant recovery. In addition, by examining selection response across two environments, these experiments will offer insights on the more general problem of constraints on selection for phenotypic plasticity.H:\popbio\abstracts\fy1999\9815873 (Weis abstract)