Overcompensation in Response to Mammalian Herbivory: Measure of True Fitness, Alternative Selection Pressures, Compara- tive Responses, and the Genetics of Overcompensation

在过去的十年里，围绕食草动物对植物的潜在有益影响展开了激烈的辩论。到目前为止，解决食草动物是否对植物有益的问题一直是一个问题，即令人信服的数据尚未公布。然而，最近的实验和观察研究表明，当骡鹿和麋鹿觅食单果的二年生鹿、猩红Gillia、Ipomopsis ggregata时，种子产量和随后的幼苗存活的相对适合度平均是未吃的对照的2.4倍。鉴于这些结果，过度补偿不能轻易消除，尽管关于草食动物对植物的潜在有益影响还需要更多的信息。有必要在更多层面上更详细地了解植物与食草动物之间的相互作用。这个项目的目标是：1.研究草食动物的长期适合性效应；2.研究次生草食动物对植物生长和繁殖的影响；3.确定是否存在除草食动物以外的选择压力，潜在地参与产生观察到的反应模式(例如，火和霜冻损害)；4.启动分子遗传学研究，以努力了解与过度补偿有关的一些潜在遗传机制；5.开始对另外两个不同的位置进行比较研究，以了解猩红Gilia的过度补偿有多常见，并开始了解这种反应的一些进化。这些研究的结果有可能对生态学、进化生物学和农业的基础和应用领域做出重要贡献。

Over the past decade, there has been a heated debate surrounding the potential beneficial effects of herbivores on plants. Up to now, the problem of resolving the question as to whether herbivory could ever be good for plants has been that convincing data have not been published. However, recent experimental and observational studies showed that when mule deer and elk browsed the monocarpic biennial, scarlet gillia, Ipomopsis aggregata, relative fitness in terms of seed production and subsequent seedling survival averaged 2.4 times that of the uneaten contols. In light of these results, over compensation cannot be easily dismissed, although more information is needed on potential beneficial effects of herbivores on plants. It is necessary to understand the interactions between plants and their herbivores at many levels in much greater detail. The goals of this project are: 1. To examine the long-term fitness effects of herbivory; 2. To examine the effects of secondary herbivory on plant growth and reproduction; 3. To determine if there are selection pressures other than herbivory potentially involved in producing the observed response patterns (e.g., fire and frost damage); 4. To initiate molecular genetic studies in an effort to understand some of the potential genetic mechanisms involved in overcompensation; and 5. To begin comparative studies on two additional diverse sites to see how common overcompensation by scarlet gilia is and to begin to understand something of the evolution of such a response. The results of these studies have the potential for making important contributions to both basic and applied fields of ecology, evolutionary biology and agriculture.