Dissertation Research: Seed Dispersal by Specialist vs. Generalist Foragers: An Empirical Test

这项研究将验证一个普遍的假设，即一个专业的食果动物（Phainopepla nitens）比一群通才的觅食动物更能传播沙漠槲寄生（Phoradendron californicum）的种子。该项目将审查种子传播的组成部分，这些组成部分可能会随着传播剂的质量（按植物所产生的费用来衡量）而变化。传播的组成部分包括处理过的种子的比例、处理过的种子的存活率和分散的种子的存活率。传播系统的复杂性，包括寄主树种、种子结块和一年中的时间对发芽和幼苗建立的影响将进行实验研究。因为每一个组成部分都可以根据每一个建立的幼苗所浪费的种子来衡量，研究人员将定量地比较由专家提供的传播成本和由一组通才提供的传播成本。这项研究将表明扩散共生实际上如何影响植物繁殖。虽然从技术上讲，专家或通才的种子传播都是互惠互利的，但这项研究将区分鸟类和植物之间的强相互作用和弱相互作用。这将通过研究槲寄生繁殖的果实防御、种子传播和幼苗建立的综合效应来完成。

This research will test the general hypothesis that a specialist frugivore (Phainopepla nitens) provides superior seed dispersal for desert mistletoe (Phoradendron californicum) than does a group of generalist foragers. The project will examine components of seed dispersal that can be expected to vary with the quality, measured in terms of costs incurred by the plant, of the dispersal agent. Such components of dispersal include proportion of seeds handled, survival of handled seeds, and survival of dispersed seeds. Complexities of the dispersal system, including impact of host tree species, seed clumping, and time of year on germination and seedling establishment will be examined experimentally. Because each of the components can be measured in terms of seeds wasted for each established seedling, researchers will quantitatively compare the cost of dispersal provided by a specialist with that provided by a group of generalists. This study will indicate how a dispersal mutualism actually influences plant reproduction. While seed dispersal by either specialists or generalists is technically mutualism, the study will distinguish strong from weak interactions between the birds and plants. This will be accomplished by examining the combined effects of fruit defense, seed dispersal, and seedling establishment for mistletoe reproduction.