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

这项研究将检验一种普遍的假设，即一种专门的果食性动物(Phainopepla Nitens)比一群多面手觅食者为沙漠槲寄生(Phoradendron CalforNicum)提供更好的种子传播。该项目将检查种子播散剂的成分，这些成分预计会随着播散剂质量的不同而变化，这些质量是根据工厂产生的成本衡量的。这些散布的组成部分包括处理的种子的比例、处理的种子的存活率和散布的种子的存活率。将通过实验研究传播系统的复杂性，包括寄主树种、种子丛生和一年中的时间对种子萌发和幼苗建立的影响。因为每一种成分都可以用每一株已建立的幼苗所浪费的种子来衡量，所以研究人员将对专家提供的传播成本与一组多面手提供的成本进行定量比较。这项研究将指出扩散互惠关系实际上是如何影响植物繁殖的。虽然专家或多面手传播种子在技术上是互惠互利的，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。这将通过检查果实防御、种子传播和幼苗建立对槲寄生繁殖的综合影响来实现。

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.