DISSERTATION RESEARCH: An Experimental Test of the Relationship Between Seed Predator Density and Recruitment Limitation in Tropical Trees

摘要-Rejmanek，Marcel(0309408)负责维持热带森林树木高度多样性的过程还没有被很好地理解。越来越多的证据表明，一个特别重要的过程是招募限制，即许多物种的种子不能在另一个物种的种子到达有利于萌发和生长的地点之前到达。因此，竞争力较弱的物种仅仅凭借在生长方面领先于竞争较强的物种而得以生存。然而，招聘限制可能并不完全是偶然的。相反，它更多的时候可能是“机会”的结果，种子被撒了出去。许多动物是种子的重要消费者和传播者，可以预见，种子是否被吃掉或散布和储存取决于处理种子的动物的类型，一个地区有多少动物来处理种子，动物对任何特定类型的种子的相对偏好，以及动物将种子藏在哪里。有人假设，当食籽动物有更多食物时，会有更多的种子被散布和储存，但这还没有得到实验验证。这项研究将以三种不同大小种子的棕榈树和多刺口袋鼠(Heteromys Desmarestianus)--伯利兹低地热带雨林中主要的哺乳动物种子捕食者/传播者--为实验对象来验证这一假设。我们会通过实验来降低麦长管藻的丰度，然后比较种子的移除率和传播率，以及在有和没有减少麦长管藻丰度的地块之间储存种子的位置。这是第一项对热带森林中种子捕食者密度和招募限制之间的关系进行实验测试的研究，是加州大学戴维斯分校、伯利兹研究与环境教育基金会和伯利兹大学的科学家合作的。资金来自生物科学局的学位论文改进补助金，以及来自国际科学与工程计划的额外资金。

Abstract- Rejmanek, Marcel (0309408)The processes that are responsible for maintaining the high levels of diversity of trees in tropical forests are not well understood. There is increasing evidence that a particularly important process is recruitment limitation, where the seeds of many species do not reach sites favorable for germination and growth before the seeds of another species do. As a result, less competitive species are able to persist simply by virtue of getting a head start in growth over more competitive species. However, recruitment limitation may not be due entirely to chance. Instead, it more often may be an outcome of the "opportunity" seeds have to be dispersed. Many animals are important consumers and dispersers of seeds, and it can be expected that whether a seed gets eaten or dispersed and cached depends on the type of animal handling the seed, how many animals there are in an area to handle the seed, the relative preference animals have for any particular type of seed, and where the animal caches the seed. It has been hypothesized that more seeds will be dispersed and cached when seed-eating animals have more food, but this has not been experimentally tested. This research would test this hypothesis with an experiment focused on three species of palm with different sized seeds, and the spiny pocket mouse (Heteromys desmarestianus), the dominant mammal seed predator/disperser in the lowland rainforests of Belize. The abundance of H. desmarestianu would be experimentally reduced, and then seed removal and dispersal rates, and where seeds are cached between plots with and without reduced abundance of H. desmarestianus would be compared. This is the first study to experimentally test the relationship between seed predator density and recruitment limitation in tropical forests, and is a collaboration between scientists from UC Davis, the Belize Foundation for Research & Environmental Education, and the University of Belize. Funding has been provided through a Dissertation Improvement Grant from the Directorate of Biological Science, with additional funds from the International Science and Engineering Program.