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

[摘要]Rejmanek， Marcel(0309408)：维持热带森林树木高度多样性的过程尚不清楚。越来越多的证据表明，一个特别重要的过程是招募限制，在这个过程中，许多物种的种子没有在另一个物种的种子到达发芽和生长的有利位置之前到达。因此，竞争力较弱的物种能够仅仅凭借比竞争更强的物种在生长中获得领先优势而存活下来。然而，招聘限制可能不完全是由于机会。相反，它更多的时候可能是“机会”的种子必须被散播的结果。许多动物都是种子的重要消费者和传播者，可以预料，一粒种子是被吃掉还是被传播和贮藏起来，取决于处理种子的动物的种类，一个地区有多少动物处理种子，动物对任何特定类型种子的相对偏好，以及动物贮藏种子的地方。据推测，当吃种子的动物有更多的食物时，更多的种子会被传播和储存起来，但这还没有经过实验验证。本研究将通过一项实验来验证这一假设，该实验主要针对三种具有不同大小种子的棕榈，以及伯利兹低地雨林中主要的哺乳动物种子捕食者/传播者——刺袋鼠（Heteromys desmarestianus）。通过实验研究，对大鼠种子的丰度进行降低，然后比较种子的移除和传播速率，以及种子在不同区域的贮藏位置。这是第一个实验测试热带森林中种子捕食者密度和招募限制之间关系的研究，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们的合作成果。研究经费由生物科学理事会的论文改进基金提供，并由国际科学与工程计划提供额外资金。

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.