Do Mammals and Insects Control Tropical Forest Diversity? A Community-level Experimental Test

这一建议挑战了关于热带森林的流行观点，即林隙期动力学是决定热带森林物种组成的更新周期中最重要的部分。本研究首次通过实验验证了热带成熟森林林下的哺乳动物和昆虫控制树种多样性的假设。这一假设对热带森林的动态、多样性、保护和管理具有重要的影响。最近的观察表明，当森林失去哺乳食草动物和种子捕食者时，它们的植物物种多样性就会降低。哺乳动物群落完整的森林具有较高的物种多样性。许多热带森林保护区的偷猎和过度捕猎正威胁着食草哺乳动物的数量。如果哺乳食草动物是重要的，那么失去动物的森林可能会加速失去树种多样性。本研究以巴拿马巴罗科罗拉多岛（Barro Colorado Island， BCI）的森林为研究对象。我们的研究结果表明，林隙不影响这些森林的物种多样性；因此，必须在种子、幼苗和树苗暴露于密集草食的林下确定树种的丰度。我们提出在物种丰富的热带森林中，验证草食和种子传播控制着树种的建立、组成和多样性的假设。在过去的十年中，对热带森林的研究主要集中在作为树种多样性主要决定因素的间隙期动态的作用上。虽然对种子捕食的研究很常见，但该项目是首次尝试对哺乳动物和昆虫食草动物对热带森林多样性的影响进行群落水平的实验测试。研究结果对热带地区生物多样性的保护和管理具有重要意义。

This proposal challenges the prevalent view about tropical forests that gap phase dynamics is the most important part of the regeneration cycle for determining species composition of tropical forests. This research is the first to experimentally test the hypothesis that mammals and insects in the understory of mature tropical forest control tree species diversity. This hypothesis has important ramifications for tropical forest dynamics, diversity, conservation, and management. Recent observations suggest that when forests lose their mammalian herbivores and seed predators they develop low plant species diversity. Forests with intact mammalian fauna have high species diversity. Poaching and over-hunting in many tropical forest reserves are threatening mammalian herbivore populations. If mammalian herbivores are important, than forests that lose their fauna are likely to lose tree species diversity at an accelerated rate. The forest on Barro Colorado Island (BCI), Panama, will be studied in this research. Our findings indicate that gaps do not affect species diversity in these forests; therefore, the abundance of tree species must be determined in the understory where seeds, seedlings, and saplings are exposed to intensive herbivory. We propose to test the hypothesis that herbivory and seed dispersal control the establishment, composition, and diversity of tree species in species-rich tropical forests. %%% For the past ten years, research in tropical forests has focused on the role of gap-phase dynamics as the primary determinant of tree species diversity. Although studies of seed predation are common, this project represents the first attempt to conduct a community-level experimental test of the effects of mammalian and insect herbivores on tropical forest diversity. The results have important implications for the conservation and management of biodiversity in tropical regions.