Dissertation Research: Relative Effects of Differential Seed and Seedling Predation by Crabs on Tropical Forest Composition and Structure

博士论文研究：螃蟹对不同种子和幼苗捕食对热带森林组成和结构的相对影响。生态学家在理论文献中已经争论了一个多世纪，争论的焦点是在异质景观上构建植物群落的主要机制。提出的机制包括植物对不同环境条件的反应、不同的种子传播、不同植物物种之间的不同竞争能力和不同的种子捕食。很少有经验性的比较研究来调查这些提出的假设的相对重要性。最近，一些研究已经讨论了草食和植物对环境条件的不同反应对观察到的红树林群落变化的意义，但还没有在陆地森林中进行类似的调查。哥斯达黎加沿海次生林的初步数据表明，食草性陆地蟹和陆地寄居蟹有能力引起热带沿海森林中观察到的森林群落结构的变化。通过植被分析、种子诱捕、蟹类封育和控制以及环境条件的调控，本研究将确定蟹类捕食种子和苗木的压力对海岸森林更新格局的相对影响。这项研究的结果将对整个热带地区的沿海森林保护工作具有实际的管理作用。研究人员与哥斯达黎加民族自治大学的教职员工和学生合作，促进了哥斯达黎加原住民和被公园管理局视为保护典范的卡波·布兰科绝对保护区之间的重要工作关系。

DOCTORAL DISSERTATION RESEARCH: Relative Effects of Differential Seed and Seedling Predation by Crabs on Tropical Forest Composition and Structure0104791- Carroll. Ecologists have debated for more than a century in the theoretical literature over the predominant mechanisms that structure plant communities over a heterogeneous landscape. Proposed mechanisms include plant response to variable environmental conditions, differential seed dispersal, differential competitive abilities among plant species, and differential seed predation. There have been few empirical comparative studies that investigate the relative importance of these proposed hypotheses. Recently, several studies have debated the significance of differential herbivory versus plant response to environmental conditions on observed mangrove community shifts, yet no comparable investigations have been conducted in terrestrial forests. Preliminary data from a secondary coastal forest in Costa Rica suggests that herbivorous land crabs and terrestrial hermit crabs have the ability to induce the shifts in forest community structure observed in tropical coastal forests. Through the use of vegetation analyses, seed traps, crab exclosures and controls, and manipulations of environmental conditions, this dissertation research will determine the relative effect of seed and seedling predation pressure by crabs on the patterns of coastal forest regeneration. The results of this study will be of practical management use in coastal forest conservation efforts throughout the tropics. Researcher collaborations with faculty and students of the Universidad Nacional Autonoma of Costa Rica fosters an essential working relationship among native Costa Ricans and the Cabo Blanco Absolute Reserve that is viewed as the model of conservation by their Park Service.