International Research Fellowship Program: The Effect of Resource Availability on Mechanisms of Ant Species Diversity

该奖项由2009年美国复苏和再投资法案(公法111-5)资助。国际研究奖学金计划使美国科学家和工程师能够在国外进行9至24个月的研究。该计划的奖项提供了联合研究的机会，并利用国外独特或互补的设施、专业知识和实验条件。该奖项将支持Jessica M.Pearce博士与Xim S.Cerda博士在西班牙Esta ion Biologica de Donana合作的为期24个月的研究奖学金。竞争被认为是对群落结构最重要的影响之一，特别是在蚂蚁聚集中。在许多群落中，蚂蚁物种在成为好的发现者(首先到达食物资源)和在行为上控制它们之间进行权衡，限制了其他物种的获取。尽管蚂蚁主宰食物的方式已经有了很好的描述，但人们对资源发现的模式和机制知之甚少。对蚂蚁群落结构的这种理解上的差距是相对重要的，因为最近的理论工作表明，可能推动聚集动态的是资源发现，而不是优势。研究表明，快速发现者可能通过设定迟缓的支配者在群落中生存所必须达到的发现率来影响群落结构。这种观点与传统的解释不同，传统的解释认为，发现是不太占优势的物种用来逃避？更多优势物种对食物资源的排斥。利用资源补充和物种转移实验，正在检验三个假设：a)蚂蚁物种发现资源的机制取决于资源可获得性；b)地中海蚂蚁群落中存在优势-发现权衡；以及c)资源可获得性通过允许缓慢行为优势物种的持续存在来增加物种丰富度。资源发现模式和机制的特点是对发现(发现成功发现的时间和比例)和特定物种的觅食密度进行广泛调查，并拍摄属于不同物种的个体觅食行为模式。人们的期望是，蚂蚁物种将在较低的资源水平上从基于个体的觅食策略转变为在较高的资源水平上基于群体和个体的组合觅食策略。通过将上述发现数据与通过行为试验收集的地中海物种的优势度排名相关联，确定了优势度发现权衡的存在和性质。考虑到权衡，预计在较高资源环境中发现的中值时间会较慢，这是由于缓慢的优势蚂蚁的出现、持续和丰富。由于资源发现是任何蚂蚁群落中竞争的关键组成部分，这项以机制为重点的研究正在产生数据，以澄清权衡如何持续和发挥作用。这些数据正被用来生成模型，这些模型探索不同的资源发现机制如何有助于不同资源可获得性水平下的物种共存。此外，仅在有限数量的社区中调查了存在支配地位-发现权衡的证据。测试权衡？S出现在一个新的蚂蚁组合中，用来检验它作为物种多样性解释的更广泛的重要性。第三，这项工作检验了新的假设，即发现，而不是主导，驱动蚂蚁组装组成。这一观点与过去对权衡的解释是一种独特的背离，而这种权衡以前没有经过经验检验。

0852917PearceThis award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).The International Research Fellowship Program enables U.S. scientists and engineers to conduct nine to twenty-four months of research abroad. The program's awards provide opportunities for joint research, and the use of unique or complementary facilities, expertise and experimental conditions abroad.This award will support a twenty-four month research fellowship by Dr. Jessica M. Pearce to work with Dr. Xim S. Cerda at the Estacion Biologica de Donana in Spain.Competition is considered one of the most significant influences on community structure, especially in ant assemblages. In many communities, ant species trade-off between the ability to be good discoverers, arriving at food resources first, and to behaviourally dominate them, limiting access by other species. Although the ways in which ants dominate food are well-characterized, little is known about the patterns and mechanisms of resource discovery. This gap in the understanding of ant community structure is relatively important because recent theoretical work suggests that resource discovery, not dominance, may drive assemblage dynamics. It is suggested that fast discoverers may influence community structure by setting the rate of discovery that slow dominants must meet to persist in the community. This perspective contrasts with the traditional interpretation that discovery is used by less dominant species to ?escape? exclusion at food resources by more dominant species. Using resource supplementation and species removal experiments, three hypotheses are being tested: a) mechanisms for resource discovery by ant species vary depending on resource availability; b) the dominance-discovery trade-off is present in Mediterranean ant communities; and c) resource availability increases species richness by allowing the persistence of slow behaviorally dominant species. Resource discovery patterns and mechanisms are being characterized by performing extensive surveys of discovery (time to discovery and proportion successful discoveries) and species-specific forager density as well as by filming the patterns of search behavior of individual foragers belonging to different species. The expectation is that ant species will shift from an individual-based foraging strategy at lower resource levels to a combined group- and individual-based foraging strategy at higher resource levels. The presence and nature of a dominance-discovery trade-off is being determined by correlating the above discovery data with dominance rankings for Mediterranean species collected via behavioral trials. Given the trade-off, it is expected that a slower median time to discovery in higher resource environments occurs as a result of the appearance, persistence, and abundance of slow dominant ants.Since resource discovery is a crucial component of competition in any ant community, this mechanism-focused research is generating data that clarify how the trade-off persists and functions. These data are being used to generate models that explore how different mechanisms of resource discovery contribute to species coexistence under different levels of resource availability. Furthermore, evidence for the existence of the dominance-discovery trade-off has only been investigated in a limited number of communities. Testing for the trade-off?s presence in a new assemblage of ants serves to examine its broader importance as an explanation for species diversity. Third, this work examines the novel hypothesis that discovery, not dominance, drives ant assemblage composition. This perspective is a unique departure from past interpretation of the trade-off that has not previously been empirically examined.