Abundance, Dynamics and Coexistence of Interacting Damselfishes: Quantifying the Contributions of Causal Processes Across Spatial Scales

本研究的目的是了解岛礁鱼类丰度变化的原因，这些岛礁鱼类的本地种群是通过交换繁殖产出而联系在一起的。过去二十年的研究表明，这些生物的本地种群规模通常是由同时运作的几个过程决定的，而理解这些过程的相对重要性的关键是幼虫供应和密度依赖性相互作用之间的相互作用。人们还日益认识到，不能孤立于其他亚种群或物种来考虑一个当地种群，需要考察多个空间尺度，以充分了解该系统的动态。最后，现在存在一些框架，可以使各种过程在确定当地丰度方面的贡献得到量化，并对环境特征（例如潜在竞争者的幼虫供应、生境的可得性、食物供应、捕食压力）的共变模式的后果进行评价。这些定量框架需要应用到实际系统中，以解决珊瑚礁鱼类的几个基本问题。这些包括影响局部丰度和动态的多个过程的相对重要性，其重要性的可变程度，竞争对手的相对丰度和共存的决定因素，种群调节发生的地点和方式，以及整个系统的动态行为是否与较小空间尺度上的动态预测不同。量化不同过程对多个物种的影响将使生态学家能够询问这些过程的强度如何随着物种的一般特征（例如，生活史特征、营养状况、环境类型）而变化。研究环境特征和密度依赖之间的共变将加深我们对这些系统的结构、调节和行为的洞察。本研究将重点研究栖息在法属波利尼西亚泻湖的两对共生物种豆娘鱼。这些浮游动物在特定区域内和特定区域之间竞争躲避捕食者的庇护空间。通过短期和长期的实验和观察，将获得应用两种不同的定量方法来理解阶段结构、人口开放人口动态所需的各种数据。特别是，输出的空间变化（时间平均成虫密度）将被估计为输入（每单位适宜栖息地的幼虫供应量）和决定局部丰度的相关参数的函数（密度无关的存活率；成虫饱和度或峰值密度；同种和异种定居的密度依赖；同种和异种相互作用的存活率的密度依赖）。除幼虫供应外，其他环境特征的变化将被估计，包括微生境的可用性和捕食压力。这些变量将跨越几个空间尺度（从-5英寸到200公里）进行测量。实证工作的数据将用于定量框架，以比较物种和空间尺度之间各种过程的相对重要性，解决与开放种群竞争物种共存有关的问题，并检查更大尺度上的动态是否与局部动态预测不同。

The aim of this study is to understand the causes of variation in abundance of reef fishes whose local populations are linked via exchange of reproductive output. Research over the past two decades has revealed that the size of a local population of these organisms typically is determined by several processes that operate simultaneously, and that the key to understanding the relative importance of these processes is the interplay between larval supply and density -dependent interactions. There also has been growing appreciation that a local population cannot be considered in isolation of other sub-populations or species, and that multiple spatial scales need to be examined to fully understand the dynamics of the system. Finally, several frameworks now exist that can allow the contributions of various processes in setting local abundance to be quantified and the consequences of patterns of covariation in environmental features (e.g., larval supply of potential competitors, habitat availability, food supply, predation pressure) to be evaluated. These quantitative frameworks need to be applied to real systems to resolve several fundamental - and largely unanswered - questions for reef fishes. These include the relative importance of the multiple processes that affect local abundance and dynamics, the degree of variability in their importance, the determinants of relative abundance and coexistence of competitors, where and how population regulation occurs, and whether the dynamical behavior of the system as a whole differs from that predicted from dynamics at smaller spatial scales. Quantifying the effects of various processes for multiple species will enable ecologists to ask how the intensity of these processes varies as a function of general characteristics of species (e.g., life history traits, trophic status, types of environments). Examining covariation between environmental features and density dependence will deepen our insight into the structure, regulation and behavior of such systems.This study will focus on two pairs of co-occurring species of damselfishes that inhabit lagoons of French Polynesia. These planktivores compete intra- -and inter-specifically for shelter space from predators. Using short- and long-term experiments and observations, the variety of data needed to apply two different quantitative approaches to understanding dynamics of stage--structured, demographically open populations will be obtained. In particular, spatial variation in output (time-averaged adult density) will be estimated as a function of input (larval supply per unit suitable habitat) and relevant parameters that determine local abundance (density-independent survivorship; adult saturation or peak density; density dependence in settlement from conspecifics and heterospecifics; density dependence in survivorship from interactions with conspecifics and heterospecifics). In addition to larval supply, variation in other environmental features that will be estimated include microhabitat availability and predation pressure. These variables will be measured across several spatial scales (from -5 in to 200 km). Data from empirical work will be used in the quantitative frameworks to compare the relative importance of various processes among species and spatial scales, to address issues related to coexistence of competing species with open populations, and to examine whether dynamics at larger scales differ from that predicted from local dynamics.