Species Diversity and Abundance in Insular Systems

本提案寻求对食物网结构、物种灭绝和生态相互作用研究的持续支持。小岛屿被用作模型系统，因为它们数量众多、简单、离散，并且具有各种组合的物种和营养类型。通过小岛屿上蜥蜴的引种实验，研究了顶端捕食者对中间捕食者、环境昆虫和树叶损害的影响。同样的现象，加上中级捕食者弥补顶级捕食者缺失的程度，在大型围栏中的蜥蜴/蜘蛛移除实验中得到了研究。第二个实验将测量有蜥蜴和没有蜥蜴的蜘蛛之间的竞争。自然灭绝研究使用了一个超过100个岛屿的系统；研究了顶级捕食者对蜘蛛灭绝率的影响，以及蜘蛛灭绝率随种群大小平均值、变异度和偏度的变化规律和生活史特征的变化规律。将研究岛屿之间和较大岛屿内蜘蛛种群分布的空间斑块性；后者将与上层捕食者的发生和密度有关。奠基者效应的特征（遗传变异的丧失）；将评估在早期支持期引入岛屿的蜥蜴种群的形态和行为变化程度。这些结果将为有关导致物种灭绝的全球相互作用的新闻提供非常有价值的信息。

This proposal seeks continuing support for research on food- web structure, species extinctions and ecological interactions. Small islands are used as a model system, because they are numerous, simple, discrete and have species and trophic types in various combinations. How top predators affect intermediate predators, ambient insects and foliage damage is studied in an introduction experiment of lizards onto small islets. The same phenomena, plus the degree to which intermediate predators compensate in top-predator absence, is studied in a lizard/spider removal experiment in large enclosures. A second experiment will measure spider competition with and without lizards. Natural extinction is studied using a system of over 100 islands; we focus on the effect of top predators on spider extinction rate, and on how extinction rate varies with mean, variability and skewness of population-size values over time and with life- history characteristics. Spatial patchiness in spider population distributions will be studied both between islands and within larger islands; the latter will be related to top predator occurrence and density. Characteristics of the founder effect (loss of genetic variability; degree of morphological and behavioral change) will be assessed for colonizing populations of lizards introduced onto islands during earlier support periods. The results will provide very valuable information on news relating to global the interactions leading to extinctions.