Variation in Herbivore Population Sizes: The Effects of Host Quality, Host Genotype, Natural Enemies and the Formation of Demes

9309298在海牛眼雏菊顶端分生组织处形成的胆小蜂Asphondylia borrichiae在内部发育。幼虫以一种专性真菌为食，这种真菌是由幼虫在胆腔中产生的。在佛罗里达州的中西部海岸，当地的果蝇种群仅分布在靠近海岸内航道的小型障碍岛和小型“废墟”岛上。岛屿之间的胆汁密度差异高达23个数量级。这可能是因为：(1)一些斑块的海牛眼是不适合的(即质量不佳或遗传抗性)，(2)一些地点未能被档案发现，(3)一些地点鼓励天敌的高水平攻击或(4)在一些岛屿上，虫胆文件已在当地适应现有的宿主斑块(即DEME地层)。三组实验将评估植物无性系、天敌和斑潜蝇的攻击水平和局部适应对斑潜蝇种群动态的重要性：(1)无瘤植物在地点之间的相互移植，(2)地点之间的相互移植，(3)在同一花园中保存一年的植物的相互移植，以消除母体影响。这个系统将使过去很少可能进行的研究了解控制四个营养级别系统的因素。在更实际的层面上，该项目可能会确定为什么某些斑块或基因类型的海牛眼对危害草食性昆虫具有抵抗力，而另一些则不能。这一点很重要，因为这种植物和其他几种海岸和沙丘植物遭受了高比率的叮咬昆虫的攻击。了解它们不同侵袭率背后的原因，可能会极大地有助于为沼泽和海滩恢复项目选择最抗虫的物种和基因类型。

9309298 Stiling The gall fly, Asphondylia borrichiae, develops internally in galls which form at the apical meristems of sea oxeye daisy, Borrichia frutescens. Larvae feed on an obligate fungus which they initiate in the gall cavity. Along the west central coast of Florida, local populations of B. frutescens are found only on small barrier islands and small "spoil" islands and adjacent to the intracoastal waterway. Gall densities between islands vary by as much as 2 3 orders of magnitude. This could be because: (1) some patches of sea oxeye are unsuitable for galls (i.e of poor quality or genetically resistant), (2) some sites fail to be discovered by the files, (3) some sites encourage high levels of attack by natural enemies or (4) on some islands, gall files have become locally adapted to existing host patches (i.e. deme formation). Three sets of experiments will assess the importance of plant clone, attack levels of natural enemies and gall fly dispersal and local adaptation on gall midge population dynamics: (1) reciprocal transplants of gall free plants between sites, (2) reciprocal transplant of galled plants between sites and (3) reciprocal transplant of plants that have been maintained in a common garden for one year to remove maternal effects. %%% This system will allow research that has rarely been possible in the past understand the factors controlling a four trophic level system. On a more practical level, this project may identify the reasons why some patches or genotypes of sea oxeye are resistant to damaging herbivorous insects while others are not. This is important because this plant and several other coastal and dune plants suffer high rates of attack by galling insects. Understanding the reasons behind their different rates of attack may greatly aid in selecting the most insect resistant species and genotypes for marsh and beach restoration projects.