RUI: The Dynamics of Biological Invasions

Schreiber0077986 研究者开发了差分和微分方程模型的数学方法，以更好地预测在什么条件下生物入侵成功以及成功入侵对生态群落结构的影响。 重点放在对人口方程的结构扰动具有鲁棒性的方法上，并适用于具有非线性动力学的系统（例如，周期性、准周期性和混沌）。 这些方法涉及到平滑遍历理论技术的使用和发展，并将这些方法应用于寄主-寄生虫相互作用和三营养食物网的模型。 两个方面的主机-寄生蜂的相互作用进行了检查。 首先，由于寄生蜂的经验蛋限制时，释放系统具有高度可变的主机密度（典型的情况下，当一个外来昆虫已达到有害生物状态），模型的主机-寄生蜂相互作用，将thisegg限制被认为是。 由于成功的生物控制只发生在寄生虫种群已经建立起来之后，因此建议的模型分析旨在确定宿主种群动态的变异性如何影响寄生虫种群的入侵率。 其次，扩展了以往关于宿主-寄生蜂系统中斑块选择策略协同进化的工作，使其包括两个重要的生物学因素：寄生蜂的性别分配策略和植物动态。 关键问题是，操纵作物异质性是否能导致行为性状的共同进化，从而同时稳定系统并增加作物产量。 第三，为了更好地理解生态群落是如何因入侵而聚集的，本建议承担了在每个营养水平上有一个以上物种的三营养系统的研究。 在这些系统中，三种生态力（表观竞争、资源竞争和行会内捕食）起着重要作用，并可能导致演替不过渡性（例如，一系列的入侵，将群落A带到群落B，B到C，C回到A）。 重点放在栖息地生产力和入侵的时间对群落组装过程的影响。 此外，该项目还包括一个旨在促进本科生研究的项目。 据估计，入侵美国的非本土物种每年在农业、林业和美国经济的其他几个部门造成1380亿美元的经济损失。 据估计，仅外来昆虫物种每年就造成130亿美元的农作物损失，大约42%的受威胁或濒危物种名单上的物种处于危险之中，主要是因为非本地物种。 由于生物入侵通常涉及几个物种之间的非线性相互作用，数学模型，作为简单的漫画，允许一个便宜的回答问题，如：什么特征使一个物种成为成功的入侵者？ 哪些生态群落最容易受到入侵后的长期变化的影响？ 如何操纵作物的异质性以最大限度地减少非本地害虫的经济影响？ 该项目建议开发分析方法，并将这些方法应用于解决这些问题和其他当前社区生态学、恢复生态学、生物控制和进化生物学感兴趣的问题的模型。

Schreiber0077986 The investigator develops mathematical methods fordifference and differential equation models to better predictunder what conditions biological invasions succeed and theimplications of successful invasions on the structure ofecological communities. An emphasis is placed on methods that arerobust to structural perturbations of the population equationsand that apply to systems with nonlinear dynamics (e.g.,periodicity, quasiperiodicity, and chaos). The methods involvethe use and development of techniques from smooth ergodic theory.Application of these methods to models of host-parasitoidinteractions and tritrophic food webs is pursued. Two aspects ofhost-parasitoid interactions are examined. First, becauseparasitoids experience egg limitation when released in systemswith highly variable host densities (the typical situation whenan exotic insect has reached pest status), a model ofhost-parasitoid interactions that incorporates thisegg-limitation is considered. As successful biological controlonly occurs after a parasitoid population has established itself,the proposed analysis of the model intends to determine howvariability in the dynamics of the host population influences theinvasion rate of the parasitoid population. Second, previous workon the coevolution of patch selection strategies inhost-parasitoid systems is extended to include two importantbiological factors, the sex-allocation strategies of parasitoidsand plant dynamics. The key issue is whether the manipulation ofcrop heterogeneity can lead to the coevolution of behavioraltraits that simultaneously stabilize the system and increase cropyields. Third, to better understand how ecological communitiesassemble due to invasions, this proposal undertakes the study oftritrophic systems with more than one species at each trophiclevel. In these systems, three ecological forces (apparentcompetition, resource competition and intraguild predation) playan important role and can lead to successional intransitivites(e.g., a sequence of invasions that takes community A tocommunity B, B to C and C back to A). Emphasis is placed on theinfluence of habitat productivity and the timing of invasions onthe community assembly process. In addition, the project includesa program designed to stimulate undergraduate research. Invading non-native species in the United States causeestimated economic losses of 138 billion dollars annually inagriculture, forestry and several other segments of the U.S.economy. Exotic insect species alone are estimated to cause 13billion dollars in crop losses annually and approximately 42% ofthe species on the threatened or endangered species lists are atrisk primarily because of nonnative species. As biologicalinvasions often involve nonlinear interactions between severalspecies, mathematical models, as simple caricatures, allow one toinexpensively answer questions such as: What characteristics makea species a successful invader? Which ecological communities aremost susceptible to large long-term changes following aninvasion? How can crop heterogeneity be manipulated to minimizethe economic impact of non-native pests? The project proposes todevelop analytical methods, and to apply these methods to modelsthat address these and other questions of current interest tocommunity ecology, restoration ecology, biological control, andevolutionary biology.