Nonrandom Dispersal of Interacting Species in Heterogeneous Landscapes

本项目通过反应-扩散-平流模型研究了非随机扩散对异质环境中竞争物种和消费者-资源相互作用的影响。生物的扩散是生态和进化过程的一个关键组成部分，许多生物的扩散取决于当地的生物和非生物因素（例如，食物、气候、竞争对手、捕食者），因此往往是非随机的。与随机运动相比，人们对非随机扩散后果的认识有限，特别是在相互作用物种的空间动力学背景下。如果两个相互竞争的物种为了响应栖息地质量而采取有偏差的运动，那么无论平流率大小都可能存在选择。是否存在某种进化上稳定的中间平流速率？如果随机扩散率和偏置移动率代表物种的两种不同特征的值，那么这两种特征如何同时进化？与空间变化相比，在时空变化的环境中，非随机扩散将如何演变？如果生物完全根据栖息地之间的适合度差异做出扩散决定，那么它是否总是比仅仅基于环境线索的策略更有利呢？非随机扩散能促进相互作用物种的空间共存吗？所有这些问题都在项目中进行了研究。从栖息地退化和气候变化到入侵物种的空间扩散，扩散在决定生物如何应对不断变化的环境方面发挥着核心作用。了解生物的扩散可以大大提高我们对如何在复杂的食物网中维持多样性的理解。入侵物种的空间扩散是一个重要而具有挑战性的问题。虽然人们对单一物种环境下生物的空间传播了解甚多，但对物种相互作用如何影响入侵物种的空间传播知之甚少。例如，人们可能会期望空间扩散受到与本地物种争夺共同有限资源的竞争的影响，并且了解外来物种在与本地物种（无论是竞争对手还是天敌）相互作用时使用的扩散策略非常重要。与本地物种相比，入侵物种可能使用了一套不同的扩散策略，这种差异可能是解释为什么某些入侵物种能够快速传播并取代本地物种，而其他入侵物种往往传播缓慢并融入本地群落的关键。了解这些问题的答案有助于制定更好的入侵物种控制管理策略。此外，该项目还包括对博士后研究人员、研究生和本科生进行数学建模和分析与入侵物种和疾病的空间传播有关的新出现的生物学问题的广泛培训。

This project investigates the effects of non-random dispersal on competing species and consumer-resource interactions in heterogeneous environments via reaction-diffusion-advection models. Dispersal of organisms is a key component of ecological and evolutionary processes and the dispersals of many organisms depend upon local biotic and abiotic factors (e.g., food, climate, competitors, predators) and as such are often nonrandom. In contrast with random movements, there is limited knowledge of the consequences of nonrandom dispersal, especially in the context of the spatial dynamics of interacting species. If two competing species adopt biased movement in response to habitat quality, there can be selection against both small and large advection rates. Is there some intermediate advection rate which is evolutionarily stable? If random dispersal rate and biased movement rate represent values for two different traits of species, how will two traits simultaneously evolve? Compared to variation in space only, how will nonrandom dispersal evolve in spatiotemporally varying environments? If organisms make dispersal decisions purely based on fitness differences between habitat locations, does it always compare favorably with strategies based only on environmental cues? Can nonrandom dispersal promote the spatial coexistence of interacting species? All of these questions are studied in the project.From habitat degradation and climate change to spatial spread of invasive species, dispersals play a central role in determining how organisms cope with a changing environment. Understanding dispersal of organisms can significantly enhance our understanding of how diversity is maintained in complex foodwebs. The spatial spread of invasive species is an important and challenging issue. While a great deal is known about the spatial spread of organisms in a single species context, very little is known about how species interactions influence the spatial spread of invasive species. For instance, one might expect spatial spread to be influenced by competition with native species for common, limiting resources, and it is very important to understand the dispersal strategies that exotic species use in response to interactions with native species, be they competitors or natural enemies. It may be that invasive species use a different set of dispersal strategies compared to native species and such differences may be crucial in explaining why certain invasive species are able to spread quickly and displace native species while others tend to spread slowly and become integrated into the native community. Understanding the answers to these questions can help develop better management strategies for invasive species control. Additionally, this project involves extensive training of postdoctoral researchers, graduate students and undergraduate students in mathematical modeling and analysis of emerging biological issues related with spatial spread of invasive species and disease.