Collaborative Research: Developing novel methods for estimating coevolutionary processes using tapeworms and their shark and ray hosts

寄生虫无处不在，许多物种已经与它们的宿主一起进化了很长一段时间，并且对它们寄生的宿主种类非常挑剔。有些出乎意料的是，最近的研究表明，许多寄生虫物种不一定与它们的宿主有相似的进化历史;相反，其他因素可能在塑造这些寄生关系中发挥作用。然而，很少有人知道其他因素，如饮食或地理分布，影响这些关系。 这在很大程度上是因为目前还没有评估其他因素重要性的方法。这项研究将开发一种方法，并将使用由鲨鱼和黄貂鱼的绦虫组成的众所周知的物种丰富的系统对其进行测试。这种方法将广泛适用于其他共同进化系统，不仅有助于我们进一步了解一般的宿主-寄生虫系统，也有助于我们了解其他涉及亲密关系的生物系统。密切的物种关联无处不在，更好地了解环境在形成物种关联方面的作用对于预测生物多样性对气候变化的反应至关重要。该研究将培养博士后研究人员和研究生在进化生物学的定量技术。该项目走向寄生虫和宿主之间的共同进化所涉及的生物影响的更机械的建模。将生成大量绦虫属的系统发育，将生成其相应的鲨鱼和鳐（板鳃亚纲）宿主的时间校准的系统发育，并将汇编可靠的寄生虫-宿主关联数据。将开发使用近似贝叶斯计算的新方法和开放源码软件工具，以便能够估计和测试寄生-宿主系统演变的模型。寄生虫进化的模型将是地理上明确的，并将包括因素，如共同物种形成，环境驱动的灭绝，地理上的限制扩散和主机转换，以及中间主机的一些影响。这些丰富的经验数据集将允许使用稳健的交叉验证方法进行假设检验。最终的结果将是一个方法框架，用于评估多种因素的贡献，除了同源性，在构建主机协会和寄生虫进化。新的软件将用于解决三个主要的研究问题，这些问题涉及寄生虫-宿主相互作用的基础因素，包括各种因素在具有不同属性的系统中发挥的相对作用。

Parasites are everywhere and many species have been with their hosts for a long evolutionary time and are extremely particular about the kinds of hosts they parasitize. Somewhat unexpectedly, recent research suggests that many parasite species do not necessarily share a similar evolutionary history with their hosts; rather other factors may be at play in shaping these parasitic associations. Yet, little is understood about which other factors, such as diet or geographic distribution, influence these relationships. This is largely because a method for assessing the importance of other factors is not currently available. This research will develop a method and will test it using a well-known and species-rich system consisted of the tapeworms of sharks and stingrays. This method will be widely applicable to other coevolutionary systems, helping to further our understanding not only of host-parasite systems in general, but also of other biological systems involving intimate associations. Close species associations are ubiquitous and better knowledge on the role of the environment in shaping species associations will be critical to forecasting biodiversity's response to climate change. The research will train postdoctoral researchers and graduate students in quantitative techniques in evolutionary biology.This project moves towards a more mechanistic modeling of the biological influences involved in the coevolution between parasites and hosts. Phylogenies will be generated for a large number of cestode genera, time-calibrated phylogenies will be generated for their corresponding shark and ray (elasmobranch) hosts and robust parasite-host association data will be compiled. New methods and open-source software tools using approximate Bayesian computation will be developed to allow the estimation and testing of models for the evolution of parasite-host systems. The models for parasite evolution will be geographically explicit and will include factors such as cospeciation, environmentally driven extinction, geographic constraints on dispersal and host-switching, and some effects of intermediate hosts. These rich empirical data sets will allow the use of robust, cross-validation methods for hypothesis testing. The end result will be a methodological framework for assessing the contributions of multiple factors, in addition to cophylogeny, in structuring host associations and parasite evolution. The new software will be used to address three main research questions regarding factors that underlie parasite-host interactions including the relative roles various factors play in systems with different properties.