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

寄生虫无处不在，许多物种与它们的宿主一起进化了很长一段时间，对它们寄生的宿主种类非常挑剔。有些出人意料的是，最近的研究表明，许多寄生虫物种并不一定与它们的宿主有着相似的进化史；相反，其他因素可能在塑造这些寄生虫联系方面发挥作用。然而，人们对饮食或地理分布等其他因素对这些关系的影响知之甚少。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，并使用一个众所周知的、物种丰富的系统进行测试，该系统由鲨鱼和黄貂绦虫组成。这种方法将广泛适用于其他共同进化系统，不仅有助于加深我们对寄主-寄生虫系统的总体理解，也有助于加深我们对涉及密切联系的其他生物系统的了解。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中的作用，将对预测生物多样性对气候变化的反应至关重要。这项研究将对博士后研究人员和研究生进行进化生物学定量技术方面的培训。该项目将转向对寄生虫和宿主之间共同进化中涉及的生物学影响进行更机械化的建模。将为大量的鞭毛虫属生成系统发育图，将为其相应的鲨鱼和射线(板翅目)宿主生成经过时间校准的系统发育图，并将汇编强有力的寄生虫-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虫-宿主系统的演化模型。寄生虫进化的模型将在地理上是明确的，并将包括协种作用、环境驱动的灭绝、扩散和宿主转换的地理限制以及中间宿主的一些影响等因素。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。最终结果将是一个方法论框架，用于评估除共生学之外的多种因素在构建寄主关联和寄生虫进化方面的贡献。新软件将用于解决三个主要研究问题，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性质的系统中扮演的相对角色。

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.