Testing the mating system model for the evolution of parasite complex life-cycles

寄生虫可以有复杂的生命周期，涉及两到三种不同的宿主物种。为什么如此复杂的生命周期会持续存在，一直困扰着生物学家。这个研究项目将检验这样一种理论，即寄生虫的复杂生命周期是由避免近亲繁殖（即与亲属交配）的需要维持或产生的。它将专门测试近亲繁殖是否对健康有负面影响，比如降低存活率或繁殖率。这项研究将对寄生吸虫进行研究，其中一些种群需要三个宿主，而另一些种群只需要两个宿主。这种寄主数量的变化为检验进化论中一种重要的交配系统模型提供了一个理想的机会。这些结果还将为与寄生虫感染新宿主物种的可能性有关的传染病传播提供关键见解。该项目为寄生虫学和群体遗传学领域的研究生和本科生提供研究机会和培训。来自弱势群体的本科生将从德州农工大学摄政学者（低收入，第一代学生）项目和路易斯·斯托克斯少数民族参与联盟中招募。该项目将测试交配系统模型，该模型提出寄生虫交配系统维持或产生复杂的生命周期，特别是失去宿主的代价是增加近亲繁殖。该项目有两个主要目标。目标1将检验该模型的基本假设，即更复杂的生命周期将比更简单的生命周期有更少的近亲繁殖。目的2将测试模型的预测，近亲繁殖的抑郁不表现在进化一个更简单的生命周期。为了解决这些问题，将在吸虫属内和种之间进行种群遗传比较。该研究系统为验证交配系统模型提供了一个机会，因为它的生命周期复杂性在种群间存在差异。将比较种群近亲繁殖的数量及其与适应度降低的潜在关联。该结果将对宿主-寄生虫生命周期和适应性的进化模型产生影响。

Parasites can have complex life cycles that involve two or three different host species. Why such complex life cycles persist has long puzzled biologists. This research project will test the theory that the complex life cycles of parasites are maintained or generated by the need to avoid inbreeding, i.e., mating with relatives. It will specifically test whether inbreeding has negative effects on fitness, such as reduced survival or reproduction. The study will be made a parasitic fluke species that has some populations that require three hosts and other populations that require only two hosts. This variation in number of hosts presents an ideal opportunity to test an important mating system model in evolutionary theory. The results will also provide key insights into infectious disease transmission relating to the potential for parasites to infect new host species. The project provides research opportunities and training for graduate and undergraduate students in the fields of parasitology and population genetics. Undergraduates from under-represented groups will be recruited from the Texas A&M Regents Scholars (low income, first generation students) program and Louis Stokes Alliance for Minority Participation. This project will test the mating system model, which proposes that parasite mating systems maintain or generate complex life cycles, specifically that the cost of losing a host is to increase inbreeding. The project has two major aims. Aim 1 will test the underlying assumption of the model that a more complex life cycle will have less inbreeding compared to a simpler life cycle. Aim 2 will test the prediction of the model that inbreeding depression is not manifested when evolving a simpler life cycle. To address these questions, population genetic comparisons will be made within and between species in the trematode genus Alloglossidium. This study system provides an opportunity to test the mating system model because of its among-population variation in life cycle complexity. Populations will be compared for the amount of inbreeding and its potential association with fitness reductions. The results will have an impact on models of evolution concerning host-parasite life cycles and fitness.