DISSERTATION RESEARCH: Investigating the role of specialist and generalist host associations in a multi-level sea anemone symbiosis

共生关系是生物多样性的重要驱动力，影响着各个层面的生物组织。作为生物多样性的热点，热带珊瑚礁的成功和多样性在很大程度上来自于多层次的共生网络。虽然这种对共生关系的依赖是公认的，但我们对遗传多样性如何在共生海洋框架内进化知之甚少。也就是说，我们对资源专业化和共同多样化的期望主要来自于有地域偏见的文献，而在人口水平上起作用的不协调的陆海过程可能导致不同的结果。本研究将通过研究加勒比珊瑚礁上以螺旋海葵为食但宿主特异性不同的多种甲壳类动物，来测试围绕共生和资源专门化的进化假设。通过基因组DNA测序，这组科学家将识别和描述以前未被识别的隐物种，测试宿主特异性的增加是否会导致物种形成的增加，以及是否可以在整个加勒比地区的这些共生体中恢复共同进化的模式。本研究将培养一名研究生，并为本科生提供海洋和分子进化科学的研究机会。将在本科生物学课程中编写教材来展示共同进化原理，并针对观赏水族贸易开展公共宣传活动，因为所有研究物种都是商业收集的。资源专门化有望在基因组上留下强烈的印记，并在物种多样化中发挥重要作用。与多面手相比，具有狭窄生态需求的物种预计具有更小，更破碎的栖息地，更小的有效种群规模，最终减少中性遗传变异。这些期望被广泛地称为专家-通才变异假说（SGVH），是经典群体遗传学理论的延伸。在共生框架内，宿主特异性对于测试SGVH的预期特别有用，因为与共生关联相结合的微进化过程将影响每个共生体的种群和进化动态。共生产生了对共享生物地理历史和共同多样化的先验期望，但宿主特异性的变化可能导致截然不同的人口历史和对历史环境条件的进化反应。因此，共生分类群的比较可以从物种生物学的内在方面解开影响整个群落的外在力量，揭示共同进化过程和共生的出现。本研究将使用高通量基因组DNA测序和基于模型的聚结分析来划分和描述隐藏的甲壳类动物谱系，研究遗传多样性进化中的专门性和通用性的作用，并探索热带西大西洋地区共同多样化、人口扩张和群落水平系统地理断裂的模式。这项研究将扩大热带、海洋、系统地理学文献的分类范围，并提供对海洋共生作用的进化过程的见解。

Symbiosis is an important driver of biodiversity and shapes all levels of biological organization. As a biodiversity hotspot, tropical coral reefs achieve much of their success and diversity from a network of multi-level symbioses. Although this reliance on symbiosis is well recognized, we know very little about how genetic diversity evolves within a symbiotic marine framework. Namely, our expectations surrounding resource specialization and co-diversification come primarily from the terrestrially biased literature, whereas discordant land-sea processes that act at the population level may lead to different outcomes. This research will test evolutionary hypotheses surrounding symbiosis and resource specialization by studying multiple crustacean species that all live on the corkscrew sea anemone on Caribbean coral reefs, yet vary in their host specificity. Using genomic DNA sequencing, the researchers will identify and describe previously unrecognized cryptic species, test whether increased host specificity leads to more incidences of speciation, and whether patterns of co-evolution can be recovered among these symbionts across the entire Caribbean. This research will train one graduate student and provide undergraduate students with research opportunities in the marine and molecular evolutionary sciences. Educational materials will be developed to demonstrate co-evolutionary principles in undergraduate biology courses, and public outreach events will target the ornamental aquarium trade as all study species are collected commercially.Resource specialization is expected to leave a strong signature on the genome and play an important role in species diversification. Species with narrow ecological requirements are expected to have smaller, more fragmented habitats, smaller effective population sizes, and ultimately, reduced neutral genetic variation compared to generalists. These expectations are broadly referred to as the specialist-generalist variation hypothesis (SGVH) and are an extension of classic population genetics theory. Within a symbiotic framework, host specificity should be especially useful for testing the expectations of the SGVH because micro-evolutionary processes coupled with symbiotic association will impact the population and evolutionary dynamics of each symbiont. Symbiosis generates an a priori expectation of shared biogeographic history and co-diversification, but variation in host specificity may lead to vastly different demographic histories and evolutionary responses to historical environmental conditions. Thus, the comparison of symbiotic taxa can potentially disentangle the extrinsic forces that effect whole communities from the intrinsic aspects of species biology, shed light on co-evolutionary processes and the emergence of the symbiosis. This research will use high-throughput genomic DNA sequencing and model-based coalescent analyses to delimit and describe cryptic crustacean lineages, examine the role of specialism and generalism on the evolution of genetic diversity, and explore patterns of co-diversification, demographic expansion, and community level phylogeographic breaks across the tropical Western Atlantic. This study will expand the taxonomic scope of the tropical, marine, phylogeographic literature and provide insight into the evolutionary processes that act on marine symbioses.