Species complexes in the sea: model systems for studying the biodiversity and evolutionary history of the Indo-West Pacific reef biota

珊瑚礁可以说是最多样化和最脆弱的沿海生态系统，目前正在经历前所未有的衰退。它们的多样性和脆弱性都受到遗传结构、时空尺度和种内和种间地理分化格局的影响。通过记录这种结构，我们对珊瑚礁生物多样性的起源和分布有了更好的了解。此外，遗传相互联系的水平和规模的数据对于预测珊瑚礁在面对压力时的反应和设计适当的保护策略至关重要。在形态物种范围的基础上，以往的工作者普遍认为珊瑚礁生物分布广泛，特别是在印度洋-西太平洋（IWP），这是最大和最多样化的海洋区域。在IWP中，广泛的物种范围意味着分布在众多广阔的开放海洋屏障上，这支持了珊瑚礁生物具有巨大传播能力的信念。过去的分子研究发现，IWP种群通常在盆地到亚盆地尺度上相互联系。然而，最近对印度尼西亚口足类动物和美洲潮上甲壳类动物的研究遇到了更精细的遗传分化。这些研究提出了一个问题：精细的遗传结构在珊瑚礁生物中是常见的吗？初步数据显示，在一些广泛分布的、与珊瑚礁相关的腹足类动物中，存在精细的遗传分化。每个物种都由许多不同的种群组成，分布范围仅限于群岛或岛屿。它们的生活史属性是许多珊瑚礁生物的典型特征，初步数据显示，在不同生活史策略的共发生分类群中存在相当大的结构。该项目的目标是记录IWP中选定的与珊瑚礁相关的腹足类动物的地理、遗传结构的程度，并利用这些模式来解决海洋生物圈中大规模、时空过程的问题。进化重要单位（esu），即有关的保护和进化单位，将在整个区域确定。关于esu的来源和动态，以及分布和多样化模式的假设，将使用序列数据进行检验。这项工作的意义在于，这些分类群具有精细尺度的遗传结构，这使它们成为海洋物种形成和生物地理学研究的模型系统，并对珊瑚礁管理和生物多样性保护具有重要意义。在海洋分类群中很少遇到精细尺度的，但深度分化的遗传结构，只有在大陆环境中才遇到；它在岛屿上的发生是前所未有的，与预期相反。能够分散到大洋洲的生物是如何在群岛范围内分化的？这一难题表明，罕见的扩散事件可能对海洋种群的扩散和分化非常重要。在独立基因树中探索遗传结构的系统发育性质，将有助于阐明关于海洋生物多样性起源和珊瑚礁生物分布的各种假设。高水平的遗传分化也意味着对珊瑚礁的保护和资源管理战略需要适当调整。了解遗传上相互联系的单位的大小和分布对于设计适当的管理单位（如海洋保护区）至关重要。一致的遗传结构描绘了珊瑚礁生物群分布的内在断裂，从而确定了自然管理单元。这个项目将导致对与珊瑚礁有关的海洋资源的更好的管理战略，并将在几个层次上产生直接的教育影响。项目团队将定期与资源经理进行交互。所研究的物种是重要的食物生物，为资源管理提供了一个很好的场所，从而影响了许多太平洋岛屿的珊瑚礁管理策略。这项工作的结果将在区域和科学文献中传播。

Coral reefs are arguably the most diverse and vulnerable coastal ecosystems and are currently undergoing unprecedented decline. Both their diversity and vulnerability are influenced by genetic structuring, the spatio-temporal scale and pattern of geographic differentiation within and among species. By documenting such structuring, we gain a better understanding of the origin and distribution of reef biodiversity. Furthermore, data on the level and scale of genetic interconnections are crucial for predicting reef response in the face of stressors and for the design of appropriate conservation strategies. On the basis of morphological species ranges, previous workers have generally characterized reef organisms as widespread, especially in the Indo-West Pacific (IWP), the largest and most diverse marine region. Wide species ranges in the IWP imply dispersal across numerous, vast, open ocean barriers, supporting the belief that reef organisms have tremendous dispersal abilities. Past molecular studies found IWP populations to be typically interconnected over basinal to sub-basinal scales. However recent studies on stomatopods in Indonesia and supratidal crustaceans in the Americas encountered finer levels of genetic differentiation. These studies raise the question: is fine-scale genetic structuring common among reef organisms? Preliminary data show fine-scale genetic differentiation in several widespread, reef-associated gastropods. Each species is composed of numerous, divergent populations with ranges limited to archipelagoes or islands. Their life history attributes are typical of many reef organisms, and initial data show considerable structuring in co-occurring taxa with different life history strategies. The goals of this project are to document the extent of geographic, genetic structuring in selected reef-associated gastropods in the IWP, and to use these patterns to address questions about large-scale, spatio-temporal processes in the marine biosphere. Evolutionarily significant units (ESUs), the relevant conservation and evolutionary units, will be identified throughout the region. Hypotheses about the source and dynamics of ESUs, and thus patterns of distribution and diversification, will be tested using sequence data. The significance of the proposed work lies in the nature of fine scale genetic structuring encountered in these taxa, which makes them model systems for studies of marine speciation and biogeography, and has major implications for reef management and conservation of biodiversity. Fine-scale, but deeply divergent genetic structuring has rarely been encountered in marine taxa and only in continental settings; its occurrence on islands is unprecedented and contrary to expectations. How can organisms capable of dispersing far into Oceania differentiate on an archipelagic scale? This conundrum implies that rare dispersal events may be highly important in the spread as well as differentiation of marine populations. Exploring the phylogenetic nature of genetic structuring in independent gene trees will shed light on a variety of hypotheses about the origin of marine biodiversity and distribution of reef organisms. High levels of genetic differentiation also imply that conservation and resource management strategies on reefs need to be appropriately scaled. Understanding the size and distribution of genetically interconnected units is crucial for designing appropriate management units, such as marine protected areas. Congruent genetic structuring delineates intrinsic breaks in the distribution of reef biota and thus identifies natural management units. This project will lead to better management strategies for reef-associated marine resources, and will also have direct educational impact at several levels. The project team will be interacting with resource managers regularly. The species studied are important food organisms, and provide an excellent venue to introduce implications for resource management and thus influence reef management strategies on numerous Pacific islands. The results of this work will be disseminated regionally as well as in the scientific literature.