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、种内和种间地理分化的时空尺度和模式的影响。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，关于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战略至关重要。根据形态物种范围，以前的工作人员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在无数广阔的开阔海洋屏障上的扩散，支持了珊瑚礁生物具有巨大扩散能力的信念。过去的分子研究发现，IWP种群通常在盆地到次盆地尺度上相互关联。然而，最近在印度尼西亚对口足类和在美洲对蹄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：细微尺度的遗传结构在珊瑚礁生物中是否普遍存在？初步数据显示，在几种分布广泛的珊瑚礁相关腹足类动物中，存在着细微的遗传分化。每个物种都由众多不同的种群组成，活动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，最初的数据显示，在具有不同生活史策略的共生类群中，它们具有相当大的结构。该项目的目标是记录国际水资源计划中选定的与礁石相关的腹足类的地理和遗传结构的范围，并利用这些模式来解决有关海洋生物圈中的大规模时空过程的问题。整个区域将确定具有进化意义的单位(ESU)，即相关的保护和进化单位。将使用序列数据来检验有关ESU的来源和动态以及由此而来的分布和多样化模式的假设。拟议工作的意义在于这些分类群所遇到的精细遗传结构的性质，这使它们成为研究海洋生物物种形成和生物地理学的模式系统，并对珊瑚礁管理和生物多样性保护具有重大影响。在海洋类群中很少遇到精细但差异很大的遗传结构，而且只有在大陆环境中才会遇到；它在岛屿上的出现是史无前例的，与预期相反。能够扩散到大洋洲的生物如何在群岛规模上进行区分？这一难题意味着，罕见的扩散事件在海洋种群的扩散和分化中可能非常重要。探索独立基因树中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说。高度的遗传分化还意味着，需要适当调整珊瑚礁的养护和资源管理战略。了解遗传上相互关联的单位的大小和分布对于设计适当的管理单位至关重要，例如海洋保护区。一致的遗传结构描述了生物群分布的内在中断，从而确定了自然管理单元。该项目将为与珊瑚礁有关的海洋资源制定更好的管理战略，并将在几个层面上产生直接的教育影响。项目组将定期与资源经理互动。所研究的物种是重要的食物生物，为介绍对资源管理的影响，从而影响许多太平洋岛屿的珊瑚礁管理战略提供了一个极好的场所。这项工作的成果将在区域范围内以及在科学文献中传播。

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.