Testing a riverine radiation. Mechanism of speciation in viviparous freshwater gastropods endemic to the Kaek River, Thailand

测试河流辐射。

• 批准号: 283403604
• 负责人: Professor Dr. Matthias Glaubrecht
• 金额: --
• 依托单位: Evolutionsbiologie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2015
• 资助国家: 德国
• 起止时间: 2014-12-31 至 2019-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/283403604?language=en
• 关键词: Testing; riverine; radiation.; Mechanism; speciation

The process of how species and biodiversity in general originates is to date essentially studied using vertebrates, although invertebrates represent the majority of all species worldwide. While allopatric speciation (geographical boundaries formed to hamper gene flow), is involved in many cases, an increasing number of evidence points at ecologically driven sympatric speciation (selection interacts with sufficiently distinct environmental parameters to enable reproductive isolation even in the absence of geographical barriers). Lacustrine snails have proven to supply ideal model organisms for studying mechanisms of speciation. However, while these systems also tend to be complex, riverine radiations are both infrequent and rarely studied. In the unique setting of the Kaek River in Thailand we have, in preliminary studies, found and evaluated the existence of less than a dozen endemic taxa of Brotia, with sym-, para- and allopatric occurrences of species, providing a perfectly suitable model system as 'natural experiment' for the study of fundamental mechanisms and factors acting in speciation. Within a phylogenetic and phylogeographic framework we suggest to analyse the role of geography and ecology along the continuous unidirectional topography of a river, at the same time taking advantage of newly available 'next generation' techniques. The innovative RAD (restriction-site associated DNA) sequencing will be used in order to investigate genome wide divergence in high resolution, thus allowing to evaluate the influence of geographical versus ecological factors. In an integrative approach we will use geometric morpho¬metrics of shell, morphological differentiation of radula, supplemented by data on life history (viviparous reproductive strategies) together with detailed ecological parameters (i.e. habitat, substrate preference) to assess phenotype-environment associations in context of intra- and interspecific genetic divergence within the endemic assemblage of riverine snails. It is the aim of the project (i) to test explicitly outlined hypotheses on the potentially geographically correlated genetic and/or ecological differentiation in speciation, with emphasis on the role of trophic specialization, and (ii) to evaluate the existence of a truly in situ, i.e. riverine adaptive radiation. This exemplary study using for the first time genomic-scale data for phylogenetic and phylogeographical analyses in freshwater gastropods, thus combining 'among species' phylogenetics and 'within species' evolutionary genetics, enables the comparative assessment of extrinsic (ecological versus geographical) factors as a driving force of speciation. In addition, it provides the basic data for further judgement on the intrinsic (i.e. genetic) causation of speciation, that way allowing not only to decipher the evolutionary history of the species and radiation involved, but to better understand those mechanisms behind the emergence of biodiversity in general.

物种和生物多样性一般如何起源的过程，迄今为止基本上是用脊椎动物来研究的，尽管无脊椎动物占全世界所有物种的大多数。虽然在许多情况下涉及到异域物种形成（形成地理边界以阻碍基因流动），但越来越多的证据表明生态驱动的同域物种形成（选择与足够不同的环境参数相互作用，即使在没有地理障碍的情况下也能实现生殖隔离）。湖泊螺类是研究物种形成机制的理想模式生物。然而，虽然这些系统也往往是复杂的，河流辐射既不常见，也很少研究。在泰国Kaek河的独特环境中，我们在初步研究中发现并评估了不到12个Brotia特有类群的存在，以及物种的对称，帕拉和异域发生，提供了一个非常合适的模型系统作为“自然实验”，用于研究物种形成的基本机制和因素。在一个系统发育和生态地理框架内，我们建议分析地理和生态的作用，沿着连续的单向地形的河流，同时利用新的可用的“下一代”技术。创新的RAD（限制性位点相关DNA）测序将被用于以高分辨率研究基因组的广泛差异，从而可以评估地理与生态因素的影响。在综合方法中，我们将使用贝壳的几何形态学、齿舌的形态分化，并辅以生活史数据（胎生生殖策略）以及详细的生态参数（即栖息地、基质偏好）来评估表型与环境的关联。河流蜗牛特有群落内种内和种间遗传分歧。该项目的目的是：（一）检验明确提出的关于物种形成中潜在的地理相关遗传和/或生态分化的假设，重点是营养专门化的作用;（二）评价是否存在真正的原地适应辐射，即河流适应辐射。这一典型的研究首次使用基因组规模的数据在淡水腹足类的系统发育和地理分布分析，从而结合“种间”的遗传学和“种内”的进化遗传学，使外部（生态与地理）因素的比较评估的驱动力的物种形成。此外，它还为进一步判断物种形成的内在（即遗传）原因提供了基本数据，这样不仅可以破译物种的进化历史和所涉辐射，而且可以更好地了解生物多样性出现背后的一般机制。