Causations of a riverine radiation: Assessment and evaluation of the morphological and genetical differentiation in a species flock of viviparous gastropods (Cerithioidea: Pachychilidae)

湖泊中的物种群经常作为模型系统进行研究，试图阐明适应性辐射的潜在进化机制。相比之下，河流辐射很少，几乎没有研究。然而，由于河流环境的特定特征，为研究物种形成的潜在因素，从而研究生物多样性的成因提供了新的视角。拟议的项目侧重于栖息在泰国中部Kaek河（Chao Praya流域）的一种特有的、形态多样的淡水腹足动物——Brotia属胎生腹足动物群。初步结果表明，湄公河流域系统可能是该物种的起源区，其物种群的单一性和快速多样化。两到三个物种在采样地点的同域发生，它们因不同的基质偏好而产生的生态分离，以及相关的营养特化（radula形态学）使这种流动辐射成为一种新的、潜在的高信息模型系统。该项目结合了复杂的采样材料和生态数据的领域与形态和分子遗传分析。我们将使用AFLP基因分型作为强大的工具，以产生良好解决的系统发育重建，并评估遗传变异和凝聚力水平（估计种群内和种群之间的基因流动），以阐明内在和外在因素在异域和/或生态物种形成过程中的作用。这将由环境表型相关性和生活史参数（作为适应度估计的育雏规模和表现）的数据来补充，这些数据对于检验关于该物种群进化原因的假设是必要的。

Species flocks in lakes have frequently been examined as model systems in an attempt to elucidate the underlying evolutionary mechanisms of adaptive radiations. In contrast, riverine radiations are rare and hardly studied. However, due to specific characteristics a riverine setting provides a new perspective for studying potential factors of speciation and, thus, the genesis of biological diversity. The proposed project focuses on an endemic, morphologically diverse species flock of viviparous freshwater gastropods of the genus Brotia inhabiting the Kaek River (Chao Praya drainage, Central Thailand). Preliminary results indicate the Mekong drainage system as a putative area of origin, the monophyly of the species flock, and its rapid diversification. Sympatric occurrence of two to three species at sampling localities, their ecological separation by varying substrate preferences, and a correlated trophic specialization (radula morphology) renders this fluviatile radiation a new and potentially highly informative model system. This project combines sophisticated sampling of material and ecological data in the field with morphological and molecular genetic analyses. We ill employing AFLP genotyping as powerful tool to produce well-resolved phylogenetic reconstructions and to assess levels of genetic variation and cohesion (estimation of gene flow within and between populations) to illuminate the role of intrinsic and extrinsic factors in the course of allopatric and/or ecological speciation. This will be supplemented by data on environment-phenotype correlation and life-history parameters (brood size and performance as estimator for fitness) that is necessary to test assumptions on the causations of the evolution of this species flock.