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被作为模型系统来研究，试图阐明适应性辐射的潜在进化机制。相比之下，河流辐射很少见，也很少被研究。然而，由于河流环境的特殊性，为研究物种形成的潜在因素，从而研究生物多样性的起源提供了新的视角。拟议项目的重点是栖息在KAEK河(泰国中部湄南河流域)的一群特有的、形态多样的胎生淡水腹足类。初步结果表明，湄公河流域是一个假定的起源地，是该种群的单系种群，其多样性迅速。两到三个物种在采样地点的共域出现，它们通过不同底物偏好进行的生态分离，以及相关的营养特化(放射状形态)，使这种河流辐射成为一个新的、潜在的高信息量模型系统。该项目将野外材料和生态数据的复杂采样与形态和分子遗传分析相结合。我们将把AFLP基因分型作为一种强有力的工具来产生良好的系统发育重建，并评估遗传变异和凝聚力的水平(估计种群内和种群间的基因流动)，以阐明内在和外在因素在异地和/或生态物种形成过程中的作用。这将得到环境-表型相关性和生活史参数(作为适合度估计器的孵化大小和性能)的数据的补充，这些数据对于检验关于该物种群体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.