Morphological differentiation, evolutionary history and biogeography of a potential cryptic species complex of terrestrial gastropods (Cyclophorus) in Vietnam

越南是世界上生物多样性水平最高的地区之一。该国的特点是无数的石灰岩岩溶露头，形成各种石灰岩生物的功能岛屿。对于这些依赖于富含钙的生境的生物来说，孤立的喀斯特露头被认为是物种形成的中心。尽管越南的石灰岩生物具有高度多样性，但对它们的研究仍然相对较少，形成其多样性的进化过程在很大程度上仍然未知。石灰岩生物中最突出的一组是广泛分布于越南的陆生腹足类Cyclophorus。这些腹足类动物有着明显的彩色图案的大壳。虽然该属的东南亚物种通常或多或少仅限于单一的喀斯特地区，但在越南存在异常广泛的形态模式。这种广泛的Cyclophorus形态型，这可能是一个复杂的神秘的物种，提供了一种可能性，以研究进化过程中的作用，特别是专注于驱动物种形成或导致趋同进化的岛屿喀斯特露头。在本项目中，我将专注于四个具体的研究目标，旨在（一）表征广泛的Cyclophorus形态型的形态多样性，（二）研究其遗传多样性，（三）测试形态和系统发育信号之间的潜在对应关系，以及（四）检测可能导致分化的驱动程序。对于研究目标I，我将使用最先进的3D几何形态测量学来分析贝壳形状和颜色图案的差异。为了实现目标二，我将研究遗传分化，使用系统发育分析的基础上的两个线粒体标记基因的DNA序列数据。在研究目标III中，将使用形态学和遗传学数据相结合的方法来检验潜在的亚形态群和系统发生谱系的对应程度。目标四侧重于外部（地理、生物和非生物）因素，将通过测试岩溶露头隔离与种群间遗传距离的对应关系等方式加以解决。在本项目中，我将使用越南最突出的石灰岩结合类群之一，揭示主要的地理和进化过程，这不仅塑造了这个腹足类组的多样性和分布，但也可能是越南喀斯特生物群一般。

Vietnam is among the regions harbouring the highest levels of biodiversity worldwide. The country is characterized by countless limestone karst outcrops, which form functional islands for various limestone-bound organisms. For these organisms, which depend on calcium-rich habitats, the insular karst outcrops are considered as centres of speciation. Although Vietnam's limestone-bound organisms are highly diverse, they are still relatively poorly studied and the evolutionary processes that have shaped their diversity remain largely unknown. One of the most prominent groups of limestone-bound organisms is the terrestrial gastropod genus Cyclophorus, which is widely distributed in Vietnam. These gastropods have large shells with conspicuous colour patterns. While the South East Asian species of this genus are typically more or less restricted to only a single karst area, in Vietnam an unusually widespread morphotype exists. This widespread Cyclophorus morphotype, which might represent a complex of cryptic species, offers the possibility to examine evolutionary processes with a particular focus on the role of the insular karst outcrops in driving speciation or leading to convergent evolution. In the present project, I will focus on four specific research goals that aim (I) to characterize the morphological diversity of the widespread Cyclophorus morphotype, (II) to examine its genetic diversity, (III) to test for a potential correspondence between morphological and phylogenetic signals, and (IV) to detect drivers that might have caused differentiation. For research goal I, I will analyse the differentiation of shell forms and colour patterns by using state-of-the-art 3D geometric morphometrics. To achieve goal II, I will study genetic differentiation by using phylogenetic analyses based on DNA sequence data of two mitochondrial marker genes. In research goal III, combined morphological and genetic data will be used for testing to which degree potential sub-morphogroups and phylogenetic lineages correspond. Goal IV, which focuses on external (geographic, biotic, and abiotic) factors, will be tackled, for example, by testing for a correspondence of karst outcrop isolation and genetic distances between populations. Within the present project, I will use one of Vietnam's most prominent limestone-bound taxa to reveal major biogeographical and evolutionary processes, which have not only shaped the diversity and distribution of this gastropod group but probably also of Vietnamese karst biota in general.