From high latitudes into the tropics: The role of palaeogeography for the biodiversification of Ordovician bryozoans of Baltoscandia

本研究旨在研究巴氏念珠菌奥陶系苔藓虫的空间多样性格局。寒武纪大爆发后，生物多样性大事件(GoBe)是显生界生物多样化的第二个脉搏。这项拟进行的研究将有助于揭示全球生物多样性进程中的新见解。该项目的中心目标是确定空间多样性在多样化中的作用。本研究将回答生物多样性在哪一层次发生，哪些生态参数驱动生物多样性，以及地方性和迁徙对生物多样性的影响有多大。苔藓虫是研究奥陶系多样性格局的理想模式群，因为它们具有许多优势，包括在大多数支系中拥有钙化的骨骼，它们的模块化组织(严格的殖民地)，在奥陶系海洋生物群中的广泛分布。它们占据了波罗的海的货架，波罗的海是一块在奥陶纪从高纬度向热带移动的古大陆。这种漂移导致了气候的逐渐变化，这肯定会影响底栖动物的多样性动态，其中包括苔藓动物。苔藓动物的快速生物多样性与波罗的海的古地理变迁相结合，是研究其时空多样性格局的有利条件。对多样性(α、β、伽马)的研究将集中在两个时间/空间横断面上：1)挪威、瑞典、爱沙尼亚和俄罗斯西北部的达里维连；2)挪威、瑞典、爱沙尼亚和俄罗斯西北部的卡蒂安。此外，还将研究巴氏念珠菌奥陶系苔藓虫动物群的古生物地理模式，以估计迁徙在生物多样性过程中的作用。在预期的研究过程中，将检验几个假设。首先，人们认为生物多样性在当地范围内很强，而隔离发挥了重要作用。其次，底质类型、深度、沉积物入渗以及可能的营养支持等生态因素影响了奥陶系苔藓虫的生物多样性。第三，大规模的移民明显抑制了生物多样性，导致α多样性(局部)增加，β多样性(区域间)减少，而伽马多样性(区域)保持不变。预计在生物多样性事件期间，多样性的所有组成部分都会增加，而在大灭绝期间，全球多样性的单独部分(阿尔法、贝塔或伽马)会受到影响。

This proposal intends study of patterns of the spatial diversity of the Ordovician bryozoans of Baltoscandia. After the Cambrian explosion, the Great Biodiversification Event (GOBE) was the second pulse of diversification of the life in the Phanerozoic. The intended study will help to reveal new insights in the processes of biodiversification during the GOBE.The central aim of the project is to identify the role of spatial diversity in the diversification. This study will answer the questions, at which level the biodiversification takes place, which ecological parameters drive it, and how strong is the influence of provinciality and migrations on the biodiversification. Bryozoans are a perfect model group for study of diversity patterns in the Ordovician because they have many advantages including possessing of calcified skeleton in the majority of clades, their modular organisation (strictly colonial), wide distribution in marine biotopes of the Ordovician. They occupied the shelves of Baltica, a palaeocontinent moved from high latitudes towards the tropics during the Ordovician. This drift resulted in a gradual climatic change which certainly affected the diversity dynamics of the benthic fauna, among them bryozoans. The combination of the fast biodiversification of bryozoans and the palaeogeographical shift of Baltica is the beneficial condition to study the temporal and spatial diversity patterns. The study of diversity (alpha-, beta-, gamma-) will be concentrated in two temporal/spatial transects: 1) Darriwilian of Norway, Sweden, Estonia, and NW Russia, and 2) Katian of Norway, Sweden, Estonia, and NW Russia. In addition, palaeobiogeographic patterns of Ordovician bryozoan faunas of Baltoscandia will be studied, in order to estimate the role for migrations in biodiversification processes. In the course of the intended study several hypotheses will be tested. Firstly, it is supposed that biodiversification was strong at the local scale, and isolation played an important role. Secondly, certain ecological factors as substrate type, depth, sediment influx, and probably nutrient support influenced the biodiversification of bryozoans in the Ordovician. Thirdly, large-scaled migration apparently suppressed the biodiversification resulting in the increase of the alpha-diversity (local) but decrease of the beta-diversity (interregional), whereas gamma-diversity (regional) remains without changes. It is expected that the all components of diversity increase during biodiversification events, whereas during mass extinctions separate parts of the global diversity (alpha-, beta-, or gamma-) are affected.