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Rates, patterns and divergence times among the Bryozoa: integrating fossil, molecular and morphological data

苔藓虫的速率、模式和分化时间：整合化石、分子和形态数据

基本信息

批准号：
NE/E015298/1
负责人：
David Littlewood
金额：
$ 36.23万
依托单位：
Natural History Museum
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2007
资助国家：
英国
起止时间：
2007 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FE015298%2F1
关键词：
Rates patterns divergence times among

项目摘要

Marine communities are complex and are subject to changes driven by both abiotic and biotic factors. Many communities are characterized by the presence of ubiquitous animal groups, regardless of latitude, depth or biogeography. Few of these groups have excellent fossil records that are easily interpreted in the light of extant taxa and biology. One such group of animals that exhibits these characteristics is the phylum Bryozoa, which has the further defining feature of being colonial. Bryozoans, or moss-animals, are colonial invertebrates found predominantly in marine environments, although one group is restricted to freshwaters. Most of the >6000 living species have fossilizable mineralized skeletons of calcium carbonate and their fossil record indicates an evolutionary history stretching back over 450 million years. Bryozoans are important components of many modern sea-bed communities. They are often early settlers on hard surfaces such as rocks, shells and seaweeds. They grow rapidly and compete actively for space and planktonic food resources. They provide three-dimensional habitats for other animals and plants in the process of community succession. Their complex skeletons are amenable to detailed morphometric analysis. Evidence of interactions with competitors may be 'frozen' in the fossil record, and modes and timings of sexual reproduction are frequently preserved in the skeleton. They are also model organisms for studying the evolutionary palaeobiology of coloniality. However, many key questions and hypotheses remain unanswered and untestable because the interrelationships between different bryozoan groups (across many taxonomic levels) are uncertain. Thus, there is an acute need for a robust evolutionary framework. We will concentrate on cyclostomes, a ubiquitous and key bryozoan group, that have maintained an important role as members of the epibenthos since their first appearance some 470 million years ago. The longevity of cyclostomes is at odds with their poor ability to compete with other bryozoans, and their relatively slow rate of morphological evolution. We will use a multigene, molecular systematic approach to investigate rates and patterns of evolution and extinction among the phylum, addressing three questions that have long been contentious: (1) When did the major subgroups of cyclostomes that live today diverge? (2) How are the three classes of bryozoans interrelated? (3) Have slow morphological rates of evolution in cyclostomes been matched by slow molecular rates of evolution? We will resolve bryozoan interrelationships using molecular markers. The phylogenies will be calibrated with well-established divergence events from the fossil record using modern statistical techniques to date divergence times. We will establish a robust framework for understanding the radiation of the entire phylum in terms of palaeobiology, patterns of extinction, developmental biology and life history strategies. Anticipated results will have an immense impact on our understanding of bryozoan evolution and systematics. This will provide an understanding of key components of present day marine biodiversity. Molecular phylogenies are critical to advancing knowledge of the phylum and will allow bryozoans to be better used as model organisms of coloniality and as indicators of marine community ecology. Our findings promise to have a major bearing on several wider issues concerning evolutionary patterns and processes, namely: (1) the relationship between molecular and morphological rates of evolution and speciation rate; (2) the influence of sustained competition between clades over geological time on evolutionary rates; (3) the effect of larval type and life-history strategies on evolutionary rates; (4) mass extinction intensities at high taxonomic level; and (5) the origin of biomineralized skeletons in aquatic invertebrates and their possible secondary loss when colonizing freshwater habitats.

海洋群落是复杂的，易受非生物和生物因素驱动的变化的影响。许多社区的特点是无处不在的动物群体的存在，无论纬度，深度或地理。这些群体中很少有优秀的化石记录，很容易根据现存的分类群和生物学进行解释。苔藓动物门就是表现出这些特征的一类动物，它具有更进一步的集群特征。苔藓动物，或苔藓动物，是主要在海洋环境中发现的群体无脊椎动物，尽管其中一组仅限于淡水。在超过6000个现存物种中，大多数都有可分解的碳酸钙矿化骨骼，它们的化石记录表明其进化历史可以追溯到4.5亿年前。苔藓动物是现代海底生物群落的重要组成部分。他们通常是早期定居者在坚硬的表面，如岩石，贝壳和海藻。它们生长迅速，并积极竞争空间和浮游食物资源。在群落演替过程中，它们为其他动植物提供了立体的栖息地。它们复杂的骨骼可以进行详细的形态测量分析。与竞争者相互作用的证据可能被“冻结”在化石记录中，并且有性生殖的模式和时间经常被保存在骨骼中。它们也是研究殖民性进化古生物学的模式生物。然而，许多关键的问题和假设仍然没有答案和无法验证，因为不同苔藓动物群体之间的相互关系（在许多分类水平）是不确定的。因此，迫切需要一个强大的进化框架。我们将集中讨论圆口动物，这是一个普遍存在的关键苔藓动物群，自从大约4.7亿年前首次出现以来，它一直作为表底生物的成员发挥着重要作用。圆口动物的寿命与它们与其他苔藓动物竞争的能力差以及它们相对缓慢的形态进化速度不一致。我们将使用多基因，分子系统的方法来调查的速度和模式的进化和灭绝的门，解决三个问题，长期以来一直有争议的：（1）什么时候的主要亚群的圆口动物生活在今天的分歧？(2)这三类苔藓虫是如何相互关联的？(3)圆口动物缓慢的形态进化速度是否与缓慢的分子进化速度相匹配？我们将使用分子标记来解决苔藓虫的相互关系。将使用现代统计技术，根据化石记录中已确立的分歧事件，对分歧时间进行校准。我们将建立一个强大的框架，了解整个门的辐射在古生物学，灭绝模式，发育生物学和生活史策略。预期的结果将对我们理解苔藓动物的进化和系统学产生巨大的影响。这将有助于了解当今海洋生物多样性的关键组成部分。分子生物学的发展对于推进苔藓动物门的知识至关重要，并将使苔藓动物更好地用作殖民性的模式生物和海洋群落生态学的指标。我们的研究结果有望对涉及进化模式和过程的几个更广泛的问题产生重大影响，即：（1）分子和形态进化速率与物种形成速率之间的关系;（2）在地质时间内分支之间持续竞争对进化速率的影响;（3）幼虫类型和生活史策略对进化速率的影响;水生无脊椎动物生物矿化骨骼的起源及其在淡水栖息地定居时可能的二次损失。