Systematics and Biogeography of Lampreys ("Agnatha":Petromyzontiformes) and the Evolution of Parasitic and Non-Parasitic Life Cycles

七鳃鳗（“无颌”：Petromyzontiformes）的系统学和生物地理学以及寄生和非寄生生命周期的进化

• 批准号: 0089507
• 负责人: Richard Mayden
• 金额: $ 20万
• 依托单位: University of Alabama Tuscaloosa
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-06-01 至 2002-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0089507&HistoricalAwards=false
• 关键词: Systematics; Biogeography; Lampreys; Agnatha; Petromyzontiformes

0089507Mayden and Roe Based on the fossil record, the greatest diversity of jawless vertebrates (agnathans) occurred during the upper Silurian and Early and Middle Devonian geological periods, approximately 420 to 380 million years ago. The majority of agnathans became extinct by the end of the Devonian (360 million years ago) with one or more lineages surviving to give rise to modern jawless vertebrates. Lampreys represent one of the two surviving groups of agnathans (hagfishes are the other group). Living lampreys are classified in the order Petromyzontiformes, which includes 40 extant species. The geographic distribution of lampreys is notable in that they are found in both Northern and Southern hemispheres, but are almost entirely absent from tropical regions. It has been hypothesized that this distribution of lampreys is the result of the breakup of the supercontinent Pangea and the post-Pangean continents of Laurasia and Gondwana. In addition to their interesting geographic distribution lampreys are also remarkable for several reasons: 1) they represent a transitional stage between invertebrate chordates and vertebrates that possess jaws, and as such allow the testing of hypotheses concerning the evolution of characters considered to be unique to vertebrates; 2) they possess a complex life history that involves metamorphosis from a sedentary, filter feeding larval form termed an ammocete, to a sexually reproducing adult; and 3) they can be divided into two groups based on whether the species are parasitic or non-parasitic. Parasitic lampreys include both anadromous species and those restricted to streams and rivers. Species with non-parasitic life-cycles are similar to those with a parasitic life-cycle except that the adults do not feed. Historically, morphological similarities between parasitic and non-parasitic species have been interpreted as evidence that extant non-parasitic species evolved independently on several occasions from different parasitic species. These hypothesized sibling species have been termed "paired species" or "satellite species." Despite agreement among lamprey researchers as to the validity of the satellite species hypothesis, no explicit phylogenetic analysis has been conducted to support such relationships. Drs. Richard Mayden and Kevin Roe at the University of Alabama are seeking to test these hypothesized relationships, and thereby test one of the most remarkable cases of multiple convergence ever suspected in vertebrates. The study will produce phylogenetic hypotheses for all lamprey species using both morphological and molecular (DNA sequences) data sets. Specific objectives are to test hypotheses concerning (1) the evolutionary origins of the parasitic and non-parasitic life histories, (2) the relationships between the various species and genera and families within Petromyzontiformes, (3) the biogeographic history of Petromyzontiformes with reference to the history of the earth and other taxa having similar distributions, and (4) the proposed relationship between lampreys and jawed vertebrates. The project is international in scope, and includes the collection of specimens on several continents (North America, South America, Europe and Australia), and involves collaboration with three acknowledged experts in lamprey biology and systematics: Drs. I. Potter and H. Gill of Murdoch University, Perth, Australia and Dr. C. Renaud from the Canadian Museum of Nature, Ottawa, Ontario, who have primary responsibility for the collection of additional specimens (important for morphological characters and molecular analyses) and the development of morphological data sets. These data will be combined with the molecular data sets based upon the complete DNA sequences of several mitochondrial genes.

0089507Mayden 和 Roe 根据化石记录，无颌脊椎动物（无颌类）的最大多样性出现在志留纪上部和泥盆纪早、中地质时期，大约 420 至 3.8 亿年前。 大多数无颌动物在泥盆纪末期（3.6亿年前）灭绝，只有一个或多个谱系幸存下来，产生了现代无颌脊椎动物。 七鳃鳗是幸存的无颌类动物的两个类群之一（盲鳗是另一类）。 现存的七鳃鳗属于 Petromyzontiformes 目，包括 40 个现存物种。 七鳃鳗的地理分布值得注意，北半球和南半球都有它们的踪迹，但热带地区几乎完全没有它们。 据推测，七鳃鳗的这种分布是盘古大陆超大陆以及后盘古大陆劳亚大陆和冈瓦纳大陆分裂的结果。 除了其有趣的地理分布之外，七鳃鳗还因以下几个原因而引人注目：1）它们代表了无脊椎动物脊索动物和有颌脊椎动物之间的过渡阶段，因此可以检验有关被认为是脊椎动物独有的特征进化的假设； 2）它们拥有复杂的生活史，包括从一种被称为“ammocete”的静坐、滤食性幼虫形态到有性繁殖的成虫的变态； 3）根据物种是寄生还是非寄生，可以将它们分为两类。 寄生七鳃鳗包括溯河产卵的物种和仅限于溪流和河流的物种。 具有非寄生生命周期的物种与具有寄生生命周期的物种相似，只是成虫不进食。 从历史上看，寄生和非寄生物种之间的形态相似性被解释为现有非寄生物种多次从不同寄生物种独立进化的证据。 这些假设的兄弟物种被称为“配对物种”或“卫星物种”。 尽管七鳃鳗研究人员对卫星物种假说的有效性达成了一致，但尚未进行明确的系统发育分析来支持这种关系。 博士。阿拉巴马大学的理查德·梅登和凯文·罗伊正在寻求测试这些假设的关系，从而测试脊椎动物中有史以来怀疑的最显着的多重趋同案例之一。 该研究将利用形态学和分子（DNA 序列）数据集对所有七鳃鳗物种提出系统发育假设。 具体目标是检验以下假设：（1）寄生和非寄生生命史的进化起源，（2）Petromyzontiformes内不同物种、属和科之间的关系，（3）Petromyzontiformes的生物地理历史参考地球和具有类似分布的其他类群的历史，以及（4）七鳃鳗和有颌脊椎动物之间的拟议关系。该项目的范围是国际性的，包括在几大洲（北美、南美、欧洲和澳大利亚）收集标本，并与七鳃鳗生物学和系统学领域的三位公认专家合作：Drs.澳大利亚珀斯默多克大学的 I. Potter 和 H. Gill 以及安大略省渥太华加拿大自然博物馆的 C. Renaud 博士，他们主要负责额外标本的收集（对于形态特征和分子分析很重要）和形态数据集的开发。 这些数据将与基于多个线粒体基因的完整 DNA 序列的分子数据集相结合。