The chapter introduces the concept of polyploidy in vertebrate evolution, particularly focusing on its role in the evolution of salmonid fishes. Polyploidy, or the doubling of chromosome sets, has been recognized as a significant process in plant evolution but is only recently acknowledged in vertebrates. Ohno and colleagues proposed that genome doubling occurred at least once in the evolution of vertebrates, approximately 500 million years ago. This event is supported by isozyme studies. Recent research has shown that polyploidy is more common than previously thought, with polyploid amphibians and reptiles being particularly prevalent. However, polyploidy has not been a major driver of evolutionary progress in these groups. In fish, several species, including primitive fish like the paddlefish and lungfish, appear to be tetraploid.密切相关的二倍体和四倍体形式在一些硬骨鱼属中被发现，如Corydoras属和Misgurnus属。此外，三种鲤科鱼类——条鳅（Barbus barbus）、鲤鱼（Cyprinus carpio）和金鱼（Carassius auratus）——也被认为是四倍体。一些单性金鱼品系与正常双性金鱼相比，是三倍体或四倍体的。在墨西哥的两个活产鱼类属（Poecilia和Poeciliopsis）中发现了最近的多倍体，这些三倍体单性形式通过雌性生殖繁殖，并具有杂交起源。此外，Echelle和Mosier最近描述了一种单性Menidia属鱼类，似乎是三倍体的。 只有两个鱼类家族因多倍体起源而形成整个家族：猫舌鱼科（Catostomidae）和鲑科（Salmonidae）。猫舌鱼科是一个大型的进化群，包含12属和58种，它们似乎共享一个四倍体起源。鲑科是第二个共享共同四倍体起源的鱼类家族，主要分为三个亚科：白鲑亚科（Coregoninae）、虹鳟亚科（Salmoninae）和鲑亚科（Oncidiinae）。The chapter introduces the concept of polyploidy in vertebrate evolution, particularly focusing on its role in the evolution of salmonid fishes. Polyploidy, or the doubling of chromosome sets, has been recognized as a significant process in plant evolution but is only recently acknowledged in vertebrates. Ohno and colleagues proposed that genome doubling occurred at least once in the evolution of vertebrates, approximately 500 million years ago. This event is supported by isozyme studies. Recent research has shown that polyploidy is more common than previously thought, with polyploid amphibians and reptiles being particularly prevalent. However, polyploidy has not been a major driver of evolutionary progress in these groups. In fish, several species, including primitive fish like the paddlefish and lungfish, appear to be tetraploid.密切相关的二倍体和四倍体形式在一些硬骨鱼属中被发现，如Corydoras属和Misgurnus属。此外，三种鲤科鱼类——条鳅（Barbus barbus）、鲤鱼（Cyprinus carpio）和金鱼（Carassius auratus）——也被认为是四倍体。一些单性金鱼品系与正常双性金鱼相比，是三倍体或四倍体的。在墨西哥的两个活产鱼类属（Poecilia和Poeciliopsis）中发现了最近的多倍体，这些三倍体单性形式通过雌性生殖繁殖，并具有杂交起源。此外，Echelle和Mosier最近描述了一种单性Menidia属鱼类，似乎是三倍体的。 只有两个鱼类家族因多倍体起源而形成整个家族：猫舌鱼科（Catostomidae）和鲑科（Salmonidae）。猫舌鱼科是一个大型的进化群，包含12属和58种，它们似乎共享一个四倍体起源。鲑科是第二个共享共同四倍体起源的鱼类家族，主要分为三个亚科：白鲑亚科（Coregoninae）、虹鳟亚科（Salmoninae）和鲑亚科（Oncidiinae）。