Department of Integrative Biology, University of Guelph, Ontario, Canada.
Heredity (Edinb). 2009 Dec;103(6):483-93. doi: 10.1038/hdy.2009.83. Epub 2009 Jul 29.
Although bisexual reproduction has considerable evolutionary benefits, several all-female vertebrates exist. Unisexual salamanders in the genus Ambystoma are common around the Great Lakes region in eastern North America. They originated from a hybridization event that involved a female that shared a common ancestor with Ambystoma barbouri 2.4 to 3.9 million years ago but, unexpectedly, A. barbouri nuclear genomes were unknown in unisexuals. Unisexual salamanders steal sperm from donors of normally bisexual species, so their reproductive mode is described as kleptogenesis. Most known unisexuals are polyploid and they all possess at least one A. laterale genome. One or more other genomes are taken from sperm donors that may include A. jeffersonianum, A. laterale, A. texanum and A. tigrinum. We examined unisexual adults and larvae in a southern Ohio pond where unisexual individuals coexist with male A. barbouri. This population provided an opportunity to test hypotheses pertaining to the role of A. barbouri in the evolution of the disparate cytoplasmic and nuclear genomes in unisexual salamanders. Microsatellite DNA loci, mitochondrial DNA sequences and genomic in situ hybridization were used to identify the genomic constitution of individuals. A. barbouri was found to be an acceptable sperm donor for unisexuals but only contributed genomes in ploidy-elevated individuals. In the absence of A. jeffersonianum, this Ohio population is likely experiencing a recent switch in sperm donors from A. jeffersonianum to A. barbouri and demonstrates the evolutionary flexibility and dynamics of kleptogenesis.
虽然两性生殖具有相当大的进化优势,但仍存在一些全雌性的脊椎动物。北美东部大湖区常见的单性蝾螈 Ambystoma 属源自于一次杂交事件,涉及一只雌性,它与 Ambystoma barbouri 的共同祖先可追溯到 240 万至 390 万年前,但令人意外的是,单性蝾螈中没有 Ambystoma barbouri 的核基因组。单性蝾螈从正常的两性物种的供体中窃取精子,因此它们的生殖模式被描述为盗精生殖。大多数已知的单性动物都是多倍体,它们都至少拥有一个 A. laterale 基因组。还有一个或多个其他基因组来自于精子供体,这些供体可能包括 A. jeffersonianum、A. laterale、A. texanum 和 A. tigrinum。我们检查了俄亥俄州南部一个池塘中的单性成体和幼虫,在那里单性个体与雄性 Ambystoma barbouri 共存。这个种群为测试与 Ambystoma barbouri 在单性蝾螈不同细胞质和核基因组进化中的作用相关的假说提供了机会。微卫星 DNA 位点、线粒体 DNA 序列和基因组原位杂交被用来识别个体的基因组构成。发现 Ambystoma barbouri 是单性动物可接受的精子供体,但仅在倍性升高的个体中贡献基因组。在没有 A. jeffersonianum 的情况下,这个俄亥俄州的种群可能最近经历了从 A. jeffersonianum 到 A. barbouri 的精子供体转变,这表明了盗精生殖的进化灵活性和动态性。