Data from: Cytonuclear evidence for hybridogenetic reproduction in natural populations of the Australian carp gudgeon (Hypseleotris: Eleotridae).

Although most vertebrates reproduce sexually, a small number of fishes, amphibians, and reptiles are known in which reproduction is asexual i.e. without meiotic recombination. In fishes, these so-called “unisexual” lineages usually comprise only females, and utilize co-occurring males of a related sexual species to reproduce via gynogenesis or hybridogenesis. Here we examine patterns of microsatellite and mitochondrial DNA (mtDNA) variation in a widespread group of freshwater fishes (carp gudgeons; Hypseleotris spp.) to investigate a long-standing proposal that this group includes unisexual forms. We show that the mtDNA genome of most carp gudgeons in tributaries of the Goulburn River belong in one of two deeply divided clades (~10% cyt b divergence) and that nuclear variation divides the same individuals into four distinct groups. Group 1 exhibits the genotypic proportions of a random mating population and has a 1:1 sex ratio. Two other groups are extremely sex-biased (98% male, 96% female), exhibit excess heterozygosity at most loci and share at least one allele per locus with group 1. We propose that these two groups represent “unisexual” hybridogenetic lineages, and that both utilize co-occurring group 1 as sexual host. Interestingly, the fourth distinct group appears to represent hybrid offspring of the two putative hybridogenetic lineages. The propagation of clonal haploid genomes by both males and females and the ability of these clones to unite and form sexually mature diploid hybrid offspring may represent a novel mechanism that contributes to the dynamics of coexistence between hybridogenetic lineages and their sexual hosts.

尽管绝大多数脊椎动物均以有性方式繁殖，但目前已发现少量鱼类、两栖类与爬行类可进行无性生殖，即不发生减数分裂重组的繁殖模式。在鱼类中，这类被称为‘单性谱系’的类群通常仅由雌性个体组成，它们会借助同域分布的近缘有性物种的雄性个体，通过雌核发育（gynogenesis）或杂交生殖（hybridogenesis）完成繁殖。本研究针对一类分布广泛的淡水鱼类——鲤鰕虎（carp gudgeons; Hypseleotris spp.）——展开分析，对其微卫星（microsatellite）DNA与线粒体DNA（mitochondrial DNA, mtDNA）的变异模式进行检测，以验证该类群中存在单性生殖类群这一长期存在的假说。研究结果显示，采集自古尔本河支流的多数鲤鰕虎个体，其线粒体基因组可归入两个分化极深的支系之一（细胞色素b基因cyt b序列分歧度约为10%）；而核基因变异则将这些个体划分为4个截然不同的类群。类群1的基因型比例符合随机交配种群的特征，且性别比例为1:1。另外两个类群存在极端的性别偏倚（雄性占比98%，雌性占比96%），在多数基因位点上表现出杂合子过剩的特征，且每个位点均至少携带一个与类群1相同的等位基因。据此我们提出，这两个类群即为单性杂交生殖谱系，且二者均以同期存在的类群1作为有性生殖宿主。值得注意的是，第四个独立类群似乎是上述两个推测的杂交生殖谱系的杂交后代。雄性与雌性个体均可传播克隆式单倍体基因组，且这些克隆基因组能够结合形成性成熟的二倍体杂交后代——这一机制或许是一种全新的驱动机制，可解释杂交生殖谱系与其有性宿主之间的共存动态。