Mikulíček P, Kautman M, Demovič B, Janko K
Department of Zoology, Faculty of Natural Sciences, Comenius University, Bratislava, Slovak Republic.
Department of Biology and Wildlife Diseases, Faculty of Veterinary Hygiene and Ecology, University of Veterinary and Pharmaceutical Sciences, Brno, Czech Republic.
J Evol Biol. 2014 Mar;27(3):628-42. doi: 10.1111/jeb.12332. Epub 2014 Feb 7.
Besides several exceptions, asexual metazoans are usually viewed as ephemeral sinks for genomes, which become 'frozen' in clonal lineages after their emergence from ancestral sexual species. Here, we investigated whether and at what rate the asexuals are able to introgress their genomes back into the parental sexual population, thus more or less importantly affecting the gene pools of sexual species. We focused on hybridogenetic hybrids of western Palaearctic water frogs (Pelophylax esculentus), which originate through hybridization between P. ridibundus and P. lessonae, but transmit only clonal ridibundus genome into their gametes. Although usually mating with P. lessonae, P. esculentus may upon mating with P. ridibundus or another hybrid produce sexually reproducing P. ridibundus offspring with the introgressed ex-clonal genome. We compared the rate of nuclear amplified fragment length polymorphism (AFLP) and mitochondrial introgression in two types of populations, that is, those where P. ridibundus occurs in isolation and those where it lives with the hybridogens. Although significant differentiation (Φpt) between sexual and clonal ridibundus genomes suggested limited gene flow between sexuals and hybridogens, a non-negligible (~5%) proportion of P. ridibundus bore introgressed mtDNA and AFLP markers. Whereas transfer of mtDNA was exclusively unidirectional, introgression of nuclear markers was bidirectional. The proportion of introgressed P. ridibundus was highest in syntopic populations with P. esculentus, proving an ongoing and site-specific interspecific genetic transfer mediated by hybridogenetic hybrids. It turns out that asexual hybrids are not just a sink for genes of sexual species, but may significantly influence the genetic architecture of their sexual counterparts.
除了少数例外情况，无性后生动物通常被视为基因组的短暂归宿，这些基因组在从祖先有性物种中出现后，在克隆谱系中“冻结”。在这里，我们研究了无性动物是否能够以及以何种速率将其基因组渗入到亲本有性种群中，从而或多或少地重要影响有性物种的基因库。我们聚焦于西古北区水蛙（食用蛙Pelophylax esculentus）的杂交起源杂种，它们起源于泽陆蛙（P. ridibundus）和池蛙（P. lessonae）之间的杂交，但仅将克隆的泽陆蛙基因组传递到它们的配子中。尽管食用蛙通常与池蛙交配，但与泽陆蛙或另一个杂种交配时，食用蛙可能会产生具有渗入的非克隆基因组的有性繁殖的泽陆蛙后代。我们比较了两种类型种群中核扩增片段长度多态性（AFLP）和线粒体渗入的速率，即泽陆蛙单独出现的种群和与杂交起源杂种共存的种群。尽管有性和克隆的泽陆蛙基因组之间存在显著分化（Φpt），表明有性个体和杂交起源杂种之间的基因流动有限，但仍有不可忽视的比例（约5%）的泽陆蛙带有渗入的线粒体DNA和AFLP标记。线粒体DNA的转移是单向的，而核标记的渗入是双向的。在与食用蛙同域分布的种群中，渗入的泽陆蛙比例最高，这证明了由杂交起源杂种介导的正在进行的且具有位点特异性的种间基因转移。结果表明，无性杂种不仅是有性物种基因的归宿，而且可能会显著影响其有性对应物的遗传结构。
