Middle East Technical University, Faculty of Science, Department of Biology, Ankara, Turkey.
Hacettepe University, Department of Biology, Ankara, Turkey.
Mol Phylogenet Evol. 2023 Dec;189:107925. doi: 10.1016/j.ympev.2023.107925. Epub 2023 Sep 12.
Among vertebrates, obligate parthenogenesis is only found in Squamata, where it always has a hybrid origin and a few lizard genera contain most of the known hybridogenous parthenogenetic taxa. Parthenogenesis thus seems to be pre-conditioned at the genus level, but it is not clear how often the encounter between two parental sexually reproducing species can result in the parthenogenetic offspring, nor whether the success of such hybridization event requires certain conditions or the specific time frame. To address this question, we studied the rock lizards of genus Darevskia, where a pair of parental species, D. valentini and D. raddei, as well as their parthenogenetic daughter species D. bendimahiensis and D. sapphirina, are found in close proximity NE of the Lake Van in East Anatolia. Using ddRAD-seq genotyping on 19 parental and 18 hybrid individuals, we found that (i) all parthenogenetic individuals from both D. bendimahiensis and D. sapphirina have a monophyletic origin tracing back to a single initial hybrid population, but their current genetic variation is geographically structured; (ii) unlike the most probable paternal ancestor, the genetically closest extant population of the maternal ancestor is not the geographically nearest one; and (iii) in the parthenogens, about 1% of loci carry multiple haplotypes, frequently differentiated by multiple substitutions. This pattern, in addition to biases in the relative frequency of haplotypes of maternal and paternal origin, does not appear compatible with a scenario of the entire parthenogenic clonal population having descended from a single pair of parental individuals. Instead, the data suggest that multiple parental individual ancestries still persist in the parthenogenetic gene pool. This supports the notion that although hybridization leading to parthenogenesis is generally rare at the level of species, it may be more common at the individual/population level once the right conditions are met.
在脊椎动物中，强制孤雌生殖仅在有鳞目动物中发现，在那里它总是具有杂种起源，并且少数蜥蜴属包含大多数已知的杂种孤雌生殖分类群。因此，孤雌生殖似乎在属的水平上受到预先限制，但不清楚两个有性繁殖的亲种之间的相遇多少次会导致孤雌生殖的后代，也不清楚这种杂交事件的成功是否需要某些条件或特定的时间框架。为了解决这个问题，我们研究了 Darevskia 属的岩蜥，其中一对亲种 D. valentini 和 D. raddei 以及它们的孤雌生殖女儿种 D. bendimahiensis 和 D. sapphirina 在东安纳托利亚的凡湖东北附近近距离存在。通过对 19 个亲种和 18 个杂种个体进行 ddRAD-seq 基因分型，我们发现：（i）来自 D. bendimahiensis 和 D. sapphirina 的所有孤雌生殖个体都具有单一的起源，追溯到一个单一的初始杂交种群，但它们目前的遗传变异是地理结构的；（ii）与最可能的父系祖先不同，遗传上最接近的母系祖先的现存种群不是地理上最近的种群；（iii）在孤雌生殖者中，大约 1%的基因座携带多个单倍型，经常通过多个取代而分化。这种模式，加上母系和父系起源的单倍型相对频率的偏差，似乎与整个孤雌生殖克隆种群都来自一对亲种个体的情景不兼容。相反，数据表明，多个亲种个体的祖先仍然存在于孤雌生殖的基因库中。这支持了这样一种观点，即尽管导致孤雌生殖的杂交在种的水平上通常很少见，但一旦满足了正确的条件，它可能在个体/种群水平上更为常见。
