Radojicic Jelena, Kristoffersen Jon Bent, Polovina Eirini-Slavka, Pavlidis Pavlos, Ladoukakis Emmanuel D
Institute of Marine Biology, Biotechnology and Aquaculture (IMBBC), Hellenic Center for Marine Research (HCMR), Heraklion, Crete, Greece.
Department of Biology, University of Crete, Voutes University Campus, Heraklion, 70013, Greece.
BMC Ecol Evol. 2025 Sep 2;25(1):91. doi: 10.1186/s12862-025-02436-1.
Heteroplasmy, the presence of more than one type of mitochondrial DNA (mtDNA) within an individual, is an exception to the maternal transmission of mtDNA and has been observed in several animal species. A central question is whether heteroplasmy among individuals and across generations is mainly influenced by genetic drift or by selection.
We quantified heteroplasmy in eight males, eight females and eight unfertilized eggs per female from a natural population of the hybrid frog species Pelophylax esculentus (between P. ridibundus and P. lessonae). After excluding sequencing error and potential sources of contamination, we found that all individuals and most of the eggs were heteroplasmic, containing 2-5 different haplotypes, from which one was very common and the rest appeared at very low frequencies (at maximum 2%). We observed a single lessonae haplotype, which was present in females and in their eggs but absent from all males. On the other hand, we observed four different ridibundus haplotypes that were present in males, females and eggs. Eggs had significantly lower heteroplasmy levels than their mothers.
The distribution of haplotypes between males and females, the difference of heteroplasmy levels between mothers and their eggs, and results from simulations suggest that drift alone is not sufficient to explain the observed patterns of heteroplasmy.
异质性是指个体内存在不止一种类型的线粒体DNA（mtDNA），这是mtDNA母系遗传的一个例外情况，并且已在多个动物物种中观察到。一个核心问题是个体间和世代间的异质性主要是受遗传漂变还是选择的影响。
我们对杂种蛙物种食用蛙（Pelophylax esculentus，由欧洲林蛙（P. ridibundus）和莱氏蛙（P. lessonae）杂交产生）自然种群中的8只雄性、8只雌性以及每只雌性的8枚未受精卵中的异质性进行了量化。在排除测序错误和潜在的污染来源后，我们发现所有个体以及大多数卵都是异质的，包含2 - 5种不同的单倍型，其中一种非常常见，其余的出现频率极低（最高为2%）。我们观察到一种仅存在于雌性及其卵中而在所有雄性中均不存在的莱氏蛙单倍型。另一方面，我们观察到四种不同的欧洲林蛙单倍型，它们存在于雄性、雌性和卵中。卵的异质性水平显著低于其母亲。
雄性和雌性之间单倍型的分布、母亲与其卵之间异质性水平的差异以及模拟结果表明，仅靠遗传漂变不足以解释观察到的异质性模式。
