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Genotypic similarities among the parthenogenetic Darevskia rock lizards with different hybrid origins.
BMC Evolutionary Biology ( IF 3.4 ) Pub Date : 2020-09-16 , DOI: 10.1186/s12862-020-01690-9
David Tarkhnishvili 1 , Alexey Yanchukov 2 , Mehmet Kürşat Şahin 3 , Mariam Gabelaia 1 , Marine Murtskhvaladze 1 , Kamil Candan 4 , Eduard Galoyan 5 , Marine Arakelyan 6 , Giorgi Iankoshvili 1 , Yusuf Kumlutaş 4 , Çetin Ilgaz 4 , Ferhat Matur 4 , Faruk Çolak 2 , Meriç Erdolu 7 , Sofiko Kurdadze 1 , Natia Barateli 1 , Cort L Anderson 1
Affiliation  

The majority of parthenogenetic vertebrates derive from hybridization between sexually reproducing species, but the exact number of hybridization events ancestral to currently extant clonal lineages is difficult to determine. Usually, we do not know whether the parental species are able to contribute their genes to the parthenogenetic vertebrate lineages after the initial hybridization. In this paper, we address the hypothesis, whether some genotypes of seven phenotypically distinct parthenogenetic rock lizards (genus Darevskia) could have resulted from back-crosses of parthenogens with their presumed parental species. We also tried to identify, as precise as possible, the ancestral populations of all seven parthenogens. We analysed partial mtDNA sequences and microsatellite genotypes of all seven parthenogens and their presumed ansectral species, sampled across the entire geographic range of parthenogenesis in this group. Our results confirm the previous designation of the parental species, but further specify the maternal populations that are likely ancestral to different parthenogenetic lineages. Contrary to the expectation of independent hybrid origins of the unisexual taxa, we found that genotypes at multiple loci were shared frequently between different parthenogenetic species. The highest proportions of shared genotypes were detected between (i) D. sapphirina and D. bendimahiensis and (ii) D. dahli and D. armeniaca, and less often between other parthenogens. In case (ii), genotypes at the remaining loci were notably distinct. We suggest that both observations (i-ii) can be explained by two parthenogenetic forms tracing their origin to a single initial hybridization event. In case (ii), however, occasional gene exchange between the unisexual and the parental bisexual species could have taken place after the onset of parthenogenetic reproduction. Indeed, backcrossed polyploid hybrids are relatively frequent in Darevskia, although no direct evidence of recent gene flow has been previously documented. Our results further suggest that parthenogens are losing heterozygosity as a result of allelic conversion, hence their fitness is expected to decline over time as genetic diversity declines. Backcrosses with the parental species could be a rescue mechanism which might prevent this decline, and therefore increase the persistance of unisexual forms.

中文翻译:

具有不同杂种起源的孤雌Darevskia蜥蜴的基因型相似性。

大多数孤雌生殖脊椎动物源自有性繁殖物种之间的杂交,但很难确定目前存在的克隆世系所固有的杂交事件的确切数目。通常,我们不知道亲本物种在初始杂交后是否能够将其基因贡献给孤雌生殖脊椎动物谱系。在本文中,我们解决了这一假设,即七种表型不同的单性生殖岩石蜥蜴(Darevskia属)的某些基因型是否可能是由单性生殖者与其推测的亲本物种的回交产生的。我们还试图尽可能精确地确定所有七种孤雌生殖的祖先种群。我们分析了所有七种孤雌生殖及其假定的an属物种的部分mtDNA序列和微卫星基因型,在该组孤雌生殖的整个地理范围内进行采样。我们的结果证实了先前对亲本物种的指定,但进一步说明了可能是孤雌生殖谱系祖先的母体种群。与单性类群的独立杂种起源的期望相反,我们发现多个单性生殖物种之间经常共享多个基因座的基因型。在(i)蓝宝石和D.bendimahiensis和(ii)D. dahli和D. armeniaca之间检测到共享基因型的比例最高,而在其他孤雌生殖之间的检测频率较低。在情况(ii)中,其余位点的基因型明显不同。我们建议这两个观察结果(i-ii)可以用两种孤雌生殖形式来解释,即它们的起源追溯到一个单一的杂交事件。然而,在情况(ii)中,单性生殖繁殖开始后,单性和父母双性恋物种之间可能偶尔发生了基因交换。确实,回交的多倍体杂种在达里夫斯基(Darevskia)相对较常见,尽管以前没有直接证据表明最近的基因流动。我们的结果进一步表明,由于等位基因转化,孤雌激素正在丧失杂合性,因此,随着遗传多样性的下降,其适应性有望随着时间的推移而下降。与亲本物种的回交可能是一种挽救机制,可以防止这种下降,从而增加单性形式的持久性。回交多倍体杂种在达里夫斯基(Darevskia)相对较频繁,尽管以前没有直接证据表明最近的基因流动。我们的结果进一步表明,由于等位基因转化,孤雌激素正在丧失杂合性,因此,随着遗传多样性的下降,其适应性有望随着时间的推移而下降。与亲本物种的回交可能是一种挽救机制,可以防止这种下降,并因此增加了单性形式的持久性。回交多倍体杂种在达里夫斯基(Darevskia)相对较常见,尽管以前没有直接证据表明最近的基因流动。我们的结果进一步表明,由于等位基因转化,孤雌激素正在丧失杂合性,因此,随着遗传多样性的下降,其适应性预计会随着时间下降。与亲本物种的回交可能是一种挽救机制,可以防止这种下降,并因此增加了单性形式的持久性。
更新日期:2020-09-16
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