Faculty of Environmental Sciences, Czech University of Life Sciences Prague, Kamýcká 129, Praha 6 - Suchdol, CZ-165 21, Czech Republic; The Czech Academy of Sciences, Institute of Botany, Zámek 1, CZ-252 43 Průhonice, Czech Republic.
Faculty of Environmental Sciences, Czech University of Life Sciences Prague, Kamýcká 129, Praha 6 - Suchdol, CZ-165 21, Czech Republic; The Czech Academy of Sciences, Institute of Botany, Zámek 1, CZ-252 43 Průhonice, Czech Republic.
Mol Phylogenet Evol. 2018 Dec;129:189-201. doi: 10.1016/j.ympev.2018.08.016. Epub 2018 Aug 29.
Hybridization and polyploidization represent an important speciation mechanism in the diploid-polyploid complex of the Chenopodium album aggregate. In the present study we successfully reconstructed the evolutionary histories of the majority of Eurasian representatives of the C. album aggregate, resulting in the most comprehensive phylogenetic analysis of this taxonomically intricate group of species to date. We applied a combination of classical karyology for precise chromosome number determination, genomic in-situ hybridization for the determination of genomic composition, flow cytometry for the estimation of genome size and sequencing of plastid (cpDNA) and nuclear (ribosomal internal transcribed spacer - ITS and the introns of the FLOWERING LOCUS T LIKE genes - FTL) markers for a phylogenetic reconstruction and the identification of parental genomes in polyploid taxa. The FTL markers identified eight well supported evolutionary lineages. Five of them include at least one diploid species, and the remaining three comprise solely the subgenomes of polyploids that probably represent extinct or unknown diploid taxa. The existence of eight basic diploid lineages explains the origin of seven Eurasian polyploid groups and brings evidence of a nearly unlimited number of subgenomic combinations. The supposed promiscuity generated new species wherever different diploid lineages met each other and gave rise to tetraploid species or whenever they met other tetraploid species to produce hexaploid species throughout their evolutionary history. Finally, we unravelled a surprisingly simple scheme of polyploid species formation within the C. album aggregate. We determined seven groups of polyploid species differing in their origin in either Eurasia or Africa and convincingly demonstrated that (1) all Chenopodium polyploid species under study are of allopolyploid origin, (2) there are eight major monophyletic evolutionary lineages represented by extant or extinct/unknown diploid taxa, (3) those monophyletic lineages represent individual subgenomes, (4) hybridization among the lineages created seven subgenomic combinations of polyploid taxa, (5) taxa represented by particular subgenome combinations were further subjected to diversification, and (6) the majority of species are relatively young, not exceeding the age of the Quaternary period.
杂种形成和多倍体化是二倍体-多倍体复合体中藜属种间分化的重要机制。在本研究中，我们成功重建了藜属复合体中大多数欧亚代表种的进化历史，这是迄今为止对该分类复杂种组最全面的系统发育分析。我们采用了经典的核型学方法进行精确的染色体数目确定，基因组原位杂交确定基因组组成，流式细胞术估计基因组大小，以及质体（cpDNA）和核（核糖体内部转录间隔区 - ITS 和 FLOWERING LOCUS T LIKE 基因的内含子 - FTL）标记的测序进行系统发育重建和多倍体分类群中亲本组的鉴定。FTL 标记鉴定出 8 个支持度高的进化支系。其中 5 个支系至少包含一个二倍体种，其余 3 个支系仅包含多倍体的亚基因组，这些亚基因组可能代表已灭绝或未知的二倍体分类群。8 个基本二倍体支系的存在解释了 7 个欧亚多倍体组的起源，并提供了几乎无限数量的亚基因组组合的证据。这种假定的杂交使不同的二倍体支系相遇的地方产生了新的物种，并产生了四倍体物种，或者当它们遇到其他四倍体物种时，在其进化历史中产生了六倍体物种。最后，我们揭示了藜属复合体中多倍体物种形成的一个惊人简单的模式。我们确定了 7 个多倍体物种组，它们在欧亚或非洲的起源不同，并令人信服地证明了：(1) 研究的所有藜属多倍体物种均为异源多倍体起源；(2) 存在 8 个主要的单系进化支系，由现存或灭绝/未知的二倍体分类群代表；(3) 这些单系支系代表单个亚基因组；(4) 支系间的杂交形成了 7 个多倍体分类群的亚基因组组合；(5) 由特定亚基因组组合代表的分类群进一步多样化；(6) 大多数物种相对较年轻，不超过第四纪的年龄。
