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<p>The genus <i>Senecio</i> L. known for its remarkable diversity in growth forms and ecological adaptations has been extensively studied. Despite this understanding, evolutionary relationship within the genus remains challenging due to high levels of phenotypic variability and frequent hybridization events. A critical review on the taxonomic history and evolution of the genus, chromosome number, genome size variation and the role of hybridization in speciation is presented. Chromosome count ranges from 2<i>n</i> = 10 to 2<i>n</i> = 184 with 2<i>n</i> = 40 being the most frequent. The genome size varies approximately 21-fold, with 2C values ranging from 1.8 to 38.6&#xa0;pg. We traced chromosomal evolution along a nuclear ribosomal internal transcribed spacer (ITS) phylogeny that included 152 taxa and found that the basic chromosome number of the genus is <i>x</i> = 5. Base number transition and duplication were the main events that led to karyotype evolution. Chromosomal data support phylogenetic studies suggesting an Old World origin of the genus. The relatively high chromosome numbers observed in species from the New World (South and North America) and Australia likely reflect derived states, consistent with diversification following dispersal from the Old World. Our findings on chromosomal evolution strongly support the exclusion of species belonging to <i>adamantinus</i>-<i>ruwenzoriensis</i> clade from <i>Senecio</i> sensu stricto.</p>

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Chromosome diversity, evolution and genome size variation in Senecio: a review and meta-study

  • 期刊论文

  • 发表日期：

    2025年9月13日

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  • Akanksha S. Jeswani,
  • Siddharthan Surveswaran,
  • Manoj M. Lekhak

摘要

The genus Senecio L. known for its remarkable diversity in growth forms and ecological adaptations has been extensively studied. Despite this understanding, evolutionary relationship within the genus remains challenging due to high levels of phenotypic variability and frequent hybridization events. A critical review on the taxonomic history and evolution of the genus, chromosome number, genome size variation and the role of hybridization in speciation is presented. Chromosome count ranges from 2n = 10 to 2n = 184 with 2n = 40 being the most frequent. The genome size varies approximately 21-fold, with 2C values ranging from 1.8 to 38.6 pg. We traced chromosomal evolution along a nuclear ribosomal internal transcribed spacer (ITS) phylogeny that included 152 taxa and found that the basic chromosome number of the genus is x = 5. Base number transition and duplication were the main events that led to karyotype evolution. Chromosomal data support phylogenetic studies suggesting an Old World origin of the genus. The relatively high chromosome numbers observed in species from the New World (South and North America) and Australia likely reflect derived states, consistent with diversification following dispersal from the Old World. Our findings on chromosomal evolution strongly support the exclusion of species belonging to adamantinus-ruwenzoriensis clade from Senecio sensu stricto.