Scholarlink

Background <p>This study explored chromosome number variation, phylogenetic divergence, and mechanisms underlying speciation in East Asian thistle <i>Cirsium</i> Mill. sect. <i>Onotrophe</i> (Cass.) DC. subsect. <i>Nipponocirsium</i> Kitam. (Compositae). The study focused on the newly identified species from Taiwan: <i>Cirsium pengii</i> Y.H. Tseng, P.C. Liao &amp; Chih Y. Chang. Utilizing phylotranscriptomic data to reconstruct evolutionary relationships between the Taiwanese and Japanese taxa of <i>Cirsium</i> subsect. <i>Nipponocirsium</i> as well as their divergence times and chromosomal characteristics. Additionally, the chromosome number, morphology, and pollen morphology of the unknown <i>Cirsium</i> taxon are compared with other known subsect. <i>Nipponocirsium</i> taxa from Taiwan.</p> Results <p>Phylotranscriptomic analysis reveals a division within subsect. <i>Nipponocirsium</i> into Japanese and Taiwanese clades. In the Taiwanese clade, <i>C. pengii</i> is basal, while <i>C. tatakaense</i> remains monophyletic with other Taiwanese species despite higher genetic diversity. The prevalent chromosome number in this subsection is tetraploid (2<i>n</i> = 4<i>x</i> = 68), common in Japanese taxa, while Taiwanese members have 2<i>n</i> = 4<i>x</i> = 64. Notably, <i>C. pengii</i> has a diploid number (2<i>n</i> = 32), indicating descending dysploidy followed by polyploidization in Taiwan. This polyploidization, driven by glaciations, likely shaped the evolution of <i>Nipponocirsium</i>. Divergence time estimates suggest the separation of Japanese and Taiwanese clades around 0.74 million years ago (Myr) during glacial periods. <i>Cirsium pengii</i> diverged around 0.47 Myr, while tetraploid species <i>C. kawakamii</i> and <i>C. tatakaense</i> diverged around 0.35 Myr. These species likely evolved in separate refugia, with distinct species boundaries confirmed through species delimitation analysis, karyotype, morphology, and pollen morphology comparisons.</p> Conclusions <p>These findings enhance our understanding of chromosomal evolution and speciation within subsect. <i>Nipponocirsium</i> and underscore the importance of integrating transcriptomic data in phylogenetic studies. This study provides a comprehensive framework for further investigations into the genetic diversity and adaptive mechanisms of this ecologically vital group.</p>

错误：搜索内容不能为空，请输入英文关键词
错误：关键词超出字数限制，请精简
高级检索

Chromosome number variation and phylogenetic divergence of East Asian Cirsium sect. Onotrophe subsect. Nipponocirsium (Compositae), with a new species from Taiwan

  • 期刊论文

  • 出版模式：

    开放获取

  • 发表日期：

    2025年2月14日

查看全文
  • Chih-Yi Chang,
  • Pei-Chun Liao,
  • Hsy-Yu Tzeng,
  • Junko Kusumi,
  • Zhi-Hui Su,
  • Yen-Hsueh Tseng

摘要

Background

This study explored chromosome number variation, phylogenetic divergence, and mechanisms underlying speciation in East Asian thistle Cirsium Mill. sect. Onotrophe (Cass.) DC. subsect. Nipponocirsium Kitam. (Compositae). The study focused on the newly identified species from Taiwan: Cirsium pengii Y.H. Tseng, P.C. Liao & Chih Y. Chang. Utilizing phylotranscriptomic data to reconstruct evolutionary relationships between the Taiwanese and Japanese taxa of Cirsium subsect. Nipponocirsium as well as their divergence times and chromosomal characteristics. Additionally, the chromosome number, morphology, and pollen morphology of the unknown Cirsium taxon are compared with other known subsect. Nipponocirsium taxa from Taiwan.

Results

Phylotranscriptomic analysis reveals a division within subsect. Nipponocirsium into Japanese and Taiwanese clades. In the Taiwanese clade, C. pengii is basal, while C. tatakaense remains monophyletic with other Taiwanese species despite higher genetic diversity. The prevalent chromosome number in this subsection is tetraploid (2n = 4x = 68), common in Japanese taxa, while Taiwanese members have 2n = 4x = 64. Notably, C. pengii has a diploid number (2n = 32), indicating descending dysploidy followed by polyploidization in Taiwan. This polyploidization, driven by glaciations, likely shaped the evolution of Nipponocirsium. Divergence time estimates suggest the separation of Japanese and Taiwanese clades around 0.74 million years ago (Myr) during glacial periods. Cirsium pengii diverged around 0.47 Myr, while tetraploid species C. kawakamii and C. tatakaense diverged around 0.35 Myr. These species likely evolved in separate refugia, with distinct species boundaries confirmed through species delimitation analysis, karyotype, morphology, and pollen morphology comparisons.

Conclusions

These findings enhance our understanding of chromosomal evolution and speciation within subsect. Nipponocirsium and underscore the importance of integrating transcriptomic data in phylogenetic studies. This study provides a comprehensive framework for further investigations into the genetic diversity and adaptive mechanisms of this ecologically vital group.