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<p>The invasion process of alien plants consists of three stages: introduction, naturalization, and invasion (spread). Genome size, ploidy, and hybridization can influence the invasion process. This study investigated how the genome size and ploidy of hybrids between the introduced triploid common dandelions (<i>Taraxacum officinale</i>) and native Japanese diploid dandelions (<i>T. japonicum</i> and <i>T. platycarpum</i>) could have influenced the naturalization and spread. Using chloroplast DNA analysis and flow cytometry, we analyzed 816 individuals across 93 sites to distinguish triploid and tetraploid hybrids from pure <i>T. officinale</i>. We then used genome-wide SNP sequencing to identify clones. Naturalization frequency was assessed by clonal diversity and spread by the geographic range of each clone. The results revealed that 80% of morphologically identified <i>T. officinale</i> were actually hybrids: 45.6% triploid and 33.1% tetraploid, with only 21.3% pure <i>T. officinale</i>. Naturalization frequency followed the order: tetraploid hybrids &lt; <i>T. officinale</i> &lt; triploid hybrids. This contradicts predictions based solely on genome size and ploidy, which suggest that triploid hybrids would have the lowest naturalization frequency due to their increased genome size without a corresponding increase in ploidy. In contrast, the extent of spread showed the following order: triploid hybrids &lt; <i>T. officinale</i> &lt; tetraploid hybrids. While triploid hybrids succeeded at naturalization, they remained geographically restricted near native parent populations, suggesting that hybridization facilitated establishment through local adaptation, but adaptation constrained broader spatial expansion. A dominant tetraploid clone was highly distributed, suggesting enhanced expansion capacity through increased ploidy levels. We discuss that hybridization facilitates invasion through distinct mechanisms at different stages: adaptive introgression could have promoted naturalization by incorporating locally adaptive traits, whereas polyploidization could have enhanced invasion extent. This study provides crucial insights into the complex role of hybridization in biological invasions.</p>

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Invasion processes of apomictic hybrids between introduced (Taraxacum officinale) and native dandelions in Japan: stage-specific roles of hybridization and ploidy levels

  • 期刊论文

  • 发表日期：

    2026年3月1日

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  • Toru Jogaki,
  • Tenuen,
  • Satoshi Nanami,
  • Akira Itoh

摘要

The invasion process of alien plants consists of three stages: introduction, naturalization, and invasion (spread). Genome size, ploidy, and hybridization can influence the invasion process. This study investigated how the genome size and ploidy of hybrids between the introduced triploid common dandelions (Taraxacum officinale) and native Japanese diploid dandelions (T. japonicum and T. platycarpum) could have influenced the naturalization and spread. Using chloroplast DNA analysis and flow cytometry, we analyzed 816 individuals across 93 sites to distinguish triploid and tetraploid hybrids from pure T. officinale. We then used genome-wide SNP sequencing to identify clones. Naturalization frequency was assessed by clonal diversity and spread by the geographic range of each clone. The results revealed that 80% of morphologically identified T. officinale were actually hybrids: 45.6% triploid and 33.1% tetraploid, with only 21.3% pure T. officinale. Naturalization frequency followed the order: tetraploid hybrids < T. officinale < triploid hybrids. This contradicts predictions based solely on genome size and ploidy, which suggest that triploid hybrids would have the lowest naturalization frequency due to their increased genome size without a corresponding increase in ploidy. In contrast, the extent of spread showed the following order: triploid hybrids < T. officinale < tetraploid hybrids. While triploid hybrids succeeded at naturalization, they remained geographically restricted near native parent populations, suggesting that hybridization facilitated establishment through local adaptation, but adaptation constrained broader spatial expansion. A dominant tetraploid clone was highly distributed, suggesting enhanced expansion capacity through increased ploidy levels. We discuss that hybridization facilitates invasion through distinct mechanisms at different stages: adaptive introgression could have promoted naturalization by incorporating locally adaptive traits, whereas polyploidization could have enhanced invasion extent. This study provides crucial insights into the complex role of hybridization in biological invasions.