A phylogenetic analysis of the Korean endemic species <i>Paraphlomis koreana</i> (Lamiaceae) inferred from nuclear and plastid DNA sequences

Abstract

<i>Paraphlomis koreana</i> (Lamiaceae) was newly named and added to Korean flora in 2014. <i>Paraphlomis</i> belongs to the tribe Paraphlomideae, along with <i>Ajugoides</i> and <i>Matsumurella</i>. However, a recent study has suggested that <i>P. koreana</i> is morphologically similar to <i>Matsumurella chinensis</i>, making them difficult to distinguish from each other. Therefore, we aimed to examine the phylogenetic placement of <i>P. koreana</i> within the tribe and compare its genetic relationship with <i>M. chinensis</i>. We sequenced an additional complete plastid genome for an individual of <i>P. koreana</i> and generated sequences of nuclear ribosomal (nr) DNA regions of internal and external transcribed spacers (ITS and ETS) for two individuals of <i>P. koreana</i>. Maximum likelihood analyses based on two nrDNA regions (ITS and ETS) and four plastid DNA markers (<i>rpl16</i> intron, <i>rpl32</i>-trnL, <i>rps16</i> intron, and <i>trnL-F</i>) covering 13 <i>Paraphlomis</i> species and <i>M. chinensis</i> were conducted. Phylogenetic analyses concordantly supported that <i>P. koreana</i> forms a monophyletic group with <i>M. chinensis</i>. Moreover, our study revealed that <i>P. koreana</i> includes nrDNA sequences of <i>M. chinensis</i> as minor intraindividual variants, suggesting that the genetic divergence between the two taxa is incomplete and may represent intraspecific variation rather than distinct species. In conclusion, our findings suggest that the independent species status of <i>P. koreana</i> within <i>Paraphlomis</i> should be reconsidered.