Kim Yeseul, Jeong Sumin, Park Inkyu, Moon Hye-Kyoung
Department of Biology and Chemistry, Changwon National University, Changwon, Republic of Korea.
Department of Biology, Kyung Hee University, Seoul, Republic of Korea.
BMC Plant Biol. 2025 Mar 4;25(1):278. doi: 10.1186/s12870-025-06272-9.
Phryma leptostachya L. is a notable example of a species with a disjunct distribution, found in both East Asia and Eastern North America. Despite the striking morphological similarities between these geographically isolated populations, molecular evidence suggests that they may have diverged sufficiently to be considered distinct taxa.
To clarify this, we analyzed the plastomes of P. leptostachya from Korea, Russia, and the USA. Their sizes ranged from 152,974 to 153,325 bp, each containing 113 genes. Differences were observed in the boundaries between large single copy (LSC)/IRa and IRb/LSC. In P. leptostachya_USA, the rps19 gene extended 30-31 bp into the IRa, and the rpl2 gene contracted 51-53 bp at the IRa/b compared to those of P. leptostachya_Korea and P. leptostachya_Russia, suggesting that expansion of the inverted repeat (IR) region occurred in P. leptostachya_USA. Regions such as psbZ-trnG, ccsA-ndhD, petA-psbJ, and psbC-trnS were identified as hotspots with sequence differences in the plastome, indicating differences among P. leptostachya variants. Phylogenetic analysis showed that P. leptostachya from Korea and Russia formed monophyletic groups, while the variety from the USA was paraphyletic. The divergence of P. leptostachya_USA occurred during the Pliocene, about 5.25 million years ago (MYA), whereas the split between P. leptostachya_Korea and P. leptostachya_Russia is estimated to have occurred approximately 0.87 MYA during the Pleistocene. The results also reveal that the family Phrymaceae underwent multiple dispersal and vicariance events from North America to East Asia, offering key insights into the phylogenetic relationships between P. leptostachya populations from Korea, Russia, and the USA. Based on the evidence, it is likely that P. leptostachya originated in North America and later migrated to East Asia via the Russian Far East and the Bering Land Bridge.
In conclusion, our study demonstrates clear molecular differences among P. leptostachya populations from various geographic locations, suggesting that these populations should be recognized as distinct species rather than conspecifics.
细叶冷水花是分布间断的一个显著例子，在东亚和北美东部均有发现。尽管这些地理上隔离的种群在形态上有惊人的相似之处，但分子证据表明它们可能已经分化到足以被视为不同的分类群。
为了阐明这一点，我们分析了来自韩国、俄罗斯和美国的细叶冷水花的质体基因组。它们的大小在152,974至153,325碱基对之间，每个都包含113个基因。在大单拷贝（LSC）/IRa和IRb/LSC之间的边界处观察到差异。在美国细叶冷水花中，rps19基因向IRa延伸30 - 31碱基对，与韩国细叶冷水花和俄罗斯细叶冷水花相比，rpl2基因在IRa/b处收缩51 - 53碱基对，这表明在美国细叶冷水花中发生了反向重复（IR）区域的扩张。诸如psbZ - trnG、ccsA - ndhD、petA - psbJ和psbC - trnS等区域被确定为质体基因组中具有序列差异的热点，表明细叶冷水花变种之间存在差异。系统发育分析表明，来自韩国和俄罗斯的细叶冷水花形成单系类群，而来自美国的变种是并系的。美国细叶冷水花的分化发生在上新世，约525万年前（百万年），而韩国细叶冷水花和俄罗斯细叶冷水花之间的分裂估计发生在更新世约87万年前。结果还揭示，冷水花科经历了从北美到东亚的多次扩散和间断事件，为来自韩国、俄罗斯和美国的细叶冷水花种群之间的系统发育关系提供了关键见解。基于这些证据，细叶冷水花可能起源于北美，后来通过俄罗斯远东地区和白令陆桥迁移到东亚。
总之，我们的研究证明了来自不同地理位置的细叶冷水花种群之间存在明显的分子差异，这表明这些种群应被视为不同的物种而非同种。
