Dohyeon Kwag1P, Eun Jung Lee2, Junhyun Hur1, Donguk Han1,3, Sang-Tae Kim1

1Dept. of Life Sciences, The Catholic University of Korea, Bucheon, Republic of Korea; 2Dept. of Life Sciences, Kongju Nat’l University, Kongju, Republic of Korea; 3PGA Eco&BIO Institute, ECO Korea, Goyang, Republic of Korea

The genus Suaeda (Amaranthaceae) comprises halophytes widely distributed in coastal marshes and tidal flats, with several species such as S. glauca, S. japonica, S. malacosperma, and S. maritima (or S. australis) naturally occurring in Korea. Despite their ecological importance, taxonomic identification remains challenging due to high morphological plasticity and a lack of clear diagnostic characteristics, alongside long-standing questions regarding the potential invasion of S. heteroptera from Eastern China and reticulate evolution among closely related taxa. To clarify these taxonomic confusions and elucidate the existence of S. heteroptera, we collected Suaeda specimens with both polymorphic and distinct morphological traits along Korean coastal regions and conducted phylogenetic analyses using chloroplast DNA markers (rpl32-trnL, psbA-trnH) and nuclear ITS. Our results revealed inconsistent group clustering and significant genetic admixture, particularly involving S. maritima and S. heteroptera, suggesting complex evolutionary relationships not explainable by simple bifurcating phylogenies. Notably, the data support a hypothesis of a hybrid origin for Korean S. heteroptera, potentially arising from hybridization between Korean S. maritima and Chinese S. heteroptera. These findings enhance our understanding of genetic diversity, hybridization, and ecological differentiation within Korean Suaeda, providing critical insights for the taxonomy, conservation, and biogeography of halophytes.