Phenotypic and genetic variations of endangered Lysimachia maritima at global distribution limit

Species can respond to environmental pressures through genetic and phenotypic variation. Lysimachia maritima (L.) Galasso, Banfi & Soldano, a perennial halophyte, is distributed sporadically along the east coast in south Korea and is designated as an endangered plant species in Korea and 'Least Concern' in the IUCN Red List. To understand the phenotypic and genetic variations of L. maritima among sites and the environmental factors contributing to these differences, field surveys and genetic analyses were conducted. The principal component analysis of the environmental characteristics revealed that soil type, temperature, soil moisture content, and organic matter content were major factors determining variations among sites. L. maritima in Goseong (GS) and Yangyang (YY) sites faced significant limitations in its distribution due to competition with Phragmites australis for limited soil water and nutrients. There were significant phenotypic differences of L. maritima among sites. In sand-based sites of GS and YY, studied growth characteristics of L. maritima except stem length in YY and the number of seed-bearing individuals were smaller than those in organic soil substrate sites of US and PH, where L. maritima grew vigorously and were almost exclusively in the sexual reproductive phase. Genetic diversity at species level was high (h= 0.31, I= 0.46) but genetic diversities at site level were low, varying among sites (h= 0.133 ∼ 0.244). Also, genetic variation of L. maritima was higher within sites (58.32%) than among sites (41.68%). This indicates that L. maritima might prefer outcrossing more than selfing. L. maritima were strongly differentiated among sites (Gst= 0.336) because of limited gene flow (Nm= 0.987). Geographical isolation might have led to differentiated genetic structure in L. maritima, contributing to the formation of its spatial genetic structure. This high genetic diversity is crucial for the biodiversity of L. maritima at its global distribution limit, and this study emphasize the necessity of conserving distribution limit in the sense of soil characteristics.