Verification of hotspots of genetic diversity in Korean population of Grateloupia asiatica and G. jejuensis (Rhodophyta) show low genetic diversity and similar geographic distribution

Background Understanding the genetic diversity and distribution patterns of seaweeds species is crucial for evaluating key regions of high genetic diversity. Identifying hotspots of high intraspecific diversity is an important step for developing conservation strategies. Grateloupia is a diverse genus of Rhodophyta, many of which are resource of numerous useful bioactive compounds; therefore, the genus is valuable target for conservation. Objective The aim of this study is to examine the genetic diversity and population structure of two Grateloupia species, Grateloupia asiatica and Grateloupia jejuensis, with the understanding of the phylogeography of the Korean genetic diversity hotspot for two species. Methods Plastid rbcL gene sequences of 134 specimens of G. asiatica and 112 specimens of G. jejuensis collected from the Korean coast were analyzed. We evaluated the number of haplotypes, genetic diversity (haplotype and nucleotide diversity), and haplotype networks of two species. Historical demographic was inferred by calculating neutrality tests and genetic differentiation was estimated using the fixation index, F-ST. Results Our results show that both species are generally similar in geographical distribution patterns, that is, relatively homogeneous with few haplotypes derived from the most frequent haplotype. The east coast of Korea is identified as a 'hotspot' with the highest genetic diversity for both species, whereas Jeju Island is identified as a 'cold spot' with the lowest genetic diversity for G. jejuensis. Analyses across most distribution ranges of the two species in Korea reveal low genetic and haplotype diversities, which could indicate that these two Grateloupia species have either experienced a historical lack of diversity or a recent reduction in diversity due to high gene flow. Conclusions The low genetic diversity values found in the present study raise considerable concern about the conservation status of these two Grateloupia species and highlight the need to locate further hotspots of genetic diversity to strengthen their resilience against further decline.

Automated summary

The study examined the genetic diversity and population structure of two Grateloupia species, revealing the East coast of Korea as a genetic diversity hotspot for both species and Jeju Island as a cold spot for one species. Low genetic diversity across most distribution ranges of the species suggests a historical lack or recent reduction in diversity due to high gene flow. Further hotspots of genetic diversity are needed for conservation efforts.