Invasive species represent promising models to study species’ responses to rapidly changing environments. Although local adaptation frequently occurs during contemporary range expansion, the associated genetic signatures at both population and genomic levels remain largely unknown. Here, we use genome-wide gene-associated microsatellites to investigate genetic signatures of natural selection in a model invasive ascidian, Ciona robusta. Population genetic analyses of 150 individuals sampled in Korea, New Zealand, South Africa and Spain showed significant genetic differentiation among populations. Based on outlier tests, we found high incidence of signatures of directional selection at 19 loci. Hitchhiking mapping analyses identified 12 directional selective sweep regions, and all selective sweep windows on chromosomes were narrow (~8.9 kb). Further analyses indentified 132 candidate genes under selection. When we compared our genetic data and six crucial environmental variables, 16 putatively selected loci showed significant correlation with these environmental variables. This suggests that the local environmental conditions have left significant signatures of selection at both population and genomic levels. Finally, we identified “plastic” genomic regions and genes that are promising regions to investigate evolutionary responses to rapid environmental change in C. robusta.

In this study, we provide the first report of the complete mitochondrial genome of Emydocephalus ijimae. The mitogenome length is 18,259 bp and includes 13 protein-coding genes, two rRNA genes, 22 tRNA genes, and three non-coding regions. The sequence presented could be very useful for further phylogenetic and evolutionary study.

Loggerhead and green turtles inhabit all oceans except the polar regions. External surfaces of sea turtles are often colonized by epibiotic chelonibiid barnacles. Barnacle taxonomy studies in Korea began in 1985, but until present, no turtle barnacles were recorded. This suggests that either the diversity and frequency of occurrence of turtle barnacles in Korean waters are low or the turtle barnacles have been understudied. This study complies with data collected over 6 years of sea turtle stranding events in Korea (2015–2020). We examined the diversity, frequency, and intensity of turtle barnacle occurrence. Of the 55 recorded strandings, loggerhead turtles were the most common (58%), followed by green turtles (33%). Only one species of barnacle, Chelonibia testudinaria, was found on both loggerhead and green turtles. The frequency of barnacle occurrence on loggerhead turtles was 28%, with an intensity of 2.4 ± 2.7 barnacles per turtle. Notably, 11% of green turtles had barnacles, with an average of one individual per turtle. The frequency and intensity of barnacle occurrence on green turtles analyzed in this study were five times lower than that on green turtle populations in Okinawan, Bornean, and Australian waters in the Indo-Pacific. Based on these new data and the available literature, we speculated that the barnacle larval pools in cold, high-latitude Korean waters are smaller than those occurring in other locations in the Indo-Pacific. The frequency and intensity of occurrence of barnacles on loggerhead turtles in Korea fall within the range recorded in other Indo-Pacific locations. The longer migratory routes of loggerhead turtles allow them to pass through different larval pools in the Indo-Pacific water, exposing them to higher barnacle abundances.

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We here report the complete mitochondrial genome of the Hydrophis melanocephalus slender-necked sea snake from Okinawa, Japan. Its length is 17,182 bp, consisting of 13 protein-coding genes, two rRNA genes, 22 tRNA genes, and three non-coding regions, providing the basis for further phylogenetic and evolutionary studies of sea snakes.

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In this study, we provide the first report of the complete mitochondrial genomic sequencing of a yellow-bellied sea snake (Hydrophis platurus) that has the broadest distribution range of all Squamata species. The mitogenome length was 18,101 bp and consisted of 13 protein-coding genes, 2 rRNA genes, 22 tRNA genes, and 3 non-coding regions. The sequence presented could be very useful for further phylogenetic and evolutionary studies.