Anocha Poommouang

The identification of sea turtle species relies on morphological characteristics, presenting challenges in incomplete or degraded specimens, with DNA barcoding now increasingly recognized for its potential in expediting species identification across various organisms. This study proposed a combination of DNA barcoding with high‐resolution melting (Bar‐HRM) analysis for accurate identification of sea turtles at the species level. Mitochondrial DNA (D‐loop, cytb , and cox1 ) and nuclear DNA ( Ahr , Bdnf , Bmp2 , C-mos , Hmgb2 , Ngf , and Pax1p1 ) were employed for Bar‐HRM to differentiate the five sea turtle species (green turtle, Chelonia mydas ; hawksbill, Eretmochelys imbricata ; leatherback, Dermochelys coriacea ; loggerhead, Caretta caretta ; and olive ridley, Lepidochelys olivacea ) commonly found in Thai waters and some tortoise species used as outgroup. Results demonstrated that Bar‐HRM using TurtleDloop2 and TurtleCytb2(R1) primers produced distinct normalized melting curves for all five species (100%) that their Tm value ranged 77°C–81°C and 81°C–83°C, respectively. The performance of the established approach was evaluated by a blind test of 30 samples, randomly selected for species identification by Bar‐HRM using both primers, with accuracy rates of 100%. The minimum DNA concentrations required to discriminate sea turtle and tortoise species using this method were 0.001 and 0.01 ng per reaction for TurtleDloop2 and TurtleCytb2(R1), respectively. Our findings suggested that Bar‐HRM using TurtleDloop2 and TurtleCytb2(R1) was a promising tool for the identification of sea turtle species, contributing to effective conservation endeavors and precise evaluations of their endangered status, thereby enhancing the efficiency of conservation planning initiatives.

Indo-Pacific bottlenose dolphins (Tursiops aduncus) are a coastal species found in Thai waters off the coasts of the Andaman Sea and the Gulf of Thailand. This species was recently re-listed as near-threatened by the IUCN Red List, though the population status in Thai seas is not known. Here, we investigated genetic diversity, population structure, maternal lineage, and demographics by analyzing skin tissue samples (n = 30) of T. aduncus stranded along the Andaman coastline of Thailand between 1990 and 2019. This study was based on 11 microsatellite loci and 265 bp mtDNA control regions compared to data available through the National Center for Biotechnology Information (NCBI). From microsatellites, the observed heterozygosity (Ho) ranged from 0.46 to 0.85. The mean fixation index (F) value for all loci was 0.10 ± 0.04, which suggests some degree of inbreeding. Two genetic clusters (the most likely K at K = 2) were observed in T. aduncus through the population structure analysis using multiple criteria. For the mtDNA control region, a total of 17 haplotypes were found for dolphins in Thai seas (14 haplotypes from our samples; three haplotypes from the NCBI database) with high levels of haplotype diversity (h) at 0.926 ± 0.027 and nucleotide diversity (π) at 0.045 ± 0.002. A decline in the effective population size from 0.05 million years ago also was observed in Thai T. aduncus through Bayesian Skyline Plots analysis. A unique set of haplotypes was identified in our samples, which may have originated from the Australian and Indian Oceans rather than the Western Pacific Ocean. These results improve our understanding of the maternal lineage of the Indo-Pacific bottlenose dolphin, which can be used for monitoring population status and establishing better conservation plans for this species in the Thai Andaman Sea.

The leatherback sea turtle (Dermochelys coriacea) is the largest and one of the most migratory turtle species, inhabiting oceans throughout the world. There has been a steady decline in leatherback populations over the past several decades due to human activities. They are considered endangered in Thailand and global, so conservation strategies are needed to study and protect the species, including determining their genetic diversity. A total of 8 microsatellite loci and 658 bp amplicon of mitochondrial DNA (mtDNA) were used to assess genetic data from 149 dead leatherback turtle hatchlings among 14 nests in five locations along the Andaman Sea, Thailand, between 2018–2020. The microsatellite findings show that the observed heterozygosity (Ho) ranged from 0.44 ± 0.09 to 0.65 ± 0.10. Population structures were further divided into two genetically distinct groups by Bayesian inference. For the mtDNA control region, our samples consisted of three haplotypes. Globally, there are 27 haplotypes of leatherback turtles, with a relatively low genetic diversity (h = 0.43). These results reveal the genetic status of leatherback turtles in Thailand and globally, and raise concerns about their relative genetic health, which highlight the need for proactive, long-term management and conservation strategies for this endangered species.

Background and Aim: The Indo-Pacific bottlenose dolphin, Tursiops aduncus, and the pantropical spotted dolphin, Stenella attenuata, are protected marine mammals in Thailand; however, knowledge regarding the populations of both species in Thai seas is minimal. We aimed to reveal the genetic diversity and population structure of two species, T. aduncus, and S. attenuata, based on inter-simple sequence repeats (ISSRs). Materials and Methods: Samples of stranded T. aduncus (n = 30) and S. attenuata (n = 23) found along Thai Andaman Sea coasts from 1998 to 2018 were used in this study. A total of 17 and 16 ISSR primers that produced clear and polymorphic bands were selected for T. aduncus and S. attenuata, respectively. Results: The highest percentages of polymorphic bands for T. aduncus and S. attenuata were 93.750% and 92.857%, respectively. Phylogenetic dendrograms indicated that the population of each species was clustered into three groups. This outcome was consistent with the genetic population structure, as both suggested three genetic clusters (ΔK = 3). Genetic diversity analysis revealed that the average Shannon's information index (I) was 1.926 ± 0.066 for T. aduncus and 1.714 ± 0.090 for S. attenuata, which indicate a high level of genetic variation. Further, low fixation index (F) values were observed for T. aduncus and S. attenuata at –0.231 ± 0.024 and –0.312 ± 0.042, respectively, suggesting that inbreeding is unlikely to have occurred for both species over the past decades. Conclusion: At least three genetic clusters of both species were found in the Thai Andaman Sea, and the diversity indices of each species indicated that these species are not at a critical level for extinction. However, monitoring their population status should be prioritized to observe any future changes in the level of diversity.

Although the existence of two cetacean species in and around Thai Seas from within the subfamily Globicephalinae, Risso’s dolphin Grampus griseus G. Cuvier, 1812, and false killer whale Pseudorca crassidens Owen, 1846, has been known for decades, current knowledge on the abundance, genetic diversity, and conservation status of these marine mammals is limited as these are rare oceanic species for Thailand’s territorial waters. Frozen skin tissue samples taken from six cetaceans (four Risso’s dolphins: two false killer whales) stranded along Thai coastlines were investigated. We aimed to identify the maternal lineage and connection of our samples throughout their distribution range. Accordingly, we analyzed the dataset of 110 and 50 mtDNA control region sequences of Risso’s dolphins and false killer whales, respectively. This dataset was retrieved from the online database of the National Center for Biotechnology Information (NCBI) and included six mtDNA sequences obtained from Thai Seas. Two unique haplotypes of Risso’s dolphins were found in the Thai Andaman Sea, whereas one haplotype identified as being from the Gulf of Thailand is a common haplotype shared with other regions of the Pacific Ocean. Two haplotypes were found for false killer whales from the Thai Andaman Sea, and these were also in common with other regions of the Indo Pacific Ocean. While shared haplotypes with other regions may imply inheritance from the same female ancestor, we speculate that distinct populations with unique genetic structures also exist in Thai Seas. Beneficially, our results could be used to monitor alterations of haplotypes or to assess the maternal genetic diversity of designated species in the future to establish baseline information for Thai Seas and adjacent waters.

The dugong (Dugong dugon) is an endangered species of marine mammals, so knowledge of genetic diversity of these populations is important for conservation planning within different habitats. In this study, six microsatellite markers were used to assess the genetic diversity and population structure of 77 dugongs from skin samples of stranded animals collected from 1994–2019 (69 from Andaman Sea and 8 from the Gulf of Thailand). Our results found that dugongs in the Andaman Sea had higher genetic variation than those in the Gulf of Thailand. Populations in Trang, Satun, and some areas of Krabi had highest diversity compared to other regions of Thailand. Bayesian genetic clustering analysis revealed that dugongs in Thailand consist of five genetic groups. Moreover, dugongs in the middle and lower Andaman Sea presented the greatest gene flow compared to other regions. However, based on calculation of inbreeding coefficients (Fis value = 0.239), dugong populations in the Sea of Thailand are experiencing some levels of inbreeding, and so may warrant special protections. These results provide important information for understanding the genetic status of dugongs that can lead to improved management and conservation of this endangered species.