Dataset Information

Genetic structure of the endangered Irrawaddy dolphin (Orcaella brevirostris) in the Gulf of Thailand.

ABSTRACT: The Irrawaddy dolphin (Orcaella brevirostris) is an endangered, small cetacean species which is widely distributed in rivers, estuaries, and coastal waters throughout the tropical and subtropical Indo-Pacific. Despite the extensive distribution of this species, little is known of individual movements or genetic exchange among regions in Thailand. Here, we evaluate the genetic diversity and genetic structure of O. brevirostris in the eastern, northern and western Gulf of Thailand, and Andaman Sea. Although phylogenetic relationships and network analysis based on 15 haplotypes obtained from 32 individuals reveal no obvious divergence, significant genetic differentiation in mitochondrial DNA (overall FST = 0.226, P < 0.001; ΦST = 0.252, P < 0.001) is apparent among regions. Of 18 tested microsatellite loci, 10 are polymorphic and successfully characterized in 28 individuals, revealing significant genetic differentiation (overall FST = 0.077, P < 0.05) among the four sampling sites. Structure analysis reveals two inferred genetic clusters. Additionally, Mantel analysis demonstrates individual-by-individual genetic distances and geographic distances follow an isolation-by-distance model. We speculate that the significant genetic structure of O. brevirostris in Thailand is associated with a combination of geographical distribution patterns, environmental and anthropogenic factors, and local adaptations.

SUBMITTER: Dai Y

PROVIDER: S-EPMC8022665 | biostudies-literature |

REPOSITORIES: biostudies-literature

ACCESS DATA

Similar Datasets

Project description:The common bottlenose dolphin, Tursiops truncatus, is widely distributed along the western coast of South America. In Ecuador, a resident population of bottlenose dolphins inhabits the inner estuarine area of the Gulf of Guayaquil located in the southwestern part of the country and is under threat from different human activities in the area. Only one genetic study on South American common bottlenose dolphins has been carried out to date, and understanding genetic variation of wildlife populations, especially species that are identified as threatened, is crucial for defining conservation units and developing appropriate conservation strategies. In order to evaluate the evolutionary link of this population, we assessed the phylogenetic relationships, phylogeographic patterns, and population structure using mitochondrial DNA (mtDNA). The sampling comprised: (i) 31 skin samples collected from free-ranging dolphins at three locations in the Gulf of Guayaquil inner estuary, (ii) 38 samples from stranded dolphins available at the collection of the "Museo de Ballenas de Salinas," (iii) 549 mtDNA control region (mtDNA CR) sequences from GenBank, and (iv) 66 concatenated sequences from 7-mtDNA regions (12S rRNA, 16S rRNA, NADH dehydrogenase subunit I-II, cytochrome oxidase I and II, cytochrome b, and CR) obtained from mitogenomes available in GenBank. Our analyses indicated population structure between both inner and outer estuary dolphin populations as well as with distinct populations of T. truncatus using mtDNA CR. Moreover, the inner estuary bottlenose dolphin (estuarine bottlenose dolphin) population exhibited lower levels of genetic diversity than the outer estuary dolphin population according to the mtDNA CR. Finally, the estuarine bottlenose dolphin population was genetically distinct from other T. truncatus populations based on mtDNA CR and 7-mtDNA regions. From these results, we suggest that the estuarine bottlenose dolphin population should be considered a distinct lineage. This dolphin population faces a variety of anthropogenic threats in this area; thus, we highlight its fragility and urge authorities to issue prompt management and conservation measures.

Project description:Sotalia guianensis is a small dolphin that is vulnerable to anthropogenic impacts. Along the Brazilian Atlantic coast, this species is threatened with extinction. A prioritized action plan for conservation strategies relies on increased knowledge of the population. The scarcity of studies about genetic diversity and assessments of population structure for this animal have precluded effective action in the region. Here, we assessed, for the first time, the genetic differentiation at 14 microsatellite loci in 90 S. guianensis specimens stranded on the southeastern Atlantic coast of the State of Espírito Santo, Brazil. We estimated population parameters and structure, measured the significance of global gametic disequilibrium and the intensity of non-random multiallelic interallelic associations and constructed a provisional synteny map using Bos taurus, the closest terrestrial mammal with a reference genome available. All microsatellite loci were polymorphic, with at least three and a maximum of ten alleles each. Allele frequencies ranged from 0.01 to 0.97. Observed heterozygosity ranged from 0.061 to 0.701. The mean inbreeding coefficient was 0.103. Three loci were in Hardy-Weinberg disequilibrium even when missing genotypes were inferred. Although 77 of the 91 possible two-locus associations were in global gametic equilibrium, we unveiled 13 statistically significant, sign-based, non-random multiallelic interallelic associations in 10 two-locus combinations with either coupling (D' values ranging from 0.782 to 0.353) or repulsion (D' values -0.517 to -1.000) forces. Most of the interallelic associations did not involve the major alleles. Thus, for either physically or non-physically linked loci, measuring the intensity of non-random interallelic associations is important for defining the evolutionary forces at equilibrium. We uncovered a small degree of genetic differentiation (FST = 0.010; P-value = 0.463) with a hierarchical clustering into one segment containing members from the southern and northern coastal regions. The data thus support the scenario of little genetic structure in the population of S. guianensis in this geographic area.

Dataset Information

Genetic structure of the endangered Irrawaddy dolphin (Orcaella brevirostris) in the Gulf of Thailand.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets