Population genomics of the white-beaked dolphin (Lagenorhynchus albirostris): Implications for conservation amid climate-driven range shifts.

Climate change is rapidly affecting species distributions across the globe, particularly in the North Atlantic. For highly mobile and elusive cetaceans, the genetic data needed to understand population dynamics are often scarce. Cold-water obligate species such as the white-beaked dolphin (Lagenorhynchus albirostris) face pressures from habitat shifts due to rising sea surface temperatures in addition to other direct anthropogenic threats. Unravelling the genetic connectivity between white-beaked dolphins across their range is needed to understand the extent to which climate change and anthropogenic pressures may impact species-wide genetic diversity and identify ways to protect remaining habitat. We address this by performing a population genomic assessment of white-beaked dolphins using samples from much of their contemporary range. We show that the species displays significant population structure across the North Atlantic at multiple scales. Analysis of contemporary migration rates suggests a remarkably high connectivity between populations in the western North Atlantic, Iceland and the Barents Sea, while two regional populations in the North Sea and adjacent UK and Irish waters are highly differentiated from all other clades. Our results have important implications for the conservation of white-beaked dolphins by providing guidance for the delineation of more appropriate management units and highlighting the risk that local extirpation may have on species-wide genetic diversity. In a broader context, this study highlights the importance of understanding genetic structure of all species threatened with climate change-driven range shifts to assess the risk of loss of species-wide genetic diversity.

Molecular Evidence for Relaxed Selection on the Enamel Genes of Toothed Whales (Odontoceti) with Degenerative Enamel Phenotypes.

Different species of toothed whales (Odontoceti) exhibit a variety of tooth forms and enamel types. Some odontocetes have highly prismatic enamel with Hunter-Schreger bands, whereas enamel is vestigial or entirely lacking in other species. Different tooth forms and enamel types are associated with alternate feeding strategies that range from biting and grasping prey with teeth in most oceanic and river dolphins to the suction feeding of softer prey items without the use of teeth in many beaked whales. At the molecular level, previous studies have documented inactivating mutations in the enamel-specific genes of some odontocete species that lack complex enamel. At a broader scale, however, it is unclear whether enamel complexity across the full diversity of extant Odontoceti correlates with the relative strength of purifying selection on enamel-specific genes. Here, we employ sequence alignments for seven enamel-specific genes (ACP4, AMBN, AMELX, AMTN, ENAM, KLK4, MMP20) in 62 odontocete species that are representative of all extant families. The sequences for 33 odontocete species were obtained from databases, and sequences for the remaining 29 species were newly generated for this study. We screened these alignments for inactivating mutations (e.g., frameshift indels) and provide a comprehensive catalog of these mutations in species with one or more inactivated enamel genes. Inactivating mutations are rare in Delphinidae (oceanic dolphins) and Platanistidae/Inioidea (river dolphins) that have higher enamel complexity scores. By contrast, mutations are much more numerous in clades such as Monodontidae (narwhal, beluga), Ziphiidae (beaked whales), Physeteroidea (sperm whales), and Phocoenidae (porpoises) that are characterized by simpler enamel or even enamelless teeth. Further, several higher-level taxa (e.g., Hyperoodon, Kogiidae, Monodontidae) possess shared inactivating mutations in one or more enamel genes, which suggests loss of function of these genes in the common ancestor of each clade. We also performed selection (dN/dS) analyses on a concatenation of these genes and used linear regression and Spearman's rank-order correlation to test for correlations between enamel complexity and two different measures of selection intensity (# of inactivating mutations per million years, dN/dS values). Selection analyses revealed that relaxed purifying selection is especially prominent in physeteroids, monodontids, and phocoenids. Linear regressions and correlation analyses revealed a strong negative correlation between selective pressure (dN/dS values) and enamel complexity. Stronger purifying selection (low dN/dS) is found on branches with more complex enamel and weaker purifying selection (higher dN/dS) occurs on branches with less complex enamel or enamelless teeth. As odontocetes diversified into a variety of feeding modes, in particular, the suction capture of prey, a reduced reliance on the dentition for prey capture resulted in the relaxed selection of genes that are critical to enamel development.

Whistle repertoire and structure reflect ecotype distinction of pantropical spotted dolphins in the Eastern Tropical Pacific.

The pantropical spotted dolphin in the Eastern Tropical Pacific (ETP) is found in two genetically and phenotypically diverged ecotypes, coastal and offshore. These habitats have distinct acoustic characteristics, which can lead to the evolution of distinct acoustic communication. Whistles are sounds widely used by dolphins to mediate species and individual recognition and social interactions. Here, we study the whistle acoustic structure and repertoire diversity of offshore and coastal pantropical spotted dolphins. Our results show that there is significantly more within- and across-group variation in whistle fundamental frequency between ecotypes than between offshore groups and between coastal groups. A Random Forest classification analysis performed with an accuracy of 83.99% and identified duration, peak and minimum frequency as the most informative variables for distinguishing between ecotypes. Overall, coastal spotted dolphins produced significantly shorter whistles that were significantly lower in frequency (peak, minimum and maximum, and start and end) than offshore dolphins. Ecotypes produced whistle repertoires that were similar in diversity, but different in contour composition, with the coastal ecotype producing more upsweep whistles than offshore dolphins. The results of this study suggest that acoustic adaptations to coastal and offshore environments could be important contributors to intraspecific variation of dolphin whistle repertoires.

The rough-toothed dolphin genome provides new insights into the genetic mechanism of its rough teeth.

The rough-toothed dolphin (Steno bredanensis) is characterized by having teeth covered in finely wrinkled vertical ridges, which is a general manifestation of amelogenesis imperfecta. The rough surfaces are hypothesized to be an evolutionary morphological trait of feeding adaptation to increase the dolphin's grip on prey. Here, we assembled a rough-toothed dolphin genome and performed the comparative genomic analysis to reveal the genetic basis of the special enamel. Results showed that genes related to enamel development or dental diseases have undergone diversified adaptive changes that may shape the special enamel morphology of this dolphin species, including positive selection (CLDN19, PRKCE, SSUH2, and WDR72), rapid evolution (LAMB3), or unique amino acid substitutions (AMTN, ENAM, MMP20, and KLK4). Meanwhile, the historical demography of rough-toothed dolphin indicated several distinct population fluctuations associated with climate change. The genome-wide heterozygosity of this dolphin is in the middle of all published data for cetaceans. Although the population is considerable, there may be population or subspecies differentiation, and with the global warming and the increasing disturbance of human activities, we should pay more attention to protection in the future. Together, our study brings new insights into the genetic mechanisms that may have driven the evolution of the special enamel morphology in rough-toothed dolphins and provides the first results of genetic heterozygosity and population historical dynamics of this species, which have important guiding implications for the conservation of this dolphin species.

A genome and single-nucleus cerebral cortex transcriptome atlas of the short-finned pilot whale Globicephala macrorhynchus.

Cetaceans (dolphins, whales, and porpoises) have large and anatomically sophisticated brains. To expand our understanding of the cellular makeup of cetacean brains and the similarities and divergence between the brains of cetaceans and terrestrial mammals, we report a short-finned pilot whale (Globicephala macrorhynchus) single-nucleus transcriptome atlas. To achieve this goal, we assembled a chromosome-scale reference genome spanning 2.25 Gb on 22 chromosomes and profiled the gene expression of five major anatomical cortical regions of the short-finned pilot whale by single-nucleus RNA-sequencing (snRNA-seq). We identified six major cell lineages in the cerebral cortex (excitatory neurons, inhibitory neurons, oligodendrocytes, oligodendrocyte precursor cells, astrocytes, and endothelial cells), eight molecularly distinct subclusters of excitatory neurons, and four subclusters of inhibitory neurons. Finally, a comparison of snRNA-seq data from the short-finned pilot whale, human, and rhesus macaque revealed a broadly conserved cellular makeup of brain cell types. Our study provides genomic resources and molecular insights into cetacean brain evolution.

Multilocus DNA metabarcoding diet analyses of small cetaceans: a case study on highly vulnerable humpback dolphins and finless porpoises from the Pearl River Estuary, China.

Accurate diet identification of top predators is crucial to fully understand their ecological roles. Compared to terrestrial animals, gathering dietary information from cetaceans is notoriously difficult. Here, we applied a multilocus metabarcoding approach to investigate the diet of vulnerable Indo-Pacific humpback dolphins and Indo-Pacific finless porpoises from the Pearl River Estuary (PRE), China. Our analyses identified 21 prey fish species from the 42 humpback dolphin stomachs, as well as 10 species of fish and 1 species of cephalopod from the 13 finless porpoise stomachs. All of the taxa were assigned to the species level, highlighting that the multimarker approach could facilitate species identification. Most of the prey species were small- and medium-sized fishes that primarily fed on zooplankton. The calculated similarity index revealed a moderated dietary overlap between the 2 cetaceans, presumably due to the feeding of the 2 predators in association with fishing vessels in the PRE. A more diverse diet was observed in humpback dolphins in the closed fishing season compared to the fishing season, implying the influence on the dolphin diet due to the availability of commercial fishery resources. However, according to the results of species rarefaction curves, our findings on the feeding habits of the 2 cetaceans are still limited by insufficient sample size and therefore should be interpreted with caution. This study represents a first attempt to apply the multilocus DNA metabarcoding technique in the diet analysis of small cetaceans, although more efforts are needed to improve this type of analysis.

Genomics reveals a genetically isolated population of the Pacific white-sided dolphin (Lagenorhynchus obliquidens) distributed in the Sea of Japan.

The processes by which animals become genetically isolated in an open environment such as the ocean have not yet been fully elucidated. Morphologically different populations of Pacific white-sided dolphin Lagenorhynchus obliquidens are observed sympatrically in the Sea of Japan. However, genetic studies that exclusively used limited mitochondrial loci or microsatellite DNA have failed to demonstrate the existence of genetically distinct populations. Here, to reveal the population structure, we analysed genome-wide population genetic data using single nucleotide polymorphisms (SNPs) gathered in 2018-2021 from all domestic captive individuals in aquaria, the majority of which originated from the wild, as well as from some stranded individuals, together covering a wide area of coastal water around Japan (n = 123). Multiplexed intersimple sequence repeat genotyping-by-sequencing analysis was performed to obtain the SNP data. Principal coordinate analysis and the clustering method structure indicated that two genetically-distinct populations exist, with little interpopulation gene flow revealed. In addition, the genotypic segregation was reflected in differences in external morphotype. Furthermore, a population demographic analysis based on the whole-genome sequences of an individual from each population indicated that sea-level changes during the Last Glacial Period probably led to allopatric divergence of this species in a limited area of the Sea of Japan, with that group subsequently sharing a distribution area with the other population. These findings yield insights into the formation of genetically isolated sympatric populations in the ocean.

Commerson's dolphin population structure: evidence for female phylopatry and male dispersal.

A key in species conservation is understanding the amount and distribution of genetic diversity and how environmental changes that occurred in the recent past may have influenced current patterns of population structure. Commerson's dolphin, Cephalorhynchus commersonii, has two subspecies, one of which is endemic to South America (C. commersonii commersonii) and little is known about its population genetics. Our objective was to investigate the population genetics of this subspecies throughout its distribution. Using 70 skin samples and information available in GenBank, 308 mitochondrial DNA sequences and 28 species-specific microsatellites were analyzed. The species presented low genetic diversity when compared to other dolphin species, but was consistent with other species within the genus. Strong population structure based on mitochondrial DNA was exhibited throughout its entire distribution, a pattern consistent with female philopatry. However, this pattern was not detected when using microsatellites, suggesting male-mediated gene flow. Demographic tests suggested a population expansion beginning approximately 15,000 years ago, after the Last Glacial Maximum. In a climate change scenario, we recommended considering each sampling location as an independent population management unit in order to evaluate the impact of possible environmental changes on the distribution of genetic information within the species.

Mitochondrial diversity and inter-specific phylogeny among dolphins of the genus Stenella in the Southwest Atlantic Ocean.

The genus Stenella is comprised of five species occurring in all oceans. Despite its wide distribution, genetic diversity information on these species is still scarce especially in the Southwest Atlantic Ocean. Some features of this genus can enhance opportunities for potential introgressive hybridization, e.g. sympatric distibution along the Brazilian coast, mixed known associations among species, karyotype uniformity and genome permeability. In this study we analyzed three genes of the mitochondrial genome to investigate the genetic diversity and occurrence of genetic mixture among eighty specimens of Stenella. All species exhibited moderate to high levels of genetic diversity (h = 0.833 to h = 1.000 and π = 0.006 to π = 0.015). Specimens of S. longirostris, S. attenuata and S. frontalis were clustered into differentiated haplogroups, in contrast, haplotypes of S. coeruleoalba and S. clymene were clustered together. We detected phylogenetic structure of mixed clades for S. clymene and S. coeruleoalba specimens, in the Southwest Atlantic Ocean, and also between S. frontalis and S. attenuata in the Northeast Atlantic Ocean, and between S. frontalis and S. longirostris in the Northwest Atlantic Ocean. These specimes were morphologically identified as one species but exhibited the maternal lineage of another species, by mitochondrial DNA. Our results demonstrate that ongoing gene flow is occurring among species of the genus Stenella reinforcing that this process could be one of the reasons for the confusing taxonomy and difficulties in elucidating phylogenetic relationships within this group.

Multi-species and multi-tissue methylation clocks for age estimation in toothed whales and dolphins.

The development of a precise blood or skin tissue DNA Epigenetic Aging Clock for Odontocete (OEAC) would solve current age estimation inaccuracies for wild odontocetes. Therefore, we determined genome-wide DNA methylation profiles using a custom array (HorvathMammalMethyl40) across skin and blood samples (n = 446) from known age animals representing nine odontocete species within 4 phylogenetic families to identify age associated CG dinucleotides (CpGs). The top CpGs were used to create a cross-validated OEAC clock which was highly correlated for individuals (r = 0.94) and for unique species (median r = 0.93). Finally, we applied the OEAC for estimating the age and sex of 22 wild Norwegian killer whales. DNA methylation patterns of age associated CpGs are highly conserved across odontocetes. These similarities allowed us to develop an odontocete epigenetic aging clock (OEAC) which can be used for species conservation efforts by provide a mechanism for estimating the age of free ranging odontocetes from either blood or skin samples.

The Irrawaddy dolphin, Orcaella brevirostris from the Mekong river Cambodia: Preliminary health and toxicological investigations.

The subpopulation of the Irrawaddy dolphin (Orcaella brevirostris) living in the Mekong River, Cambodia, is considered to be critically endangered. The aim of the investigation was to gain information about the genetic variation, health status and exposure to toxic compounds of these dolphins. Tissue samples from 27 Irrawaddy river dolphins found dead along the Mekong River between 2004 and 2009 were analysed with regards to genetics, pathology and ecotoxicology. Genetic maternal lineage detection, based on polymorphisms of the mitochondrial d-loop sequences, was performed. Data indicate a genetic separation of the Mekong dolphins from both the coastal population and the Mahakam dolphins. Pathological investigations revealed acute moderate multifocal suppurative bronchopneumonia, moderate periportal hepatic lipidosis, moderate diffuse hepatic atrophy and acute severe diffuse suppurative leptomeningitis. Residue levels of organochlorines and polybrominated diphenyl ethers in Irrawaddy dolphins from the Mekong River were lower than the concentrations reported for other cetaceans in the coastal and riverine waters of Asia, except for Dichlorodiphenyltrichloroethane. A high percentage of organic mercury compared to the immuno-toxic methylmercury was observed. Due to numerous confounding factors, it is not possible to relate levels of pollutants to observed morphological lesions. However, it is likely that chemical contaminants do adversely impact on the health of the Irrawaddy dolphins at present, and have also affected previous generations.

Species identification from seized animal oil: a case study of suspected Gangetic dolphin (Platanista gangetica).

Poaching of South Asian river dolphins is considered one of the main reasons for the rapid decline of their natural populations. To curb the escalated rate of poaching, high numbers of oil and meat seizures are recovered with subsequent convictions by the law enforcement agencies. In this connection, we report a case where suspected animal oil was confiscated by the forest official of West Bengal. We extracted DNA and successfully amplified partial fragments of Cytb and 16S rRNA mitochondrial genes. The generated sequences identified that the seized oil belonged to the Ganges river dolphin (Platanista gangetica) which is protected as Schedule I under the Wildlife (Protection) Act, 1972 of India and listed as "Endangered" under IUCN and APPENDIX I in CITES. In routine case work analysis, oil samples are not preferred for forensic DNA investigation due to low DNA yield and presence of inhibitors or contaminants leading to high failure rate. However, the present study generates hope for identifying species from seized animal oil and supports law enforcement in successful prosecution of the case.

Microsatellite markers for the endangered franciscana dolphin (Pontoporia blainvillei).

The franciscana (Pontoporia blainvillei) is the most threatened small cetacean in the South Atlantic. In this study we report the development of 13 microsatellite markers for franciscanas through next-generation sequencing, and the characterization of those loci in 38 samples from the species' northernmost population (Espírito Santo, Brazil). Besides providing diversity indices for the new, specific loci, we also report on the transferability of heterologous loci which had not been screened in franciscanas before, and review all loci used in previous studies. Expected heterozygosity in the new loci ranged between 0.107 and 0.595, and all but one were in Hardy Weinberg Equilibrium. These are the first microsatellite loci isolated from franciscanas, and they are an important addition to heterologous markers that were available previously.

Early divergence and differential population histories of the Indo-Pacific humpback dolphin in the Pacific and Indian Oceans.

The currently recognized Indo-Pacific humpback dolphin occurs in estuaries and surrounding shallow waters from the South China Sea to the Asian coast of the Indian Ocean. However, a recent study suggested that the humpback dolphin from the Bay of Bengal may represent a distinct phylogenetic species. In this study, we sequenced 915-bp mtDNA segments from five geographic populations in both Chinese and Thai waters; together with previously published sequences, these data revealed that the ancestral Indo-Pacific humpback dolphin might have split during the transition from the Oligocene to Miocene (23.45 Mya, 95% HPD: 16.65-26.55 Mya), and then dispersed along the Pacific and Indian Ocean coasts of Asia. Genetic differentiation was detected between most of the examined populations, except for only a few pairwise populations in the northern South China Sea. Genetic differentiation/distance between the humpback dolphins from the northern and southern South China Sea met the sub-species threshold value proposed for marine mammals, whereas that between the humpback dolphins in the Pacific and the Indian Ocean was above the species threshold. Bayesian inference of historic gene flow indicated low but constant northward gene flow along the Indian Ocean coast; however, there was a recent abrupt increase in gene flow in the Pacific region, likely due to the shortening coastline at the low stand of sea level. Our results revealed that the current taxonomic classification of Indo-Pacific humpback dolphins may not reflect their phylogeography.

Complete mitogenome of Ganges river dolphin, Platanista gangetica gangetica and its phylogenetic relationship with other cetaceans.

The Ganges river dolphin, Platanista gangetica gangetica is one of the endangered cetaceans. Due to increasing anthropogenic activities, it has faced a significant reduction in distribution range since the late 1800s and has even gone extinct from most of the early localities. The investigation of complete mitogenome holds significant relevance for identifying evolutionary relationships and monitoring the endangered species. Herein, we report and characterize for the first time the 16,319 bp complete mitochondrial genome of P. g. gangetica. It comprises 13 protein-coding genes, 22 transfer RNA (tRNA) genes, two ribosomal RNA genes, and one control region (CR). The genome composition was A + T biased (59.6%) and exhibited a positive AT-skew (0.104) and negative GC-skew (- 0.384). All the genes were encoded on the heavy strand, except eight tRNAs and the ND6 gene. In the CR, an 18 bp tandem repeat sequence was observed. Our Bayesian Inference (BI) and Maximum Likelihood (ML) based phylogenetic analysis indicated that studied river dolphins were polyphyletic and the placement of Platanista was to be more basal than other river dolphins (Lipotes, Inia and Pontoporia). The pairwise genetic distance of Platanista with other cetaceans was varied, with an overall close affinity with whales. The model-based BI and ML phylogenetic analysis indicated that Platanista clustering with Ziphiidae with high to moderate supportive values (PP/BP = 98/68). The results of this study provide insights important for the conservation genetics and further evolutionary studies of the freshwater river dolphins.

Specific capture and whole-genome phylogeography of Dolphin morbillivirus.

Dolphin morbillivirus (DMV) is considered an emerging threat having caused several epidemics worldwide. Only few DMV genomes are publicly available. Here, we report the use of target enrichment directly from cetacean tissues to obtain novel DMV genome sequences, with sequence comparison and phylodynamic analysis. RNA from 15 tissue samples of cetaceans stranded along the Italian and French coasts (2008-2017) was purified and processed using custom probes (by bait hybridization) for target enrichment and sequenced on Illumina MiSeq. Data were mapped against the reference genome, and the novel sequences were aligned to the available genome sequences. The alignment was then used for phylogenetic and phylogeographic analysis using MrBayes and BEAST. We herein report that target enrichment by specific capture may be a successful strategy for whole-genome sequencing of DMV directly from field samples. By this strategy, 14 complete and one partially complete genomes were obtained, with reads mapping to the virus up to 98% and coverage up to 7800X. The phylogenetic tree well discriminated the Mediterranean and the NE-Atlantic strains, circulating in the Mediterranean Sea and causing two different epidemics (2008-2015 and 2014-2017, respectively), with a limited time overlap of the two strains, sharing a common ancestor approximately in 1998.

Phylogenomics of the genus Tursiops and closely related Delphininae reveals extensive reticulation among lineages and provides inference about eco-evolutionary drivers.

Phylogeographic inference has provided extensive insight into the relative roles of geographical isolation and ecological processes during evolutionary radiations. However, the importance of cross-lineage admixture in facilitating adaptive radiations is increasingly being recognised, and suggested as a main cause of phylogenetic uncertainty. In this study, we used a double digest RADseq protocol to provide a high resolution (~4 Million bp) nuclear phylogeny of the Delphininae. Phylogenetic resolution of this group has been especially intractable, likely because it has experienced a recent species radiation. We carried out cross-lineage reticulation analyses, and tested for several sources of potential bias in determining phylogenies from genome sampling data. We assessed the divergence time and historical demography of T. truncatus and T. aduncus by sequencing the T. aduncus genome and comparing it with the T. truncatus reference genome. Our results suggest monophyly for the genus Tursiops, with the recently proposed T. australis species falling within the T. aduncus lineage. We also show the presence of extensive cross-lineage gene flow between pelagic and European coastal ecotypes of T. truncatus, as well as in the early stages of diversification between spotted (Stenella frontalis; Stenella attenuata), spinner (Stenella longirostris), striped (Stenella coeruleoalba), common (Delphinus delphis), and Fraser's (Lagenodelphis hosei) dolphins. Our study suggests that cross-lineage gene flow in this group has been more extensive and complex than previously thought. In the context of biogeography and local habitat dependence, these results improve our understanding of the evolutionary processes determining the history of this lineage.

Genomics of Population Differentiation in Humpback Dolphins, Sousa spp. in the Indo-Pacific Ocean.

Speciation is a fundamental process in evolution and crucial to the formation of biodiversity. It is a continuous and complex process, which can involve multiple interacting barriers leading to heterogeneous genomic landscapes with various peaks of divergence among populations. In this study, we used a population genomics approach to gain insights on the speciation process and to understand the population structure within the genus Sousa across its distribution in the Indo-Pacific region. We found 5 distinct clusters, corresponding to S. plumbea along the eastern African coast and the Arabian Sea, the Bangladesh population, S. chinensis off Thailand and S. sahulensis off Australian waters. We suggest that the high level of differentiation found, even across geographically close areas, is likely determined by different oceanographic features such as sea surface temperature and primary productivity.

Whole Genome Sequencing of Chinese White Dolphin (Sousa chinensis) for High-Throughput Screening of Antihypertensive Peptides.

Chinese white dolphin (Sousa chinensis), also known as the Indo-Pacific humpback dolphin, has been classified as "Vulnerable" on the IUCN Red List of Threatened Species. It is a special cetacean species that lives in tropical and subtropical nearshore waters, with significant differences from other cetaceans. Here, we sequenced and assembled a draft genome of the Chinese white dolphin with a total length of 2.3 Gb and annotation of 18,387 protein-coding genes. Genes from certain expanded families are potentially involved in DNA replication and repairing, suggesting that they may be related to adaptation of this marine mammal to nearshore environments. We also discovered that its historical population had undergone a remarkable bottleneck incident before the Mindel glaciation. In addition, a comparative genomic survey on antihypertensive peptides (AHTPs) among five representative mammals with various residential habitats (such as remarkable differences in exogenous ion concentrations and sea depth) revealed that these small bioactive peptides were highly conserved among these examined mammals, and they had the most abundant hits in collagen subunit proteins, especially for two putative AHTP peptides Gly-Leu-Pro (GLP) and Leu-Gly-Pro (LGP). Our genome assembly will be a valuable resource for further genetic researches on adaptive ecology and conservation biology of cetaceans, and for in-depth investigations into bioactive peptides in aquatic and terrestrial mammals for development of peptide-based drugs to treat various human cardiovascular diseases.

Quality and quantity of genetic relatedness data affect the analysis of social structure.

Kinship plays a fundamental role in the evolution of social systems and is considered a key driver of group living. To understand the role of kinship in the formation and maintenance of social bonds, accurate measures of genetic relatedness are critical. Genotype-by-sequencing technologies are rapidly advancing the accuracy and precision of genetic relatedness estimates for wild populations. The ability to assign kinship from genetic data varies depending on a species' or population's mating system and pattern of dispersal, and empirical data from longitudinal studies are crucial to validate these methods. We use data from a long-term behavioural study of a polygynandrous, bisexually philopatric marine mammal to measure accuracy and precision of parentage and genetic relatedness estimation against a known partial pedigree. We show that with moderate but obtainable sample sizes of approximately 4,235 SNPs and 272 individuals, highly accurate parentage assignments and genetic relatedness coefficients can be obtained. Additionally, we subsample our data to quantify how data availability affects relatedness estimation and kinship assignment. Lastly, we conduct a social network analysis to investigate the extent to which accuracy and precision of relatedness estimation improve statistical power to detect an effect of relatedness on social structure. Our results provide practical guidance for minimum sample sizes and sequencing depth for future studies, as well as thresholds for post hoc interpretation of previous analyses.