Pacific Ocean Populations Research Articles

Genetic-environment associations explain genetic differentiation and variation between western and eastern North Pacific rhinoceros auklet (Cerorhinca monocerata) breeding colonies.

Animals are strongly connected to the environments they live in and may become adapted to local environments. Examining genetic-environment associations of key indicator species, like seabirds, provides greater insights into the forces that drive evolution in marine systems. Here we examined a RADseq dataset of 19,213 SNPs for 99 rhinoceros auklets (Cerorhinca monocerata) from five western Pacific and 10 eastern Pacific breeding colonies. We used partial redundancy analyses to identify candidate adaptive loci and to quantify the effects of environmental variation on population genetic structure. We identified 262 candidate adaptive loci, which accounted for 3.0% of the observed genetic variation among western Pacific and eastern Pacific breeding colonies. Genetic variation was more strongly associated with pH and maximum current velocity, than maximum sea surface temperature. Genetic-environment associations explain genetic differences between western and eastern Pacific populations; however, genetic variation within the western and eastern Pacific Ocean populations appears to follow a pattern of isolation-by-distance. This study represents a first to quantify the relationship between environmental and genetic variation for this widely distributed marine species and provides greater insights into the evolutionary forces that act on marine species.

0162 Sleep in Pacific Ocean Populations: A Scoping Review

Abstract Introduction Sleep research focused on individuals categorized as Native Hawaiian/Pacific Islander suggests that sleep deficiencies(short sleep, insomnia symptoms) are highly prevalent among adults. Given the large degree of diversity related to family origin of Pacific ocean populations and assimilation, a more robust understanding of unique risk factors related to sleep challenges for these heterogenous communities is warranted. We are conducting a scoping review of studies that examine associations of health, practice, sociodemographic, and influential mechanisms with sleep in Pacific ocean populations. Methods A literature search conducted in Medline, Embase, Psychinfo, and Cochrane encompassed three domains: sleep-related and sleep-disorder terms, oceanic island and ancestry names, and sub-population names inclusive of the geographic regions of Polynesia, Micronesia, and Melanesia. The primary search retrieved 2364 articles. Studies were selected by abstract and full text analysis by one reviewer, followed by independent data extraction by four reviewers. Using a standardized form, synthesis of results and assessment of sample demographics, sampling strategy, sleep data source and findings, theoretical framework, and covariates was conducted per article. Inclusion criteria included articles with at least one quantitative sleep-related finding for a Pacific island population. We excluded non-primary research articles. Studies that categorically combined other racial/ethnic groups with Pacific ocean populations(Asian/Pacific Islander) or geographic regions(Asian-Pacific region) in reporting findings were excluded. Results Of the 99 articles included in the review, 18 included children/adolescents, 56 included adults, 13 included multiple age groups, and 12 reported no or only mean participant age. Seventy-two studies allowed participants to self-identify their major ethnic group as a single race(e.g., Tongan, Kirbati). Seventeen studies included objective methods(e.g., actigraphy). The most common sleep-related factors were issues of sleep patterns(n=51), physical health(n=43), mental health(n=28), socioeconomic deprivation(n=26), daytime sleepiness/fatigue(n=20), sleep disorders or symptoms (snoring)(n=17), sleep-supporting practices(n=9), and integration into main culture/born in US(n=3). Conclusion Preliminary results suggest that few studies have examined identifiable factors that may impact sleep within diverse Pacific ocean communities, with most studies focused on adults, self-reporting, and sleep pattern problems. Future studies should examine underlying mechanisms related to sleep deficiencies in both children and adults to better understand variability in risk across the lifespan. Support (If Any)

Genetic structure of marine and lake forms of Pacific herring Clupea pallasii.

The Pacific herring (Clupea pallasii) is one of the most important species in the commercial fisheries distributed in the North Pacific Ocean and the northeastern European seas. This teleost has marine and lake ecological forms a long its distribution in the Holarctic. However, the level of genetic differentiation between these two forms is not well known. In the present study, we used ddRAD-sequencing to genotype 54 specimens from twelve wild Pacific herring populations from the Kara Sea and the Russian part of the northwestern Pacific Ocean for unveiling the genetic structure of Pacific herring. We found that the Kara Sea population is significantly distinct from Pacific Ocean populations. It was demonstrated that lake populations of Pacific herring differ from one another as well as from marine specimens. Our results show that fresh and brackish water Pacific herring, which inhabit lakes, can be distinguished as a separate lake ecological form. Moreover, we demonstrate that each observed lake Pacific herring population has its own and unique genetic legacy.

Otolith shape as a classification tool for Chinook salmon (Oncorhynchus tshawytscha) discrimination in native and introduced systems

Chinook salmon (Oncorhynchus tshawytscha) are widely distributed across the globe, with native stocks in the North Pacific Ocean and self-sustained populations in both the Northern and Southern hemispheres. In their native range, Chinook salmon face many conservation and management challenges, including depleted stocks, loss of genetic diversity, and hatchery influences, whereas naturalized range expansion poses a threat to novel ecosystems. Therefore, ways to improve stock discrimination would be a useful tool for fishery managers. Here, we evaluated otolith shape variation in Chinook salmon as a potential tool for stock discrimination using wavelet coefficients and Fourier harmonics in three case studies at multiple spatial scales. We adopted a simple Classification Tree model that used otolith shape variation to separate Chinook salmon groups. We found best performance of the model occurring between hemispheres, followed by Oregon basins, within-watershed Elk River, Oregon, and lastly among South American basins. Otolith shape analysis is a promising tool for stock discrimination if used in conjunction with other methods to better understand plasticity of anadromous species that use pan-environmental systems.

DNA Zip‐coding: identifying the source populations supplying the international trade of a critically endangered coastal shark

AbstractThere is an urgent need for population‐specific trade information for overexploited sharks, as international trade regulations are becoming an important tool for their conservation [i.e., listings on the Convention on International Trade in Endangered Species (CITES)]. We tested a genetic stock identification (GSI) workflow to quantify the relative contributions of different source populations of the CITES‐listed scalloped hammerhead shark Sphyrna lewini to international trade hubs for products such as dried fins. We grouped published mitochondrial control region sequences from wild‐captured sharks sampled in 15 locations into 9 differentiated populations that provide broad coverage of the species global distribution. GSI simulations established that these populations are highly identifiable and we trialed this approach to assess the provenance of processed fin trimmings collected randomly from the retail market of Hong Kong, one of the world’s largest shark fin trade hubs in 2014–2015 (N = 72). In this pilot survey, we found over 75% of scalloped hammerhead fin trimmings came from two Pacific Ocean populations, but mostly from the Eastern Pacific (61.4%, of all trimmings; se 7.1%) where this species is listed as ‘Endangered’ under the United States Endangered Species Act. Six of the nine populations were found in this sample of the market, indicating near global sourcing of scalloped hammerhead fins in Hong Kong. We suggest technical and sampling considerations for employing GSI at fin trade hubs in the future to investigate regional sourcing of scalloped hammerheads and other coastal sharks in international trade. Random GSI in trade hubs could revolutionize our understanding of global shark trade dynamics and provide critical information required to effectively implement shark fisheries management and trade restrictions.

Genetic isolation by distance in the yellowfin goby populations revealed by RAD sequencing

Population genetic studies of marine species sometimes find no clear patterns of genetic differentiation, but signals of geographic gene flow typified by isolation by distance (IBD) due to high dispersal ability. A previous study of mitochondrial DNA of the yellowfin goby Acanthogobius flavimanus indicated that this species also does not have clearly differentiated population groups around the Japanese archipelago, in contrast with other coastal goby species that have highly differentiated groups between the Sea of Japan and Pacific Ocean populations. Here, to clearly reveal phylogeographic structures of the yellowfin goby around the Japanese archipelago, we conducted large-scale RAD-sequencing analysis of their nuclear genomic SNP loci. As a result, IBD patterns were confirmed across the yellowfin goby populations, and the larval dispersal distance of this species was revealed to be approximately 19 km on average. In addition, different larval dispersal distances were estimated for its Sea of Japan and Pacific Ocean populations, suggesting that different coastal environments and/or ecological features may affect its dispersal rates. These results would provide foundations for ecological and conservation studies of the yellowfin goby and coastal fishes having similar dispersal strategy to this species.

Genetic population structure of the convict surgeonfish Acanthurus triostegus: a phylogeographic reassessment across its range.

This study investigates the genetic population structure and connectivity of Acanthurus triostegus in five Indo-Pacific biogeographic regions (western and eastern Indian Ocean, western, central and eastern Pacific Ocean), using a mitochondrial DNA marker spanning the ATPase8 and ATPase6 gene regions. In order to assess the phylogeography and genetic population structure of A. triostegus across its range, 35 individuals were sampled from five localities in the western Indian Ocean and complemented with 227 sequences from two previous studies. Results from the overall analysis of molecular variance (AMOVA) without a priori grouping showed evidence of significant differentiation in the Indo-Pacific, with 25 (8.3%) out of 300 pairwise ΦST comparisons being significant. However, the hierarchical AMOVA grouping of Indian and Pacific Ocean populations failed to support the vicariance hypothesis, showing a lack of a genetic break between the two ocean basins. Instead, the correlation between pairwise ΦST values and geographic distance showed that dispersal of A. triostegus in the Indo-Pacific Ocean follows an isolation-by-distance model. Three haplogroups could be deduced from the haplotype network and phylogenetic tree, with haplogroup 1 and 2 dominating the Indian and the Pacific Ocean, respectively, while haplogroup 3 exclusively occurring in the Hawaiian Archipelago of the central Pacific Ocean.

Genetic signals of artificial and natural dispersal linked to colonization of South America by non-native Chinook salmon (Oncorhynchus tshawytscha).

Genetics data have provided unprecedented insights into evolutionary aspects of colonization by non‐native populations. Yet, our understanding of how artificial (human‐mediated) and natural dispersal pathways of non‐native individuals influence genetic metrics, evolution of genetic structure, and admixture remains elusive. We capitalize on the widespread colonization of Chinook salmon Oncorhynchus tshawytscha in South America, mediated by both dispersal pathways, to address these issues using data from a panel of polymorphic SNPs. First, genetic diversity and the number of effective breeders (N b) were higher among artificial than natural populations. Contemporary gene flow was common between adjacent artificial and natural and adjacent natural populations, but uncommon between geographically distant populations. Second, genetic structure revealed four distinct clusters throughout the Chinook salmon distributional range with varying levels of genetic connectivity. Isolation by distance resulted from weak differentiation between adjacent artificial and natural and between natural populations, with strong differentiation between distant Pacific Ocean and Atlantic Ocean populations, which experienced strong genetic drift. Third, genetic mixture analyses revealed the presence of at least six donor geographic regions from North America, some of which likely hybridized as a result of multiple introductions. Relative propagule pressure or the proportion of Chinook salmon propagules introduced from various geographic regions according to government records significantly influenced genetic mixtures for two of three artificial populations. Our findings support a model of colonization in which high‐diversity artificial populations established first; some of these populations exhibited significant admixture resulting from propagule pressure. Low‐diversity natural populations were likely subsequently founded from a reduced number of individuals.

Structure and phylogeography of two tropical predators, spinner (Stenella longirostris) and pantropical spotted (S. attenuata) dolphins, from SNP data.

Little is known about global patterns of genetic connectivity in pelagic dolphins, including how circumtropical pelagic dolphins spread globally following the rapid and recent radiation of the subfamily delphininae. In this study, we tested phylogeographic hypotheses for two circumtropical species, the spinner dolphin (Stenella longirostris) and the pantropical spotted dolphin (Stenella attenuata), using more than 3000 nuclear DNA single nucleotide polymorphisms (SNPs) in each species. Analyses for population structure indicated significant genetic differentiation between almost all subspecies and populations in both species. Bayesian phylogeographic analyses of spinner dolphins showed deep divergence between Indo-Pacific, Atlantic and eastern tropical Pacific Ocean (ETP) lineages. Despite high morphological variation, our results show very close relationships between endemic ETP spinner subspecies in relation to global diversity. The dwarf spinner dolphin is a monophyletic subspecies nested within a major clade of pantropical spinner dolphins from the Indian and western Pacific Ocean populations. Population-level division among the dwarf spinner dolphins was detected—with the northern Australia population being very different from that in Indonesia. In contrast to spinner dolphins, the major boundary for spotted dolphins is between offshore and coastal habitats in the ETP, supporting the current subspecies-level taxonomy. Comparing these species underscores the different scale at which population structure can arise, even in species that are similar in habitat (i.e. pelagic) and distribution.

Redescriptions of Pterois radiata and Pterois cincta (Scorpaenidae: Pteroinae) with notes on geographic morphological variations in P. radiata

The lionfishes (Scorpaenidae: Pteroinae) Pterois radiata Cuvier in Cuvier and Valenciennes 1829 and Pterois cincta Ruppell 1838 are both redescribed as valid, although the latter has previously been regarded as a junior synonym of the former. Pterois (Pseudomonopterus) vittata Sauvage 1878 and Scorpaena barffi Curtiss 1944 are regarded as junior synonyms of P. radiata. Pterois radiata and P. cincta are easily distinguished from their congeners by usually having XII, 11 dorsal-fin rays and 16–17 pectoral-fin rays, in addition to five broad vertical bands on the side of the body and a single broad horizontal band on the side of the caudal peduncle. Pterois cincta can be distinguished from P. radiata by having extremely long fin rays [e.g., longest pelvic-fin soft ray length 48.2–71.9 (mean 60.0) % of standard length in P. cincta, 36.8–53.3 (44.7) % in P. radiata]; and relatively narrow main bands and broad additional (inserted) markings on the side of the body. Pterois radiata is widespread throughout the Indo-Pacific, ranging from the east coast of Africa eastward to French Polynesia, and from northwestern Australia northward to southern Japan; in contrast, P. cincta is restricted to the Red Sea, with the exception of several doubtful records. Intraspecific geographical variations in several morphological characters were recognized between Indian and Pacific Ocean P. radiata, the former having fewer scales on parts of the body, and occasionally absence of additional markings (between the second and third and fourth and fifth bands) on the sides of the body. Geographical variations in the number of pectoral-fin rays in Pacific Ocean populations of P. radiata are also documented and morphological changes with growth of the two species described in detail. A neotype is proposed for P. radiata.

An introduced population of Chorda asiatica (Chordaceae, Laminariales) in Puget Sound, Pacific coast of North America

SummaryNortheastern Pacific Ocean and northwestern Atlantic Ocean populations of Chorda species, which have not been examined in previous phylogenetic studies, were investigated. All specimens that were collected in Hood Canal, Puget Sound, WA, USA, Pacific coast of North America, showed identical ITS‐5.8S rDNA sequences, and they were included in the clade of Japanese Chorda asiatica. With morphological data added to the molecular data, they were identified as C. asiatica and were concluded to be non‐indigenous populations, most likely introduced with oyster spat together with Sargassum muticum. Specimens collected in New York, NY, USA, Atlantic coast of North America, were genetically closest to C. filum from Newfoundland and were identified as C. filum. The genetic divergence of the North Atlantic populations of C. filum was relatively small compared to that of Japanese C. asiatica considering their broader distributional ranges on both sides of the Atlantic.

Phylogeography of the humbug damselfish,Dascyllus aruanus(Linnaeus, 1758): evidence of Indo-Pacific vicariance and genetic differentiation of peripheral populations

The phylogeographical structure of coral-associated reef fishes may have been severely affected, more than species from deeper habitats, by habitat loss during periods of low sea level. The humbug damselfish, Dascyllus aruanus, is widely distributed across the Indo-West Pacific, and exclusively inhabits branching corals. We used mitochondrial cytochrome b sequence and seven microsatellite loci on D. aruanus samples (260 individuals) from 13 locations across the Indo-West Pacific to investigate its phylogeographical structure distribution-wide. A major genetic partition was found between the Indian and Pacific Ocean populations, which we interpret as the result of geographical isolation on either side of the Indo-Pacific barrier during glacial periods. The peripheral populations of the Red Sea and the Society Islands exhibited lower genetic diversity, and substantial genetic differences with the other populations, suggesting relative isolation. Thus, vicariance on either side of the Indo-Pacific barrier and peripheral differentiation are considered to be the main drivers that have shaped the phylogeographical patterns presently observed in D. aruanus.

A review of the genus Pempheris (Perciformes, Pempheridae) of the Red Sea, with description of a new species.

Four species of the fish genus Pempheris are recognized for the Red Sea: P. adusta Bleeker, 1877; P. mangula Cuvier, 1829; P. nesogallica Cuvier in Cuvier & Valenciennes, 1831; and a new species P. tominagai. All are wide-ranging in the western Indian Ocean, and P. mangula has migrated via the Suez Canal to the eastern Mediterranean Sea. Morphological and genetic analysis of 15 species in this genus show that P. adusta, a widely distributed species, that can't be divided into different species, because of the continuity of morphologies and distribution, and lack of variance in genetics between Indian Ocean, Red Sea, and Pacific Ocean populations. This confirms that the two subspecies described by Randall et al. (2013) are both synonyms of P. adusta. Pempheris adusta is distinguished from other species by a blackish spot on pectoral fin base, pored lateral-line scales 56-64, scale rows above lateral line 4 1/2-6 1/2, distinct blackish band on outer edge of anal fin, and blackish band on posterior edge of caudal fin. Pempheris mangula was named by Cuvier (1829) in a footnote making reference to a drawing and short description in Russell (1803) of a Pempheris from southeast India, giving only the native name ''Mangula-Kutti'', and listing no specimen. The wide distribution of this species, from the Indian Ocean to the Red Sea is also demonstrated by morphological and genetic analysis. Thus, the specimen collected from southern India is herein designated as the neotype. This species is distinguished from other species by its huge eye, deep body, blackish tip of the dorsal fin, pored lateral-line scales 49-60, and scale rows above lateral line 4 1/2-5 1/2. The extant syntype of Kossmann & Räuber's P. rhomboidea is designated as the lectotype of the species; however, P. rhomboidea is a synonym of P. mangula. In addition, Kossmann & Räuber's Pempheris erythraea and P. russellii Day, 1888 are also synonyms of P. mangula. Of two existing syntypes of P. nesogallica from Mauritius, one is designated as the lectotype, the other is re-identified as P. mangula; P. nesogallica is presently known only from the southern Red Sea. This species has a similar morphology to P. mangula, but can be distinguished by a smaller eye than P. mangula, and lack irregular faint longitudinal light stripes on the body side. Pempheris tominagai are distinguished from P. schwenkii Bleeker 1855, formerly misidentified, by the form of posterior nostril, scale counts, color of caudal fin, and by a 2.1% mitochondrial DNA sequence divergence.

Fluctuating Asymmetry in the Saddle Patch Shape of the Pacific Ocean Killer Whale (Orcinus orca) Populations

The killer whale (Orcinus orca) is a top predator and one of the most contaminated marine mammal species in the world. Due to different prey preferences and life styles, killer whale populations accumulate persistent pollutants differently, and therefore are exposed differently to this stress. Stress may express itself in a population as an increase in the relative number of individuals with asymmetric presentation of a trait that is normally symmetrical. This phenomenon is called fluctuating asymmetry. There are many environmental and genetic factors that can cause fluctuating asymmetry. We have used the symmetry of the killer whale's saddle patch pattern behind the dorsal fin as an indicator of fluctuating asymmetry in six Pacific Ocean populations. The southern resident killer whale population seems to be remarkably more asymmetrical than the other studied populations. Although many possible environmental factors could cause asymmetry, we suggest that small population size, development of reproductively isolated ecotypes and possible inbreeding as genetic factors are causing asymmetry in the southern resident population.

Phylogeography of the crown-of-thorns starfish: genetic structure within the Pacific species

Previous studies of the population genetic structure of the corallivorous crown-of-thorns starfish (COTS) Acanthaster planci in the Pacific Ocean showed high levels of gene flow that were assumed to reflect a high dispersal potential. However, the phylogeographic analyses of the Pacific crown-of-thorns starfish species of this study, using the highly variable mitochondrial control region and the most complete geographic coverage to date, contradict this view. Results show high levels of overall genetic structure (ΦST = 0.198), suggesting a complex history of range restrictions and expansions, a pattern that we hypothesize results from changes in topography and oceanography associated with sea-level changes. However, results also show signatures of ongoing gene flow between populations isolated in the past and high levels of genetic connectivity even among distant populations. Combined, these results indicate that while there are significant limits to genetic exchange among populations among Pacific Ocean populations of the crown-of-thorns starfish, the high larval dispersal potential of this species is often achieved as well.

Molecular phylogeny of the Robust clade (Faviidae, Mussidae, Merulinidae, and Pectiniidae): An Indian Ocean perspective

Recent phylogenetic analyses have demonstrated the limits of traditional coral taxonomy based solely on skeletal morphology. In this phylogenetic context, Faviidae and Mussidae are ecologically dominant families comprising one third of scleractinian reef coral genera, but their phylogenies remain partially unresolved. Many of their taxa are scattered throughout most of the clades of the Robust group, and major systematic incongruences exist. Numerous genera and species remain unstudied, and the entire biogeographic area of the Indian Ocean remains largely unsampled. In this study, we analyzed a portion of the mitochondrial cytochrome c oxidase subunit 1 gene and a portion of ribosomal DNA for 14 genera and 27 species of the Faviidae and Mussidae collected from the Indian Ocean and New Caledonia and this is the first analysis of five of these species. For some taxa, newly discovered evolutionary relationships were detected, such as the evolutionary distinctiveness of Acanthastrea maxima, the genetic overlap of Parasimplastrea omanensis and Blastomussa merleti, and the peculiar position of Favites peresi in clade XVII together with Echinopora and Montastraea salebrosa. Moreover, numerous cases of intraspecific divergences between Indian Ocean and Pacific Ocean populations were detected. The most striking cases involve the genera Favites and Favia, and in particular Favites complanata, F. halicora, Favia favus, F. pallida, F. matthaii, and F. rotumana, but divergence also is evident in Blastomussa merleti, Cyphastrea serailia, and Echinopora gemmacea. High morphological variability characterizes most of these taxa, thus traditional skeletal characteristics, such as corallite arrangement, seem to be evolutionary misleading and are plagued by convergence. Our results indicate that the systematics of the Faviidae and the Mussidae is far from being resolved and that the inclusion of conspecific populations of different geographical origin represents an unavoidable step when redescribing the taxonomy and systematics of scleractinian corals. More molecular phylogenies are needed to define the evolutionary lineages that could be corroborated by known and newly discovered micromorphological characters.

Genetically separate populations of the ocean-skater Halobates sericeus (Heteroptera: Gerridae) have been maintained since the late Pleistocene

The oceanic water strider (or ocean‐skater) Halobates sericeus Eschscholtz has a disjunct distribution in the Pacific Ocean, with northern and southern populations widely separated by an equatorial zone. It is sensitive to sea surface conditions and, consequently, its distribution and population structure may provide an insight into environmental changes on the ocean surface on both recent and historical time scales. We assessed the genetic diversity and population structure of H. sericeus in the Pacific Ocean using three gene markers – cytochrome oxidase subunit I (COI), elongation factor 1I± and internal transcribed spacer 1 (ITS‐1). These markers indicate that both populations are evolutionarily distinct with limited gene flow, having separated 20 000–50 000 years ago. This suggests that physical conditions and/or biotic interactions on the surface of the Pacific Ocean have provided significant barriers to gene flow since the late Pleistocene or earlier, creating biotic stability over large geographical and temporal scales in spite of a long history of global climate change. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105, 797–805.

Driftnet fishery threats sea turtles in the Atlantic Ocean

Fisheries are recognised as a major threat to sea turtles worldwide. Oceanic driftnets are considered the main cause of the steep decline in Pacific Ocean populations of the leatherback sea turtle Dermochelys coriacea. The world’s largest leatherback population nests in West Africa and migrates across the Atlantic Ocean to feed off the South American coast. There, the turtles encounter a range of fisheries, including the Brazilian driftnet fishery targeting hammerhead sharks. From 2002 to 2008, 351 sea turtles were incidentally caught in 41 fishing trips and 371 sets. Leatherbacks accounted for 77.3% of the take (n = 252 turtles, capture rate = 0.1405 turtles/km of net), followed by loggerheads Caretta caretta (47 individuals, capture rate = 0.0262 turtles/km of net), green turtles Chelonia mydas (27 individuals, capture rate = 0.0151 turtles/km of net) and unidentified hard-shelled turtles (25 individual, capture rate = 0.0139 turtles/km of net) that fell off the net during hauling. Immediate mortality (i.e., turtles that were dead upon reaching the vessel, excluding post-release mortality) was similar among the species and accounted for 22.2 to 29.4% of turtles hauled onboard. The annual catch by this fishery ranged from 1,212 to 6,160 leatherback turtles, as estimated based on bootstrap procedures under different fishing effort scenarios in the 1990s. The present inertia in law and enforcement regarding gillnet regulations in Brazil could result in the reestablishment of the driftnet fishery, driving rates of leatherback mortality to levels similar to those observed in previous decades. This development could potentially lead to the collapse of the South Atlantic leatherback population, mirroring the decline of the species in the Pacific. In light of these potential impacts and similar threats to other pelagic mega fauna, we recommend banning this type of fishery in the region.

Oceanic dispersal in a sedentary reef shark (Triaenodon obesus): genetic evidence for extensive connectivity without a pelagic larval stage

AbstractAim Most reef fishes are site‐attached, but can maintain a broad distribution through their highly dispersive larval stage. The whitetip reef shark (Triaenodon obesus) is site‐attached, yet maintains the largest Indo‐Pacific distribution of any reef shark while lacking the larval stage of bony (teleost) fishes. Here we use mitochondrial DNA (mtDNA) sequence data to evaluate the enigma of the sedentary reef shark that maintains a distribution across two‐thirds of the planet.Location Tropical Pacific and Indian Oceans.Methods We analysed 1025 base pairs of the mtDNA control region in 310 individuals from 25 locations across the Indian and Pacific Oceans. Phylogeographic and population genetic analyses were used to reveal the dispersal and recent evolutionary history of the species.Results We resolved 15 mtDNA control region haplotypes, but two comprised 87% of the specimens and were detected at nearly every location. Similar to other sharks, genetic diversity was low (h = 0.550 ± 0.0254 and π = 0.00213 ± 0.00131). Spatial analyses of genetic variation demonstrated strong isolation across the Indo‐Pacific Barrier and between western and central Pacific locations. Pairwise ΦST comparisons indicated high connectivity among archipelagos of the central Pacific but isolation across short distances of contiguous habitat (Great Barrier Reef) and intermittent habitat (Hawaiian Archipelago). In the eastern Pacific only a single haplotype (the most common one in the central Pacific) was observed, indicating recent dispersal (or colonization) across the East Pacific Barrier.Main conclusions The shallow haplotype network indicates recent expansion of modern populations within the last half million years from a common ancestor. Based on the distribution of mtDNA diversity, this began with an Indo‐West Pacific centre of origin, with subsequent dispersal to the Central Pacific and East Pacific. Genetic differences between Indian and Pacific Ocean populations are consistent with Pleistocene closures of the Indo‐Pacific Barrier associated with glacial cycles. Pairwise population comparisons reveal weak but significant isolation by distance, and notably do not indicate the high coastal connectivity observed in other shark species. The finding of population structure among semi‐contiguous habitats, but population connectivity among archipelagos, may indicate a previously unsuspected oceanic dispersal behaviour in whitetip reef sharks.

Comparative phylogeography and connectivity of sibling species of the marine copepod Clausocalanus (Calanoida)

Connectivity of the marine epipelagic environment is subject to presence of subtle barriers that can be difficult to identify and to signals from the geological history of the oceans. This study examines the effects of species' geographical distribution on their population structure as mediated by differential effects of the recent geological history of the oceans. For this purpose, we studied the sequence variation of the mitochondrial cytochrome oxidase c subunit I (COI) gene in samples of two sibling species of the calanoid copepod genus Clausocalanus. Analyses included molecular population genetic, phylogeographic, and phylogenetic approaches. The cosmopolitan Clausocalanus arcuicornis is shown to have a single panmictic population across this species' extensive geographic range, with sufficient gene flow – despite vast distances and geological and oceanographic barriers – to maintain genetic cohesion. In contrast, the biantitropical Clausocalanus lividus exhibits clear differentiation between Atlantic and Pacific Ocean populations, suggesting a vicariance process that started after the rise of the Isthmus of Panama.