Aleutian Islands Research Articles

Boron isotopes identify deep-slab serpentinite in the source of Aleutian arc magma

Seafloor lavas of the Western Aleutian arc have isotopically heavy boron (δ11B to +13.4‰) that is negatively correlated with B content (ppm). Endmember samples are primitive dacites and rhyodacites (δ11B > +10‰, SiO2 = 63%−70%, Mg# > 0.60) with adakitic trace-element and isotopic characteristics that require roles for residual garnet and rutile in their formation. The source of isotopically heavy B is likely serpentinite in the mantle section of the subducting plate, which dewaters into an inverted geothermal gradient and drives melting within the overlying volcanic section at depths where prior effects of seawater alteration were minimal. Most volcanic rocks from the Aleutian Island locations have 10−30 ppm B with an average δ11B of ∼+1.0‰ ± 1.3‰, reflecting a mixed source dominated by subducted sediment. A subset of island samples has B that is isotopically light (δ11B < −2.4‰) and at low concentrations (<11.0 ppm), which is typical of arc lavas globally from rear-arc settings where depth-to-slab is high, and where δ11B may be interpreted to reflect a source in dehydrated (isotopically light) altered oceanic crust. Mass balance modeling indicates that isotopically heavy B from deep-slab serpentinite is present in the Aleutian source arc-wide but is typically masked by sediment-derived B at volcanic centers outside of the westernmost segment of the arc.

Continental crustal growth in the post-collisional setting: Insights from the Late Triassic high-Mg andesites in the eastern Central Asian Orogenic Belt

The Central Asian Orogenic Belt represents the most important site of crustal growth in the Phanerozoic. However, the intricate evolution of multi-ocean regimes has given rise to uncertainties surrounding the processes of Mesozoic tectonic evolution and the dynamics of crustal growth. In this study, we conducted detailed geochronological and geochemical analyses of andesites collected from the eastern Central Asian Orogenic Belt. Zircon U-Pb dating results show that these andesites formed during the Late Triassic (ca. 235 Ma), and the Ti-in-zircon thermometer reveals high magma temperatures (>1100 °C) during their genesis. The elevated Mg# values at moderate SiO2 content of these Late Triassic andesites indicate an affinity with high-Mg andesites (HMAs). Notably, the andesites exhibit relatively low K2O/Na2O ratios, high Sr/Y ratios, significant depletion of Nb and Ta, and trace element patterns resembling typical HMAs from the western Aleutian Islands. These characteristics suggest that they likely originated from the partial melting of subducted eclogite. Furthermore, the HMAs display relatively high zircon εHf(t) values and depleted whole-rock Sr-Nd isotopic compositions, which is indicative of a depleted mantle source. Therefore, we propose that these andesites were generated through the interaction of the subducting slab−derived melts and overlying mantle wedge. Considering that the final closure of the Paleo-Asian Ocean took place before the Late Triassic, these andesites probably erupted in a post-collisional setting. The formation of these HMAs could be best explained by the upwelling asthenosphere triggered by the break-off of the oceanic slab, which also contributed to continental crustal growth in Northeast China.

Recent surveys of the sea otter (Enhydra lutris) population on Kuril Islands

Context Sea otters, an endangered species, require regular assessments of their distribution and abundance. These animals inhabit the coastal waters of the North Pacific, traversing from Japan through the Kurils, southern Kamchatka, Commander and Aleutian Islands, and the coasts of North America, to California. Although populations in America and the Commander Islands have been consistently monitored over recent decades, the same cannot be said for the Kuril Islands. Aim This study aims to estimate the state of sea otter populations on the Kuril Islands. Methods The study area encompassed a section of the Kuril archipelago, including Iturup, Urup, Broughton, Chirpoy, and Simushir Islands, surveyed from 2019 to 2023. Sea otters were counted along sections of the coastline, and published sources on other Kuril Islands were analysed. Key results There are several hundred sea otters within surveyed area, whereas in 1960–1980 ~2000 were reported. The total number of sea otters on the archipelago hardly exceeds 3000. The initial or normal number is not known, but the information on hunting indicates that it was much bigger. Up to the end of 19th century, at least ‘one thousand individuals’ had been harvested annually over several decades; this means that the total number was at least several tens of thousands. Conclusions Sea otter populations on the Kuril Islands are in decline, with poaching in the recent past identified as significant contributing factor in a part of the archipelago. Implications Urgent conservation measures are imperative to address the decline of sea otter populations.

Isotopic variability of short-tailed Albatrosses bone collagen (<i>Phoebastria albatrus</i>) in the Bering Sea area during the holocene

The short-tailed Albatross (Phoebastria albatrus) is a rare bird species today, whose numbers declined significantly in the Holocene due to human fishing activities. Bone remains of albatrosses from archaeological sites of Chukotka, Kamchatka and Aleutian Islands, and from coastal sediments of the Commander Islands were used to analyze the content of stable carbon and nitrogen isotopes in bone collagen. Analysis showed that the isotopic niches of Aleutian and Commander albatrosses diverged during the Holocene. Short-tailed albatrosses of the Aleutian Islands are closer to Holocene albatrosses of Vancouver Island (Canada) by isotopic characteristics.

Shorter Migration Distance and Breeding Latitude Correlate With Earlier Egg-Laying Across the Northeastern Pacific Ocean Range of the Rhinoceros Auklet (Cerorhinca monocerata).

Models of migratory behavior predict trade-offs between fitness costs and benefits with respect to migration distance. Shorter migration distances may confer a fitness benefit by facilitating earlier breeding, however this is rarely investigated. We tested this hypothesis using a large-scale geolocation (GLS) dataset from 109 rhinoceros auklets (Cerorhinca monocerata), a differentially migrating seabird, that was tagged at 12 breeding colonies along the Pacific Coast of North America, spanning southern California to the eastern Aleutian Islands, Alaska. Using GLS-based position estimates, we determined the geographic centroid of the pelagic areas occupied by birds in winter (1 January-28 February) and then calculated the distance between their wintering centroids and colony of origin. We then used GLS light-intensity and salt-water immersion (wet/dry) data to determine each individual's date of egg-laying the following spring. Rhinoceros auklets were very widely distributed across the northeastern Pacific Ocean in winter. Among all individuals, the distance between winter centroids and breeding colonies ranged from < 100 to > 2500 km, being greater among individuals originating from colonies at higher latitudes. As predicted, migration distance and colony latitude were positively related to lay date: after accounting for colony-level differences in phenology, individuals that migrated shorter distances tended to lay their eggs earlier, a pattern that emerged across all populations. Our study links the migration distance of rhinoceros auklets to a fitness-related outcome, underscoring the selective pressure that migration exerts on subsequent breeding activity.

Shrinking suitable habitat of a sub-Arctic foundation kelp under future climate scenarios.

Climate change has profound effects on the distribution of kelp forests in the Arctic and sub-Arctic. However, studies on the responses of kelps to climate change, particularly along the sub-Arctic regions of the Alaska coast, are limited. Eualaria fistulosa is a foundational kelp species in the Aleutian Islands, with an east-west distribution that extends from Japan to southern southwest Alaska. In this study, we utilized a species distribution model (SDM) to explore changes in the future habitat suitability of E. fistulosa under contrasting Shared Socioeconomic Pathway (SSP) scenarios. Our model exhibited relatively high predictive performance, validating our SDM predictions. Notably, the SDM results indicate that minimum sea surface temperature, annual range in sea surface temperatures, and annual mean current velocities are the three most important predictor variables determining E. fistulosa's distribution. Furthermore, the projected geographic distribution of Eualaria is generally consistent with its observed occurrence records. However, under high emission scenarios (SSP5-8.5), E. fistulosa is predicted to contract its distribution range by 9.0% by 2100, with widespread disappearance along the southeast Alaskan coast and limited northward migration to Kamchatka Krai in Russia and Bristol Bay in Alaska. These findings contribute valuable insights for conservation strategies via addressing climate-induced alterations in sub-Arctic kelp distribution.

Phascolion kamchatikus sp. nov., the first interstitial sipunculan (Sipuncula, Phascolionidae) from the Pacific Ocean

A new species of meiobenthic sipunculan, Phascolion kamchatikus sp. nov. collected from coarse sand and shell hash in shallow waters in the northwestern Pacific, is described and illustrated using light and electron microscopy. This new species is well distinguished from all other congeners by a unique combination of main taxonomic characters. This is the only sipunculan having only two primary tentacles in both juvenile and sexually mature worms. There are no hooks and holdfast papillae in the adult stages. Because of the presence of three nearly equal in size retractor muscles forming a retractor column divided for most of its length, this species is assigned to the subgenus Isomya of the genus Phascolion. Unlike most other species of the genus Phascolion, P. kamchatikus sp. nov. has an interstitial mode of life moving among the coarse sand grains and shell hash accumulated between rocks and stones in shallow water areas alongside the Pacific coast of Kamchatka, Aleutian Islands and Alaska Peninsula. Phascolion kamchatikus sp. nov. constitutes the only third interstitial species of the phylum Sipuncula. This is also the ninth species of Phascolion in the northwestern Pacific and the first interstitial representative of this genus in the Pacific Ocean.

The migration history of the Kamchatka rhododendron (Therorhodion camtschaticum s.l.) indicates two distinct dispersal routes towards Eastern Beringia

Abstract The Kamchatka rhododendron (Therorhodion camtschaticum s.l.) is a small, cold-resistant arcto-alpine shrub species with a controversial taxonomy and a wide Beringian distribution, from northern Eurasia to Arctic North America. Some authors regard T. camtschaticum and the closely related Therorhodion glandulosum as separate species while others suggest that they represent regionally differentiated subspecies. In order to resolve this relationship, we sampled 33 populations within the native species ranges, using three fragments of plastid DNA (ptDNA) and ten nuclear microsatellites (nSSR). We recovered two genetic lineages consistent with species rather than subspecies. The distribution of these genetic lineages are consistent with two different migration pathways of species from western Beringia to eastern Beringia: (i) for T. glandulosum a northern pathway from northern East Asia to the Seward Peninsula in northern Alaska; and (ii) for T. camtschaticum a southern pathway from the southern part of western Beringia to the Aleutian Islands and the seashore of south-east Alaska. The northern route extends from the Okhotsk seashore through the Kolyma region, Chukotka, and central and northern Kamchatka. The southern route begins at the Sikhote-Alin ridge, and goes through Sakhalin Island, the Kuril Islands, and southern Kamchatka. Demographic analysis using nSSR data inferred a divergence time between T. camtschaticum and T. glandulosum long before the Last Glacial Maximum.

Utilising bryophyte herbarium material as a source of fungal novelty: a case study presenting new records of Bryobroma gymnomitrii (Döbbeler) Döbbeler on Gymnomitrion Corda in Britain and North America

ABSTRACT Introduction Bryophyte herbarium material often contains inadvertently collected bryophilous fungi preserved with their host plant tissues, providing snapshots of the biotic aspects of bryophyte ecology in space and time. During an ongoing project to study bryophilous fungi on leafy liverworts in the genus Gymnomitrion, new records of the bryophilous ascomycete Bryobroma gymnomitrii (≡ Bryomyces gymnomitrii) were discovered in herbarium material from areas in which the fungus was previously unknown. While many host vouchers were screened, the fungus was observed in only five collections. Using B. gymnomitrii as a case study, some of the advantages and limitations associated with the utility of bryophyte collections for bryo-mycological analyses are considered. Methods More than 400 herbarium specimens from across Europe and North America were screened for the presence of fungi by different researchers at the following four herbaria: ALA, BBSUK, NMW and OSC. Key results and conclusions Bryobroma gymnomitrii appears to be specific to Gymnomitrion concinnatum and G. corallioides, forming gregarious, black perithecioid fruitbodies on the lower parts of host shoots. The study expands the known distribution of the fungus from a stronghold in northern and northeastern Europe to include the Aleutian Islands in Alaska. One of the host bryophytes, G. corallioides, is threatened by deterioration of its high-altitude Arctic-montane habitats, especially along the southern parts of its range, including Britain and Ireland. Our work supports the concept that research utilising herbarium material may provide valuable, unexpected outcomes, with bryophytes as important sources of fungi that have been inadvertently collected in the past.

Bioregionalization of the subarctic Pacific based on phytoplankton phenology and composition

The subarctic Pacific is generally perceived as relatively homogeneous since the North Pacific Subpolar Gyre dominates the water circulation in the area. However, previous research showed significant spatial differences in phytoplankton abundance and community structure. This study aimed to identify regions associated with distinct phytoplankton phenology and composition to comprehensively describe the main phytoplankton variability patterns across the subarctic Pacific. To this end, satellite GlobColour time series observations and an extensive in situ phytoplankton pigment dataset were used in the analysis. Five bioregions were identified, based on the Self-Organized Mapping technique, using a greater than 20-year satellite data series. The bioregions in the open Pacific waters were dominated by green algae, haptophytes, and pelagophytes and were divided into the areas affected by the North Pacific Transition Zone and beyond. The other bioregions were defined around the Pacific basin margins where the diatom contribution was generally higher, with a particular distinction of waters surrounding the Kuril and the Aleutian Islands. Our bioregion designations allow for future evaluation of the processes controlling the physical and biological dynamics within each bioregion, which has direct implications for foraging conditions available to higher trophic levels, including potential food resource competition.

Spatial and cumulative organochlorine and mercury exposure assessments in Steller Sea lions of Alaska: Emphasizing pups

Steller sea lions (SSL) are sentinels for monitoring environmental contaminants in remote areas of the Aleutian Islands, Alaska. Therefore, concentrations of several organochlorines (OCs) were measured in blood from 123 SSL pups sampled from 3 regions; the western Aleutian Islands (WAI), central Aleutian Islands (CAI), and the central Gulf of Alaska. Blood, blubber, and milk from 12 adult female SSL from WAI, CAI and southeast Alaska also were analyzed. Findings included the following. SSL pups had higher concentrations of some OCs and mercury (Hg) on rookeries in the WAI than those more easterly. Pups had significantly higher blood concentrations of many OC classes than adult females sampled within the same region; some pups had PCB concentrations exceeding thresholds of concern (∑PCBs >8600 ng/g lw). ∑PCB concentration in pup whole blood was positively correlated with the trophic marker, δ15N within the regions sampled, along with two PCB congeners (PCB138 and PCB153). This suggests that the dams of pups with higher ∑PCBs, PCB138, and PCB153 concentrations were feeding on more predatory prey. Adult female blubber ∑DDT and hexachlorocyclohexane concentrations were also positively correlated with δ15N values. Several pups (mostly from WAI) had blood Hg concentrations and/or blood PCB concentrations (surrogate for overall OC exposures) of concern. The finding that WAI SSL pups have been exposed to multiple contaminants calls for future investigation of their cumulative exposure to a mixture of contaminants especially their transplacental and then transmammary exposure routes.

Whole genome resequencing of sablefish at the northern end of their range reveals genetic panmixia and large putative inversions

Abstract Sablefish (Anoplopoma fimbria) are a highly mobile species that support important commercial fisheries in the North Pacific Ocean. Information on the genetic stock structure of sablefish is vital for constructing management strategies that ensure the long-term viability of the species. Most previous genetic studies on sablefish have found panmixia throughout the majority of their range, but a recent study suggested that a population structure may exist. Here, we use low-coverage whole genome resequencing to investigate genetic structure in the northern end of the species’ range (from Washington State, USA to the Bering Sea and Aleutian Islands, AK, USA). Additionally, we reanalyzed an existing genomic dataset containing 2661 markers to test specific hypotheses about genetic structure by sex. Genome resequencing data from 119 individuals screened at 7 110 228 markers revealed no evidence of population structure, and reanalysis of the existing genomic dataset supported the same conclusion. Differentiation across the genome was largely driven by variation at two putative inversions located ∼1 megabase apart, which did not display any signals of geographic differentiation. Our study further supports the conclusion of genetic panmixia in sablefish throughout its northern range.

Alaskan Russian: Cultural and Historical Trace of the Russian Expansion in North America

The article analyzes approaches to creating a chronology of Russia’s exploration of Alaska and the Aleutian Islands, highlights historical periods relevant for the main purpose of our research. The goal is to describe the Russian language as a dynamic and integral part of a unique culture formed in the Creole communities, uniting the paternal culture of Russian colonists and the maternal cultures of the indigenous population. This culture lies in the center of social interactions and makes its core. The issue is topical for the present study, since it contributes to our understanding of the phenomena of the interaction of cultures. The Russian period of Alaska is recognized by researchers, both domestic and international, as an important and special epoch in the life of the American state, an epoch which to a great extent determined its history. Alaskan Russian was an intermediary language for the people from the continent and the native speakers of indigenous languages. It was used in communication until the middle of the 20th century. At the moment, the Alaskan Russian language exists as a cultural artifact: to a certain extent, it is known by a few descendants of Creoles of very advanced age. The purpose of this study is to create a historical context of the formation of the Alaskan Russian language and to describe conditions for its uprise and preservation on the territory of Russian America. We show that the existence of permanent functional settlements in which Russian language was spoken – in the family, in the community, and for trade and professional contacts – determined consolidation of the Russian language, in a number of places in Alaska up to the middle of the XX century. The data presented in the article confirm that the Orthodox tradition and the Russian language that have survived to this day are the main features of Russia’s long-term cultural influence in Alaska. The study used both universal scientific methods and special methods of historical research determined by the specifics of the problem, namely: the problem-chronological method, the method of comparative analysis, the systematic method. Exploring the influence of language on social life, the author adheres to the methods of linguistic anthropology and historical anthropology

Russian-Spanish Relations During the Development of North American Territories in the Second Half of the 18th century

The article is about the relations between Russia and Spain in the second half of the 18th century. The article identifies the factors that influenced the nature of the emerging interaction between the powers: it shows the ambivalence of Russian-Spanish relations, on the one hand, due to the growing fears of the Spanish authorities provoked by Russia’s advance towards California, and, on the other, to the development of mutually beneficial trade relations. We draw attention to aspects related to Russia’s discovery of the Aleutian archipelago and Alaska and the activity of Russian merchants. The reaction of the Spanish court to messages of Spanish diplomats in Russia about Russian discoveries in America is shown. The analysis of the texts of diplomatic reports (1761−1792) has shown that the Spanish ambassadors were skeptical about the success of Russian expeditions to the American continent but changed their mind in the second half of 1760s. The article also examines the trade and economic aspect in the relations between the powers, showing the intention of Spain and Russia to establish direct trade. At the same time, we note that the nature of such interaction was influenced by the general political situation, which was determined by the leading powers of that time. The article has been written using historical and philological methods and approaches and aims to show the various aspects and stages of Russian-Spanish relations during the period of colonization of the Northwest of America. The results of the study can be used in practical activities of diplomatic services within the framework of international dialogue.

Foraging niche, sex-specific resource partitioning, and mercury concentrations of male Steller sea lions in Alaska

With their large size, the foraging behaviors of adult male Steller sea lions Eumetopias jubatus may have significant impacts on marine food webs and ecosystems. Limited studies from scat suggest that male and female Steller sea lions exhibit some dietary differences, and bycatch rates tend to be higher for males; however, most foraging ecology data are from adult females. Here we aimed to (1) characterize the isotopic foraging niches of adult male Steller sea lions in the Aleutian Islands and Bering Sea (n = 18), (2) assess sex-specific resource partitioning between male and female Steller sea lions (n = 18) in this region, and (3) identify male foraging strategies associated with greater total mercury concentrations ([THg]), a contaminant of concern in the region. Vibrissae collected from males bycaught in commercial fisheries from 1998-2017 were sectioned, and sequential segments were analyzed for bulk stable isotope ratios (δ15N and δ13C values) and [THg]. Individuals exhibited temporal oscillations in both δ15N and δ13C values that reflect significant summer to winter variation in foraging. Male Steller sea lions had larger isotopic niches than females, and limited overlap of isotopic niches suggests a moderate degree of sex-specific resource partitioning in this system. [THg] were positively associated with δ15N, and individuals exhibited evidence of bioaccumulation with age. These findings represent contemporary isotopic values and the first reported Hg levels for non-pup male Steller sea lions in a region where the population is considered endangered. Together, they provide a reference for assessing shifts in foraging patterns relative to future environmental fluctuations.

ECMWF Ensemble Forecasts of Six Tropical Cyclones That Formed during a Long-Lasting Rossby Wave Breaking Event in the Western North Pacific

The ECMWF‘s ensemble (ECEPS) predictions are documented for the lifecycles of six tropical cyclones (TCs) that formed during a long-lasting Rossby wave breaking event in the western North Pacific. All six TC tracks started between 20° N and 25° N, and between 136° E and 160° E. All five typhoons recurved north of 30° N, and the three typhoons that did not make landfall had long tracks to 50° N and beyond. The ECEPS weighted mean vector motion track forecasts from pre-formation onward are quite accurate, with track forecast spreads that are primarily related to initial position uncertainties. The ECEPS intensity forecasts have been validated relative to the Joint Typhoon Warning Center (JTWC) Working Best Track (WBT) intensities (when available). The key results for Tokage (11 W) were the ECEPS forecasts of the intensification to a peak intensity of 100 kt, and then a rapid decay as a cold-core cyclone. For Hinnamnor (12 W), the key result was the ECEPS intensity forecasts during the post-extratropical transition period when Hinnamnor was rapidly translating poleward through the Japan Sea. For Muifa (14 W), the key advantage of the ECEPS was that intensity guidance was provided for longer periods than the JTWC 5-day forecast. The most intriguing aspect of the ECEPS forecasts for post-Merbok (15 W) was its prediction of a transition to an intense, warm-core vortex after Merbok had moved beyond 50° N and was headed toward the Aleutian Islands. The most disappointing result was that the ECEPS over-predicted the slow intensification rate of Nanmadol (16 W) until the time-to-typhoon (T2TY), but then failed to predict the large rapid intensification (RI) following the T2TY. The tentative conclusion is that the ECEPS model‘s physics are not capable of predicting the inner-core spin-up rates when a small inner-core vortex is undergoing large RI.

Historical fragmentation and stepping-stone gene flow led to population genetic differentiation in a coastal seabird.

Understanding the forces that shape population genetic structure is fundamental both for understanding evolutionary trajectories and for conservation. Many factors can influence the geographic distribution of genetic variation, and the extent to which local populations differ can be especially difficult to predict in highly mobile organisms. For example, many species of seabirds are essentially panmictic, but some show strong structure. Pigeon Guillemots (Cepphus columba; Charadriiformes: Alcidae) breed in small colonies scattered along the North Pacific coastline and feed in shallow nearshore waters year-round. Given their distribution, gene flow is potentially lower and population genetic structure is stronger than in most other high-latitude Northern Hemisphere seabirds. We screened variation in the mitochondrial control region, four microsatellite loci, and two nuclear introns in 202 Pigeon Guillemots representing three of five subspecies. Mitochondrial sequences and nuclear loci both showed significant population differences, although structure was weaker for the nuclear loci. Genetic differentiation was correlated with geographic distance between sampling locations for both the mitochondrial and nuclear loci. Mitochondrial gene trees and demographic modeling both provided strong evidence for two refugial populations during the Pleistocene glaciations: one in the Aleutian Islands and one farther east and south. We conclude that historical fragmentation combined with a stepping-stone model of gene flow led to the relatively strong population differentiation in Pigeon Guillemots compared to other high-latitude Northern Hemisphere seabird species. Our study adds to growing evidence that Pleistocene glaciation events affected population genetic structure not only in terrestrial species but also in coastal marine animals.

Generativity as a Traditional Way of Life: Successful aging among Unangan Elders in the Aleutian Pribilof Islands.

Predominantly Western-based biomedical models of successful aging have been used to research, understand, and explain successful aging among diverse populations. With an increasingly heterogeneous older adult population nationwide, scholars have been exploring Indigenous understandings of successful aging. To add to the accumulation of knowledge of diverse Alaska Native populations, this study involved semi-structured qualitative interviews with 20 Unangan Elders from the Aleutian and Pribilof Islands. This community-based participatory research study explores the aging experiences and conceptualization of successful aging of these Elders from this remote and culturally distinct region of Alaska. Thematic analysis was employed to identify themes related to successful aging within this specific region, which supported our previous four themes, or characteristics, of Alaska Native successful aging: physical health, social support and emotional well-being, generativity as a traditional way of life, and community engagement and Inidgenous cultural generativity. Each of these themes or characteristics of Eldership is intertwined and together support successful aging within two remote communities in the Bering Sea. The findings of this study illuminate how Alaska Native Elders can live in geographically diverse regions of the State, yet the values and teachings they possess on successful aging possess the same cultural values and teachings. This study highlighted two new emerging constructs that influence Alaska Native Elders' successful aging based on geographical location. Findings contribute to the thematic saturation of the four main successful aging domains while outlining the importance of future research to conduct deeper investigations into the role of environment and history on Elders' perceptions and understanding of aging.

Incomplete isolation in the nonbreeding areas of two genetically separated but sympatric short-tailed albatross populations

The short-tailed albatross Phoebastria albatrus, a globally Vulnerable species recovering from near-extinction, breeds mainly on 2 island groups in the north-western Pacific: Torishima and Senkaku Islands. Recently, it became clear that this is a species complex, composed of 2 populations (‘Torishima’ and ‘Senkaku’ types) that are distinct from both genetic and morphological perspectives, and which mate assortatively on Torishima. We tested the hypothesis of premating isolation as a possible mechanism for genetic differentiation and shifted breeding date in short-tailed albatrosses. Using light-based geolocation and molecular analysis, we examined whether adults from the 2 populations breeding on Torishima differed in their at-sea distribution during the nonbreeding period (June-September) and in their return dates. From 22 bird tracks collected from 12 birds over 4 yr, we identified 2 distinct nonbreeding areas: around the Aleutian Islands in the Bering Sea and near the Kuril Islands in the Okhotsk Sea. All 6 tracks of Torishima-type birds migrated directly to the Bering Sea in all years. In contrast, most of the Senkaku-type birds migrated along northeast Japan to the Okhotsk Sea (9 tracks), with the others moving to the Bering Sea (7 tracks). There was no clear difference in the dates of return to Torishima between the 2 bird types. Overall, no absolute pre-mating isolation in space or time was observed in short-tailed albatrosses, but we highlighted notable divergences in the nonbreeding distribution of both types. This result suggests that Torishima- and Senkaku-type populations should be treated as separate management units.

Analysis of Japanese Defeats at The Battle of Midway in 1942

Analysis of Japanese Defeats at The Battle of Midway in 1942