High-latitude Island Research Articles

Geolocation of a demersal fish (Pacific cod) in a high-latitude island chain (Aleutian Islands, Alaska)

BackgroundFish geolocation methods are most effective when they are customized to account for species behavior and study area characteristics. Here, we provide an example of customizing a hidden Markov model (HMM) for reconstructing movement pathways of a high-latitude demersal fish species in a remote island chain using Pop-up Satellite Archival Tag (PSAT) data. Adult Pacific cod were tagged with PSATs while occupying winter spawning grounds in the Aleutian Islands in February 2019. We adapted a demersal fish application of the HMM to (1) add light-based longitude to the data likelihood model, (2) account for possible off-bottom behavior of demersal fishes in the maximum daily depth likelihood, and (3) modify the model framework to accommodate convoluted island topography in the study area. A simulation study was conducted to explore the two primary modifications to the model framework, reflecting boundary for the movement kernel and the Viterbi method of pathway reconstruction, under known conditions.ResultsGeolocation was performed on satellite-transmitted and detailed archival data sets from 6 adult Pacific cod at liberty for 21–277 days. Migration from winter spawning to summer foraging areas (range 60–395 km) was detected for the 4 tagged fish that were at liberty for more than 90 days. Light-based longitude was the primary geolocation variable for detecting migrations with precision (root mean square error) estimates of 0.56 degrees during winter and 1.3 degrees during the summer. Simulation studies confirmed the effectiveness of model framework modifications and generated guidelines for use in specific applications.ConclusionsThis study demonstrates that post-spawning migrations of Pacific cod in the Aleutian Islands can be detected and characterized using PSAT data. Initial insights into migrations, summer foraging areas, and associated development of appropriate analysis tools will support future Pacific cod movement studies in the Aleutian Islands as well as other regions of Alaska. The adaptations to the HMM presented here will benefit current and future research on demersal fish in other regions as well as fish species that occupy areas with convoluted shorelines or island chain topography.

Improving the framework for assessment of ecological change in the Arctic: A circumpolar synthesis of freshwater biodiversity

Abstract Climate warming and subsequent landscape transformations result in rapid ecological change in Arctic freshwaters. Here we provide a synthesis of the diversity of benthic diatoms, plankton, macrophytes, macroinvertebrates, and fish in Arctic freshwaters. We developed a multi‐organism measure of α diversity to characterise circumpolar spatial patterns and their environmental correlates, and we assessed ecoregion‐level β diversity for all organism groups across the Arctic. Alpha diversity was lowest at high latitudes and elevations and where dispersal barriers exist. Diversity was positively related to temperature, and both temperature and connectivity limited diversity on high latitude islands. Beta diversity was highly variable among ecoregions for most organism groups, ranging from 0 (complete similarity) to 1 (complete dissimilarity). The high degree of dissimilarity within many ecoregions illustrates the uniqueness of many Arctic freshwater communities. Northward range expansion of freshwater taxa into Arctic regions may lead to increased competition for cold‐stenothermic and cold‐adapted species, and ultimately lead to the extinction of unique Arctic species. Societal responses to predicted impacts include: (1) actions to improve detection of changes (e.g., harmonised monitoring, remote sensing) and engagement with Arctic residents and Indigenous Peoples; and (2) actions to reduce the impact of unwanted changes (e.g., reductions of CO2 emissions, action against the spread of invasive species). Current Arctic freshwater monitoring shows large gaps in spatial coverage, while time series data are scarce. Arctic countries should develop an intensified, long‐term monitoring programme with routine reporting. Such an approach will allow detection of long‐term changes in water quality, biodiversity, and ecosystem services of Arctic freshwaters.

Phylogenomic Data Reveal Widespread Introgression Across the Range of an Alpine and Arctic Specialist.

Understanding how gene flow affects population divergence and speciation remains challenging. Differentiating one evolutionary process from another can be difficult because multiple processes can produce similar patterns, and more than one process can occur simultaneously. Although simple population models produce predictable results, how these processes balance in taxa with patchy distributions and complicated natural histories is less certain. These types of populations might be highly connected through migration (gene flow), but can experience stronger effects of genetic drift and inbreeding, or localized selection. Although different signals can be difficult to separate, the application of high-throughput sequence data can provide the resolution necessary to distinguish many of these processes. We present whole-genome sequence data for an avian species group with an alpine and arctic tundra distribution to examine the role that different population genetic processes have played in their evolutionary history. Rosy-finches inhabit high elevation mountaintop sky islands and high-latitude island and continental tundra. They exhibit extensive plumage variation coupled with low levels of genetic variation. Additionally, the number of species within the complex is debated, making them excellent for studying the forces involved in the process of diversification, as well as an important species group in which to investigate species boundaries. Total genomic variation suggests a broadly continuous pattern of allele frequency changes across the mainland taxa of this group in North America. However, phylogenomic analyses recover multiple distinct, well supported, groups that coincide with previously described morphological variation and current species-level taxonomy. Tests of introgression using D-statistics and approximate Bayesian computation reveal significant levels of introgression between multiple North American taxa. These results provide insight into the balance between divergent and homogenizing population genetic processes and highlight remaining challenges in interpreting conflict between different types of analytical approaches with whole-genome sequence data. [ABBA-BABA; approximate Bayesian computation; gene flow; phylogenomics; speciation; whole-genome sequencing.].

Factors correlating with serum birch pollen IgE status in pregnant women in Hokkaido, Japan: The Japan Environment and Children's Study (JECS)

BackgroundBirch pollen allergy affects pregnant women, and such allergy may affect the development of allergic diseases in their children. Using nationwide birth cohort data, this study aimed to investigate the prevalence of birch pollen IgE positivity and to identify correlating factors in pregnant women in Hokkaido, Japan, a high-latitude island. MethodsParticipants included 6856 pregnant women. Participants responded to questionnaires regarding lifestyle factors and history of allergies. Data regarding parity, height, and pre-pregnancy weight were collected from medical records. Blood samples were obtained from participants during the first trimester of pregnancy, and serum allergen-specific IgE titers were determined. ResultsThe serum of 30.2% participants was positive for birch pollen IgE (≥0.35 UA/mL). Such positivity significantly correlated with a history of other allergic diseases, particularly food allergy and allergic rhinitis/hay fever. In multivariate logistic regression analysis, pre-pregnancy high body mass index (BMI ≥ 25) significantly correlated with birch pollen IgE positivity [odds ratio (OR), 1.24; 95% CI, 1.05–1.47; reference BMI, 18.5–24.9] and higher income (≥10 million yen per year; OR,0.55; 95% CI, 0.37–0.81; reference, household income < 2 million yen per year), and second quintile level physical activity (OR,0.75; 95% CI, 0.63–0.88; reference, the first quintile of physical activity) had significant protective effects. ConclusionsBirch pollen IgE positivity in pregnant women was positively associated with food allergy, allergic rhinitis, pre-pregnant high BMI, and was negatively associated with light exercise and high household income in Hokkaido. Trial registrationUMIN000030786.

Functional and numerical responses of shrews to competition vary with mouse density.

For decades, ecologists have debated the importance of biotic interactions (e.g., competition) and abiotic factors in regulating populations. Competition can influence patterns of distribution, abundance, and resource use in many systems but remains difficult to measure. We quantified competition between two sympatric small mammals, Keen’s mice (Peromyscus keeni) and dusky shrews (Sorex monticolus), in four habitat types on Prince of Wales Island in Southeast Alaska. We related shrew density to that of mice using standardized regression models while accounting for habitat variables in each year from 2010–2012, during which mice populations peaked (2011) and then crashed (2012). Additionally, we measured dietary overlap and segregation using stable isotope analysis and kernel utilization densities and estimated the change in whole community energy consumption among years. We observed an increase in densities of dusky shrews after mice populations crashed in 2012 as expected under competitive release. In addition, competition coefficients revealed that the influence of Keen’s mice was dependent on their density. Also in 2012, shrew diets shifted, indicating that they were able to exploit resources previously used by mice. Nonetheless, increases in shrew numbers only partially compensated for the community energy consumption because, as insectivores, they are unlikely to utilize all food types consumed by their competitors. In pre-commercially thinned stands, which exhibit higher diversity of resources compared to other habitat types, shrew populations were less affected by changes in mice densities. These spatially and temporally variable interactions between unlikely competitors, observed in a relatively simple, high-latitude island ecosystem, highlight the difficulty in assessing the role of biotic factors in structuring communities.

Regional genetic differentiation among northern high-latitude island populations of a broadcast-spawning coral

Knowledge of genetic connectivity is useful for understanding of the recovery potential of coral populations after various disturbances, such as coral mass bleaching. Population genetic studies in corals are mostly restricted to Australian and Caribbean species; studies in the northern Pacific are relatively limited. Using microsatellite markers, the population genetics of Acropora sp. 1 was examined between two regions in Japan, the Okinawa-Aka and Bonin Islands, which are separated by approximately 1,500 km of open water in a high-latitude area. Statistically significant but small genetic differentiation in Acropora sp. 1 was detected between and within these regions. Genetic diversity was not obviously reduced in populations of the Bonin Islands, which are relatively isolated. Thus, some level of connectivity appears to be maintained between the two regions, likely because of the high dispersal ability of this broadcast spawner.

Diversification at high latitudes: speciation of buntings in the genusPlectrophenaxinferred from mitochondrial and nuclear markers

High-latitude diversification is a process characterized by speciation and extinction due to climatically driven vicariance and dispersal events. McKay's buntings (Plectrophenax hyperboreus) are high-latitude island endemic songbirds, and their global range is restricted to Beringia. Snow buntings (P. nivalis), their closest relatives, are distributed throughout the Holarctic, breeding in available habitat surrounding the island range of McKay's buntings. We sequenced 1123 base pairs of mitochondrial DNA for 40 individuals of each species and analysed a total of 913 AFLPs for 57 individuals. Both marker types suggested weak but significant genetic differentiation. Analysis of sequence data indicated divergence occurring when the current breeding range of McKay's buntings was a hill on the Beringian steppe (approximately 18,400 to approximately 73,700 years before present), suggesting that snow buntings were restricted to lower latitudes by ice sheets. Ancestral effective population size estimates indicate a founder event in McKay's buntings followed by an expansion and then a reduction in effective size. Rising sea levels and asymmetric hybridization from McKay's buntings into the postglacially-colonizing population of snow buntings could account for this reduction. Reproductive isolation is likely maintained through differential arrival dates on breeding grounds and the high breeding density of McKay's buntings. This recent, high-latitude divergence best fits a model of founder event speciation driven by vicariance and oscillations in habitat due to climate change.

Ancient DNA reveals late survival of mammoth and horse in interior Alaska.

Causes of late Quaternary extinctions of large mammals ("megafauna") continue to be debated, especially for continental losses, because spatial and temporal patterns of extinction are poorly known. Accurate latest appearance dates (LADs) for such taxa are critical for interpreting the process of extinction. The extinction of woolly mammoth and horse in northwestern North America is currently placed at 15,000-13,000 calendar years before present (yr BP), based on LADs from dating surveys of macrofossils (bones and teeth). Advantages of using macrofossils to estimate when a species became extinct are offset, however, by the improbability of finding and dating the remains of the last-surviving members of populations that were restricted in numbers or confined to refugia. Here we report an alternative approach to detect 'ghost ranges' of dwindling populations, based on recovery of ancient DNA from perennially frozen and securely dated sediments (sedaDNA). In such contexts, sedaDNA can reveal the molecular presence of species that appear absent in the macrofossil record. We show that woolly mammoth and horse persisted in interior Alaska until at least 10,500 yr BP, several thousands of years later than indicated from macrofossil surveys. These results contradict claims that Holocene survival of mammoths in Beringia was restricted to ecologically isolated high-latitude islands. More importantly, our finding that mammoth and horse overlapped with humans for several millennia in the region where people initially entered the Americas challenges theories that megafaunal extinction occurred within centuries of human arrival or were due to an extraterrestrial impact in the late Pleistocene.

Distribution of broad-Leaved evergreen plants on islands of Incheon, middle part of Yellow Sea

To elucidate the distribution of broad-leaved evergreen plants of the central part of the Yellow Sea, we surveyed 136 islands of Incheon from May 2006 to March 2008. In the present survey, twelve broad-leaved evergreen species were found on 77 islands, which included 28 inhabited and 49 uninhabited islands. Among them, the most popular plants were the following: Euonymus japonicus Thunb., Elaeagnus macrophylla Thunb., Camellia japonica L., and Cyrtomium falcatum (L.f.) C. Presl. These plants were found growing on Baengnyeong Island, the northmost island among those surveyed, near N 37˚ 60'. On the other hand the following four species are found up to Deokjeok-myeon only, near N 37˚ 10': Hedera rhombea (Miq.) Bean,, Quercus acuta Thunb. ex Murray for. acuta, Neolitsea sericea (Blume) Koidz., and Trachelospermum asiaticum (Siebold & Zucc.) Nakai. However, these plants are usually found growing in the southern or southwestern coastal region of the Korean Peninsula. Thus the distribution of the broad-leaved evergreen plants growing on these high latitude islands might be influenced by a warm current of the Yellow Sea. The distribution of broad-leaved evergreen plants on each island is described.

The significance of the giant clam Tridacna squamosa at Tubuai, Austral Islands, French Polynesia

Gilbert et al. (2007) report Tridacna squamosa at »20 m depth oV Tubuai (23°20 S, 145°20 W) an Indo-west PaciWc species previously unknown in French Polynesia. They go on to propose that the discovery corroborates a peripheral dispersal hypothesis of Randall (1995): e.g., some species colonized remote islands of the eastern Polynesia from the west via high latitude islands such as the Australs before they dispersed to the more central, tropical reaches. T. squamosa, however, had already been recorded as a questionable fossil from the Tuamotus, and as extant in easternmost Polynesia (Pitcairn 25°04 S 130°65 W; Paulay 1989), and Newman and Gomez 2003 had proposed a reliction hypothesis to account for the apparent longitudinal disjunction between the Marshall and/or Cook Islands to Pitcairn (»160°E to 130°W). Furthermore, they noted that similar disjunctions can be found in Veron (2000) for as many as 31 species of otherwise widely distributed zooxanthellate corals. The Tridacninae completely died out in the tropical Atlantic, evidently due to restriction of the tropics in general. Therefore, reliction to the Indo-west PaciWc was at the subfamilial level. Like Tridacna maxima, T. squamosa ranges throughout the tropics from East Africa to the Marshall and Cook Islands, but it has a greater depth range (0–25.5 m; Juinio et al 1989). Of the living species, only the SW PaciWc relic, Tridacna mbalavuana, is found at greater depths. Where found in eastern Polynesia, T. squamosa is also restricted to deep water, and this is interpreted as a sign of reliction rather than some ecological complication such as lack of appropriate habitat or dispersal limitations. Thus, a reliction rather than a peripheral dispersal hypothesis seems to apply. But whatever the case may be, why T. squamosa is so restricted would remain puzzling even if it turned out simply to be very patchy rather than completely absent from the central reaches of western French Polynesia.

THE BIRDS OF ST. MATTHEW ISLAND, BERING SEA

St. Matthew Island (60° 24′ N, 172° 42′ W) and its small nearby satellites, Hall Island and Pinnacle Rock, are isolated in the northcentral Bering Sea. This infrequently visited location occupies a geographic position with a deep Bering Land Bridge history and is in an area of interdigitation of the Old World, New World, and Beringian avifaunas. It is known for its three Beringian endemics, a bird (McKay’s Bunting, Plectrophenax hyperboreus), a small mammal, and a plant. This level of endemism is striking for a high-latitude island. The only previous summary of the avifauna of St. Matthew island (Hanna 1917) included 37 species. Our report considers more than 125 species and synthesizes data on presence and absence, abundance, and phenology. Because visits have been infrequent and concentrated during summer, our understanding of migration in this region remains poor, but the area is clearly affected by both the Old and New world migration systems. There is sufficient evidence to show that some profound changes among the island’s breeding birds have occurred during the past century. In particular, the breeding range of Glaucous-winged Gulls (Larus glaucescens) has been extended north to include St. Matthew, a change that is correlated with a northward shift in the extent of sea ice (Maslanik et al. 1996). King and Common eiders (Somateria spectabilis and S. mollissima) also have shown substantial changes in summer abundance. Other changes in the summer avifauna (e.g., among shorebirds) may reflect the dynamics of edge-of-range phenomena. Because of its central position in a region undergoing profound climate change and its demonstrated track record in showing avifaunal shifts, St. Matthew Island may represent an important bellwether for monitoring the biological effects of further climate change in the northern Bering Sea.