Fecal DNA analysis coupled with the sighting records re-expanded a known distribution of dugongs in Ryukyu Islands after half a century.

DNA analysis of large herbivore feces samples collected from seagrass beds at two distant sites (Irabu Island in Miyako Islands and Kushi in Okinawa Island) in the Ryukyu Islands proved that some of these feces were from dugongs, which had been treated in recent studies as extinct in this region since the last stranding of a deceased individual in 2019. In addition, local knowledge of sightings of animals thought to be dugongs and confirmed cases of dugong feeding trails since 2010 were compiled to estimate its recent distribution. This is the first scientific report on the presence of this mammal in the Ryukyu Islands within the last four years, and particularly in the Miyako Islands within the last half-century. As the Ryukyu Islands are known to be the northern limit of the dugong's fragmented distribution in East Asia, conservation efforts are therefore needed.

Subsurface temperature estimates from a Regional Ocean Modelling System (ROMS) reanalysis provide accurate coral heat stress indices across the Main Hawaiian Islands.

As ocean temperatures continue to rise, coral bleaching events around the globe are becoming stronger and more frequent. High-resolution temperature data is therefore critical for monitoring reef conditions to identify indicators of heat stress. Satellite and in situ measurements have historically been relied upon to study the thermal tolerances of coral reefs, but these data are quite limited in their spatial and temporal coverage. Ocean circulation models could provide an alternative or complement to these limited data, but a thorough evaluation against in situ measurements has yet to be conducted in any Pacific Islands region. Here we compared subsurface temperature measurements around the nearshore Main Hawaiian Islands (MHI) from 2010 to 2017 with temperature predictions from an operational Regional Ocean Modeling System (ROMS) to evaluate the potential utility of this model as a tool for coral reef management. We found that overall, the ROMS reanalysis presents accurate subsurface temperature predictions across the nearshore MHI region and captures a significant amount of observed temperature variability. The model recreates several temperature metrics used to identify coral heat stress, including predicting the 2014 and 2015 bleaching events around Hawai'i during the summer and fall months of those years. The MHI ROMS simulation proves to be a useful tool for coral reef management in the absence of, or to supplement, subsurface and satellite measurements across Hawai'i and likely for other Pacific Island regions.

Land-use change interacts with island biogeography to alter bird community assembly.

Anthropogenic activities have reshaped biodiversity on islands worldwide. However, it remains unclear how island attributes and land-use change interactively shape multiple facets of island biodiversity through community assembly processes. To answer this, we conducted bird surveys in various land-use types (mainly forest and farmland) using transects on 34 oceanic land-bridge islands in the largest archipelago of China. We found that bird species richness increased with island area and decreased with isolation, regardless of the intensity of land-use change. However, forest-dominated habitats exhibited lower richness than farmland-dominated habitats. Island bird assemblages generally comprised species that share more similar traits or evolutionary histories (i.e. functional and/or phylogenetic clustering) than expected if assemblages were randomly assembled. Contrary to our expectations, we observed that bird assemblages in forest-dominated habitats were more clustered on large and close islands, whereas assemblages in farmland-dominated habitats were more clustered on small islands. These contrasting results indicate that land-use change interacts with island biogeography to alter the community assembly of birds on inhabited islands. Our findings emphasize the importance of incorporating human-modified habitats when examining the community assembly of island biota, and further suggest that agricultural landscapes on large islands may play essential roles in protecting countryside island biodiversity.

Mutualisms weaken the latitudinal diversity gradient among oceanic islands.

The latitudinal diversity gradient (LDG) dominates global patterns of diversity1,2, but the factors that underlie the LDG remain elusive. Here we use a unique global dataset3 to show that vascular plants on oceanic islands exhibit a weakened LDG and explore potential mechanisms for this effect. Our results show that traditional physical drivers of island biogeography4-namely area and isolation-contribute to the difference between island and mainland diversity at a given latitude (that is, the island species deficit), as smaller and more distant islands experience reduced colonization. However, plant species with mutualists are underrepresented on islands, and we find that this plant mutualism filter explains more variation in the island species deficit than abiotic factors. In particular, plant species that require animal pollinators or microbial mutualists such as arbuscular mycorrhizal fungi contribute disproportionately to the island species deficit near the Equator, with contributions decreasing with distance from the Equator. Plant mutualist filters on species richness are particularly strong at low absolute latitudes where mainland richness is highest, weakening the LDG of oceanic islands. These results provide empirical evidence that mutualisms, habitat heterogeneity and dispersal are key to the maintenance of high tropical plant diversity and mediate the biogeographic patterns of plant diversity on Earth.

Digest: A model for speciation in island systems.

Ecological pulses, marked by rapid environmental shifts, shape species dynamics such as speciation. Princepe et al. 2024 explore how intermittent migration, seabed depth, and sea-level changes influence species richness in islands. Their model, revealing nuanced richness patterns and migration impacts, contributes to understanding island evolution and offers insights into real-world cases. Examining the Philippines Archipelago, known for rich biodiversity, parallels emerge, showcasing the complex interplay of isolation, land bridges, and sea-level shifts in shaping genetic diversity. Overall, the findings enhance our understanding of population evolution in dynamic island environments.

[In Makemo, a nurse in a remote island setting]. / À Makemo, une infirmière en milieu insulaire isolé.

A nurse graduating in 2018, Noémie's guiding principle has always been her desire to discover IDE practice outside our borders. To this end, once she had her diploma in hand, and in parallel with her nursing practice in her native Isère region, she enriched her knowledge by taking a university diploma (DU) in "international solidarity action in humanitarian health". When she obtained her diploma, she decided to settle in French Polynesia, a French territory at the end of the world. Here, she shares her experiences as a nurse in an isolated island environment, highlighting the added value of this experience.

Population genomic and biophysical modeling show different patterns of population connectivity in the spiny lobster Jasus frontalis inhabiting oceanic islands.

Knowledge about connectivity between populations is essential for the fisheries management of commercial species. The lobster Jasus frontalis inhabits two oceanic island groups, the Juan Fernández Archipelago and the Desventuradas Islands, separated by 800 km. Since this species is primarily exploited in the Juan Fernández Archipelago, knowledge of the connectivity patterns among islands is foundational for species management. Here, we used variability at single-nucleotide polymorphisms (SNPs) and individual-based modeling (IBM) to estimate the genetic structure and connectivity between J. frontalis populations in these island groups. The variability at 9090 SNPs suggests two genetic populations, one in the Juan Fernández Archipelago and one in the Desventuradas Islands. Furthermore, IBM suggests an asymmetric connectivity pattern, with particles moving from the Juan Fernández Archipelago to the Desventuradas Islands but not vice versa. Since the IBM analysis suggests asymmetric larval movement between the islands, and the genetic analysis indicates isolation between the Juan Fernández Archipelago and the Desventuradas Islands, larval retention mechanisms such as small-scale oceanographic processes or behavior could hinder larval movement between islands. This study highlights the importance of using more than one methodology to estimate population connectivity.

Risk classification of low-lying coral reef islands and their exposure to climate threats.

The bio-physical responses of low-lying coral islands to climate change are of concern. These islands exist across a broad range of bio-physical conditions, and vulnerabilities to rising and warming seas, ocean acidification and increased storminess. We propose a risk-based classification that scores 6 island eco-morphometric attributes and 6 bio-physical ocean/climate conditions from recent open-access data, to assign islands with respect to 5 risk classes (Very Low, Low, Moderate, High and Very High). The potential responses of 56 coral islands in Australia's jurisdiction (Coral Sea, NW Shelf and NE Indian Ocean) to climate change is considered with respect to their bio-physical attributes and eco-morphometrics. None of the islands were classed as Very Low risk, while 8 were classed as Low (14.3 %), 34 were Moderate (60.7 %), 11 were High (19.6 %), and 3 were Very High (5.4 %). Islands in the Very High risk class (located on the NW Shelf) are most vulnerable due to their small size (mean 10 Ha), low elevation (mean 2.6 m MSL), angular/elongated shape, unvegetated state, below average pH (mean 8.05), above average rates of sea-level rise (SLR; mean 4.6 mm/yr), isolation from other islands, and frequent tropical storms and marine heatwaves. In contrast, islands in the Low (and Very Low) risk class are less vulnerable due to their large size (mean 127 Ha), high elevation (mean 8.5 m MSL), sub-angular/round shape, vegetated state, near average pH (mean 8.06), near average SLR rates (mean 3.9 mm/yr), proximity to adjacent islands, and infrequent cyclones and marine heatwaves. Our method provides a risk matrix to assess coral island vulnerability to current climate change related risks and supports future research on the impacts of projected climate change scenarios. Findings have implications for communities living on coral islands, associated ecosystem services and coastal States that base their legal maritime zones on these islands.

Generalist and topologically central avian frugivores promote plant invasion unequally across land-bridge islands.

Seed dispersal by frugivorous birds facilitates plant invasions, but it is poorly known how invasive plants integrate into native communities in fragmented landscapes. We surveyed plant-frugivore interactions, including an invasive plant (Phytolacca americana), on 22 artificial land-bridge islands (fragmented forests) in the Thousand Island Lake, China. Focusing on frugivory interactions that may lead to seed dispersal, we built ecological networks of studied islands both at the local island (community) and at landscape (metacommunity) levels. On islands with P. americana, we found that P. americana impacted local avian frugivory networks more on islands with species-poor plant communities and on isolated islands. Moreover, as P. americana interacted mainly with local core birds (generalists), this indicates reduced seed dispersal of native plants on invaded islands. At the landscape level, P. americana had established strong interactions with generalist birds that largely maintain seed-dispersal functions across islands, as revealed by their topologically central roles both in the regional plant-bird trophic network and in the spatial metanetwork. This indicates that generalist frugivorous birds may have facilitated the dispersal of P. americana across islands, making P. americana well integrated into the plant-frugivore mutualistic metacommunity. Taken together, our study demonstrates that the impact of plant invasion is context-dependent and that generalist native frugivores with high dispersal potential may accelerate plant invasion in fragmented landscapes. These findings highlight the importance of taking the functional roles of animal mutualists and habitat fragmentation into account when managing plant invasions and their impact on native communities.

Digest: Islands promote population differentiation in dispersive swallows.

How can highly dispersive species give rise to genetically distinct populations? This seemingly paradoxical pattern is common among insular birds, but not in those with continental distributions. Broyles and Myers sequence the genomes of almost 150 individuals from the island-dwelling Pacific swallow (Hirundo tahitica) and its continental counterpart, the welcome swallow (H. neoxena). They find strong population structure only among island populations and attribute this to a behavioral reduction in dispersal propensity following island colonization. However, wing shape remains consistent across populations, suggesting it might not accurately reflect dispersal propensity in this group. This study illustrates the interplay between dispersal, isolation, and divergence, offering insights into how geographic factors affect speciation and population differentiation on islands.

Skeletal Mg content in common echinoderm species from Deception and Livingston Islands (South Shetland Islands, Antarctica) in the context of global change.

Echinoderms with high levels of magnesium (Mg) in their skeletons may be especially sensitive to ocean acidification, as the solubility of calcite increases with its Mg content. However, other structural characteristics and environmental/biological factors may affect skeletal solubility. To better understand which factors can influence skeletal mineralogy, we analyzed the Mg content of Antarctic echinoderms from Deception Island, an active volcano with reduced pH and relatively warm water temperatures, and Livingston Island. We found significant interclass and inter- and intraspecific differences in the Mg content, with asteroids exhibiting the highest levels, followed by ophiuroids and echinoids. Specimens exposed to hydrothermal fluids showed lower Mg levels, which may indicate local environmental effects. These patterns suggest that environmental factors such as seawater Mg2+/Ca2+ ratio and temperature may influence the Mg content of some echinoderms and affect their susceptibility to future environmental changes.

Adaptive and non-adaptive convergent evolution in feather reflectance of California Channel Islands songbirds.

Convergent evolution is widely regarded as a signature of adaptation. However, testing the adaptive consequences of convergent phenotypes is challenging, making it difficult to exclude non-adaptive explanations for convergence. Here, we combined feather reflectance spectra and phenotypic trajectory analyses with visual and thermoregulatory modelling to test the adaptive significance of dark plumage in songbirds of the California Channel Islands. By evolving dark dorsal plumage, island birds are generally less conspicuous to visual-hunting raptors in the island environment than mainland birds. Dark dorsal plumage also reduces the energetic demands associated with maintaining homeothermy in the cool island climate. We also found an unexpected pattern of convergence, wherein the most divergent island populations evolved greater reflectance of near-infrared radiation. However, our heat flux models indicate that elevated near-infrared reflectance is not adaptive. Analysis of feather microstructure suggests that mainland-island differences are related to coloration of feather barbs and barbules rather than their structure. Our results indicate that adaptive and non-adaptive mechanisms interact to drive plumage evolution in this system. This study sheds light on the mechanisms driving the association between dark colour and wet, cold environments across the tree of life, especially in island birds.

Strong attachment as an adaptation of flightless weevils on windy oceanic islands.

Enhanced attachment ability is common in plants on islands to avoid potential fatal passive dispersal. However, whether island insects also have increased attachment ability remains unclear. Here we measured the attachment of a flightless weevil, Pachyrhynchus sarcitis kotoensis, from tropical islands, and compared it with documented arthropods from the mainland. We examined the morphology and material gradient of its attachment devices to identify the specific adaptive modifications for attachment. We find that the weevil has much stronger attachment force and higher safety factor than previously studied arthropods, regardless of body size and substrate roughness. This probably results from the specific flexible bases of the adhesive setae on the third footpad of the legs. This softer material on the setal base has not been reported hitherto and we suggest that it acts as a flexible hinge to form intimate contact to substrate more effectively. By contrast, no morphological difference in tarsomeres and setae between the weevil and other beetles is observed. Our results show the remarkably strong attachment of an island insect and highlights the potential adaptive benefits of strong attachment in windy island environment. The unique soft bases of the adhesive hairs may inspire the development of strong biomimetic adhesives.

Floating marine debris influx in the intertidal zone of offshore islands in Bangladesh: A case study of Manpura Island.

Marine Debris is all-pervading in the world's oceans. In this research, for the first time, Floating Marine Debris (FMD) accumulation in the intertidal zone of Manprua island, an offshore island of Bangladesh, is reported. The assessment has been done by integrating both physical investigations and questionnaire survey. The Study shows high debris density on the windward and river-facing sides of the island. The density of debris items in this area varies from 550,000 to 60,000 items per km2 (8.5 to 0.08 g/m2) for transect samples during low tide and 350,000 to 60,000 items per km2 (5.76 to 1.20 g/m2) for net samples during high tide. However, the most damaging debris items are uprooted trees and water hyacinths because they hinder fishing activities. This study provides baseline information on FMD in the Meghna Estuary, which can be used as a reference for sustainable monitoring and management of marine pollution.

Genetic continuity and change among the Indigenous peoples of California.

Before the colonial period, California harboured more language variation than all of Europe, and linguistic and archaeological analyses have led to many hypotheses to explain this diversity1. We report genome-wide data from 79 ancient individuals from California and 40 ancient individuals from Northern Mexico dating to 7,400-200 years before present (BP). Our analyses document long-term genetic continuity between people living on the Northern Channel Islands of California and the adjacent Santa Barbara mainland coast from 7,400 years BP to modern Chumash groups represented by individuals who lived around 200 years BP. The distinctive genetic lineages that characterize present-day and ancient people from Northwest Mexico increased in frequency in Southern and Central California by 5,200 years BP, providing evidence for northward migrations that are candidates for spreading Uto-Aztecan languages before the dispersal of maize agriculture from Mexico2-4. Individuals from Baja California share more alleles with the earliest individual from Central California in the dataset than with later individuals from Central California, potentially reflecting an earlier linguistic substrate, whose impact on local ancestry was diluted by later migrations from inland regions1,5. After 1,600 years BP, ancient individuals from the Channel Islands lived in communities with effective sizes similar to those in pre-agricultural Caribbean and Patagonia, and smaller than those on the California mainland and in sampled regions of Mexico.

Large floating abandoned, lost or discarded fishing gear (ALDFG) is frequent marine pollution in the Hawaiian Islands and Palmyra Atoll.

Abandoned, lost, or discarded fishing gear (ALDFG) is a major source of marine debris with significant ecological and economic consequences. We documented the frequency, types, sizes, and impacts of ALDFG recovered from Hawai'i and Palmyra Atoll in the Central North Pacific Ocean (CNPO) from 2009 to 2021. A total of 253 events weighing 15 metric tons were recovered, including 120 drifting fish aggregating device (dFAD) components, 61 conglomerates, fewer distinct nets, lines, buoys, and unique gear. The Hawaiian Islands were dominated by conglomerates and Palmyra Atoll by dFADs. DFADs were connected to the Eastern Pacific tropical tuna purse seine fishery. Windward O'ahu experienced up to seven events or 1800 kg of ALDFG per month. Across Hawai', ALDFG was present on 55 % of survey days, including hotspots with 100 % occurrence. Coral reef damage, entangled wildlife, navigational and removal costs are reported. The data highlight the large magnitude of ALDFG and associated impacts in the CNPO.

Quantification and distribution of marine microdebris in the surface waters of Livingston Island (South Shetland Islands, Antarctica).

Microdebris are ubiquitous and the Southern Ocean is no exception. Despite the recent increment in Antarctic studies assessing this threat, there is still scarce information available. Here, we quantified the microdebris in surface water, and their distribution within two bays of Livingston Island (South Shetlands, Antarctica). The two studied bays included one with human presence and one pristine, barely visited. Microdebris pollution was found in all samples with a mean concentration of 0.264 ± 0.185 items/m3. Fibres (82.19 %) were the main item, with polyester (61.67 %) as the main plastic polymer, followed by nylon (29.54 %). No differences in the distribution pattern were observed, with microdebris being homogeneously distributed along the two bays. Our results suggest that nearshore waters of Livingston Island are prone to the accumulation and retention of microdebris. The composition of the microdebris also points to Antarctic local activities as principal contamination contributors.

Social vulnerability, impacts and adaptations strategies in the face of natural hazards: insight from riverine islands of Bangladesh.

BACKGROUND: Bangladesh is one of the countries at risk of natural disasters due to climate change. In particular, inhabitants of its riverine islands (char) confront ongoing climatic events that heighten their vulnerability. This study aims to assess social vulnerability, impacts, and adaptation strategies to climate change in the riverine island areas of Bangladesh. METHODS: A mixed-method approach incorporating qualitative and quantitative procedures was used on data collected from 180 households of riverine islands in Gaibandha, Bangladesh. The social vulnerability of riverine island communities was assessed based on their adaptation capacity, sensitivity, and exposure to climatic stressors. RESULTS: The findings show that char dwellers' vulnerability, impacts, and adaptation capability to climate change vary significantly depending on their proximity to the mainland. Social vulnerability factors such as geographical location, fragile and low-grade housing conditions, illiteracy and displacement, climate-sensitive occupation and low-income level, and so on caused to the in-height vulnerability level of these particular areas. This study also displays that climate change and its associated hazards cause severe life and livelihood concerns for almost all households. In this case, the riverine dwellers employed several adaptation strategies to enhance their way of life to the disaster brought on changing climate. However, low education facilities, deficiency of useful information on climate change, poor infrastructure, and shortage of money are still the supreme hindrance to the sustainability of adaptation. CONCLUSION: The findings underscore the importance of evaluating the susceptibility of local areas to climate change and emphasize the need for tailored local initiatives and policies to reduce vulnerability and enhance adaptability in communities residing in char households.

Sub-tropical benthic/epiphytic dinoflagellates of Aotearoa New Zealand and Rangitahua Kermadec Islands.

Temperatures and temperature anomalies have been increasing in the sub-tropical regions of Aotearoa New Zealand and these changes may impact on harmful algal bloom (HAB) events. Benthic and epiphytic dinoflagellates, particularly the toxin producers, are the focus of this study as it is predicted that under future climate conditions they may produce more toxins or marine animals may become more susceptible to them. The results of past expeditions to Rangitahua Kermadec Islands and sampling trips to Northland, Aotearoa New Zealand, are summarised and the results of the most recent trips to both regions are presented. The macroalgal habitats of the dinoflagellates are also characterised. Dinoflagellate species not previously identified in Rangitahua include Coolia canariensis, C. palmyrensis, and C. tropicalis, all identified by DNA sequencing of the large subunit ribosomal RNA region. Gambierdiscus polynesiensis was again isolated and produced 44-methylgambierone and gambierone, and one isolate produced ciguatoxins, the cause of Ciguatera Poisoning. An Ostreopsis tairoto isolate, as analysed by the oxidative cleavage method, produced a palytoxin (PLTX)-like amine oxidation fragment, but when analysed for PLTX-like analogues using a new intact method none were detected indicating an 'unknown' PLTX-like compound is produced by this isolate. Isolates of O. cf. siamensis (Ostreopsis sp. 9), collected in Northland, were also analysed using the oxidative cleavage method, with the common PLTX-like amine fragment and the amide fragment corresponding to bishomoPLTX detected in all isolates. Again, the intact method indicated no detections in the isolates, again suggesting an unknown compound was being produced by these isolates. Prorocentrum hoffmannianum isolates produced okadaic acid (OA) and isoDTX-1 and P. lima isolates produced OA, DTX-1, and isoDTX-1. It is expected that new species of potentially harmful, benthic dinoflagellates will continue to be recorded in Aotearoa New Zealand and the results from Rangitahua provide a guide to the HAB species to expect in sub-tropical Northland as the oceans continue to warm.