Island Ecosystems Research Articles

Climatic drought and trophic disruption in an endemic subalpine Hawaiian forest bird

Overexploitation, habitat conversion, and introduced species have caused unprecedented extinctions and heavily degraded native bird populations in island ecosystems. In the Hawaiian Islands, stemming these losses has proven difficult as the highly specialized avifauna are often impacted – among other things – by poorly understood trophic disruptions as well as persistent climatic shifts. Here we investigate these dynamics by examining the trophic positions of 7 different taxa of producers and consumers across the last century in the subalpine māmane (Sophora chrysophylla) forest ecosystem on the island of Hawaiʻi. From museum collections and contemporary sampling, we analyzed the stable nitrogen (δ15N) values of producers and consumers to identify trophic and source amino acids and derive trophic enrichment constants specific to this food web. This enables us to reconstruct the diet of the palila (Loxioides bailleui), a critically endangered finch whose population recently declined 90 %. Our results show that from 1890 to 2006, the palila trophic position declined from 2.6 to 2.2, with cascading implications for its diet. Bayesian mixing model reconstructions indicate that palila trophic position changes likely arose from a 76 % decline (69.3 % to 16.6 % of diet) in the consumption of native moth caterpillars, and a 172 % increase (30.7 % to 83.4 %) in native plants. From the available ecosystem variables, exploratory Bayesian multiple regressions selected surface temperature changes, and the interactions of surface temperatures with drought and caterpillar parasitism as the primary drivers of these trophic changes. Despite the predicted increases of warming and drought, management interventions may build resiliency in this unique island ecosystem.

Methods to compare sites concerning a category’s change during various time intervals

ABSTRACT This paper presents new methods to analyze a category’s change through a time series of maps, even when the time intervals have inconsistent durations. The methods include an option to facilitate comparison among sites by expressing results as an annual percentage of each site’s unified size. A site’s unified size is the union of where the category exists at any of the site’s time points. The methods also specify gross losses, gross gains, eight trajectories, and three components: Quantity, Exchange, and Alternation. The illustrative application compares maps of the marsh category for three Long-Term Ecological Research sites: Plum Island Ecosystems (PIE), Georgia Coastal Ecosystems (GCE), and the Virginia Coast Reserve (VCR). The application analyzes marsh’s changes during two time intervals that have unequal durations within each site’s distinct temporal extent. Results show that PIE has the fastest change during each site’s temporal extent. Gross change is more than double the quantity change for all sites. Exchange accounts for most of the change in GCE, while Alternation accounts for most of the change in PIE and VCR. The methods provide more information than popular methods that quantify annual net change. Our timeseriesTrajectories R package performs the analysis and is available for free at https://github.com/bilintoh/timeseriesTrajectories.

Remote sensing-based decadal landform monitoring in island ecosystem

Remote sensing-based decadal landform monitoring in island ecosystem

Review of Waste Management in Indonesian Small Islands in the Last Five Years (2018-2023)

Indonesia is a maritime country composed of 16,771 islands consisting of large islands and small islands. One of the environmental problems that occur in small islands. Waste management is a shared focus because sources of water, soil and air pollution can come from waste. Waste management on small islands is very important because small islands have a much higher vulnerability than large islands.. This article aims to identify and analyze waste management in Indonesia's Small Islands and evaluate if its implementation has utilized the technology and concepts of the Industrial Revolution 4.0. Based on the findings of a review of 14 articles published from 2018-2023, with 15 islands as research objects, it was found that most of the small islands used as research objects had not managed their waste properly. The waste is eventually dumped into the sea. The unmanaged factor of this waste can be caused by the geographical conditions on the island which are bordered by the sea, the lack of waste management facilities, the limited land area on small islands and the low awareness and participation of the community in waste management. The rest, several islands have carried out the process of storage, processing, collection and destruction quite well. The waste is turned into handicrafts (bags and souvenirs), ecobricks, garden decorations and plant fertilizers for organic waste as well as the development of innovative waste into diesel fuel. Unfortunately, the intended application based on the Industrial Revolution 4.0 has not been reflected in waste management on these small islands. This is expected to be information and input for the government and managers as a model for other small islands in an effort to manage waste generation on the island's mainland and garbage contamination in the sea.

Effect of Organic Substrates on Macro-propagation of Banana under Island Conditions

Banana is an important tropical fruit crop grown globally and is the world’s most important agricultural food commodity. Plantation crops take a major share of cultivated area in Andaman and Nicobar Islands. Banana is one of the important fruit crops that is highly suitable to grow as intercrop in plantation based cropping system. Local varieties of banana like Korangi, Mitta Champa, Khatta Champa and Cheenakela are cultivated by the farmers traditionally to meet the local demand. However, in recent past growing commercial varieties of banana has become popular in the Island due to consumer demand. Traditionally banana is propagated by suckers and wide variability was observed in sucker production among the commercial varieties. Due to this large scale multiplication of banana through suckers could not meet the planting material demand in the Island. Hence, a study was undertaken during 2020-2022 to standardize the macro-propagation technology using different organic substrates in the commercial variety ‘Poovan’. Nine different organic substrate combinations were used in the present study to enhance the efficacy of lateral bud development and plantlet production. Suckers weighing 1.0 to 1.5 kg were used as the propagule. Among all the organic media combinations tested, significant differences were observed in terms of plantlet production, root and shoot growth. The treatment T8 (Coircompost: sawdust: FYM: vermicompost (1:1:1:1) with Arka microbial consortia @10 kg) produced maximum number of primary (5.60) and secondary buds (12.07) during primary and secondary capitation of decorticated mother rhizome. Early bud emergence (11.5 days), maximum number of plantlets (12-13 per mother rhizome), maximum shoot length (46.43 cm), maximum shoot girth (3.03 cm) and maximum number of leaves (4.50) were also observed in the treatment T 8. Minimum number of days was taken (52.70 days) for plantlet separation during secondary capitation in the same treatment T 8 suggesting that the treatment combination (Coircompost: sawdust: FYM: vermicompost (1:1:1:1) with Arka microbial consortia @10 kg) was effective for macro-propagation of banana Cv. Poovan under Island ecosystem.

Population Genomics of Adaptive Radiations: Exceptionally High Levels of Genetic Diversity and Recombination in an Endemic Spider From the Canary Islands.

The spider genus Dysdera has undergone a remarkable diversification in the oceanic archipelago of the Canary Islands, with ~60 endemic species having originated during the 20 million years since the origin of the archipelago. This evolutionary radiation has been accompanied by substantial dietary shifts, often characterised by phenotypic modifications encompassing morphological, metabolic and behavioural changes. Hence, these endemic spiders represent an excellent model for understanding the evolutionary drivers and to pinpoint the genomic determinants underlying adaptive radiations. Recently, we achieved the first chromosome-level genome assembly of one of the endemic species, D. silvatica, providing a high-quality reference sequence for evolutionary genomics studies. Here, we conducted a low coverage-based resequencing study of a natural population of D. silvatica from La Gomera island. Taking advantage of the new high-quality genome, we characterised genome-wide levels of nucleotide polymorphism, divergence and linkage disequilibrium, and inferred the demographic history of this population. We also performed comprehensive genome-wide scans for recent positive selection. Our findings uncovered exceptionally high levels of nucleotide diversity and recombination in this geographically restricted endemic species, indicative of large historical effective population sizes. We also identified several candidate genomic regions that are potentially under positive selection, highlighting relevant biological processes, such as vision and nitrogen extraction as potential adaptation targets. These processes may ultimately drive species diversification in this genus. This pioneering study of spiders that are endemic to an oceanic archipelago lays the groundwork for broader population genomics analyses aimed at understanding the genetic mechanisms driving adaptive radiation in island ecosystems.

From planning to implementation: a multi-stakeholder partnership for managing plant invasions in tropical island ecosystems

From planning to implementation: a multi-stakeholder partnership for managing plant invasions in tropical island ecosystems

Lucayan charred wood selection patterns: a comparative study of variability in fragile island ecosystems of the central and northern Bahamas

Lucayan charred wood selection patterns: a comparative study of variability in fragile island ecosystems of the central and northern Bahamas

Molecular screening of selected vector-borne pathogens circulating in owned dogs in the Caribbean archipelago of Guadeloupe (France)

Vector-borne diseases represent a major health challenge, both because of the complexity of their control, their common zoonotic nature, or the pathology they can cause in the individual. In tropical areas, surveillance of these diseases is even more important, since the activity of vectors is usually continuous throughout the year. To develop effective prophylaxis and surveillance programs, it is important to know the identity and prevalence of these pathogens as well as their distribution in a given territory. In Guadeloupe, a French archipelago located in the Lesser Antilles of the Caribbean, no information exists about vector-borne diseases in companion animals. With this aim, blood samples were obtained from 46 owned dogs with outdoor access from five different veterinary clinics located in the two mainland islands, and the presence of DNA of the main canine vector-borne pathogens (CVBP) was investigated through diverse PCR protocols. At least one pathogen was detected in 30.4 % of the dogs. The most frequently detected CVBP was Coxiella burnetii (17.4 %), followed by Dirofilaria immitis (8.7 %), and Candidatus Mycoplasma haematoparvum, Hepatozoon canis and Rickettsia spp. (2.2 % in all cases). One dog was coinfected with Candidatus M. haematoparvum and D. immitis. All samples were negative for Anaplasma spp., Ehrlichia spp., Bartonella spp., Borrelia burgdorferi sensu lato, piroplasmids, and Leishmania spp. No significant differences in pathogen occurrence were observed between the two main islands or according to the dog's sex and age groups. This study contributes to filling a relevant gap in the knowledge of vector-borne diseases in the Caribbean.

Co-introduction into a delicate island ecosystem: metastrongyloid nematodes (superfamily Metastrongyloidea) of veterinary and medical importance circulating in aquatic and terrestrial environments of Tenerife (Canary Islands).

Metastrongyloid nematodes typically reside as adults in the cardiopulmonary systems of their mammalian definitive hosts, potentially causing severe diseases. Of particular concern are Angiostrongylus cantonensis and A. costaricensis, which can cause eosinophilic meningitis and abdominal angiostrongyliasis, respectively, in their accidental human hosts. Several metastrongyloid species of medical and veterinary importance have been documented in the Canary Islands. However, the gastropod species acting as intermediate hosts for some of these nematodes in the archipelago remained unknown. This study aimed to investigate the occurrence of metastrongyloid nematodes in terrestrial and aquatic gastropods, including both endemic and non-native species, on Tenerife. Foot samples from terrestrial and aquatic gastropods were analyzed using a multiplex PCR targeting the Internal Transcribed Spacer 1 (ITS1), allowing the specific detection of A. cantonensis, A. vasorum, Aelurostrongylus abstrusus, Crenosoma striatum, Troglostrongylus brevior, and Crenosoma vulpis. Five metastrongyloid species, namely C. striatum, A. cantonensis, Ae. abstrusus, A. vasorum, and an unidentified metastrongyloid, were identified within both non-native and endemic terrestrial gastropods. In the aquatic snail Physella acuta, only A. cantonensis and C. striatum were detected. This study confirms the introduction of various metastrongyloids associated with non-native mammalian fauna and provides new data on the occurrence of these nematodes in non-native and endemic gastropod species, including their presence in aquatic environments on the Canary Islands.

Differential exposure to second-generation anticoagulant rodenticides in raptors from continental and insular regions of the Iberian Peninsula

The global impact of anticoagulant rodenticides (ARs) on non-target species is well-recognized. Birds of prey, as apex predators, are highly vulnerable to AR exposure and are widely used as biomonitors for priority pollutants in Europe. This study investigates differential SGAR exposure in raptors from insular versus continental regions, hypothesizing greater exposure in insular areas due to ecological factors like reduced prey diversity, intensive rodenticide use, and resistant rodent populations. We analyzed the livers of 190 common kestrels (Falco tinnunculus) and 104 common buzzards (Buteo buteo) across the Iberian Peninsula and its archipelagos using LC-MS/MS to assess their role as AR sentinels and the differences between insular and continental areas. Results revealed a high prevalence (>80%) of second-generation anticoagulant rodenticides (SGARs), with brodifacoum and bromadiolone, being the most frequent. Multiple SGAR detections were also common (≈50%). A binomial logistic regression showed that species and region significantly influence the likelihood of SGAR exposure. Kestrels had a greater probability of exceeding 100 ng/g wet weight (ww) compared to buzzards. Raptors from insular territories were ten times more likely to have higher SGAR concentrations than those from continental areas. However, the legal restriction on SGAR bait concentrations that came into effect in 2018 did not significantly impact exposure levels. This study highlights the need for targeted conservation efforts to mitigate AR exposure risk in vulnerable island ecosystems.

The Protection and Management of Wapiti in Desert Oases: Bare Land Poses a Limitation to Wapiti Conservation.

The Helan Mountains, situated in the heart of the desert, act as a dividing line between China's arid and semi-arid zones. Often referred to as a "desert oasis", they create an ecological island with a uniquely distinctive geographical location, making this area a focal point of contemporary research. Ungulates play a critical role in this ecosystem. The Alashan wapiti (Cervus canadensis alashanicus), an isolated population of China's smallest wapiti (Cervus canadensis) subspecies, is found exclusively within the Helan Mountains Nature Reserve. The conservation of this isolated population is fraught with challenges, particularly during winter, the harshest season for northern ungulates. Winter habitats are crucial for ensuring population stability. Therefore, we used certain methods, such as factor screening and model parameter optimization to assess habitat suitability using multi-scale species distribution models. The optimized results show that suitable habitats overlap with areas of high vegetation coverage in the Helan Mountains, covering just 588.32 km2, which is less than a quarter of the reserve's total area. The bare land area and winter NDVI are the two primary factors influencing habitat suitability, with other factors having minimal impact, underscoring the critical importance of food resources for the Alashan wapiti. The limited availability of these resources poses significant conservation challenges. Our findings provide a more precise foundation for targeted habitat protection and restoration efforts. We recommend enhancing the protection and restoration of food resources, effectively conserving vegetated areas, and preventing desertification.

Landscape, Human Disturbance, and Climate Factors Drive the Species Richness of Alien Invasive Plants on Subtropical Islands.

Invasive alien plants (IAPs) pose a significant threat to island biodiversity and severely impact ecosystems. Understanding the species-area relationship and environmental determinants of growth forms for IAP species on subtropical islands is crucial for establishing an IAP's early warning mechanism, enhancing island ecological management, and protecting the ecosystems of Fujian and other subtropical islands. The study identified significant species-area relationships for IAPs and different life-form plants (trees, shrubs, and herbs), with slopes of 0.27, 0.16, 0.15, and 0.24, respectively. The small island effect does not apply to all species. Isolation has little effect on species richness, and the IAPs on Fujian islands do not conform to the isolation effect in island biogeography. Landscape factors are the main determinants of IAPs and different life-form species richness, with area, shape index, and perimeter-area ratio being the three primary landscape factors. These environmental factors are closely related to habitat heterogeneity. Besides landscape factors, different life forms respond differently to environmental factors. Climate drives the species richness distribution of shrubs and herbs, while trees are mainly influenced by human activities. Overall, landscape, human disturbance, and climate jointly drive the distribution of IAPs, with landscape factors being the most significant.

Dismantling Ships to Revitalize Coral Reefs with Artificial Reefs

Australia's Great Barrier Reef is an immense swath of coral made up of about 2,900 reefs, 600 mainland islands, and 300 coral atolls. It stretches for 2,200 kilometers, ranging in width from 30 km to 740 km. This natural wonder is visible from space and is the largest structure in the world made solely by living organisms. The corals that form this barrier are essential for marine biodiversity and were elected as a World Heritage Site in 1981. However, the Great Barrier Reef faces serious challenges, including bleaching caused by rising temperatures and the impacts of climate change. One strategy for revitalizing reefs is the use of sunken old ships to create artificial reefs. This approach not only conserves the marine environment, but also promotes scientific research and the production of bioproducts. Artificial ship reefs provide substrates for the marine community and simulate environments similar to natural reefs, contributing to the protection and revitalization of this important barrier reef. It is essential to develop strategies to preserve the oceans and mitigate the impacts of human activities, ensuring the survival of this ecosystem and protecting it as a treasure.

Arthropod traits as proxies for abundance trends in the Azorean Islands

Human activities drive ecological transformation, impacting island ecosystems from species diversity to ecological traits, mainly through habitat degradation and invasive species. Using two unique long‐term datasets we aim to evaluate whether species traits (body size, trophic level, dispersal capacity and habitat occupancy) can predict temporal variations in the abundance of endemic, indigenous (endemic and native non‐endemic) and exotic arthropods in the Azores Islands. We found that body size is crucial to predict arthropod abundance trends. Small‐bodied herbivorous arthropods showed a decrease in abundance, while large‐bodied indigenous arthropods increased in abundance, mainly in well‐preserved areas. Also, large‐bodied exotic arthropods increased in abundance across the entire archipelago. Moreover, endemic canopy dwellers increased in abundance, while endemic ground‐dwellers decreased in abundance. Simultaneously, exotic arthropods showed the opposite result, increasing in abundance in the ground while decreasing in abundance in the canopy. Finally, habitat influenced both endemic and exotic spider abundance trends. Endemic spiders that occupy solely natural habitats experienced a decline in abundance, while exotic spiders in the same habitats increased in abundance. Our study underscores the significance of arthropod species traits in predicting abundance changes in island ecosystems over time, as well as the importance of monitoring species communities. Conservation efforts must extend beyond endangered species to protect non‐threatened ones, given the increased extinction risk faced by even common species on islands. Monitoring and restoration programs are essential for preserving island ecosystems and safeguarding endemic arthropod populations.

Stable Isotope Analysis and Chronology Building at the Hokfv-Mocvse Cultural Site, the Earliest Evidence for South Atlantic Shell-Ring Villages

Abstract Circular shell rings along the South Atlantic coast of the United States are vestiges of the earliest sedentary villages in North America, dating to 4500–3000 BP. However, little is known about when Indigenous communities began constructing these shell-ring villages. This article presents data from the Hokfv-Mocvse Shell Ring on Ossabaw Island, Georgia. Although shell rings are often associated with the earliest ceramics in North America, no ceramics were encountered in our excavations at Hokfv-Mocvse, and the only materials recovered were projectile points similar to points found over 300 km inland. Bayesian modeling of radiocarbon dates indicates that the ring was occupied between 5090 and 4735 cal BP (95% confidence), making it the earliest dated shell ring in the region. Additionally, shell geochemistry and oyster paleobiology data suggest that inhabitants were living at the ring year-round and had established institutions at that time to manage oyster fisheries sustainably. Hokfv-Mocvse therefore provides evidence for Indigenous people settling in year-round villages and adapting to coastal environments in the region centuries before the adoption of pottery. The establishment of villages marks a visible archaeological shift toward settling down and occupying island ecosystems on a more permanent basis and in larger numbers than ever before in the region.

Anthropogenic disturbance has altered the habitat of two Azorean endemic coastal plants

BackgroundAnthropogenic threats are causing alteration of coastal areas worldwide. Most of the coastal biodiversity is endangered, taking a particular toll on island ecosystems, like the Azores. To better understand the biotic and abiotic factors constraining the distribution and conservation status of two endemic plants, Azorina vidalii (Campanulaceae) and Lotus azoricus (Fabaceae), we performed a global survey of coastal plant communities in the archipelago, also covering environmental descriptors, natural and anthropogenic threats. Moreover, we revised their IUCN conservation status and estimated the population fractions within protected areas.ResultsNon-indigenous plants were commonly found in plots with or without the target endemics, contributing to the absence of well-defined coastal plant communities. Nonetheless, indigenous taxa commonly occurred at the plots with L. azoricus. With a larger area of occurrence, A. vidalii ecological niche differed from that of L. azoricus, the latter being restricted to dry and rocky sea cliffs, mostly in Santa Maria Island. Besides the presence of invasive plants, signs of habitat destruction, trampling and grazing, and of natural threats, such as coastal erosion, were commonly observed.ConclusionsOccurrence data indicated an endangered status for both species, although this would change to critically endangered for L. azoricus when using smaller-sized occurrence cells. Both species are threatened since their habitat is restricted to a very narrow vegetation belt, strongly limited by sea influence and human pressure, and with the frequent presence of invasive plants. While focusing on two endemic plants, our study allowed a broader view of the impact of anthropogenic disturbance on Azorean coastal plant communities.

Birds influence vegetation coverage and structure on sandy biogeomorphic islands in the Dutch Wadden Sea

Small uninhabited islands form important roosting and breeding habitats for many coastal birds. Previous studies have demonstrated that guano can promote ecosystem productivity and functionality on island ecosystems. Here, we assess the role of external nutrient input by coastal birds on the vegetation structure and coverage on sandy biogeomorphic islands, where island-forming processes depend on vegetation-sedimentation feedbacks. As a first step, we investigated whether breeding birds affect vegetation productivity on sandy back-barrier islands in the Wadden Sea. Using a combination of bird observations and plant stable isotope (δ15N) analyses, we demonstrate that (i) breeding birds transport large quantities of nutrients via their faecal outputs to these islands annually and that (ii) this external nitrogen source influences vegetation development on these sandy, nutrient-limited, islands. Based on these results we discuss how this avian nutrient pump could impact island development and habitat suitability for coastal birds and discuss future directions for research. In general, we conclude that avian subsidies have the potential to affect both the ecological and biogeomorphic functioning of coastal soft-sediment systems. However, the strength and scale of especially these biogeomorphic interactions are not fully understood. For the conservation of both threatened coastal birds and sandy back-barrier islands and the design of appropriate management strategies, we argue that three-way interactions between birds, vegetation and sandy island morphodynamics need to be further elucidated.

Low-intensity urbanisation alters community composition across multiple trophic levels on Lipsi Island, Greece.

Urbanisation has reduced the abundance and diversity of many taxonomic groups, and the effects may be more pronounced on islands, which have a smaller regional species pool to compensate. Green spaces within urban environments may help to safeguard wildlife assemblages, and the associated habitat heterogeneity can even increase species diversity. Here, total abundance and species diversity of butterflies, birds, and vegetation at nine rural and nine urban locations were quantified on Lipsi Island, Greece. Sites were assessed using Pollard walks for butterflies, point-count surveys for birds, and quadrats for vegetation. There was no significant difference in the abundance or species diversity of butterflies or vegetation among rural and urban locations, which could pertain to the low building density within urbanised areas and the minimal extent of urbanisation on the island. However, urban areas hosted a significantly greater abundance, richness, and diversity of birds compared to rural sites. The community composition of butterflies, birds, and vegetation also differed significantly between urban and rural locations, highlighting the impact of urbanisation on species across a broad range of trophic groups. This study contributes to ecological knowledge on the impacts of urbanisation across multiple trophic levels in island ecosystems, with comparisons across a gradient of island size and urbanisation intensity needed in future research.

Impacts of coyote colonization on coastal mammalian predators

Extreme ecosystem modification by humans has caused drastic reductions in populations and ranges of top mammalian predators, while simultaneously allowing synanthropic mesopredator species to expand. These conditions often result in inflated local densities of highly adaptable mesopredators that disrupt trophic dynamics and place unsustainable predation pressure on native prey populations. Colonization of a dominant predator may lead to top-down control of mesopredators and restore trophic balance. Coyotes are a novel colonizer of some coastal barrier islands of eastern North America, offering an opportunity to test how the addition of an apex predator impacts an established guild of mesopredators. To assess their trophic impact, we conducted 75,576 camera trapping hours over an 18-month study period, capturing > 1.5 million images across 108 coastal camera sites. Using two-species occupancy and habitat use models, we found sizeable effects of coyote habitat use on that of red foxes and free-ranging domestic cats, suggesting that coyotes function as apex predators in barrier island ecosystems. In fact, the only factor that determined the spatial pattern of highly ubiquitous red foxes was the sympatric habitat use of the largest carnivore in the food web—coyotes. That ‘novel’ apex predators can become established in coastal food webs illustrates the highly dynamic nature of conservation challenges for habitats and species at the edge of the sea.