Occurrence Of Invasive Species Research Articles

Occupancy dynamics of free ranging American mink (Neogale vison) in Greece.

Identifying the environmental factors that determine the occurrence of invasive species is essential in defining and implementing effective control campaigns. Here, we applied multi-season occupancy models to analyze American mink (Neogale vison) track data collected using 121 floating rafts, as a function of factors occurring at multiple spatial scales. Our overall aim was to identify those factors that determine the use, colonization or abandonment of rafts by free ranging individuals found in western Macedonia, Greece. We found that increasing values of shrubs and rock cover at the micro-habitat scale were positively associated with the species' probability of raft use, as was the density of medium-sized rivers at the landscape scale. Colonization was found to increase with increasing amounts of shrub and reed cover; however, both variables were not informative. Conversely, the distance from the nearest fur farm was highly informative in predicting raft abandonment by the species. Effective control actions may require removal by trapping along rocky or densely vegetated riverbanks or lake shores located in the vicinity of the established fur farms in the area. Habitat management, although possible, may be difficult to implement due to the ability of the species to adapt. Finally, fur farms should maximize security and establish an early warning and rapid eradication system in case of future escapes.

Response of vulnerable karst forest ecosystems under different fire severities in the Northern Dinaric Karst mountains (Slovenia)

BackgroundThis study deals with wildfires in marginal areas of the Mediterranean climatic and biogeographical regions (Northern Mediterranean) where fires were not common. The aim of the research was to determine the differences in floristic composition and traits at different intensities of fire damage and to analyze the changes in forest ecosystems during the wildfires that took place in the summer of 2022. The study included both the zonal forests and non-native black pine (Pinus nigra) forests. Remote sensing techniques linked to the vegetation data sampled in the field during the 2023 vegetation season, the very first season after the fires, were also used in the fire assessment.ResultsThe study confirmed that satellite data analysis, orthophoto interpretation, and on-site vegetation sampling provide equivalent information on fire severity, opening up the possibility of transferring knowledge to similar post-fire sites without field sampling in the future. TWINSPAN classification analysis divided the sampled plots into clusters based on tree species prevalence and fire severity. The diagnostic species of the clusters were calculated using a fidelity measure. Ordination revealed that the first axis on the detrended correspondence analysis (DCA) correlated with wildfire severity. Ecological conditions and strategies, life forms, chorotypes, seed dispersal classes, and regeneration traits were analyzed along this gradient. We found that post-fire sites became warmer, drier, and lighter, which favored the growth of ruderal, theropytic, cosmopolitan, anemochorous and post-fire emergent species. After the fire, a “wave” of annual ruderal species was observed.ConclusionsThe results indicate that post-fire recovery can be left to natural processes without human intervention, except in the case of non-native pine stands where planting or seeding may be necessary. Otherwise, it is essential to control the possible occurrence of invasive species. Isolated adaptations of species to fire have also been observed, such as heat-stimulated germination. Such adaptations could develop in regions exposed to frequent fires and where fires act as an evolutionary factor.

Detecting the invasive Lespedeza cuneata in grasslands using commercial small satellite imagery

ABSTRACT Lespedeza cuneata (L. cuneata) is an invasive legume threatening grassland ecosystems of several states in the U.S. Mapping the occurrence of invasive species is the necessary first step to control their spread. Imaging spectroscopy or hyperspectral remote sensing imagery has shown its effectiveness in detecting invasive plants. However, challenges such as limited access to hyperspectral imagery, coarse temporal resolution, high costs, and lack of standardized analysis approaches have limited their application in monitoring biological invasions. Here, we aimed to take advantage of fine spatial and temporal resolution of PlanetScope multispectral satellite data and develop an effective approach to detect L. cuneata in a naturally assembled grassland ecosystem. To achieve this objective, we first sampled a suite of foliar functional traits in the field and identified key traits that distinguish L. cuneata from native plants. We then used our airborne hyperspectral data to select vegetation indices that are associated with the key traits while focusing on those indices that are applicable to satellite-derived multispectral data. We developed seven machine learning models and a decision fusion approach using layers of vegetation indices to map L. cuneata during the growing season. Using our approach, we were able to map L. cuneata with high level of accuracy using PlanetScope multispectral imagery. Our results suggested that the optimal period for detecting L. cuneata in our site was mid-to-late growing season, with an overall classification accuracy of 80.49 ± 5.69% (mid-August) and 82.02 ± 4.66% (end of September), respectively. Our study contributes to developing a cost-effective solution for mapping and monitoring invasive plants, which is essential for effective control of biological invasions.

Distribution, drivers and restoration priorities of plant invasions in India

Abstract Biological invasions threaten biodiversity and human wellbeing, with developing tropical countries being more vulnerable. Despite the urgency to reduce impacts of invasions, management interventions are constrained by unavailability of timely information on invasive species occurrence, potential drivers and restoration priorities. Generating this information at biogeographic scales can be costly, unless integrated with multi‐objective biodiversity monitoring. Invasive plant monitoring is integrated with India's national‐scale tiger population assessment, wherein natural areas are sampled at 25 km2 scale to inventory plants. In 2018, a total of 158,979 plots were sampled covering ~358,550 km2. We used 206,393 locations of high concern invasive plants to model their distribution using socio‐ecological covariates and identify potential drivers of invasions. Considering the invasion magnitude and financial constraints in management, we further identified priority restorations sites at national‐scale to maximise biodiversity outcomes. High‐concern invasive plants were recorded from ~254,880 km2 (72% sampled area) and modelled to invade in total ~750,905 km2 (66%) Indian natural systems. While open and deciduous ecosystems were the highest invaded by woody plants, areas with extreme climate and less anthropic pressure were least invaded. Since managing invasions across their range seemed futile due to costly (~13.5 billion USD for one‐time management) and ineffective strategies, restoration priority was assigned to least invaded areas (11% protected areas, 23% multi‐use) to maximise biodiversity returns. Synthesis and applications: India implemented national‐scale invasive plant monitoring by integrating it with the umbrella project on tiger assessment. Embarking on this big data, we show that two‐thirds of India's natural areas are under multiple plant invasions, owing to the legacy of anthropogenic modifications. Our study offers a restoration priority model, empowering policymakers to devise adaptive strategies for restoring invaded biomes and maximizing biodiversity returns.

Population parameters of the non-indigenous invasive shrimp Palaemon macrodactylus Rathbun, 1902 (Caridea: Palaemonidae) from the southeastern Caspian Sea, with implications for range expansions, threats and conservation

Knowledge on invasive species is critical for the conservation. This study is the first documentation on population parameters of oriental shrimp (Palaemon macrodactylus) in the southern Caspian Sea, where the occurrence of invasive species is of great importance. The samples were collected using a small beach seine (35 m long and 2.5 m height) monthly from April 2019 to March 2020, and a total of 1643 specimens of P. macrodactylus were sampled. The growth form of the males was negative and that of females positive allometric nature. From the size-frequency distributions, the shrimp's lifespan was estimated to be about 2 years for both sexes. High recruitment can take place over nearly all months of late summer and autumn. The VBGF parameters were L∞ = 65.00 mm, K = 0.82 y−1, and t0 = −0.80 for males, and TL∞ = 71.00 mm, K = 0.51 y−1 and t0 = −0.59 for females. The estimated Z was 3.65 and 3.10 year−1 for males and females, respectively. The total sex ratio was significantly biased toward females in the population. Length group analysis showed a clear pattern of female dominance in lengths larger than 29 mm. Based on the occurrence of ovigerous females, the reproductive period lasts for seven months (April–October). Fecundity, as the number of both eyed and non-eyed eggs per clutch of females, varied from 71 to 2308 eggs shrimp−1 with a mean of 1074 ± 553.8 (±SD) eggs shrimp−1. The estimated relative number of eggs in a clutch of ovigerous females varies between 1208.8 and 1714, with a mean value of 889.1 eggs. female−1. The egg diameter averaged 0.675 ± 0.063 mm (±SD), ranging from 0.512 to 0.812 mm. The relationships of the total and relative number of eggs in a clutch of ovigerous females with their size were statistically significant, while the egg diameter in ovigerous females was independent of shrimp size (length and weight). P. macrodactylus underwent a life-history strategy including high abundance, short life span, high mortality rate, long reproductive season, and female dominance that showed characteristics of r-strategist species, promoting the invasion of this shrimp in the Caspian Sea as a new area of introduction. We are convinced that P. macrodactylus established in the Caspian Sea it is in the last stage of invasion (impact on the ecosystem).

Citizen science can complement professional invasive plant surveys and improve estimates of suitable habitat

AbstractAimCitizen science is a cost‐effective potential source of invasive species occurrence data. However, data quality issues due to unstructured sampling approaches may discourage the use of these observations by science and conservation professionals. This study explored the utility of low‐structure iNaturalist citizen science data in invasive plant monitoring. We first examined the prevalence of invasive taxa in iNaturalist plant observations and sampling biases associated with these data. Using four invasive species as examples, we then compared iNaturalist and professional agency observations and used the two datasets to model suitable habitat for each species.LocationHawai'i, USA.MethodsTo estimate the prevalence of invasive plant data, we compared the number of species and observations recorded in iNaturalist to botanical checklists for Hawai'i. Sampling bias was quantified along gradients of site accessibility, protective status and vegetation disturbance using a bias index. Habitat suitability for four invasive species was modelled in Maxent, using observations from iNaturalist, professional agencies and stratified subsets of iNaturalist data.ResultsiNaturalist plant observations were biased towards invasive species, which were frequently recorded in areas with higher road/trail density and vegetation disturbance. Professional observations of four example invasive species tended to occur in less accessible, native‐dominated sites. Habitat suitability models based on iNaturalist versus professional data showed moderate overlap and different distributions of suitable habitat across vegetation disturbance classes. Stratifying iNaturalist observations had little effect on how suitable habitat was distributed for the species modelled in this study.Main ConclusionsOpportunistic iNaturalist observations have the potential to complement and expand professional invasive plant monitoring, which we found was often affected by inverse sampling biases. Invasive species represented a high proportion of iNaturalist plant observations, and were recorded in environments that were not captured by professional surveys. Combining the datasets thus led to more comprehensive estimates of suitable habitat.

Current Status of and Threats to Sicilian Turtles

Based on the critical review of the literature published in the last 22 years, an attempt was made to evaluate the current knowledge gap on the distribution and status of the native Testudines taxa occurring in Sicily (namely Caretta caretta, Emys trinacris, and Testudo hermanni hermanni), as well as the available knowledge of the only non-native species with putative viable populations occurring on the island, i.e., Trachemys scripta. Summarizing the current information, all of the Testudines species occurring in Sicily showed a fragmented and incompletely-known distribution, and only scarce data are available about their phenology. Moreover, despite their inclusion of international and national laws (Bern Convention, CITES, Habitat directive), all three native species are facing several threats (e.g., habitat alteration, the occurrence of invasive species, parasite spillover) leading to a reduction of their populations on the island. Future monitoring programs on the island should be enhanced, with an emphasis on those taxa in decline. Moreover, involve Citizen Science programs should also be implemented in order to increase the awareness of non-experts and facilitate the monitoring task.

ADOPTION STRATEGIES AND IMPACT OF CLIMATE CHANGE ON RICE CULTIVATION PRACTICES

Climate change is contemporary global threat to this planet. Greenhouse gases which are responsible for global warming and its impact is accelerated by anthropogenic activities. Increasing temperature is creating influence on rice cultivation, production and productivity. In this regard, this study was conducted on Dilasaini Rural municipality of Baitadi district during the period of Jan to Feb 2018 to assess the impact of climate change on rice production and adaptation strategy. Interview survey, key informant interview, focus group discussion were conducted in collecting primary information. Sixty households were sampled from a total of 1538 households with random sampling for interviews survey. The data were analyzed using SPSS computer software. Temperature and precipitation data analysis between 1987 to 2015 showed some changes. Temperature was in increasing trend. The maximum mean temperature was increasing at 0.057°C/year and the minimum mean temperature was increasing at 0.0075°C/decade. Total rainfall was decreasing by 25.22 mm/yr. It was found that some special signs of climate change are experienced by rural communities of the study area. Local communities perceived increasing warm days and shortening cold/winter days. Almost 100 percent respondents have experienced increasing temperature and unusual rainfall events with direct impacts on rice production. Most of the farming communities experienced unusual weather patterns with negative impacts on rice production, increasing water scarcity and increased frequency of weather related disasters. The indicators to this were decrease in the production of crops, occurrence of invasive species at alarming rate and infestation of pests and diseases. As the farmer are practicing the cultivation of the local seed instead of hybrid varieties of the crop as the production is decreasing due to lack of resistance power of the local variety with changing climate, new diseases and pest infestation. On the other hand, changing climate of the area is showing effect on the flowering time of rice species and so were the germination, harvesting and maturing times of rice had changed. All these changes in rice had influenced on the food security of the people in study area, the income from agriculture had decreased, so people are separating from their traditional occupation, way of life and they are seeking alternative professions. Adaptation strategy has not been used due to lack of proper knowledge on adaptation methodology so the farmer of the study area are facing problem to cope with the situation and ultimately facing problem of food security.

Testing a Generalizable Machine Learning Workflow for Aquatic Invasive Species on Rainbow Trout (Oncorhynchus mykiss) in Northwest Montana.

Biological invasions are accelerating worldwide, causing major ecological and economic impacts in aquatic ecosystems. The urgent decision-making needs of invasive species managers can be better met by the integration of biodiversity big data with large-domain models and data-driven products. Remotely sensed data products can be combined with existing invasive species occurrence data via machine learning models to provide the proactive spatial risk analysis necessary for implementing coordinated and agile management paradigms across large scales. We present a workflow that generates rapid spatial risk assessments on aquatic invasive species using occurrence data, spatially explicit environmental data, and an ensemble approach to species distribution modeling using five machine learning algorithms. For proof of concept and validation, we tested this workflow using extensive spatial and temporal hybridization and occurrence data from a well-studied, ongoing, and climate-driven species invasion in the upper Flathead River system in northwestern Montana, USA. Rainbow Trout (RBT; Oncorhynchus mykiss), an introduced species in the Flathead River basin, compete and readily hybridize with native Westslope Cutthroat Trout (WCT; O. clarkii lewisii), and the spread of RBT individuals and their alleles has been tracked for decades. We used remotely sensed and other geospatial data as key environmental predictors for projecting resultant habitat suitability to geographic space. The ensemble modeling technique yielded high accuracy predictions relative to 30-fold cross-validated datasets (87% 30-fold cross-validated accuracy score). Both top predictors and model performance relative to these predictors matched current understanding of the drivers of RBT invasion and habitat suitability, indicating that temperature is a major factor influencing the spread of invasive RBT and hybridization with native WCT. The congruence between more time-consuming modeling approaches and our rapid machine-learning approach suggest that this workflow could be applied more broadly to provide data-driven management information for early detection of potential invaders.

Impact of Malaysian palm oil on sustainable development goals: co-benefits and trade-offs across mitigation strategies.

Palm oil (PO) is an important source of livelihood, but unsustainable practices and widespread consumption may threaten human and planetary health. We reviewed 234 articles and summarized evidence on the impact of PO on health, social and economic aspects, environment, and biodiversity in the Malaysian context, and discuss mitigation strategies based on the sustainable development goals (SDGs). The evidence on health impact of PO is equivocal, with knowledge gaps on whether moderate consumption elevates risk for chronic diseases, but the benefits of phytonutrients (SDG2) and sensory characteristics of PO seem offset by its high proportion of saturated fat (SDG3). While PO contributes to economic growth (SDG9, 12), poverty alleviation (SDG1, 8, 10), enhanced food security (SDG2), alternative energy (SDG9), and long-term employment opportunities (SDG1), human rights issues and inequities attributed to PO production persist (SDG8). Environmental impacts arise through large-scale expansion of monoculture plantations associated with increased greenhouse gas emissions (SDG13), especially from converted carbon-rich peat lands, which can cause forest fires and annual trans-boundary haze; changes in microclimate properties and soil nutrient content (SDG6, 13); increased sedimentation and change of hydrological properties of streams near slopes (SDG6); and increased human wildlife conflicts, increase of invasive species occurrence, and reduced biodiversity (SDG14, 15). Practices such as biological pest control, circular waste management, multi-cropping and certification may mitigate negative impacts on environmental SDGs, without hampering progress of socioeconomic SDGs. While strategies focusing on improving practices within and surrounding plantations offer co-benefits for socioeconomic, environment and biodiversity-related SDGs, several challenges in achieving scalable solutions must be addressed to ensure holistic sustainability of PO in Malaysia for various stakeholders.Supplementary InformationThe online version contains supplementary material available at 10.1007/s11625-021-01052-4.

Economic activity and distribution of an invasive species: Evidence from night-time lights satellite imagery data

This study addresses economic and ecological aspects related to aquatic invasive species occurrence and spread. The relative importance of these two factors driving the probability of occurrence of Elodea canadensis species in lakes of Sweden is quantified. Night-time lights data, a proxy for economic activity, is generated from satellite imagery and mapped to key environmental variables known to constrain the species' distribution. Economic and environmental data are then matched with the species' observational records at the lake scale. Evidence from a spatial probit model shows a robust positive relationship between economic activity and invasion of uninvaded lakes.

Comment on "Global distribution of earthworm diversity".

Phillips et al (Reports, 25 October 2019, p. 480) incorrectly conclude that tropical earthworm communities are less diverse and abundant than temperate communities. This result is an artifact generated by some low-quality datasets, lower sampling intensity in the tropics, different patterns in richness-area relationships, the occurrence of invasive species in managed soils, and a focus on local rather than regional richness.

АНАЛИЗ ВИДОВОГО СОСТАВА, ПРОБЛЕМЫ ИДЕНТИФИКАЦИИ И ПУТЕЙ РАССЕЛЕНИЯ ЧУЖЕРОДНЫХ ВИДОВ РЫБ В БАССЕЙНЕ РЕКИ ВОЛГИ

The article describes the intensive economic activity in the second half of the 20th century, which, along with apparent global climatic changes in recent decades, led to an increase in the number of alien fish species in the water bodies of the Volga basin. There has been presented the data on the occurrence of invasive species in scientific catches in the Volga River reser-voirs, as well as in its unregulated areas and delta. The invaders’ share in the fish species composition varied from 8 to 32%, depending on the geography of sampling. Special attention is paid to the reasons and pathways of invasive species’ dispersal, as well as to changes in the genetic structure of their populations taking place during acclimatization to the new conditions. It has been proposed to utilize a combined genetic-morphological approach in order to enhance the species identification of found invaders. Collected material can be used in the development of control methods, as well as for suppressing the abundance of dangerous or undesirable invasive species

Suitability of the Weber-Gut risk assessment methodology used in Central Europe for determining invasive woody plant species in Estonian historical parks

Abstract The main objective of this research was to assess the suitability of the risk assessment methodology developed by Weber & Gut for Central Europe in order to determine the invasive species in the dendroflora of this region's historical parks. In order to do so a region was chosen where the number of old parks is high (Estonia) and then the following characteristics were studied: 1) the distribution of invasive species; 2) the viability of invasive species. Research results showed that the risk assessment for Central Europe developed by Weber & Gut is not suitable for determining invasive tree and shrub species in the historical parks of Estonia. The research viewed 18 species (classified as a high-risk category) and only half of them had characteristics inherent to invasive behaviour (produces reproductive offspring, often in very large numbers, at a considerable distance from parent plants, and thus has the potential to spread over a considerable area). Even in a small territory (45,339 km2), the regional differences in the occurrence of invasive species were substantial. No independent mass reproduction of most of the invasive species was detected during the use of the Weber-Gut risk assessment system. This research showed that the dangers of invasive species cannot be assessed based on one methodology, but each species should be assessed according to their habitat and specifics of the species.

Occurrence of invasive species and seasonal dynamics of fruit flies (Diptera: Drosophilidae) species in Uşak province, Turkey

In Turkey, studies on Drosophilidae species, which are not considered agriculturally harmful, have not been deepened about their presence, diversity and seasonal population changes, until Drosophila suzukii began to spread worldwide. As a result of this, in recent years researches on the fauna of Drosophilidae and their relationships with each other have been accelerated. In the current study, Drosophilidae species and their seasonal changes in a fruit orchard and a vineyard were monitored in 2017-2018. A total of 304 traps were examined and 21,688 individuals belonging to 7 genera and 13 species were identified. Drosophila subobscura was the most abundant species in traps in both years. Furthermore, in the present study, invasive Zaprionus tuberculatus has been identified for the first time in western Turkey

IMPACT OF SHIP'S BALLAST WATER ON INVASIVE SPECIES OCCURRENCE, AND AS A CONSEQUENCE ON ENVIRONMENTAL AND PUBLIC HEALTH: A SHORT REVIEW

Water is one of the main ways of transportation. The reduction of water pressure on the ship hull, controlling ship submergence, compensate for the impact of losing weight from fuel or water consumption, help to the existence of lateral balance and stability are the factors that show all ships need ballasting. Ballast water contains a large number of organisms from different species, which are in different life stages (egg, Larvae, Cysts, Spores, or adult). These aquatic invasive species cause damage to fisheries, aquaculture, water supply system, industrial infrastructure, biodiversity, and habitat. The study aims to review open information sources and analyze them to identify the Impact of ship's ballast water on invasive species occurrence, and as a consequence on environmental and public health effects. The search for sources was carried out for the keywords «ballast water», «ecology», «environment», «public health» and «invasive species», as well as for various combinations of these words through the Google Scholar. Restrictions in the search for sources amounted to: since 2005 and in relevance. The features of one of the reasons for the spread of invasive species and negative environmental consequences for aqua systems and public health are studied. The study's practical value lies in the fact that the study results can be used to train workers from water transport and ensure the environmental safety of aqua systems. Predation, parasitism, competition, the introduction of new pathogens, genetic changes, habitat alterations, species shift, and loss of biodiversity are the most important ecological impacts. Exotic species, which are often brought with ballast water, cause change to ecosystem function by changing in a nutrient cycle and a decrease in water quality. It is established that some invasive species including Vibrio Cholera and Giardia duodenalis that are transported by ballast water also affect the public health by increasing the risk of pathogens and parasitism.

Assessment of tree species diversity and benefits in selected recreation centres for biodiversity conservation in Ibadan Metropolis, Nigeria

The present study assessed the trees species diversity and the benefits that arise from their presence in five selected recreation centers in the urban area of Ibadan: Agodi Gardens, Ibadan Recreation Club, National Museum of Unity, Ibadan Golf Club and Ibadan Polo Club. The selected areas were purposively chosen due to the presence of tree species in the urban landscape. Both primary and secondary data were used for the study. Agodi Garden had in total 537 individuals, 46 tree species within 25 families. Ibadan Recreation Club had the total number of 148 trees, whereas 32 species within 22 families were represented. National Museum of Unity had a total number of 770 trees, classified in 23 species within 17 families. Ibadan Polo Club had a total number of 97 trees, 20 species and 15 families were represented. Ibadan Golf Club had a total number of 915 trees, 31 species and 9 families. Fabaceae family had the highest occurrence in Ibadan Recreation Club, National Museum of Unity, Ibadan Golf Club and Ibadan Polo Club, while Verbenaceae was more represented in Agodi Gardens. The study has shown the high occurrence of invasive species in tropical environment based on their regeneration potential. Data collected on total number of tree species, frequency of occurrence and families were subjected to descriptive analysis. A semi-structured questionnaire was used to obtain information. These centers serve as ex-situ urban centers/parks that still maintain and conserve various tree species and are important resources for social, economic and educational use. Biodiversity indices were also analyzed and it can be concluded that the type of organization and the main activity of the centers strongly influence the species diversity. The trend of Shannon-Wiener diversity index (H') showed that Ibadan Polo Club was the most diverse. Despite the higher number of individual trees encountered in NMUI, the H' value was very low, indicating the dominance of a few tree species within the area. From EH values obtained in the study, it can be concluded that trees species are most evenly distributed in IPC, followed by IRC, AG, IGC and lastly by NUMI.

INVASIONS OF ALIEN VASCULAR PLANTS TO NATURAL AND SEMI-NATURAL HABITATS IN TOWNS OF THE REPUBLIC OF KARELIA

Information on the occurrence of invasive species in towns of the Republic of Karelia is provided. In total, 47 invasive species have been recorded. The number of neophytes varies widely among towns – from 14 species in the youngest Town of Kostomuksha to 43 species in the largest City of Petrozavodsk. Invasive species have colonized all major types of natural and semi-natural biotopes occurring in towns of Karelia. The highest invasibility is characteristic of forests (including forest margins) and meadows; shores, banks, and rocky biotopes have somewhat lower invasibility; mires, aquatic and coastal habitats were invaded by two species each.

Invasive toads are close to but absent from Komodo National Park

The islands of Komodo National Park in the Wallacea region are the habitats of Komodo dragon (Varanus komodoensis). Although the Wallacea islands have lower species richness compared to the other large islands in Indonesia, they are rich in endemics, and the occurrence of invasive species would therefore threatened the ecological, economic and social balance of the regions. Several papers have hinted at the possibility of the invasion of Komodo National Parks by Asian toads, a situation which would potentially affect the survival of the Komodo dragon. To detect the presence of the invansive toad Duttaphrynus melanostictus in Komodo National Park and its surroundings areas we carried out an amphibian survey using a Visual Encounter Survey method during February to April 2018. The surveyed location consisted of two main islands within Komodo National Park (Rinca island and Komodo island), Flores island (Labuan Bajo and Cumbi village) and Sumbawa island (Sape). Two species of amphibians were found in Komodo National Park (Rinca island and Komodo island), while seven species of amphibians were found across all four locations. No D. melanostictus toads were found in Flores (including in Komodo National Park), however the toad was found to be abundant in Sape (Sumbawa island).

Network‐scale effects of invasive species on spatially‐structured amphibian populations

Understanding the factors affecting the dynamics of spatially‐structured populations (SSP) is a central topic of conservation and landscape ecology. Invasive alien species are increasingly important drivers of the dynamics of native species. However, the impacts of invasives are often assessed at the patch scale, while their effects on SSP dynamics are rarely considered. We used long‐term abundance data to test whether the impact of invasive crayfish on subpopulations can also affect the whole SSP dynamics, through their influence on source populations. From 2010 to 2018, we surveyed a network of 58 ponds and recorded the abundance of Italian agile frog clutches, the occurrence of an invasive crayfish, and environmental features. Using Bayesian hierarchical models, we assessed relationhips between frog abundance in ponds and a) environmental features; b) connectivity within the SSP; c) occurrence of invasive species at both the patch‐ and the SSP‐levels. If spatial relationships between ponds were overlooked, we did not detect effects of crayfish presence on frog abundance or trends. When we jointly considered habitat, subpopulation and SSP features, processes acting at all these levels affected frog abundance. At the subpopulation scale, frog abundance in a year was related to habitat features, but was unrelated to crayfish occurrence at that site during the previous year. However, when we considered the SSP level, we found a strong negative relationship between frog abundance in a given site and crayfish frequency in surrounding wetlands during the previous year. Hence, SSP‐level analyses can identify effects that would remain unnoticed when focussing on single patches. Invasive species can affect population dynamics even in not invaded patches, through the degradation of subpopulation networks. Patch‐scale assessments of the impact of invasive species can thus be insufficient: predicting the long‐term interplay between invasive and native populations requires landscape‐level approaches accounting for the complexity of spatial interactions.