Musée national d'histoire naturelle de Luxembourg

In Europe, various conservation programs adopted to maintain or restore biodiversity have experienced differing levels of success. However, a synthesis about major factors for success of biodiversity-related conservation programs across ecosystems and national boundaries, such as incentives, subsidies, enforcement, participation, or spatial context, is missing. Using a balanced scorecard survey among experts, we analyzed and compared factors contributing to success or failure of three different conservation programs: two government programs (Natura 2000 and the ecological measures of the Water Framework Directive) and one conservation program of a non-governmental organization (NGO; Rewilding Europe), all focusing on habitat and species conservation. The experts perceived the NGO program as more successful in achieving biodiversity-related aims than governmental conservation legislation. Among the factors perceived to influence the success of biodiversity conservation, several stood out: Biodiversity-damaging subsidies, external economic interests competing with conservation goals or policies conflicting with biodiversity conservation were recognized as major factors for the lack of conservation success. Outreach to raise societal interest and awareness as well as stakeholder involvement were perceived as closely related to the success of programs. Our expert survey demonstrated that external factors from economy and policy often hinder success of conservation programs, while societal and environmental factors rather contribute to it. This study implies that conservation programs should be designed to be as inclusive as possible and provides a basis for developing a standardized methodology that explicitly considers indirect drivers from areas such as economy, policy and society.

Population outbreaks are characterized by irruptive changes in population density and connectivity resulting in rapid demographic and spatial expansion, often at the landscape scale. Outbreaks are common across multiple taxa, many of which inhabit northern ecosystems. Outbreaks of Lepidopteran defoliators in forest ecosystems are a particularly compelling example of this phenomenon, given the massive spatial scales over which these outbreaks can occur, their frequency, and socioeconomic impacts. The eastern spruce budworm (SBW) is a native outbreaking Lepidopteran defoliator of North American boreal forests. Cyclic outbreaks of the SBW influence ecosystem functioning and resilience, as well as forest productivity, timber supply, and other socioeconomic values related to management and mitigation. Despite these significant impacts, the ecological and biological drivers and outcomes of these outbreaks remain poorly understood. Here, we present an extensive genotypic dataset for 1998 geo‐referenced SBW individuals collected between the years of 2012 and 2017, during the rising and peak phases of an outbreak that began approximately in 2006. Our sampling covers an unprecedented scope in the extent and number of individuals collected between 2012 and 2017 from Quebec, and in 2015 from New Brunswick (Canada) and from Maine (USA), from multiple SBW life stages, including early and late instar larvae (L2–L6), pupae, and adult moths. Genomic DNA extraction was followed by library preparation and high‐throughput sequencing using Genotyping‐by‐Sequencing (GBS). Samples were genotyped for single nucleotide polymorphisms (SNPs) and aligned to the bw6 version of the SBW genome. This dataset represents one of the most extensive genotypic datasets to date for a boreal insect and is unique as it includes multiple years during a developing (ongoing, at time of sampling) outbreak. Sampling effort covered areas close to the epicenter of the outbreak (Quebec/Canada) and adjacent areas affected by the outbreak progress. This dataset also provides genome‐wide characterization of SBW populations from Quebec, serving as a standard for the identification of future samples regarding their locality of origin, structure and connectivity. These data represent a valuable novel resource for further study of the spatial and temporal dynamics of SBW, and how spatial genetic diversity and gene flow are affected by population outbreaks. These data provide a temporal snapshot of SBW genetic diversity, which can serve as baseline for future studies regarding outbreaks, and the impact of human‐induced environmental changes on complex population dynamics. This genotype dataset comprises a unique representation of genomic‐level composition and variation observed in subsequent generations of an irruptive, cyclic outbreaking species and is of utmost importance for exploring and describing how accelerated demographic variation impacts the development of spatial genetic structure across heterogeneous landscapes. We believe this dataset is essential to management and conservation biology initiatives not only for SBW and boreal forests but also for providing a starting point for broader evolutionary and ecological studies of complex population dynamics. Furthermore, the knowledge, data collection, and curation framework we present here can be used to inform similar spatial temporal baseline studies of other outbreaking (e.g., mountain pine beetle, red‐backed voles) and invasive species (e.g., spongy moth and emerald ash borer). The data are released under a CC BY 4.0 license.

Background Vector-borne pathogens (VBPs) are increasing in significance in veterinary medicine and public health settings, with wildlife playing a potentially crucial role in their transmission. Eurasian badgers (Meles meles) are widely distributed across Europe. However, information currently available on the prevalence of VBPs in badgers is limited. The objective of the current study was to investigate the occurrence of Anaplasmataceae, Bartonella spp., Mycoplasma spp., Rickettsia spp., Piroplasmida, Trypanosomatida and Filarioidea in badgers and subsequently, based on the results, assess the potential risk to domestic animals, other wildlife and humans. Methods Between 2017 and 2021, blood or spleen samples from 220 badgers were collected in nine continental European countries: Austria (n = 7), Bosnia and Herzegovina (n = 2), Croatia (n = 22), France (n = 44), Germany (n = 16), Hungary (n = 7), Italy (n = 16), Romania (n = 80) and Serbia (n = 26). VBPs were identified by performing PCR analysis on the samples, followed by Sanger sequencing. Additionally, to distinguish between different Babesia lineages we performed restriction fragment length polymorphism (RFLP) analysis on piroplasm-positive samples, using HinfI as restriction enzyme. A phylogenetic analysis was performed on Mycoplasma spp. Results The pathogens identified were Babesia sp. badger type A (54%), B (23%), and C (37%); Trypanosoma pestanai (56%); Mycoplasma sp. (34%); Candidatus Mycoplasma haematomelis (8%); Candidatus Mycoplasma haematominutum (0.5%); and Ehrlichia spp. (2%). Rickettsia spp., Bartonella spp. and filarioid nematodes were not detected among the tested samples. Conclusions The large sample size and diverse study populations in this study provide valuable insights into the distribution and epidemiology of the analyzed pathogens. Some of the VBPs identified in our study show high similarity to those found in domestic animals, such as dogs. This finding suggests that badgers, as potential reservoirs for these pathogens, may pose a threat not only to other wildlife but also to domestic animals in close vicinity. Continuous surveillance is essential to monitor VBPs in wildlife as a means to enable the assessment of their impact on other wildlife species, domestic animals and human health. Graphical Abstract

The Sea of Galilee is a unique large freshwater or slightly oligohaline natural lake in the Levant. Therefore, it represents an important aquatic habitat in the region that also provides invaluable ecosystem services for the local communities. To improve our knowledge of the lake’s ecosystem and the use of disarticulated ostracod valves and preserved carapaces, micro-crustacean remains commonly used in palaeolimnology and palaeoceanography, as proxies for palaeoenvironmental reconstructions, and to examine the post-mortem dispersal of ostracod remains, 68 surface-sediment samples were collected from the lake bottom in 2012 and analysed for the ostracod assemblages. Both, the noded and smooth, forms of Cyprideis torosa dominate in the Sea of Galilee, with the former more abundant than the latter. Relatively abundant and found at half of the 68 sampling locations or more, are also Ilyocypris hartmanni, I. cf. nitida, Darwinula stevensoni and Neglecandona angulata. In addition, ten less abundant ostracod taxa were recorded in the lake. Of all 15 taxa recorded in our study, ten were also recorded in a study of the Sea of Galilee’s ostracod fauna conducted already in the 1960s. The newly recorded five taxa are relatively rare, and they were mostly found in the region of the Jordan River delta or near the southeastern shore of the lake which were not included in the survey of the 1960s. Thus, there is no evidence for a significant change in the ostracod fauna of the lake over the last half-century. In comparison to the ostracod assemblage from a late Pleistocene archaeological excavation site at the southwestern margin of the lake, the assemblage from the recent survey is slightly less diverse, probably because of the long duration of ca. 5000 years integrated by the sedimentary section of the archaeological site and also due to nearby freshwater inflows from which valves and carapaces were probably washed to the site’s location. Our study also shows that ostracod valves and carapaces are typically relatively abundant in most of the surface-sediment samples collected from locations at 18 m or shallower. In contrast, very few valves and carapaces were recorded at depths greater than 18 m, which is a zone affected by seasonal anoxia in the Sea of Galilee. These few ostracod remains were apparently transported by currents and waves to the central, deeper part of the lake, but their low number shows that such post-mortem dispersal of ostracod remains is insignificant in the deeper part of the lake. Thus, our study provides support for palaeoenvironmental and palaeoclimate reconstructions based on ostracod records from single sediment cores obtained from depths unaffected by post-mortem transport and seasonal or permanent anoxia.

We introduce the database of European vascular plant red lists, a compilation of red list categories designated to taxa during in-country conservation assessments. Version 1.0 of the database is a standalone static dataset with open access in an end-user friendly format. Its aim is to fulfil the objectives of European Cooperation in Science and Technology (COST) Action 18201, ConservePlants. The database synthesizes data across 42 red lists from 41 countries, with participation of 39 out of a total of 44 European countries and two additional Mediterranean countries. The database contains 51,109 records representing 21,481 original taxonomic names with 37 different red list categories. During data harmonisation, 20,312 of the original taxonomic names were assigned to 17,873 unique accepted taxonomic names with scientific authorships across 184 families, 1650 genera and 15,593 species; and red list categories were standardised to 13 unique categories. We see this database as a source of information in diverse plant conservation activities and suitable for various stakeholders.

The raccoon roundworm (Baylisascaris procyonis), a gastrointestinal nematode parasite of the raccoon (Procyon lotor), is the causative agent of a zoonotic disease that can cause severe neurological sequelae and even fatal cases. The parasite is now established in Europe and, while not present in all raccoon populations, it is currently expanding its range. Understanding the geographic distribution of the roundworm is a necessity for public health. Here, we report the first detections of the raccoon roundworm from Luxembourg. We used genetic techniques to test whether the roundworm originated from a distinct introduction event or entered the country by natural dispersal. We detected two roundworms in a raccoon that was road-killed in Echternach, northeastern Luxembourg. Furthermore, in a wildlife rescue centre, roundworms were detected in the latrine of an enclosure containing seven raccoons. Using different genetic techniques, we showed the Echternach roundworms to originate from the nearest German population, while the rescue centre roundworms were genetically distinct. By genotyping the host from a roundworm DNA extract, we identified a raccoon originating from southwest Luxembourg as the host of at least one roundworm. Roundworms are thus colonising Luxembourg both by natural dispersal and from an introduced population. The (potential) hosts all originated from the local population, suggesting that imported/introduced roundworms have already spread to the local raccoon population. Authorities should act as though the parasite is already widespread in the country, raising awareness among the public and individuals with occupational contact with raccoons.

Key Biodiversity Areas (KBAs) represent the largest global network of sites critical to the persistence of biodiversity, which have been identified against standardised quantitative criteria. Sites that hold very high biodiversity value or potential are given specific attention on site‐based conservation targets of the Kunming‐Montreal Global Biodiversity Framework (GBF), and KBAs are already used in indicators for the GBF and the Sustainable Development Goals. However, most of the species that trigger KBA status are birds and to maximise benefits for biodiversity under the actions taken to fulfil the GBF, countries need to update their KBAs to represent important sites across multiple taxa. Here we introduce KBAscope, an R package to identify potential KBAs using multiple taxonomic groups. KBAscope provides flexible, user‐friendly functions to edit species data (population, range maps, area of occupancy, area of habitat and localities); apply KBA criteria; and generate outputs to support the delineation and validation of KBAs. The details of the analysis – such as the spatial units tested or the KBA criteria applied – can be decided according to the scope of the analysis. We demonstrate the functionality of KBAscope by using it to identify potential KBAs in Greece based on multiple terrestrial taxonomic groups and four sizes of grid cells (4 km², 25 km², 100 km², 225 km²).

Premise Strong elevational and latitudinal gradients allow the study of genetic differentiation in response to similar environmental changes. However, it is uncertain whether the environmental changes along the two types of gradients result in similar genetically based changes in quantitative traits. Peripheral arctic and alpine populations are thought to have less evolutionary potential than more central populations do. Methods We studied quantitative traits of the widespread Anthyllis vulneraria in a common garden. Plants originated from 20 populations along a 2000‐m elevational gradient from the lowlands to the elevational limit of the species in the Alps, and from 20 populations along a 2400‐km latitudinal gradient from the center of the distribution of the species in Central Europe to its northern distributional margin. Results Most traits showed similar clinal variations with elevation and latitude of origin, and the magnitude of all measured traits in relation to mean annual temperature was similar. Higher Q ST values than F ST values in several traits indicated diversifying selection, but for others Q ST was smaller than F ST . Genetic diversity of quantitative traits and neutral molecular markers was not correlated. Plasticity in response to favorable conditions declined with elevation and less strongly with latitude of origin, but the evolvability of traits did not. Conclusions The clinal variation suggests adaptive differentiation of quantitative traits along the two gradients. The evolutionary potential of peripheral populations is not necessarily reduced, but lower plasticity may threaten their survival under rapidly changing climatic conditions.

The Antarctic Slope Front and the associated Antarctic Slope Current dynamically regulate the exchanges of heat across the continental shelf break around Antarctica. Where the front is weak, relatively warm deep waters reach the ice shelf cavities, contributing to basal melting and ultimately affecting sea level rise. Here, we present new 2017–2021 records from two moorings deployed on the upper continental slope (530 and 738 m depth) just upstream of the Filchner Trough in the southeastern Weddell Sea. The structure and seasonal variability of the frontal system in this region, central to the inflow of warm water toward the large Filchner‐Ronne Ice Shelf, is previously undescribed. We use the records to describe the mean state and the seasonal variability of the regional hydrography and the southern part of the Antarctic Slope Current. We find that (a) the current is, contrary to previous assumptions, bottom‐enhanced, (b) the isotherms slope upwards toward the shelf break, and more so for warmer isotherms, and (c) the monthly mean thermocline depth is shallowest in February‐March and deepest in May‐June while (d) the current is strongest in April‐June. On monthly timescales, we show that (e) positive temperature anomalies of the de‐seasoned records are associated with weaker‐than‐average currents. We propose that the upward‐sloping isotherms are linked to the local topography and conservation of potential vorticity. Our results contribute to the understanding of how warm ocean waters propagate southward and potentially affect basal melt rates at the Filchner‐Ronne Ice Shelf.

Belemnite rostra are very abundant in Mesozoic marine deposits in many regions. Despite this abundance, soft-tissue specimens of belemnites informing about anatomy and proportions of these coleoid cephalopods are extremely rare and limited to a few moderately large genera like Passaloteuthis and Hibolithes. For all other genera, we can make inferences on their body proportions and body as well as mantle length by extrapolating from complete material. We collected data of the proportions of the hard parts of some Jurassic belemnites in order to learn about shared characteristics in their gross anatomy. This knowledge is then applied to the Bajocian genus Megateuthis, which is the largest known belemnite genus worldwide. Our results provide simple ratios that can be used to estimate belemnite body size, where only the rostrum is known.

Recent finds of lichenicolous fungi from the Netherlands are described and discussed. Echinothecium micareae spec. nov. and Lichenochora verrucariae spec. nov. are described as new for science. An additional 31 species are reported for the first time from the Netherlands: Abrothallus cladoniae, Arthonia diploiciae, A. rinodinicola, Cladophialophora cladoniae, Dacampia cyrtellae, Dactylospora microspora, Didymocyrtis cladoniicola, D. consimilis, D. physciae, Diplotomma parasiticum, Epithamnolia pertusariae, Gonatophragmium lichenophilum, Lichenohendersonia varians, Lichenostigma chlaroterae, L. cosmopolites, Nectria brutia, Nectriopsis physciicola, Niesslia cladoniicola, Opegrapha hochstetteri, O. opaca, Phaeoseptoria peltigerae, Phaeospora lecanorae, Polycoccum aksoyi, P. laursenii, Pronectria diplococca, Pseudocercospora lichenum, Stigmidium fuscatae, Tremella candelariellae, T. occultixanthoriae, Trimmatostroma acetabuli and Zwackhiomyces diederichii. Notes are provided on these and some other interesting lichenicolous fungi. There are currently 240 species of lichenicolous fungi known from the Netherlands.

Hoverflies (Syrphidae) are essential pollinators, and their severe decline jeopardizes their invaluable contribution to plant diversity and agricultural production. However, we know little about the dispersal abilities of hoverflies in urbanized landscapes, limiting our understanding of the spatiotemporal dynamics of plant-pollinator systems and reducing our ability to preserve biodiversity in the context of global change. Previous work has not addressed how urbanization affects the functional connectivity of hoverflies and whether dispersal is a limiting factor in their population dynamics. In this study, we investigated the spatial genetic structure of two nonmigratory species of hoverflies in two urban areas. We collected more than a thousand specimens of each Syritta pipiens and Myathropa florea, each, by hand netting in two western European urbanized study areas of 490 and 460 km 2 in 2021, and we genotyped them at 14 and 24 microsatellite loci, respectively. Based on spatial and nonspatial Bayesian clustering methods, we failed to reject the null hypothesis of panmixia, suggesting that both species exhibited high genetic connectivity despite urbanization. The distribution of allele frequencies was not correlated with geographic distance, implying that isolation-by-distance was negligible at the investigated spatial scale in both species. Although anthropogenic land cover changes generally have dramatic consequences on biodiversity, these hoverfly species retain high connectivity, which suggests that dispersal is not a strong limiting factor in their metapopulational dynamics. However, high effective population size and its confounding effect on signals of genetic drift may limit our ability to conclude confidently about landscape effects on gene flow in those two species. Provided we maintain or restore habitat, recolonization may be prompt even in urban areas.

Human infection by Baylisascaris procyonis can result in larva migrans syndromes, which can cause severe neurological sequelae and fatal cases. The raccoon serves as the definitive host of the nematode, harboring adult worms in its intestine and excreting millions of eggs into the environment via its feces. Transmission to paratenic hosts (such as rodents, birds and rabbits) or to humans occurs by accidental ingestion of eggs. The occurrence of B. procyonis in wild raccoons has been reported in several Western European countries. In France, raccoons have currently established three separate and expanding populations as a result of at least three independent introductions. Until now the presence of B. procyonis in these French raccoon populations has not been investigated. Between 2011 and 2021, 300 raccoons were collected from both the south-western and north-eastern populations. The core parts of the south-western and north-eastern French raccoon populations were free of B. procyonis. However, three worms (molecularly confirmed) were detected in a young raccoon found at the edge of the north-eastern French raccoon population, close to the Belgian and Luxemburg borders. Population genetic structure analysis, genetic exclusion tests and factorial correspondence analysis all confirmed that the infected raccoon originated from the local genetic population, while the same three approaches showed that the worms were genetically distinct from the two nearest known populations in Germany and the Netherlands. The detection of an infected raccoon sampled east of the northeastern population raises strong questions about the routes of introduction of the roundworms. Further studies are required to test wild raccoons for the presence of B. procyonis in the area of the index case and further east towards the border with Germany.

The intensification of agriculture and urbanisation has precipitated the decline of numerous species, including the northern crested newt (Triturus cristatus). To mitigate the impacts of habitat degradation and loss, restoration initiatives depend on evidence-based decision-making to identify priority sites for conservation efforts. Here, we employed a multidisciplinary approach, drawing on population genetics, species distribution modelling (SDMs) and landscape genetics to develop a spatial prioritisation framework for the creation and/or restoration of crested newt breeding ponds in Luxembourg. For the genetic analyses, more than 1000 crested newts from 98 ponds across Luxembourg were genotyped at 15 microsatellite loci to assess genetic diversity and spatial clustering. The relationship between newt presence and environmental variables was evaluated using SDMs. Priority restoration areas were identified with PRIORITZR, integrating genetic diversity, habitat suitability and connectivity. The population genetic structure was characterised by spatial clustering, which followed an isolation-by-distance pattern. Five sites were identified as significantly differentiated from the remaining populations, warranting targeted conservation efforts. Standing water bodies and proximity to the nearest occupied pond were the most important predictors of crested newt presence. The highest gain in habitat suitability through the creation of new ponds was predicted to occur in southwest Luxembourg. Based on the country-wide predicted occurrence of crested newts and gains in habitat suitability, areas of highest restoration potential were identified in close proximity to existing crested newt populations. The produced maps of priority restoration areas should inform future conservation efforts of the crested newt in Luxembourg. While the importance of preserving genetic diversity is widely recognised, the theory-practice gap frequently precludes the incorporation of genetic aspects into in situ conservation measures or management policies. This case study demonstrates the integration of multidisciplinary analyses within an evidence-based framework to guide species conservation efforts.

The intracellular protozoan Toxoplasma gondii is distributed worldwide and infects many species of warm-blooded animals. Most mammals, including humans, can serve as intermediate hosts. This pathogen, with its zoonotic potential, causes toxoplasmosis, a condition that can range from subclinical to fatal in humans. It is therefore important to assess the occurrence of the pathogen, even if only indirectly through the detection of antibodies. Epidemiological data on the seroprevalence in wild animals, including invasive species, are rare in Poland. Therefore, we tested 197 wild raccoons (Procyon lotor) and 89 raccoon dogs (Nyctereutes procyonoides) from Zgorzelec County, southwestern Poland, for the presence of antibodies. Samples were collected between January 2019 and December 2020 and analysed using a commercial indirect modified agglutination test (MAT, cut-off 1:25). The statistical analysis revealed significant differences in seroprevalence between the two predatory species. Of the 197 surveyed raccoons, 96 (48.73%; 95% confidence interval (CI): 41.73–55.73%) tested positive, while 25 of the 89 raccoon dogs (28.09%; 95% CI: 18.70–37.48%) were positive. Regarding risk factors, body weight and sex influenced the presence of T. gondii antibodies in both the species, with a higher likelihood of seropositivity among heavier animals and females, respectively. For raccoon dogs, juveniles were more likely to be seropositive than adults at a given weight. Our results suggest that T. gondii infection is widespread in the regional raccoon and raccoon dog populations, indicating a high level of parasite circulation in the environment.

Population genetics is a valuable tool for assessing the impact of human‐altered landscapes on genetic connectivity in various species. However, when applied to insects, challenges arise due to potentially large effective population sizes (), high dispersal capacities and the recency of anthropogenic impacts. This study assessed the population genetic structure of two pollinators across a human‐altered landscape in Luxembourg. Samples from the ashy mining bee ( Andrena cineraria , N = 201) and the greater bee fly ( Bombylius major, N = 637) were genotyped at 25 microsatellite loci, including a genotyping‐by‐amplicon‐sequencing approach for A. cineraria . Despite high statistical power of > 0.002 in B. major and > 0.0025 in A. cineraria , no deviations from genetic homogeneity were detected. For both species, there was no evidence for isolation‐by‐distance or genetic clustering. Genetic homogeneity was most likely the result of high levels of gene flow that compensate for the effects of genetic drift. Estimates of ranged between several thousand to tens of thousands, although precision was low. Simulations highlighted that genetic lag times can substantially affect our ability to detect recent (<50 generations) population differentiation when is very large. Lag times were shorter with data from 25,000 simulated di‐allelic loci, but only when sample sizes remained high. Insect genetic studies should consider lag times due to large and ensure sample size and markers offer adequate power to reject the null hypothesis of no landscape effect on genetic connectivity.

Toxoplasma gondii is an obligate intracellular protozoan that causes toxoplasmosis in warm-blooded animals. Although most infections in humans and animals are subclinical, an infection can nevertheless be fatal. One of the important characteristics in the epidemiology of this parasite is waterborne transmission. The American mink (Neogale vison), a mammal closely adapted to freshwater ecosystems, is a potential sentinel for T. gondii. We analysed meat juice from the heart of 194 wild minks collected between 2019 and 2022 in five study areas from Germany and Poland and tested for the presence of antibodies against T. gondii. The analysis was performed using a commercial enzyme-linked immunosorbent assay test (ELISA). Antibodies were detected in 45.36% (88/194, 95% confidence interval (CI): 38.39–52.41%) of the analysed animals. While the prevalence values ranged from 37.50% to 49.30%, there was no significant difference in seroprevalence between the study areas. Juveniles were less likely to carry T. gondii antibodies than adults (odds ratio: 0.216), whereas there was no significant difference in prevalence between the sexes (odds ratio: 0.933). The results of our study show that contact with T. gondii is widespread in minks, and the parasite is common in inland freshwater ecosystems in Germany and Poland. This indicates that watercourses play an important role in the spread of T. gondii oocysts.

Background Batrachochytrium dendrobatidis (Bd) and Batrachochytrium salamandrivorans (Bsal) are two pathogenic fungi that are a significant threat to amphibian communities worldwide. European populations are strongly impacted and the monitoring of the presence and spread of these pathogens is crucial for efficient decision-making in conservation management. Results Here we proposed an environmental DNA (eDNA) monitoring of these two pathogenic agents through droplet digital PCR (ddPCR) based on water samples from 24 ponds in Luxembourg. In addition, amphibians were swabbed in eight of the targeted ponds in order to compare the two approaches at site-level detection. This study allowed the development of a new method taking below-Limit of Detection (LOD) results into account thanks to the statistical comparison of the frequencies of false positives in no template controls (NTC) and below-LOD results in technical replicates. In the eDNA-based approach, the use of this method led to an increase in Bd and Bsal detection of 28 and 50% respectively. In swabbing, this resulted in 8% more positive results for Bd. In some samples, the use of technical replicates allowed to recover above-LOD signals and increase Bd detection by 35 and 33% respectively for eDNA and swabbing, and Bsal detection by 25% for eDNA. Conclusions These results confirmed the usefulness of technical replicates to overcome high levels of stochasticity in very low concentration samples even for a highly sensitive technique such as ddPCR. In addition, it showed that below-LOD signals could be consistently recovered and the corresponding amplification events assigned either to positive or negative detection via the method developed here. This methodology might be particularly worth pursuing in pathogenic agents’ detection as false negatives could have important adverse consequences. In total, 15 ponds were found positive for Bd and four for Bsal. This study reports the first record of Bsal in Luxembourg. Supplementary Information The online version contains supplementary material available at 10.1186/s12862-023-02189-9.

Biological invasions are a major threat to biodiversity and have particularly devastating impacts on island ecosystems. The New Caledonia archipelago is considered a biodiversity hotspot due to its diverse native flora. Javan rusa deer (Rusa timorensis) were introduced to New Caledonia in 1870 and the population consists of several hundred thousand individuals today. They directly threaten rare endemic species and affect the composition and structure of the vegetation. While a rusa deer management plan has identified ten priority areas for deer control operations, removing deer could be offset by the dispersal of animals back into the control areas. Here, we genotyped 628 rusa deer using 16 microsatellite markers to analyse the genetic structure of the animals in New Caledonia. We aimed to assess fine-scale genetic structure, to identify natural barriers to deer movement and to assess functional connectivity by optimising individual-based landscape resistance models. Our results suggested that rusa deer formed a single genetic population on the main New Caledonian island. The isolation-by-distance pattern suggested that female dispersal was limited, whereas males had larger dispersal distances. We assessed functional connectivity using different genetic distance metrics and all models performed poorly (mR² ≤ 0.0043). Landscape features thus hardly affected deer movement. The characteristics of our results suggested that they were not an artefact of the colonisation history of the species. Achieving an effective reduction of deer population sizes in specific management areas will be difficult because of the deer’s high dispersal capabilities and impossible without very substantial financial investment.