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Biological invasions by nonindigenous species can have negative effects on economies and ecosystems. To limit this impact, current research on biological invasions uses functional traits to facilitate a mechanistic understanding of theoretical and applied questions. Here we aimed to assess the role of functional traits in the progression of crayfish species through different stages of invasion and determine the traits associated with invasive success. A dataset of thirteen functional traits of 15 species currently occurring or available for sale in the Netherlands was evaluated. Six of these crayfish appeared invasive. Important traits distinguishing successful from unsuccessful invaders were a temperate climate in the native range, a medium to high egg count and producing more than one egg clutch per year. The most successful invaders had different functional trait combinations: Procambarus clarkii has a higher reproductive output, can migrate over longer distances and possesses a higher aggression level; Faxonius limosus is adapted to a colder climate, can reproduce parthenogetically and has broader environmental tolerances. Using a suit of functional traits to analyse invasive potential can help risk management and prevention. For example, based on our data Procambarus virginalis is predicted to become the next successful invasive crayfish in the Netherlands. [ABSTRACT FROM AUTHOR]

Assessing mosquito biodiversity is important for disease surveillance and ecosystem health assessments. Such studies are particularly needed in regions like the Caribbean, which have experienced a series of recent mosquito borne disease outbreaks but received little attention regarding its invertebrate biodiversity. Here, we report on results from a mosquito survey on the Dutch Leeward Islands (Sint Eustatius, Sint Maarten and Saba), carried out in April and October 2018, which is the first integrative survey since those conducted by Van der Kuyp (1947) and Wagenaar Hummelinck (1949). Moreover, we present a novel key for adults and fourth instar larvae of the mosquitoes of the Dutch Leeward Islands. Overall, eleven species were recorded, eight on Sint Maarten, five on Saba and two on Sint Eustatius. Two new potential disease vectors, Culex nigripalpus and Aedes taeniorhynchus, were recorded on Sint Maarten. One previously recorded species, Cx. habilitator, was not retrieved from any of the islands, which is further discussed in the paper. Species indicative of natural forest which previously occurred on all three islands were absent from Sint Eustatius and Sint Maarten but still present on Saba. In contrast, species indicative of human inhabitation, Ae. aegypti and Cx. quinquefasciatus, were highly abundant on Sint Maarten and Sint Eustatius and present in low numbers on Saba. Overall, the results of this study emphasize the importance of biodiversity surveys and indicate that frequent mosquito inventories may contribute to a better understanding of mosquito community composition and distribution of potential vector species. [ABSTRACT FROM AUTHOR]

Freshwater habitats are under stress from agricultural land use, most notably the influx of neonicotinoid pesticides and increased nutrient pressure from fertilizer. Traditional studies investigating the effects of stressors on freshwater systems are often limited to a narrow range of taxa, depending heavily on morphological expertise. Additionally, disentanglement of multiple simultaneous stressors can be difficult in field studies, whereas controlled laboratory conditions do not accurately reflect natural conditions and food webs. To overcome these drawbacks, we investigated the impacts of two agricultural stressors (the neonicotinoid insecticide thiacloprid and fertilizer) in full‐factorial design in a semi‐natural research site, using environmental DNA sampling to study three different taxonomic groups representing three trophic levels: bacteria (decomposers), phytoplankton (primary producers), and chironomids (consumers). The results show considerable impact of both stressors across trophic levels, with an additive effect of fertilizer and thiacloprid on community composition at all levels. These findings suggest that agricultural stressors affect the entire food web, either directly or through cascade reactions. They are also consistent with morphological assessments that were performed in the same study site, even at a lower number of replicates. The study presented shows that the use of multimarker environmental DNA provides a more comprehensive assessment of stressor impacts across multiple trophic levels, at a higher taxonomic resolution than traditional surveys. Additionally, many putative novel bioindicators for both agricultural stressors were discovered. We encourage further investigations into stressors impacts at different trophic levels, which will lead to more effective monitoring and management of freshwater systems. [ABSTRACT FROM AUTHOR]

DNA-based identification through the use of metabarcoding has been proposed as the next step in the monitoring of biological communities, such as those assessed under the Water Framework Directive (WFD). Advances have been made in the field of metabarcoding, but challenges remain when using complex samples. Uneven biomass distributions, preferential amplification and reference database deficiencies can all lead to discrepancies between morphological and DNA-based taxa lists. The effects of different taxonomic groups on these issues remain understudied. By metabarcoding WFD monitoring samples, we analyzed six different taxonomic groups of freshwater organisms, both separately and combined. Identifications based on metabarcoding data were compared directly to morphological assessments performed under the WFD. The diversity of taxa for both morphological and DNA-based assessments was similar, although large differences were observed in some samples. The overlap between the two taxon lists was 56.8% on average across all taxa, and was highest for Crustacea, Heteroptera, and Coleoptera, and lowest for Annelida and Mollusca. Taxonomic sorting in six basic groups before DNA extraction and amplification improved taxon recovery by 46.5%. The impact on ecological quality ratio (EQR) scoring was considerable when replacing morphology with DNA-based identifications, but there was a high correlation when only replacing a single taxonomic group with molecular data. Different taxonomic groups provide their own challenges and benefits. Some groups might benefit from a more consistent and robust method of identification. Others present difficulties in molecular processing, due to uneven biomass distributions, large genetic diversity or shortcomings of the reference database. Sorting samples into basic taxonomic groups that require little taxonomic knowledge greatly improves the recovery of taxa with metabarcoding. Current standards for EQR monitoring may not be easily replaced completely with molecular strategies, but the effectiveness of molecular methods opens up the way for a paradigm shift in biomonitoring. [ABSTRACT FROM AUTHOR]

Six species of dragonflies are recorded for the island of Sint Eustatius, Lesser Antilles. Breeding records are established for four out of the six species, despite the lack of natural fresh water sources. DNA barcoding was used to match the larvae with the adults. [ABSTRACT FROM AUTHOR]

The bioassessment of aquatic ecosystems is currently based on various biotic indices that use the occurrence and/or abundance of selected taxonomic groups to define ecological status. These conventional indices have some limitations, often related to difficulties in morphological identification of bioindicator taxa. Recent development of DNA barcoding and metabarcoding could potentially alleviate some of these limitations, by using DNA sequences instead of morphology to identify organisms and to characterize a given ecosystem. In this paper, we review the structure of conventional biotic indices, and we present the results of pilot metabarcoding studies using environmental DNA to infer biotic indices. We discuss the main advantages and pitfalls of metabarcoding approaches to assess parameters such as richness, abundance, taxonomic composition and species ecological values, to be used for calculation of biotic indices. We present some future developments to fully exploit the potential of metabarcoding data and improve the accuracy and precision of their analysis. We also propose some recommendations for the future integration of DNA metabarcoding to routine biomonitoring programs. [ABSTRACT FROM AUTHOR]

• A standardized protocol yields reproducible bulkDNA metabarcoding results. • Highly abundant and large species are shared most often between laboratories. • Need for standardization when comparing alpha diversity between different studies. • Betadiversity patterns are robust to changes in the metabarcoding wetlab protocol. DNA metabarcoding can be used in marine environmental monitoring if results are reproducible between labs and robust against modifications to the lab protocol. In this interlaboratory study, we conducted a ring test where subsamples of blended macrobenthos samples were distributed to four laboratories located in Belgium, the Netherlands, Germany and Denmark. Samples were processed by a standardized lab protocol and by an adapted protocol, and the resulting datasets were analyzed with the same bioinformatics pipeline. Different biodiversity indicators were calculated. Our results show that bulkDNA metabarcoding of marine macrobenthos offers a highly reproducible assessment of alpha diversity patterns when using a standardized protocol, since comparable species numbers, Shannon indices and Inverse Simpson indices were found between laboratories. Especially high abundant species and species with large body sizes were shared between the laboratories. The need for using a standardized protocol to enhance comparability in alpha diversity between different studies was shown. Beta diversity patterns are less subjected to changes in the metabarcoding protocol and were almost identical between different laboratories, as the main clustering was always based on the macrobenthic community, independent of the used protocol or the laboratory that conducted the work. We conclude that DNA metabarcoding for marine environmental monitoring is an appropriate method when the aim is to study changes in community patterns and advocate its implementation in routine monitoring programs of national and European authorities, providing that a standardized protocol is implemented and/or a detailed description of the protocol is available. [ABSTRACT FROM AUTHOR]

We calculated a Living Planet Index (LPI) for the Netherlands, based on 361 animal species from seven taxonomic groups occurring in terrestrial and freshwater habitats. Our assessment is basically similar to the global LPI, but the latter includes vertebrate species and trends in population abundance only. To achieve inferences on trends in biodiversity more generally, we added two insect groups (butterflies and dragonflies) and added occupancy trends for species for which we had no abundance trends available. According to the LPI, the state of biodiversity has slightly increased from 1990 to 2014. However, large differences exist between habitat types. We found a considerable increase in freshwater animal populations, probably because of improvement of chemical water quality and rehabilitation of marshland habitats. We found no trend in the LPI for woodland populations. In contrast, populations in farmland and open semi-natural habitats (coastal dunes, heathland and semi-natural grassland) declined, which we attribute to intensive agricultural practices and nitrogen deposition, respectively. The LPI shows that, even in a densely populated western European country, ongoing loss of animal biodiversity is not inevitable and may even be reversed if adequate measures are taken. Our approach enabled us to produce summary statistics beyond the level of species groups to monitor the state of biodiversity in a clear and consistent way. [ABSTRACT FROM AUTHOR]

PCR-free techniques such as meta-mitogenomics (MMG) can recover taxonomic composition of macroinvertebrate communities, but suffer from low efficiency, as >90% of sequencing data is mostly uninformative due to the great abundance of nuclear DNA that cannot be identified with current reference databases. Current MMG studies do not routinely check data for information on macroinvertebrate-associated bacteria and gene functions. However, this could greatly increase the efficiency of MMG studies by revealing yet overlooked diversity within ecosystems and making currently unused data available for ecological studies. By analysing six 'mock' communities, each containing three macroinvertebrate taxa, we tested whether this additional data on bacterial taxa and functional potential of communities can be extracted from MMG datasets. Further, we tested whether differential centrifugation, which is known to greatly increase efficiency of macroinvertebrate MMG studies by enriching for mitochondria, impacts on the inferred bacterial community composition. Our results show that macroinvertebrate MMG datasets contain a high number of mostly endosymbiont bacterial taxa and associated gene functions. Centrifugation reduced both the absolute and relative abundance of highly abundant Gammaproteobacteria, thereby facilitating detection of rare taxa and functions. When analysing both taxa and gene functions, the number of features obtained from the MMG dataset increased 31-fold ('enriched') respectively 234-fold ('not enriched'). We conclude that analysing MMG datasets for bacteria and gene functions greatly increases the amount of information available and facilitates the use of shotgun metagenomic techniques for future studies on biodiversity. [ABSTRACT FROM AUTHOR]