DOI: 10.3897/neobiota.108.190976

Authors: Tom Van den Neucker, Jan Soors, Arnaud Jacobs, Jane Reniers, Soria Delva, Nikol Kmentová, Maarten P.M. Vanhove, Bram D’hondt, Kevin Scheers, Louis Bronne, Christine Ewers, Laura Abraham, Quentin Groom, David Halfmaerten, Sabrina Neyrinck, Karin Breugelmans, Thierry Backeljau, Jean-Lou Justine, Romain Gastineau, Leigh Winsor, Tim Adriaens

Abstract: Multiple species of land planarians have become established outside their natural ranges. Some are considered invasive because of their rapid spread and adverse effects on ecosystems. Once established, land planarians are difficult to manage. Therefore, it is crucial to document their presence and spread and assess their risk. This study provides an annotated checklist and distribution maps of all non-native land planarians recorded in Belgium, as well as a climate-matching analysis and a Harmonia+ risk assessment for each species. A climate-matching analysis and a risk assessment were also conducted for two species that do not occur in Belgium but are included in the European Union’s list of invasive alien species of Union Concern: Platydemus manokwari and Arthurdendyus triangulatus. Thus far, nine non-native land planarian species have been recorded in Belgium: Anisorhynchodemus cf. signata, Bipalium kewense, Caenoplana coerulea, C. variegata, Diversibipalium multilineatum, Dolichoplana striata, Marionfyfea adventor, Obama nungara, and Parakontikia ventrolineata. Climate-matching percentages were highest for A. triangulatus, M. adventor, C. variegata, and O. nungara. Obama nungara is the only species that received a very high environmental risk score. Diversibipalium multilineatum and P. manokwari both received high environmental risk scores. The overall risk score was medium for O. nungara and D. multilineatum and low for all other species. The information presented in this review may provide a basis for developing suitable detection and monitoring methods and rapid-response strategies for high-risk non-native land planarians.

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DOI: 10.3897/neobiota.103.159848

Authors: Thomas J. Verleye, Thomas R. H. Kerkhove, Gert Van Hoey, Hans Pirlet, Francis Kerckhof, Ann-Katrien Lescrauwaet, Leen Vandepitte, Jan Mees

Abstract: Based on a thorough literature review and expert consultation, this study provides an inventory of all introduced non-indigenous species (iNIS) reported for Belgian marine and brackish waters. The data indicate a strong increase in iNIS in the study area from the 1990s onward, averaging 2.2 newly detected species per year, with a cumulative total of 108 iNIS between 1800 and 2024. The majority of these iNIS have the Northwestern Pacific or Northwestern Atlantic as their native region and are primarily introduced in Western Europe via shipping or aquaculture. In addition to compiling the inventory, the context in which the iNIS are detected is examined, distinguishing between official monitoring programs, project-based data collection efforts, and citizen science initiatives. Our findings indicate that while the EU aims to promote coordination between its Marine Strategy Framework Directive (MSFD) and Water Framework Directive (WFD), a misalignment occurs in the practical implementation of iNIS monitoring at the Belgian level. For example, a coherent and integrated monitoring framework across marine, brackish, and freshwater systems is still lacking. Furthermore, despite the EU’s ambition to ensure comprehensive iNIS monitoring, no legal framework currently mandates targeted monitoring in coastal ports, despite their well-documented role as hotspots for new marine introductions. After all, iNIS monitoring is only mandatory under the MSFD, which in essence applies only seaward from the coastal baseline and therefore does not cover waters within these ports. In addition, while the EU’s IAS Regulation has recently incorporated a few marine species on the Union list, its monitoring requirements remain primarily focused on terrestrial and freshwater species. As a result, observations published by citizens with significant expertise in the field represent the primary source of marine iNIS data in coastal port areas in recent decades in Belgium. The fragmentary nature of iNIS data complicates the efficient flow of information to international or European iNIS reference databases that support policy and decision-making. Yet, even species officially reported by Member States under MSFD Descriptor 2 are not always included in these reference databases. Nonetheless, accurate data on iNIS presence and distribution are essential for effectively targeting and managing iNIS.

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DOI: 10.3897/neobiota.94.121987

Authors: Adwine Vanslembrouck, Kevin Scheers, Xavier Vermeersch, Rens Hendrickx, Anna Schneider, Jacobus De Witte, Isra Deblauwe, Wim Van Bortel, Friederike Reuss, Ruth Müller

Abstract: The invasive mosquito species Aedes albopictus (Skuse, 1894) is rapidly spreading in Europe, posing an increasing threat because of its high vector competence for chikungunya and dengue virus. An integrative and eco-friendly control of these populations is required to prevent mosquito-borne disease outbreaks. Traditionally-used insecticides or other chemical control agents are often expensive, harmful to the environment, strictly controlled or completely banned in several countries. Additionally, insecticide resistance is a potential threat. One possibility for biological control agents is the use of native aquatic beetles as natural predators of mosquitoes to boost Bacillus thuringiensis israelensis (Bti) interventions. Thirty predatory aquatic beetle taxa were caught in Belgium and kept at the Institute of Tropical Medicine’s insectary to test predation rate and prey choice on Aedes albopictus and Culex pipiens Linnaeus, 1758. Predation rates suggest at least four efficient dytiscid predators that are known to inhabit small, temporary habitats in Europe. Further experiments on prey choice reveal a clear preference for Aedes albopictus over alternative larval prey (Culex pipiens, Daphnia sp., Chaoboridae). We found a strong ecological overlap of the feeding niche of A. albopictus and the hunting zone of dytiscid predators in the benthic layer of small waterbodies. Our findings on the efficacy are very encouraging to further assess the potential of native predacious diving beetles as a biological control agent against the invasive A. albopictus in Europe.

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DOI: 10.3897/neobiota.90.113421

Authors: Olivier Hendrik Berteloot, Alexandre Kuhn, Gertie Peusens, Tim Beliën, Louis Hautier, Thomas Van Leeuwen, Patrick De Clercq

Abstract: The brown marmorated stink bug, Halyomorpha halys, native to East Asia, is an invasive pest of economic importance. It has invaded North America and many European countries and is further expanding its range. In Belgium, it was first observed in 2011. Halyomorpha halys is known to cause severe damage in commercial fruit orchards and vegetable crops. A dramatic and unmitigated expansion of H. halys in its adventive range could lead to significant economic implications for agricultural production. In this study, occurrence data of H. halys since its first observation in Belgium was analysed together with molecular information to map the populations and evaluate the genetic diversity of this pest. The genetic diversity of H. halys in Belgium was compared to data from other invaded and native countries reported in previous studies to identify possible invasion routes. The analysis of 1176-bp of mitochondrial DNA cytochrome c oxidase I and II genes (COI and COII) led to the discovery of two novel COI-COII haplotype combinations currently unique to Belgium. The invasion of H. halys in Belgium is likely the result of multiple and ongoing introductions from its native region and from already invaded countries in Europe, particularly Italy. The expansion of the brown marmorated stink bug populations in Belgium is recent and ongoing. Presently, it appears to thrive best in northern Belgium.

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DOI: 10.3897/neobiota.84.94109

Authors: Alex Stemmelen, Bastien Castagneyrol, Quentin Ponette, Simone Prospero, Gilles San Martin, Salome Schneider, Hervé Jactel

Abstract: The number of non-native invasive pests and pathogens has increased dramatically in recent years, with disastrous consequences for the health of forests worldwide. Multiple studies have shown that mixed forests may suffer less damage from insect pests than single species forest. This “associational resistance” can be notably explained by the fact that heterospecific neighbours make it more difficult for herbivores to locate and then exploit their host tree. However, the validity of these findings in the case of non-native, invasive pests and pathogens remains to be demonstrated. In this study, we monitored over two hundred Douglas firs in pure and mixed plots of a tree diversity experiment to assess the damage from the non-native gall midge Contarinia pseudotsugae and the non-native needle cast Nothophaeocryptopus gaeumannii. The probability of Swiss needle-cast infection was lower in Douglas fir trees surrounded by heterospecific neighbours. Gall midge damage was lower on Douglas firs surrounded by taller neighbours, consistent with the hypothesis of reduced host Apparency. Douglas fir trees that were more damaged by C. pseudotsugae were also more often infected by N. gaeumannii. Our study thus provides partial support of the associational resistance hypothesis of mixed forests against exotic pests and pathogens. Promoting forest species diversity at the stand level could, therefore, offer interesting prospects for reducing the impact of biological invasions, especially those involving both pests and pathogens.

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DOI: 10.3897/neobiota.73.72566

Authors: Lena Homberger, Jiawu Xu, Dirk Brandis, Tin-Yam Chan, Heleen Keirsebelik, Monika Normant-Saremba, Jonas Schoelynck, Ka Hou Chu, Christine Ewers-Saucedo

Abstract: Cryptic biological invasions are largely unrecognised, leading to an underestimation of the number of invading taxa and their potential impacts. The Chinese mitten crab, Eriocheir sinensis, is a highly invasive species with serious economic and ecological impacts in Europe. Recently, mitochondrial DNA (mtDNA) of the Japanese mitten crab, E. japonica, has been discovered in populations from The Netherlands, Poland and Germany, but the taxonomic status and time of introduction of specimens carrying this mtDNA are uncertain. To this end, we investigated the morphology and variation of the mitochondrial cytochrome c oxidase subunit I (COI) gene of mitten crabs collected in central-western Europe between 1998 and 2020. Mitten crabs from Belgium harboured a Japanese mitten crab COI haplotype in 33% to 65% of individuals, even in our earliest samples from 1998. All other studied populations carried only Chinese mitten crab COI haplotypes. Morphologically, many of the juvenile Belgian mitten crabs showed intermediate traits between the two species, while all investigated adult mitten crabs, regardless of their mitochondrial haplotype or country of origin, were morphologically assigned to E. sinensis. This intermediate morphology of the juveniles and genetic-morphological discrepancy of adults suggests that Japanese mitten crabs introgressed with Chinese mitten crabs, which could have happened both before and after the introduction of mitten crabs to Europe. A specific Chinese mitten crab COI haplotype, found in Belgium, was previously only known from Vladivostok (Russia), where Chinese and Japanese mitten crab hybrids naturally occur. This Far East region is, therefore, a plausible source for at least part of the mitten crab mitochondrial diversity in Belgium.

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DOI: 10.3897/neobiota.72.78511

Authors: Ruben Van De Walle, François Massol, Martijn L. Vandegehuchte, Dries Bonte

Abstract: Disturbance is thought to enhance the probability of invasive species establishment, a prerequisite for naturalisation. Coastal dunes are characterised by disturbance in the form of sand dynamics. We studied the effect of this disturbance on the establishment and spread of an invasive plant species (Senecio inaequidens) in European coastal dunes. Local sand dynamics dictate the spatial configuration of marram grass (Calamagrostis arenaria). Therefore, marram grass configuration was used as a reliable proxy for disturbance. Since marram grass plays a crucial role in natural dune formation, we evaluated the possible effects S. inaequidens could have on this process, if it is able to naturalise in European coastal dunes. We expected the highest probability of S. inaequidens establishment at intermediate marram grass cover because too low cover would increase sand burial, whereas high cover would increase competition. However, our results indicate that S. inaequidens is quite capable of handling higher levels of sand burial. Thus, the probability of S. inaequidens establishment was high under low marram cover but slightly lowered when marram cover was high, hinting at the importance of competition. We expected a negative impact of Senecio-altered soils on marram grass growth mediated by soil biota. However, marram grass grew better in sand gathered underneath Senecio plants due to abiotic soil modifications. This enhanced growth may be caused by Senecio leaf litter elevating nutrient concentrations in an otherwise nutrient-poor substrate. If such increased plant growth is a general phenomenon, further expansion of S. inaequidens could accelerate natural succession in European coastal dunes.

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DOI: 10.3897/neobiota.64.56027

Authors: Aurore Fanal, Grégory Mahy, Adeline Fayolle, Arnaud Monty

Abstract: Identifying emerging invasive species is a priority to implement early preventive and control actions. In terms of the number of invasive tree species, forestry represents the second largest pathway of introduction, with an invasive debt likely existing for alien conifers in Europe. In the early 1900s, a network of arboreta was established in southern Belgium to assess the wood production potential of prospective conifer and broadleaved species. Here, we use eight arboreta as natural experiments to identify alien conifers presenting invasive behavior. Through systematic sampling, we quantified the natural regeneration of alien conifers and recorded local environmental variables. For each species, regeneration density, dispersal distances, and age structure were analyzed. Generalized mixed effects models were fitted to test the effect of planted area and tree-stand type on regeneration. The environmental space occupied by regenerating alien conifers was evaluated using principal component analysis. Out of 31 planted alien species, 15 (48%) were identified in natural regeneration, of which eight (26%) exhibited important regeneration density and dispersal distances. The most invasive species were Tsuga heterophylla and Abies grandis, confirming earlier field observations. Both large planted areas and areas planted with alien conifer species increased the density of regeneration. Species that had the highest regeneration density tolerated a wide range of environmental conditions, including shaded understory, which could lead to the invasion of mature, undisturbed forests. This study showed that 17% of the studied alien conifers are potentially invasive because they show important regeneration, long-distance dispersal, and, of importance, have already produced offspring that have matured and are capable of creating new satellite populations. In conclusion, our results provide a guideline for future planting operations, recommending extreme caution when planting these species in the temperate forests of Western Europe.

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DOI: 10.3897/neobiota.23.5665

Authors: Alexandra Zieritz, Belinda Armas, David C. Aldridge

Abstract: This dataset represents a registry of species that are not native but recorded to live in the wild of at least one of the four countries that comprise the Two Seas Area, i.e. Great Britain, France, Belgium and the Netherlands. For each of the 6,661 species, subspecies and hybrids listed, we provide detailed information on its status in each country, taxonomic affiliation and environment inhabited. The data were collected by review of 36 web- and print-based sources over an eight-month period. Further systematic scanning of three of the most relevant scientific journals, i.e. Neobiota, Aquatic Invasions and BioInvasions Records, recovered 19 additional relevant publications from which information was included in the registry. As a result, the registry will serve as a basis for developing effective, cross-boundary strategies to manage and control non-native species, which can have severe ecological and economic impacts. The registry can further be used as a general reference for both scientists and practitioners, as well as a tool to assess reliability and comprehensiveness of other well-known databases such as the DAISIE portal.

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