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1.AbstractConnectivity is a species- and landscape-specific measure that is key to species conservation in fragmented landscapes. However, information on connectivity is often lacking, especially for insects which are known to be severely declining. Patterns of gene flow constitute an indirect measure of functional landscape connectivity. We studied the population genetic structure of the rare digger wasp Bembix rostrata in coastal and inland regions in and near Belgium. The species is restricted to sandy pioneer vegetations for nesting and is well known for its philopatry as it does not easily colonize vacant habitat. It has markedly declined in the last century, especially in the inland region where open sand habitat has decreased in area and became highly fragmented. To assess within and between region connectivity, we used mating system independent population genetic methods suitable for haplodiploid species. We found more pronounced genetic structure in the small and isolated inland populations as compared to the well-connected coastal region. We also found a pattern of asymmetrical gene flow from coast to inland, including a few rare dispersal distances up to 200 to 300 km based on assignment tests. We point to demography, wind and difference in dispersal capacities as possible underlying factors that can explain the discrepancy in connectivity and asymmetrical gene flow between the different regions. Despite B. rostrata being a poor colonizer, gene flow between existing populations appeared not highly restricted, especially at the coast. Therefore, to improve the conservation status of B. rostrata, the primary focus should be to preserve and create sufficient habitat for this species to increase the number and quality of (meta)populations, rather than focusing on landscape connectivity itself.

Gastrointestinal microbiota fulfill pivotal roles in providing a host with nutrition and protection from pathogenic microorganisms. Up to date, most microbiota research has focused on humans and other mammals, whereas birds and especially wild birds lag behind. Within the field of the avian gut microbiome, research is heavily biased towards poultry. In this study, we analyzed the gut microbiome of the Eurasian nuthatch (Sitta europaea), using faecal samples of eight nestlings originating from three nuthatch nests in the south of Ghent (Belgium), using Illumina sequencing of the 16S rRNA gene. Relative frequency analysis showed a dominance of Firmicutes and Actinobacteria and to a lesser extent Proteobacteria. Bacteroidetes and other phyla were relatively rare. At higher taxonomic levels, a high degree of inter-individual variation in terms of overall microbiota community structure as well as dominance of certain bacteria was observed, but with a higher similarity for the nestlings sharing the same nest. When comparing the nuthatch faecal microbiome to that of great tit nestlings that were sampled during the same breeding season and in the same forest fragment, differences in the microbial community structure were observed, revealing distinct dissimilarities in the relative abundancy of taxa between the two bird species. This study is the first report on the nuthatch microbiome and serves as a reference study for nuthatch bacterial diversity and can be used for targeted screening of the composition and general functions of the avian gut microbiome.

1. Communities across trophic levels, and the functional roles they play, are vital for the sustained provision of ecosystem services. In forest systems, diversification of overstorey composition has been shown to be a key driver of biodiversity, but its influence on across-trophic level relationships remains scarcely known. Species across trophic levels in varied overstorey compositions are also differentially susceptible to fragmentation context. We hypothesise that fragmentation will disrupt community relationships associated with particular overstorey compositions. 2. We test this hypothesis using a tree diversity research platform across 53 deciduous woodland plots in central Belgium. We estimate species' abundances within nine, generally taxonomic, community groups across trophic levels: understorey vegetation; leaf miners and gall formers; woodlice, millipedes; carabid beetles, harvestmen, spiders, birds, bats. We use multiple co-inertia analyses to examine how taxonomic and trophic role community matrices covary across gradients of overstorey composition, via three different tree species diversification pathways, and fragmentation. 3. For all trophic role groups, across all plots, there was at least one significant pairwise comparison. Apart from comparisons involving bats, there was at least one significant pairwise correlation between taxonomic groups too. These results indicate correlated community matrices across trophic levels. Overstorey composition related to community tightness, that is, the level of co-ordinated change among taxonomic and/or trophic role groups as revealed by multiple co-inertia analyses. Notably, diversifying woodlands of beech Fagus sylvatica or red oak Quercus rubra with pedunculate oak Quercus robur correlated with increased taxonomic community tightness. Diversifying pedunculate oak forest stands with other overstorey species related to unchanged community tightness. Evidence was lacking for fragmentation affecting community tightness, singly or by interacting with overstorey composition. 4. Synthesis. Overall, changing tree species composition and fragmentation level affected across-trophic level community relationships differently. Yet, we demonstrated a clear signal that diversifying monoculture stands with particular species correlated with greater community tightness, and co-ordinated change among sets of community groups, across trophic levels and regardless of fragmentation context. We postulate that having tighter community relationships suggests that measures to improve biodiversity at one trophic level (i.e. trees) could affect other groups, and their associated roles, in a co-ordinated manner.

In the European Union, all bat species are strictly protected and member states must ensure their conservation. However, if populations are genetically structured, conservation units that correspond to whole countries may be too large, putting small populations with specific conservation requirements at risk. Geoffroy’s bat (Myotis emarginatus) has undergone well-documented declines at its north-western European range edge between the 1960 and 1990s and is considered to be negatively affected by habitat fragmentation. Here we analysed the species’ genetic population structure and diversity to identify subpopulations with reduced genetic diversity and to scientifically inform conservation management. We generated 811 microsatellite-based genetic profiles obtained from 42 European nursery colonies and analysed a total of 932 sequences of the hypervariable region II of the mitochondrial control region sampled from across Europe. While two geographically widespread genetic populations were inferred to be present in north-western Europe, both nuclear and mitochondrial genetic diversity were lowest in the areas that had experienced a decline during the last century. A microsatellite-based analysis of demographic history did not permit, however, to unequivocally link that reduced genetic diversity to the population contraction event. Given the large geographic extent of the genetic populations, preserving the connectivity of mating sites requires concerted conservation efforts across multiple political jurisdictions. Genetic monitoring ought to be done on a regular basis to ensure that large-scale connectivity is maintained and further loss of genetic diversity is prevented.

Tracking devices have become small enough to be widely applied to arthropods to study their movement. However, possible side effects of these devices on arthropod performance and behaviour are rarely considered. We performed a systematic review of 173 papers about research in which tracking devices-radio frequency identification (RFID), harmonic radar and radio telemetry tags-were attached to terrestrial arthropods. The impact of such tags was quantified in only 12% of the papers, while in 40% the potential impact was completely disregarded. Often-cited rules of thumb for determining appropriate tag weight had either no empirical basis or were misconstrued. Several properties of a tracking device (e.g. weight, balance, size, drag) can affect different aspects of an arthropod's life history (e.g. energy, movement, foraging, mating). The impact can differ among species and environments. Taken together, these tag effects can influence the reliability of obtained movement data and conclusions drawn from them. We argue that the impact of tracking devices on arthropods should be quantified for each (a) study species, (b) tag type, and (c) environmental context. As an example, we include a low-effort impact study of the effect of an RFID tag on a digger wasp. Technological advancements enable studying the movement of arthropods in unprecedented detail. However, we should adopt a more critical attitude towards the use of tracking devices on terrestrial arthropods. The benefits of tracking devices should be balanced against their potential side effects on arthropods and on the reliability of the resulting data.

Habitat fragmentation and forestry practices affect forest structure and composition, and hence, their intrinsic value for biodiversity conservation. While higher tree species diversity is commonly proposed to result in habitat of higher quality for forest species, how these tree diversity and tree composition effects interact with forest fragmentation in terms of critical resources and demographic effects on forest birds remains poorly understood. We investigated here possible synergistic effects of forest fragmentation and tree species composition on the breeding performance of two common, insectivorous forest birds in a human-dominated landscape in northern Belgium. We monitored the breeding performance of Great Tits and Blue Tits in 53 plots across independent gradients of tree species composition and forest fragmentation. In addition, data on the biomass of the main food source of these two species (i.e. caterpillars) was collected during the breeding season. Both tree composition and habitat fragmentation impacted the breeding performance of Great and Blue Tits. Effects of tree species composition were mainly driven by tree species identity, rather than by tree species diversity, and the highest breeding performance was obtained in monocultures of Pedunculate Oaks. Fragmentation effects were only observed in resource-poor Beech monocultures with breeding performance declining with reduction in forest area. Structural Equation Modelling revealed diverse and species-specific pathways: for Great Tits tree composition effects on breeding performance were driven by resource availability while for Blue Tits these effects were driven by variation in clutch size. Thus, forestry practices aiming at promoting forest-dependent birds could benefit from including tree species that support high arthropod numbers and by maintaining forest patches of larger sizes.

To better understand natural regeneration of trees and forest dynamics it is important to gain insight into the drivers of invertebrate herbivory. In mature forests, associational resistance of trees resulting from a high diversity of neighbouring trees is common, and can have cascading effects on tree growth through resource concentration effects or through changes in top-down control. While the underlying biological processes are known to be influenced by the forest’s spatial properties, we lack insights on how resource concentration, top-down control and fragmentation jointly affect sapling performance in fragmented landscapes. We therefore experimentally quantified effects of the proportion of conspecific trees in the overstorey (resource concentration), avian top-down control (natural enemies) and distance to the forest edge on invertebrate herbivory levels and sapling growth. The assessments were made on planted saplings of Fagus sylvatica, Quercus robur and Quercus rubra in 53 experimental plots and birds were excluded by means of exclosures from a subset of these saplings. Excluding avian top-down control increased herbivory on each tree species. Increased herbivory led to decreased sapling growth in F. sylvatica and Q. rubra. On Q. robur saplings, top-down control was stronger closer to the forest edge. Furthermore, in this species, herbivory inside the exclosures increased with an increasing proportion of conspecific trees in the overstorey, while such a resource concentration effect was not observed outside the exclosures. Our results show the importance for forest management of conserving insectivorous birds and promoting a mixed overstorey, which can decrease sapling herbivory when bird abundance is low. More generally, our study provides insight into the complex, multitrophic interactions that drive sapling growth in forest stands located within fragmented landscapes.

Contemporary forest management strives to satisfy contrasting demands on forest ecosystems by promoting multiple ecosystem services. These services are affected in varied manners by alternative management actions operating at local or landscape scales, potentially leading to trade-offs and synergies. We here studied ecosystem functions and biodiversity data across ecosystem compartments in 53 mature forest plots varying in stand-level (tree species composition) and landscape-level (degree of fragmentation) characteristics. We show that more than two-thirds of the 20 trade-offs and synergies between functions and diversity variables were driven by variation in tree species composition and fragmentation. Interestingly, more fragmented landscapes had higher landscape-level forest functioning, but this came at the expense of forest biodiversity. At the same time, mixed forest stands had higher levels of biodiversity than monocultures without affecting forest functioning. Diversifying forest stands thus represents a potential management strategy that promotes both ecosystems functioning and biodiversity in fragmented landscapes.

The microbiome of wild birds has been associated with health status and risk of disease development, but underlying metabolomic mechanisms are still unknown. Metabolites produced by microbial organisms may affect host metabolic processes and by doing so influence host health. Here we provide for the first time data on the faecal metabolome of wild great tits (Parus major) by analyzing metabolites associations with age, sex, season and body condition. Using untargeted metabolomics, we analyzed faecal samples from 112 great tits that were caught in a deciduous forest fragment in Flanders (Belgium) during late autumn and 19 animals that were re-captured during early spring. In this study, no significant associations between the faecal metabolites and age, sex and body condition were observed. However, season was shown to be a discriminating factor for the metabolomic composition of great tits, suggesting an impact of environmental factors.

Gastrointestinal microbiota fulfill pivotal roles in providing a host with nutrition and protection from pathogenic microorganisms. Up to date, most microbiota research has focused on humans and other mammals, whereas birds and especially wild birds lag behind. Within the field of the avian gut microbiome, research is heavily biased towards poultry. In this study, we analyzed the gut microbiome of the Eurasian nuthatch (Sitta europaea), using faecal samples of eight nestlings originating from three nuthatch nests in the south of Ghent (Belgium), using Illumina sequencing of the 16S rRNA gene. Relative frequency analysis showed a dominance of Firmicutes and Actinobacteria and to a lesser extent Proteobacteria. Bacteroidetes and other phyla were relatively rare. At higher taxonomic levels, a high degree of inter-individual variation in terms of overall microbiota community structure as well as dominance of certain bacteria was observed, but with a higher similarity for the nestlings sharing the same nest. When comparing the nuthatch faecal microbiome to that of great tit nestlings that were sampled during the same breeding season and in the same forest fragment, differences in the microbial community structure were observed, revealing distinct dissimilarities in the relative abundancy of taxa between the two bird species. This study is the first report on the nuthatch microbiome and serves as a reference study for nuthatch bacterial diversity and can be used for targeted screening of the composition and general functions of the avian gut microbiome.

Global habitat destruction is bringing species to the edge. Consequently, understanding species dispersal behaviour is becoming essential in order to safeguard vital meta-populations. Nevertheless, dispersal is too often seen as unconditional rather than triggered by habitat cues. We applied radio telemetry on female European stag beetles [Lucanus cervus (L., 1758)] in a mosaic landscape to investigate the hypothesis that dispersal is habitat driven, in this case by canopy closure and presence of suitable dead wood, SDW. We found that the decision to disperse depended on canopy closure and that dispersal distance depended both on SDW availability and canopy closure. Long distance dispersal (by flying), in contrast to small distance dispersal (mainly walking), is shown to be a successful strategy to reach locations with lower canopy closure. We conclude that dispersal of female stag beetles is not unconditional but shaped by habitat resources. It is therefore likely that habitat also affects dispersal of other insects and should be considered in future dispersal studies. For the conservation of the European stag beetle, our results imply that it is essential to provide stepping stones of suitable dead wood, preferably every 100 m and not more than 1 km apart. These stepping stones should be provided in open to half-shaded conditions. Management systems such as coppicing which provide periodic sun-exposure and sufficient amounts of (underground) dead wood are good management procedures for conservation of the stag beetle but they need to be performed at small scales to ensure suitable habitat proximity.

Knowledge about phylogeographical structuring and genetic diversity is of key importance for the conservation of endangered species. Comparative phylogeography of a host and its parasite has the potential to reveal cryptic dispersal and behaviour in both species, and can thus be used to guide conservation management. In this study, we investigate the phylogeographic structure of the Bechstein’s bat, Myotis bechsteinii, and its ectoparasitic bat fly, Basilia nana, at 12 sites across their entire distribution. For both species, a mitochondrial sequence fragment (ND1 and COI respectively) and nuclear microsatellite genotypes (14 and 10 loci respectively) were generated and used to compare the phylogeography of host and parasite. Our findings confirm the presence of three distinct genetic subpopulations of the Bechstein’s bat in (1) Europe, (2) the Caucasus and (3) Iran, which remain isolated from one another. The genetic distinctiveness of host populations in the Caucasus region and Iran emphasize that these populations must be managed as distinct evolutionarily significant units. This phylogeographical pattern is however not reflected in its parasite, B. nana, which shows evidence for more recent dispersal between host subpopulations. The discordant genetic pattern between host and parasite suggest that despite the long-term genetic isolation of the different host subpopulations, long-range dispersal of the parasite has occurred more recently, either as the result of secondary contact in the primary host or via secondary host species. This indicates that a novel pathogenic threat to one host subpopulation may be able to disperse, and thus have important consequences for all subpopulations.

Bats are major consumers of arthropods, including many agricultural pest species, and can thus reduce and prevent crop damage. However, few, if any, data is available on the potential role of bats in pest control in central Europe. Evidence that bats prey upon locally important pest species would be an important first step to demonstrate their value to local farmers and facilitate conservation measures. In this pilot study, we used a DNA metabarcoding approach to investigate the diet composition of common pipistrelles and brown long-eared bats captured in orchards in Belgium. We show that the spotted wing drosophila (Drosophila suzukii), one of the most harmful pest species in this region, was part of the diet of common pipistrelles. This pest species was recorded in one of the five samples from common pipistrelles. Our results indicate that bats can be valuable assets for biological pest suppression in West-European orchards, thus setting a path for future studies.

Forest fragments in highly disturbed landscapes provide important ecosystem services ranging from acting as biodiversity reservoir to providing timber or regulating hydrology. Managing the tree species richness and composition of these fragments to optimize their functioning and the deliverance of multiple ecosystem services is of great practical relevance. However, both the strength and direction of tree species richness and tree species composition effects on forest ecosystem multifunctionality may depend on the landscape context in which these forest remnants are embedded. Taking advantage of an observatory network of 53 temperate forest plots varying in tree species richness, tree species composition, and fragmentation intensity we measured 24 ecosystem functions spanning multiple trophic levels and analyzed how tree species diversity-multifunctionality relationships changed with fragmentation intensity. Our results show that fragmentation generally increases multifunctionality and strengthens its positive relationship with diversity, possibly due to edge effects. In addition, different tree species combinations optimize functioning under different fragmentation levels. We conclude that management and restoration of forest fragments aimed at maximizing ecosystem multifunctionality should be tailored to the specific landscape context. As forest fragmentation will continue, tree diversity will become increasingly important to maintain forest functioning.

Citizen scientists make important contributions to the collection of occurrence data of non-native species. We present two datasets comprising more than 520,000 records of 1,771 non-native species from Flanders and the Brussels Capital Region in Belgium, Western Europe, collected through the website http://www.waamemingen.be hosted by Stichting Natuurinformatie and managed by the nature conservation NGO Natuurpunt. Most records were collected by citizen scientists, mainly since 2008. Waarnemingen.be aims at recording all species, native and non-native, and it is shown here that this kind of biodiversity portals are also particularly well suited to collect large amounts of data on non-native species. Both datasets presented here are also discoverable through the Global Biodiversity Information Facility (GBIF).

Host–parasite interactions are ubiquitous in nature. However, how parasite population genetic structure is shaped by the interaction between host and parasite life history remains understudied. Studies comparing multiple parasites infecting a single host can be used to investigate how different parasite life history traits interplay with host behaviour and life history. In this study, we used 10 newly developed microsatellite loci to investigate the genetic structure of a parasitic bat fly (Basilia nana). Its host, the Bechstein’s bat (Myotis bechsteinii), has a social system and roosting behaviour that restrict opportunities for parasite transmission. We compared fly genetic structure to that of the host and another parasite, the wing-mite, Spinturnix bechsteini. We found little spatial or temporal genetic structure in B. nana, suggesting a large, stable popula- tion with frequent genetic exchange between fly populations from different bat colo- nies. This contrasts sharply with the genetic structure of the wing-mite, which is highly substructured between the same bat colonies as well as temporally unstable. Our results suggest that although host and parasite life history interact to yield similar transmission patterns in both parasite species, the level of gene flow and eventual spa- tiotemporal genetic stability is differentially affected. This can be explained by the dif- ferences in generation time and winter survival between the flies and wing-mites. Our study thus exemplifies that the population genetic structure of parasites on a single host can vary strongly as a result of how their individual life history characteristics interact with host behaviour and life history traits.

The hatching success of a bird’s egg is one of the key determinants of avian reproductive success, which may be compromised by microbial infections causing embryonic death. During incubation, outer eggshell bacterial communities pose a constant threat of pathogen translocation and embryo infection. One of the parental strategies to mitigate this threat is the incorporation of maternal immune factors into the egg albumen and yolk. It has been suggested that habitat changes like forest fragmentation can affect environmental factors and life-history traits that are linked to egg contamination. This study aims at investigating relationships between microbial pressure, immune investment and hatching success in two abundant forest bird species and analyzing to what extent these are driven by extrinsic (environmental) factors. We here compared (1) the bacterial load and composition on eggshells, (2) the level of immune defenses in eggs, and (3) the reproductive success between great (Parus major) and blue (Cyanistes caeruleus) tits in Belgium and examined if forest fragmentation affects these parameters. Analysis of 70 great tit and 34 blue tit eggshells revealed a similar microbiota composition (Enterobacteriaceae, Lactobacillus spp., Firmicutes and Bacteroidetes), but higher bacterial loads in great tits. Forest fragmentation was not identified as an important explanatory variable. Although a significant negative correlation between hatching success and bacterial load on the eggshells in great tits corroborates microbial pressure to be a driver of embryonic mortality, the overall hatching success was only marginally lower than in blue tits. This may be explained by the significantly higher levels of lysozyme and IgY in the eggs of great tits, protecting the embryo from increased infection pressure. Our results show that immune investment in eggs is suggested to be a species-specific adaptive trait that serves to protect hatchlings from pathogen pressure, which is not directly linked to habitat fragmentation.

Background & aim – In general, biodiversity has positive effects on ecosystem functioning. In forests, understorey vegetation is influenced by both the composition and species richness of the overstorey through species-specific effects on environmental conditions at the forest floor. Forest fragmentation is also known to influence understorey vegetation composition and richness. However, the combined effects of tree species diversity and forest fragmentation have not been studied yet. With the TREEWEB research platform, consisting of 53 forest plots along a tree species diversity and forest fragmentation gradient, we aim to unravel the combined effects of tree species diversity, tree species identity and forest fragmentation on the understorey composition and diversity.Methods – The TREEWEB platform includes forest plots of three tree species richness levels, containing all possible species combinations of Quercus robur, Quercus rubra and Fagus sylvatica. Complete dilution is avoided in the design, allowing separation between tree species identity and diversity effects. Vegetation surveys were conducted in all plots to investigate the species richness, species diversity, compositional turnover and cover of the herb layer as well as the shrub layer cover.Key results – Within the TREEWEB platform, overstorey-understorey diversity relationships were mainly characterised by tree species identity effects. No clear effects of tree species diversity and forest fragmentation on understorey composition and diversity were found.Conclusion – Tree species identity effects were most important in explaining the observed patterns in the understorey vegetation. Further in-depth research will allow us to disentangle which mechanisms underlie these patterns and whether effects of fragmentation are more pronounced at higher trophic levels.

Endemic infections with the common avian pathogen Salmonella enterica subspecies enterica serovar Typhimurium (Salmonella Typhimurium) may incur a significant cost on the host population. In this study, we determined the potential of endemic Salmonella infections to reduce the reproductive success of blue (Cyanistes caeruleus) and great (Parus major) tits by correlating eggshell infection with reproductive parameters. The fifth egg of each clutch was collected from nest boxes in 19 deciduous forest fragments. Out of the 101 sampled eggs, 7 Salmonella Typhimurium isolates were recovered. The low bacterial prevalence was reflected by a similarly low serological prevalence in the fledglings. In this study with a relatively small sample size, presence of Salmonella did not affect reproductive parameters (egg volume, clutch size, number of nestlings and number of fledglings), nor the health status of the fledglings. However, in order to clarify the impact on health and reproduction a larger number of samples have to be analyzed. Phage typing showed that the isolates belonged to the definitive phage types (DT) 193 and 99, and multi-locus variable number tandem repeat analysis (MLVA) demonstrated a high similarity among the tit isolates, but distinction to human isolates. These findings suggest the presence of passerine-adapted Salmonella strains in free-ranging tit populations with host pathogen co-existence.

Bats display marked seasonality throughout the temperate zone and use different habitats during different parts of the year. Unfortunately, detailed information regarding seasonal distribution and movements is often lacking, thereby hampering the development of adequate conservation measures. In this study we used radio telemetry to track females of the endangered Bechstein's bat (Myotis bechsteinii) from autumn swarming sites to their summer maternity colony ranges. We were able to tag 22 individuals, 18 of which were subsequently recovered at nine roost sites up to 20.6 km away. Females from multiple colonies visited the same swarming site on a single night. Concurrently, we recovered females from a single maternity colony at different swarming sites on the same night. The catchment area of the investigated swarming sites measured 27.1 km2, and was skewed to the northwest. Tagged bats were recovered in forest fragments ranging in size from 5.42 to 128.98 ha. Notably, all but one of the recovered roosts ...

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