How non-target chironomid communities respond to mosquito control: Integrating DNA metabarcoding and joint species distribution modelling.

The conservation and management of riparian ecosystems rely on understanding the ecological consequences of anthropogenic stressors that impact natural communities. In this context, studies investigating the effects of anthropogenic stressors require reliable methods capable of mapping the relationships between taxa occurrence or abundance and environmental predictors within a spatio-temporal framework. Here, we present an integrative approach using DNA metabarcoding and Hierarchical Modelling of Species Communities (HMSC) to unravel the intricate dynamics and resilience of chironomid communities exposed to Bacillus thuringiensis var. israelensis (Bti). Chironomid emergence was sampled from a total of 12 floodplain pond mesocosms, half of which received Bti treatment, during a 16-week period spanning spring and summer of 2020. Subsequently, we determined the community compositions of chironomids and examined their genus-specific responses to the Bti treatment, considering their phylogenetic affiliations and ecological traits of the larvae. Additionally, we investigated the impact of the Bti treatment on the body size distribution of emerging chironomids. Our study revealed consistent responses to Bti among different chironomid genera, indicating that neither phylogenetic affiliations nor larval feeding strategies significantly contributed to the observed patterns. Both taxonomic and genetic diversity were positively correlated with the number of emerged individuals. Furthermore, our findings demonstrated Bti-related effects on chironomid body size distribution, which could have relevant implications for size-selective terrestrial predators. Hence, our study highlights the value of employing a combination of DNA metabarcoding and HMSC to unravel the complex dynamics of Bti-related non-target effects on chironomid communities. The insights gained from this integrated framework contribute to our understanding of the ecological consequences of anthropogenic stressors and provide a foundation for informed decision-making regarding the conservation and management of riparian ecosystems.

Subsidy Quality Affects Common Riparian Web-Building Spiders: Consequences of Aquatic Contamination and Food Resource.

Anthropogenic stressors can affect the emergence of aquatic insects. These insects link aquatic and adjacent terrestrial food webs, serving as high-quality subsidy to terrestrial consumers, such as spiders. While previous studies have demonstrated that changes in the emergence biomass and timing may propagate across ecosystem boundaries, the physiological consequences of altered subsidy quality for spiders are largely unknown. We used a model food chain to study the potential effects of subsidy quality: Tetragnatha spp. were exclusively fed with emergent Chironomus riparius cultured in the absence or presence of either copper (Cu), Bacillus thuringiensis var. israelensis (Bti), or a mixture of synthetic pesticides paired with two basal resources (Spirulina vs. TetraMin®) of differing quality in terms of fatty acid (FA) composition. Basal resources shaped the FA profile of chironomids, whereas their effect on the FA profile of spiders decreased, presumably due to the capacity of both chironomids and spiders to modify (dietary) FA. In contrast, aquatic contaminants had negligible effects on prey FA profiles but reduced the content of physiologically important polyunsaturated FAs, such as 20:4n-6 (arachidonic acid) and 20:5n-3 (eicosapentaenoic acid), in spiders by approximately 30% in Cu and Bti treatments. This may have contributed to the statistically significant decline (40%-50%) in spider growth. The observed effects in spiders are likely related to prey nutritional quality because biomass consumption by spiders was, because of our experimental design, constant. Analyses of additional parameters that describe the nutritional quality for consumers such as proteins, carbohydrates, and the retention of contaminants may shed further light on the underlying mechanisms. Our results highlight that aquatic contaminants can affect the physiology of riparian spiders, likely by altering subsidy quality, with potential implications for terrestrial food webs. Environ Toxicol Chem 2023;42:1346-1358. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Dataset of the de novo assembly and annotation of the marbled crayfish and the noble crayfish hepatopancreas transcriptomes.

OBJECTIVES: Crayfish plague disease, caused by the oomycete pathogen Aphanomyces astaci represents one of the greatest risks for the biodiversity of the freshwater crayfish. This data article covers the de novo transcriptome assembly and annotation data of the noble crayfish and the marbled crayfish challenged with Ap. astaci. Following the controlled infection experiment (Francesconi et al. in Front Ecol Evol, 2021, https://doi.org/10.3389/fevo.2021.647037 ), we conducted a differential gene expression analysis described in (Bostjancic et al. in BMC Genom, 2022, https://doi.org/10.1186/s12864-022-08571-z ) DATA DESCRIPTION: In total, 25 noble crayfish and 30 marbled crayfish were selected. Hepatopancreas tissue was isolated, followed by RNA sequencing using the Illumina NovaSeq 6000 platform. Raw data was checked for quality with FastQC, adapter and quality trimming were conducted using Trimmomatic followed by de novo assembly with Trinity. Assembly quality was assessed with BUSCO, at 93.30% and 93.98% completeness for the noble crayfish and the marbled crayfish, respectively. Transcripts were annotated using the Dammit! pipeline and assigned to KEGG pathways. Respective transcriptome and raw datasets may be reused as the reference transcriptome assemblies for future expression studies.

Host-pathogen coevolution drives innate immune response to Aphanomyces astaci infection in freshwater crayfish: transcriptomic evidence.

BACKGROUND: For over a century, scientists have studied host-pathogen interactions between the crayfish plague disease agent Aphanomyces astaci and freshwater crayfish. It has been hypothesised that North American crayfish hosts are disease-resistant due to the long-lasting coevolution with the pathogen. Similarly, the increasing number of latent infections reported in the historically sensitive European crayfish hosts seems to indicate that similar coevolutionary processes are occurring between European crayfish and A. astaci. Our current understanding of these host-pathogen interactions is largely focused on the innate immunity processes in the crayfish haemolymph and cuticle, but the molecular basis of the observed disease-resistance and susceptibility remain unclear. To understand how coevolution is shaping the host's molecular response to the pathogen, susceptible native European noble crayfish and invasive disease-resistant marbled crayfish were challenged with two A. astaci strains of different origin: a haplogroup A strain (introduced to Europe at least 50 years ago, low virulence) and a haplogroup B strain (signal crayfish in lake Tahoe, USA, high virulence). Here, we compare the gene expression profiles of the hepatopancreas, an integrated organ of crayfish immunity and metabolism. RESULTS: We characterised several novel innate immune-related gene groups in both crayfish species. Across all challenge groups, we detected 412 differentially expressed genes (DEGs) in the noble crayfish, and 257 DEGs in the marbled crayfish. In the noble crayfish, a clear immune response was detected to the haplogroup B strain, but not to the haplogroup A strain. In contrast, in the marbled crayfish we detected an immune response to the haplogroup A strain, but not to the haplogroup B strain. CONCLUSIONS: We highlight the hepatopancreas as an important hub for the synthesis of immune molecules in the response to A. astaci. A clear distinction between the innate immune response in the marbled crayfish and the noble crayfish is the capability of the marbled crayfish to mobilise a higher variety of innate immune response effectors. With this study we outline that the type and strength of the host immune response to the pathogen is strongly influenced by the coevolutionary history of the crayfish with specific A. astaci strains.

Making waves: Pulling the plug-Climate change effects will turn gaining into losing streams with detrimental effects on groundwater quality.

In many parts of the world, climate change has already caused a decline in groundwater recharge, whereas groundwater demand for drinking water production and irrigation continues to increase. In such regions, groundwater tables are steadily declining with major consequences for groundwater-surface water interactions. Predominantly gaining streams that rely on discharge of groundwater from the adjacent aquifer turn into predominantly losing streams whose water seeps into the underground. This reversal of groundwater-surface water interactions is associated with an increase of low river flows, drying of stream beds, and a switch of lotic ecosystems from perennial to intermittent, with consequences for fluvial and groundwater dependent ecosystems. Moreover, water infiltrating from rivers and streams can carry a complex mix of contaminants. Accordingly, the diversity and concentrations of compounds detected in groundwater has been increasing over the past decades. During low flow, stream and river discharge may consist mainly of treated wastewater. In losing stream systems, this contaminated water seeps into the adjoining aquifers. This threatens both ecosystems as well as drinking and irrigation water quality. Climate change is therefore severely altering landscape water balances, with groundwater-surface water-interactions having reached a tipping point in many cases. Current model projections harbor huge uncertainties and scientific evidence for these tipping points remains very limited. In particular, quantitative data on groundwater-surface water-interactions are scarce both on the local and the catchment scale. The result is poor public or political awareness, and appropriate management measures await implementation.

Spontaneous rate of clonal single nucleotide mutations in Daphnia galeata.

Mutations are the ultimate source of heritable variation and therefore the fuel for evolution, but direct estimates of mutation rates exist only for few species. We estimated the spontaneous single nucleotide mutation rate among clonal generations in the waterflea Daphnia galeata with a short-term mutation accumulation approach. Individuals from eighteen mutation accumulation lines over five generations were deep sequenced to count de novo mutations that were not present in a pool of F1 individuals, representing the parental genotype. We identified 12 new nucleotide mutations in 90 clonal generational passages. This resulted in an estimated single nucleotide mutation rate of 0.745 x 10-9 (95% c.f. 0.39 x 10-9-1.26 x 10-9), which is slightly lower than recent estimates for other Daphnia species. We discuss the implications for the population genetics of Cladocerans.

Emerging Midges Transport Pesticides from Aquatic to Terrestrial Ecosystems: Importance of Compound- and Organism-Specific Parameters.

Emerging aquatic insects have the potential to retain aquatic contaminants after metamorphosis, potentially transporting them into adjacent terrestrial food webs. It is unknown whether this transfer is also relevant for current-use pesticides. We exposed larvae of the nonbiting midge, Chironomus riparius, to a sublethal pulse of a mixture of nine moderately polar fungicides and herbicides (logKow 2.5-4.7) at three field relevant treatment levels (1.2-2.5, 17.5-35.0, or 50.0-100.0 µg/L). We then assessed the pesticide bioaccumulation and bioamplification over the full aquatic-terrestrial life cycle of both sexes including the egg laying of adult females. By applying sensitive LC-MS/MS analysis to small sample volumes (∼5 mg, dry weight), we detected all pesticides in larvae from all treatment levels (2.8-1019 ng/g), five of the pesticides in the adults from the lowest treatment level and eight in the higher treatment levels (1.5-3615 ng/g). Retention of the pesticides through metamorphosis was not predictable based solely on pesticide lipophilicity. Sex-specific differences in adult insect pesticide concentrations were significant for five of the pesticides, with greater concentrations in females for four of them. Over the duration of the adults' lifespan, pesticide concentrations generally decreased in females while persisting in males. Our results suggest that a low to moderate daily dietary exposure to these pesticides may be possible for tree swallow nestlings and insectivorous bats.

Diversity and dispersal of aquatic invertebrate species from surface and groundwater: Development and application of microsatellite markers for the detection of hydrological exchange processes.

Groundwater is one of our most important resources, however groundwater ecosystems are among the most understudied habitats of the planet earth. Studies on groundwater organisms are hampered by the difficult accessibility of species, the lack of morphological differentiation and the limitation for laboratory cultures. One important approach to overcome these shortcomings is to provide sensitive genetic methods to unravel patterns of biodiversity, population structure and gene flow in natural populations. In this study we present five sets of microsatellite markers developed for the isopods Asellus aquaticus and Proasellus slavus, the cyclopoides Paracyclops fimbriatus and Acanthocyclops sensitivus and the harpacticoide Bryocamptus echinatus (Crustacea). Two of these species were subjected to detailed population genetic analyses: We studied 501 specimens of Asellus aquaticus from four different regions in Northern Germany using nine microsatellite markers and 70 specimens of Bryocamptus echinatus using nine microsatellite markers from three different sampling sites in South-Western Germany. Our results show that genetic diversity is high (A. aquaticus: 10 to 20 and B. echinatus: 4 to 18 alleles per locus) among populations of aquatic invertebrates, populations are highly differentiated (FST > 0.2) and genetic differentiation was associated with geographic patterns. Applications of molecular genetic methods and their use for the detection of hydrological exchange processes relevant for drinking water suppliers are demonstrated and discussed.

Hybridization Dynamics and Extensive Introgression in the Daphnia longispina Species Complex: New Insights from a High-Quality Daphnia galeata Reference Genome.

Hybridization and introgression are recognized as an important source of variation that influence adaptive processes; both phenomena are frequent in the genus Daphnia, a keystone zooplankton taxon in freshwater ecosystems that comprises several species complexes. To investigate genome-wide consequences of introgression between species, we provide here the first high-quality genome assembly for a member of the Daphnia longispina species complex, Daphnia galeata. We further resequenced 49 whole genomes of three species of the complex and their interspecific hybrids both from genotypes sampled in the water column and from single resting eggs extracted from sediment cores. Populations from habitats with diverse ecological conditions offered an opportunity to study the dynamics of hybridization linked to ecological changes and revealed a high prevalence of hybrids. Using phylogenetic and population genomic approaches, we provide first insights into the intra- and interspecific genome-wide variability in this species complex and identify regions of high divergence. Finally, we assess the length of ancestry tracts in hybrids to characterize introgression patterns across the genome. Our analyses uncover a complex history of hybridization and introgression reflecting multiple generations of hybridization and backcrossing in the Daphnia longispina species complex. Overall, this study and the new resources presented here pave the way for a better understanding of ancient and contemporary gene flow in the species complex and facilitate future studies on resting egg banks accumulating in lake sediment.

Ecology of predator-induced morphological defense traits in Daphnia longispina (Cladocera, Arthropoda).

Inducible defenses against predators are widespread among plants and animals. For example, some Daphnia species form neckteeth against predatory larvae of the dipteran genus Chaoborus. Though thoroughly studied in D. pulex, knowledge about neckteeth in other Daphnia species is limited. The occurrence of this trait in the D. longispina species complex is only sporadically reported and the specific shape of neckteeth or the occurrence of other morphological defense traits is scarcely known in this widespread group. Here, we explored neckteeth occurrence in a large number of D. longispina populations across Scandinavia and studied neckteeth formation and other morphological defense traits on three D. longispina clones in the laboratory. In the study region, neckteeth on juvenile D. longispina s. str. were observed frequently in permanent ponds, but only when Chaoborus spp. larvae were present. In the laboratory experiments, all three D. longispina clones developed neckteeth (very similar to D. pulex) in response to Chaoborus kairomone exposure. The D. longispina clones also developed a longer tail spine, wider body, and larger neckteeth pedestal in response to predation threat-likely as a defense against the gape-limited predator. The intensity of neckteeth expression also depended on the clone studied and the concentration of Chaoborus kairomone. Our results demonstrate that neckteeth on D. longispina can be common in nature and that D. longispina can also induce other morphological defenses against predators. The similarity of neckteeth in D. longispina and D. pulex imposes yet unresolved questions on the evolutionary origin in these distantly related Daphnia groups.

Mosquito control actions affect chironomid diversity in temporary wetlands of the Upper Rhine Valley.

The Upper Rhine Valley, a "hotspot of biodiversity" in Germany, has been treated with the biocide Bacillus thuringiensis var. israelensis (Bti) for mosquito control for decades. Previous studies discovered Bti nontarget effects in terms of severe chironomid abundance reductions. In this study, we investigated the impact of Bti on species level and addressed the community composition of the nontarget family Chironomidae by use of community metabarcoding. Chironomid emergence data were collected in three mosquito-control relevant wetland types in the Upper Rhine Valley. For all three sites the chironomid species composition, based on operational taxonomic units (OTUs), was different to varying degrees in the Bti-treated samples versus control samples, ranging from a significant 63% OTU reduction to an OTU replacement. We assumed that predatory chironomids are less prone to Bti than filter feeders, as the latter feed on floating particles leading to direct ingestion of Bti. However, a comparable percentage of predators and filter feeders (63% and 65%, respectively) was reduced in the Bti samples, suggesting that the feeding strategy is not the main driver for Bti sensitivity in chironomids. Finally, our data was compared to a three-year-old data set, indicating possible chironomid community recovery due to species recolonization a few years after the last Bti application. Considering the currently discussed worldwide insect decline we recommend a rethinking of the usage of the biocide Bti, and to prevent its ongoing application especially in nature protection reserves to enhance ecological resilience and to prevent boosting the current biodiversity loss.

Population transcriptomics in Daphnia: The role of thermal selection.

The complex interplay of forces influencing genetic divergence among populations complicates the discovery of the genetic basis underlying local adaptation. Here, we utilized for the first time a combined reverse ecology and population transcriptomic approach to assess the contribution of thermal selection to population differentiation, thereby considering transcriptome-wide variation in both gene expression profiles and DNA sequences. We compared transcriptomes among four Daphnia galeata populations and identified transcripts potentially responding to local thermal selection based on an extensive literature search for candidate genes possibly under thermal selection in arthropods. Over-representation of temperature-relevant candidate genes among transcripts strongly contributing to sequence divergence among two populations indicates that local thermal selection acted on the coding sequence level. We identified a large number of transcripts, which may contribute to local thermal adaptation based on outlier tests and distinctive expression profiles. However, among these, temperature-relevant candidate genes were not over-represented compared to the global gene set, suggesting that thermal selection played a minor role in divergence among Daphnia populations. Interestingly, although the majority of genes contributing strongly to sequence divergence did not contribute strongly to divergence at the expression level and vice versa, the affected gene functions were largely consistent between the two data sets. This suggests that genetic and regulatory variation constitutes alternative routes for responses to natural selection. Our combined utilization of a population transcriptomics approach and literature-based identification of ecologically informative candidate genes represents a useful and powerful methodology with a wide range of applications in evolutionary biology.

Divergent clades or cryptic species? Mito-nuclear discordance in a Daphnia species complex.

BACKGROUND: Genetically divergent cryptic species are frequently detected by molecular methods. These discoveries are often a byproduct of molecular barcoding studies in which fragments of a selected marker are used for species identification. Highly divergent mitochondrial lineages and putative cryptic species are even detected in intensively studied animal taxa, such as the crustacean genus Daphnia. Recently, eleven such lineages, exhibiting genetic distances comparable to levels observed among well-defined species, were recorded in the D. longispina species complex, a group that contains several key taxa of freshwater ecosystems. We tested if three of those lineages represent indeed distinct species, by analyzing patterns of variation of ten nuclear microsatellite markers in six populations. RESULTS: We observed a discordant pattern between mitochondrial and nuclear DNA, as all individuals carrying one of the divergent mitochondrial lineages grouped at the nuclear level with widespread, well-recognized species coexisting at the same localities (Daphnia galeata, D. longispina, and D. cucullata). CONCLUSIONS: A likely explanation for this pattern is the introgression of the mitochondrial genome of undescribed taxa into the common species, either in the distant past or after long-distance dispersal. The occurrence of highly divergent but rare mtDNA lineages in the gene pool of widespread species would suggest that hybridization and introgression in the D. longispina species complex is frequent even across large phylogenetic distances, and that discoveries of such distinct clades must be interpreted with caution. However, maintenance of ancient polymorphisms through selection is another plausible alternative that may cause the observed discordance and cannot be entirely excluded.

Community barcoding reveals little effect of ocean acidification on the composition of coastal plankton communities: Evidence from a long-term mesocosm study in the Gullmar Fjord, Skagerrak.

The acidification of the oceans could potentially alter marine plankton communities with consequences for ecosystem functioning. While several studies have investigated effects of ocean acidification on communities using traditional methods, few have used genetic analyses. Here, we use community barcoding to assess the impact of ocean acidification on the composition of a coastal plankton community in a large scale, in situ, long-term mesocosm experiment. High-throughput sequencing resulted in the identification of a wide range of planktonic taxa (Alveolata, Cryptophyta, Haptophyceae, Fungi, Metazoa, Hydrozoa, Rhizaria, Straminipila, Chlorophyta). Analyses based on predicted operational taxonomical units as well as taxonomical compositions revealed no differences between communities in high CO2 mesocosms (~ 760 µatm) and those exposed to present-day CO2 conditions. Observed shifts in the planktonic community composition were mainly related to seasonal changes in temperature and nutrients. Furthermore, based on our investigations, the elevated CO2 did not affect the intraspecific diversity of the most common mesozooplankter, the calanoid copepod Pseudocalanus acuspes. Nevertheless, accompanying studies found temporary effects attributed to a raise in CO2. Differences in taxa composition between the CO2 treatments could, however, only be observed in a specific period of the experiment. Based on our genetic investigations, no compositional long-term shifts of the plankton communities exposed to elevated CO2 conditions were observed. Thus, we conclude that the compositions of planktonic communities, especially those in coastal areas, remain rather unaffected by increased CO2.

A genotype-phenotype association approach to reveal thermal adaptation in Daphnia galeata.

Altering thermal environments impose strong selection pressures on organisms, whose local persistence depends on adaptive phenotypic plastic and genetic responses. Thus far, adaptive change is monitored using phenotypic shifts or molecular markers, although inevitable obstacles are inherent in both methods. In order to circumvent these, it is necessary to find a causal link between adaptive alleles and fitness. Combining both approaches by linking genetic analyses and life-history measurements, a potential genotype-phenotype relationship can be assessed and adaptation at the molecular level demonstrated. For our study, clonal lineages of the freshwater keystone species D. galeata from seven different populations distributed along a latitudinal gradient across Europe were tested for local thermal adaptation in common garden experiments. Fitness-related life-history responses were quantified under different thermal regimes and experimental clones were genotyped at three candidate gene marker loci to investigate a potential genotype-phenotype association. The analyses of the life-history data showed a significant temperature effect on several fitness-related life-history traits recorded in our experiments. However, we could not detect evidence for a direct association at neither candidate gene locus between genotypes and life-history traits. The observed phenotypic shifts might therefore not be based on the tested marker loci EA, M and TF, or in general not coding sequence-based and thus rather reveal phenotypic plasticity in response to thermal variation. Nonetheless, we revealed significant genotype by environment (GxE) interactions at all tested loci, potentially reflecting a contribution of marker loci to certain life-history trait values and contribution of multiple genetic loci to phenotypic traits.

Feral Cat Globetrotters: genetic traces of historical human-mediated dispersal.

Endemic species on islands are highly susceptible to local extinction, in particular if they are exposed to invasive species. Invasive predators, such as feral cats, have been introduced to islands around the world, causing major losses in local biodiversity. In order to control and manage invasive species successfully, information about source populations and level of gene flow is essential. Here, we investigate the origin of feral cats of Hawaiian and Australian islands to verify their European ancestry and a potential pattern of isolation by distance. We analyzed the genetic structure and diversity of feral cats from eleven islands as well as samples from Malaysia and Europe using mitochondrial DNA (ND5 and ND6 regions) and microsatellite DNA data. Our results suggest an overall European origin of Hawaiian cats with no pattern of isolation by distance between Australian, Malaysian, and Hawaiian populations. Instead, we found low levels of genetic differentiation between samples from Tasman Island, Lana'i, Kaho'olawe, Cocos (Keeling) Island, and Asia. As these populations are separated by up to 10,000 kilometers, we assume an extensive passive dispersal event along global maritime trade routes in the beginning of the 19th century, connecting Australian, Asian, and Hawaiian islands. Thus, islands populations, which are characterized by low levels of current gene flow, represent valuable sources of information on historical, human-mediated global dispersal patterns of feral cats.

Phenotypic plasticity in life-history traits of Daphnia galeata in response to temperature - a comparison across clonal lineages separated in time.

Climatic changes are projected to result in rapid adaptive events with considerable phenotypic shifts. In order to reconstruct the impact of increased mean water temperatures during past decades and to reveal possible thermal micro-evolution, we applied a resurrection ecology approach using dormant eggs of the freshwater keystone species Daphnia galeata. To this end, we compared the adaptive response of D. galeata clones from Lake Constance of two different time periods, 1965-1974 ("historical") versus 2000-2009 ("recent"), to experimentally increased temperature regimes. In order to distinguish between genetic versus environmentally induced effects, we performed a common garden experiment in a flow-through system and measured variation in life-history traits. Experimental thermal regimes were chosen according to natural temperature conditions during the reproductive period of D. galeata in Central European lakes, with one additional temperature regime exceeding the currently observable maximum (+2°C). Increased water temperatures were shown to significantly affect measured life-history traits, and significant "temperature × clonal age" interactions were revealed. Compared to historical clones, recent clonal lineages exhibited a shorter time to first reproduction and a higher survival rate, which may suggest temperature-driven micro-evolution over time but does not allow an explicit conclusion on the adaptive nature of such responses.

Review on environmental alterations propagating from aquatic to terrestrial ecosystems.

Terrestrial inputs into freshwater ecosystems are a classical field of environmental science. Resource fluxes (subsidy) from aquatic to terrestrial systems have been less studied, although they are of high ecological relevance particularly for the receiving ecosystem. These fluxes may, however, be impacted by anthropogenically driven alterations modifying structure and functioning of aquatic ecosystems. In this context, we reviewed the peer-reviewed literature for studies addressing the subsidy of terrestrial by aquatic ecosystems with special emphasis on the role that anthropogenic alterations play in this water-land coupling. Our analysis revealed a continuously increasing interest in the coupling of aquatic to terrestrial ecosystems between 1990 and 2014 (total: 661 studies), while the research domains focusing on abiotic (502 studies) and biotic (159 studies) processes are strongly separated. Approximately 35% (abiotic) and 25% (biotic) of the studies focused on the propagation of anthropogenic alterations from the aquatic to the terrestrial system. Among these studies, hydromorphological and hydrological alterations were predominantly assessed, whereas water pollution and invasive species were less frequently investigated. Less than 5% of these studies considered indirect effects in the terrestrial system e.g. via food web responses, as a result of anthropogenic alterations in aquatic ecosystems. Nonetheless, these very few publications indicate far-reaching consequences in the receiving terrestrial ecosystem. For example, bottom-up mediated responses via soil quality can cascade over plant communities up to the level of herbivorous arthropods, while top-down mediated responses via predatory spiders can cascade down to herbivorous arthropods and even plants. Overall, the current state of knowledge calls for an integrated assessment on how these interactions within terrestrial ecosystems are affected by propagation of aquatic ecosystem alterations. To fill these gaps, we propose a scientific framework, which considers abiotic and biotic aspects based on an interdisciplinary approach.

Differentiation in neutral genes and a candidate gene in the pied flycatcher: using biological archives to track global climate change.

Global climate change is one of the major driving forces for adaptive shifts in migration and breeding phenology and possibly impacts demographic changes if a species fails to adapt sufficiently. In Western Europe, pied flycatchers (Ficedula hypoleuca) have insufficiently adapted their breeding phenology to the ongoing advance of food peaks within their breeding area and consequently suffered local population declines. We address the question whether this population decline led to a loss of genetic variation, using two neutral marker sets (mitochondrial control region and microsatellites), and one potentially selectively non-neutral marker (avian Clock gene). We report temporal changes in genetic diversity in extant populations and biological archives over more than a century, using samples from sites differing in the extent of climate change. Comparing genetic differentiation over this period revealed that only the recent Dutch population, which underwent population declines, showed slightly lower genetic variation than the historic Dutch population. As that loss of variation was only moderate and not observed in all markers, current gene flow across Western and Central European populations might have compensated local loss of variation over the last decades. A comparison of genetic differentiation in neutral loci versus the Clock gene locus provided evidence for stabilizing selection. Furthermore, in all genetic markers, we found a greater genetic differentiation in space than in time. This pattern suggests that local adaptation or historic processes might have a stronger effect on the population structure and genetic variation in the pied flycatcher than recent global climate changes.

The evolutionary time machine: using dormant propagules to forecast how populations can adapt to changing environments.

Evolutionary changes are determined by a complex assortment of ecological, demographic, and adaptive histories. Predicting how evolution will shape the genetic structures of populations coping with current (and future) environmental challenges has principally relied on investigations through space, in lieu of time, because long-term phenotypic and molecular data are scarce. Yet, dormant propagules in sediments, soils, and permafrost are convenient natural archives of population histories from which to trace adaptive trajectories along extended time periods. DNA sequence data obtained from these natural archives, combined with pioneering methods for analyzing both ecological and population genomic time-series data, are likely to provide predictive models to forecast evolutionary responses of natural populations to environmental changes resulting from natural and anthropogenic stressors, including climate change.