Effects Of Environmental Disturbances Research Articles

Niche-based approach to explore the impacts of environmental disturbances on biodiversity.

Globally, species are increasingly at risk from compounding threatening processes, an increasingly prominent driver of which is environmental disturbances. To facilitate effective conservation efforts following such events, methods that evaluate potential impacts across multiple species and provide landscape-scale information are needed to guide targeted responses. Often, the geographic overlap between a disturbance and species' distribution is calculated and then used as a proxy for potential impact. However, such methods do not account for the important influence of environmental heterogeneity throughout species' ranges. To address this shortcoming, we quantified the effects of environmental disturbances on species' environmental niche space. Using the Australian 2019 and 2020 Black Summer fires as a case study, we applied a niche-centric approach to examine the potential impacts of these fires on 387 vertebrate species. We examined the utility of established and novel niche metrics to assess the potential impacts of large-scale disturbance events on species by comparing the potential effects of the fires as determined by our various niche measures to those derived from geographic-based measures of impact. We examined the quality of environmental space affected by the disturbance by quantifying the position in niche space where the disturbance occurred (center or margin), the uniqueness of the environmental space that was burned, and the degree to which the remaining, unburned portion of the niche differed from a species' original prefire niche. There was limited congruence between the proportion of geographic and niche space affected, which showed that geographic-based approaches in isolation may have underestimated the impact of the fires for 56% of modeled species. For each species, when combined, these metrics provided a greater indication of postdisturbance recovery potential than geographic-based measures alone. Accordingly, the integration of niche-based analyses into conservation assessments following large-scale disturbance events will lead to a more nuanced understanding of potential impacts and guide more informed and effective conservation actions.

Trophic interactions between two sympatric mesocarnivores in an anthropized landscape from the Mexican highlands

The study of diets in North American carnivores has been assessed from different methods, essentially analyzing the composition of their diet, and classifying the species based on the breadth of their trophic niche. Still, studies that explore aspects of their interactions are limited. This work studies the predator-prey relationship through an interaction network analysis approach, nesting, and the analysis of core vs peripheral individuals, for two sympatric species of the Mexican highlands, the bobcat (Lynx rufus) and the coyote (Canis latrans). In addition, the effect on the structure of the interaction networks under two conditions of environmental disturbance was evaluated. In environments with high disturbance: A network was obtained for 46 bobcats and 18 coyotes, identifying six bobcats and five core coyotes; and in environments with low disturbance, the network was obtained for 134 bobcats and 38 coyotes, identifying 30 bobcats and eight core coyotes. Three of the analyzed networks presented a nested pattern with the WNOFD metric (High disturbance: L. rufus: Nesting = 0.51, p < 0.05, C. latrans: 4.13, p < 0.05; Low disturbance: L. rufus, 0.91, p < 0.05) and only one network with the NOFD metric was nested (Low disturbance = C. latrans, 19.51, p < 0.05). There was an effect of environmental disturbance on the evaluated networks; in highly disturbed environments, the structure and composition of the interactions are different for both species. Unlike conventional methods for studying the diet of carnivores, our results provide a different methodology that allows characterizing the network of trophic relationships between predators and their prey, evaluating whether their relationships are nested, and analyzing information at the level of individuals and sexes. In subsequent studies, it is relevant to investigate the fragility of the network due to the loss of essential components of its structure, which will allow establishing measures for its conservation. Also, presents for the first time the structure of the trophic interaction network for two sympatric mesocarnivores from the Mexican highlands, as a tool to study their relationships and show mechanisms of their coexistence.

Path following control for large inland ships in a restricted waterway using the nonlinear terminal sliding mode method

In order to solve the problem of path following for large ships travelling in restricted waterways, an adaptive Line-Of-Sight (LOS) guidance with the Nonlinear Terminal Sliding Mode (NTSM) algorithm is proposed in this paper. Compared to classical Sliding Mode Controller (SMC) and Adaptive Sliding Mode Controller (ASMC), the proposed system enables large ships to track the desired path much faster, meanwhile, the course stability can also be achieved with the controller saturation and environmental disturbance. To solve the problems of high nonlinearity and uncertainty of ship motion in restricted waters, the mathematical model with Extended state observer (ESO) is proposed to linearize problem. A drift angle observer is established to observe the drift angle during the vessel's navigation, and the LOS guidance law is used to achieve accurate tracking of the desired trajectory. The simulation results show that the inland ships under the control of the proposed scheme can accurately track the desired trajectory in a restricted waterway. The proposed algorithm has good robustness under the effect of environmental disturbances.

Fish Beta Diversity Patterns across Environmental Gradients in 63 European Shallow Lakes: Effects of Turbidity, Nutrient Enrichment, and Exotic Species

The beta diversity among lakes is affected by natural environmental sorting, dispersal constraints, and anthropogenic disturbances. We hypothesized that fish beta diversity would increase towards lower latitudes and be higher in less disturbed lakes at within-region scale, but environmental disturbances could affect these patterns due to community homogenization or heterogenization (e.g., gain of exotic species) among lakes. We used generalized dissimilarity modeling to assess the relative importance of geographic distance, climate, and environmental heterogeneity on fish beta diversity across Denmark, Belgium/The Netherlands, and Spain. We also tested whether differences in beta diversity changed between lake types (e.g., clear vs. turbid lakes and lakes with vs. without exotics fish) within-region and across latitude. Beta diversity increased from Denmark to Spain and geographic distance and climate variability were the main drivers of community change across latitude, but the rate of change varied between lake types. At the within-region scale, factors such as turbidity, lake size, and presence of exotics had varying impacts on beta diversity (i.e., increasing, decreasing, or no effect) across the three regions. Our findings suggest that understanding the effects of environmental disturbances on beta diversity requires consideration of both biogeographic and local factors.

An analysis of historical bottlenose dolphin (Tursiops truncatus) strandings in the Mississippi Sound, USA using classification and regression trees (CART)

Trends in bottlenose dolphin (Tursiops truncatus) strandings can be used to examine several factors associated with mortality and life history and are essential for detecting unusual mortality events (UMEs). This study characterised stranding trends in the Mississippi Sound (MS) region of the northern Gulf of Mexico (GoM) from 1996–2009 using kernel density estimation (KDE) and classification and regression tree (CART) analysis. An annual mean of 26.1 strandings (n = 14), SD = 13.7, 95% CI [18.2, 34.0] and a peak in strandings during spring (March–May) were evident from our analyses. Neonates stranded almost exclusively in spring indicating that this is the dominant breeding and calving season in this area. Spatial distributions revealed that the majority of dolphins stranded along central and western portions of the MS Sound near Gulfport, MS and on Ship Island during the spring and summer months, but were more often found in the eastern MS Sound during winter and autumn. Our CART analyses indicated that 1996, which contained a declared UME, was anomalous from other years as the number of adult, sub-adult and juvenile strandings was relatively high during the autumn and winter. Further, our analyses showed that the location of those strandings on Ship Island in autumn and winter was unique from all other years in the historical record. These results represent historical conditions that can be used as a baseline for future studies of the effects of environmental disturbances, including UMEs, in MS. This research also demonstrates the versatility and usefulness of CART for describing historical trends, detecting departures from the norm and explaining UMEs within the framework of a single analysis. This approach represents an objective assessment tool that could be used to assist governmental agencies with determining the onset of a UME and could help support or refute the cause of these events.

Effect of environmental disturbances on crossflow instability

Wind tunnel experiments on the receptivity of three-dimensional boundary layers were performed in a range of freestream turbulence intensities, Tu, from 0.01%—the lowest level ever achieved in this type of work—up to 0.41%. This work confirms that for Tu=0.01%, and presumably below this level, the transition process is dominated by stationary modes. These are receptive to surface roughness and generate Type-I and Type-II secondary instabilities that eventually cause the transition to turbulence. The saturation amplitude of these stationary waves is highly sensitive to the level of environmental disturbances; the former is here recorded to be the highest in the literature, with the latter being the lowest. Travelling modes are still present; however, their influence on the transition process is marginal. At matched surface roughness levels, when the level of environmental disturbance is enhanced to Tuge 0.33%, the travelling modes acquire more importance, strongly influencing the laminar/turbulent transition process, whilst the initial amplitude and growth of the stationary modes are hindered. For this level of Tu, is the interaction of steady and unsteady disturbances that produces highly amplified waves (Type-III), that quickly lead to nonlinear growth and anticipated turbulence. Finally, a simple rule of thumb is proposed, where the transition front was found to move forward by roughly 10% chord for an increase in one order of magnitude in the Tu levels.Graphical abstract

The biogeography and co-occurrence network patterns of bacteria and microeukaryotes in the estuarine and coastal waters

Community and diversity shifts of bacteria and microeukaryotes with strong environmental and spatial variations have been unveiled in the Pearl River Estuary (PRE) and northern coastal part of South China Sea (SCS). However, it is not clear what the determining factors shape the microbial community and how the biotic interactions respond to the estuarine and oceanic environment. Here, we established the multiple regression models (MRM) and co-occurrence networks on microbial communities in PRE and SCS habitats. The results showed that there were significant differences of the abiotic factors affecting the bacterial and microeukaryotic communities between PRE and SCS habitats. Salinity explained the largest variations to the microbial community dissimilarities in PRE. Whereas spatial and environmental factors determined the microbial community dissimilarities in SCS. Positive relations between parasitic lineages (e.g. Perkinsea and Cercozoa) and algal taxa (Dinophyceae, Cryptophyta, Chlorophyta and Ochrophyta) dominated in the PRE network. While parasites Syndiniales positively correlated with other Syndiniales and protists in SCS. Strong positive associations among autotrophic and heterotrophic groups were revealed in both niches. Therefore, the biotic interactions are also important and may be responsible for the unexplained variations of the abiotic factors from MRM models. Microbial network in the PRE estuarine water had weakened resistance to environmental disturbances, while the SCS network had greater capacity to maintain network stability. This study shed light on the different mechanisms of abiotic and biotic factors in shaping the compositions of bacteria and microeukaryotes between PRE and SCS niches, and highlights the weakening effect of environmental disturbances on the microbial network stability.

Development of epigenetic biomarkers for the identification of sex and thermal stress in fish using DNA methylation analysis and machine learning procedures.

The sex ratio is a key ecological demographic parameter crucial for population viability. However, the epigenetic mechanisms operating during gonadal development regulating gene expression and the sex ratio remain poorly understood. Moreover, there is interest in the development of epigenetic markers associated with a particular phenotype or as sentinels of environmental effects. Here, we profiled DNA methylation and gene expression of 10 key genes related to sex development and stress, including steroidogenic enzymes, and growth and transcription factors. We provide novel information on the sex-related differences and on the influence of elevated temperature on these genes in zebrafish, a species with mixed genetic and environmental influences on sex ratios. We identified both positive (e.g., amh, cyp11c and hsd11b2) and negative (e.g., cyp11a1 and dmrt1) correlations in unexposed males, and negative correlation (amh) in exposed females between DNA methylation and gene expression levels. Further, we combined DNA methylation analysis with machine learning procedures and found a series of informative CpGs capable not only of correctly identifying sex (based on cyp19a1a DNA methylation levels) but also of identifying whether males and females had been exposed to abnormally elevated temperature when young (based on amh and foxl2a DNA methylation levels, respectively). This was achieved in the absence of conspicuous morphological alterations of the gonads. These DNA methylation-based epigenetic biomarkers represent molecular resources that can correctly recapitulate past thermal history and pave the way for similar findings in other species to assess potential ecological effects of environmental disturbances in the context of climate change.

Inferring spatially varying animal movement characteristics using a hierarchical continuous-time velocity model.

Understanding the spatial dynamics of animal movement is an essential component of maintaining ecological connectivity, conserving key habitats, and mitigating the impacts of anthropogenic disturbance. Altered movement and migratory patterns are often an early warning sign of the effects of environmental disturbance, and a precursor to population declines. Here, we present a hierarchical Bayesian framework based on Gaussian processes for analysing the spatial characteristics of animal movement. At the heart of our approach is a novel covariance kernel that links the spatially varying parameters of a continuous-time velocity model with GPS locations from multiple individuals. We demonstrate the effectiveness of our framework by first applying it to a synthetic data set and then by analysing telemetry data from the Serengeti wildebeest migration. Through application of our approach, we are able to identify the key pathways of the wildebeest migration as well as revealing the impacts of environmental features on movement behaviour.

Microbial hierarchical correlations and their contributions to carbon-nitrogen cycling following a reservoir cyanobacterial bloom

Unraveling how microbial co-occurrences respond to cyanobacterial blooms is central to our understanding of the stability of aquatic ecosystems. Here, we examined the effects of a Microcystis bloom on the inter-domain eukaryotic and two size-fractionated bacterial networks in a subtropical reservoir. Eukaryotes, especially protists, had a central role in microbial networks, followed by particle-attached (PA) bacteria and free-living (FL) bacteria. Eukaryotes had more negative correlations with PA bacteria than with FL bacteria. The environmental changes related to the Microcystis bloom (i.e., water temperature, pH, chlorophyll a, total carbon, total organic carbon and nitrite nitrogen) strongly affected eukaryotes and PA bacteria network as reflected by the dynamics of community composition in major modules. Importantly, the network complexity and stability significantly increased in the post-bloom periods, and eukaryotes (especially protists) enhanced the stability of the microbial network. Compared to keystone FL bacteria, eukaryotic and PA bacterial hubs mainly determined the network structure and key functional potentials (i.e., nitrogen cycling, carbon fixation and carbon degradation). Thus, some keystone eukaryotes and PA bacteria might be used as indicators of the structure and function stability of microbial communities in reservoir ecosystems. Our study highlights the importance of considering microbial cross-kingdom and multiple size-fractionation correlations in evaluating the effects of environmental disturbances on microbial networks.

Distinct stages of the intestinal bacterial community of Ampullaceana balthica after salinization.

Environmental disturbances influence bacterial community structure and functioning. To investigate the effect of environmental disturbance caused by changes in salinity on host-protected bacterial communities, we analyzed the microbiome within the gastrointestinal tract of Ampullaceana balthica in different salinities. A. balthica is a benthic gastropod found in fresh- and mesohaline waters. Whereas the total energy reserves of A. balthica were unaffected by an increase of salinity to 3, a high mortality rate was detected after a shift from freshwater to salinity 6 suggesting a major disruption of energy homeostasis. The shift to salinity 6 also caused a change in the gastrointestinal bacterial community composition. At salinity 3, the bacterial community composition of different host individuals was related either to the freshwater or salinity 6 gastrointestinal bacterial community, indicating an ambivalent nature of salinity 3. Since salinity 3 represents the range where aquatic gastropods are able to regulate their osmolarity, this may be an important tipping point during salinization. The change in the intestinal microbiome was uncoupled from the change in the water bacterial community and unrelated to the food source microbiome. Our study shows that environmental disturbance caused by salinity acts also on the host-protected microbiome. In light of the sea-level rise, our findings indicate that salinization of the near-shore freshwater bodies will cause changes in organisms’ intestinal microbiomes if a critical salinity threshold (presumably ∼3) is exceeded.

Spatial and temporal distribution dataset of benthic macroalgae during the 2015-2016 tropical monsoonal cycle in Malaysia.

The effects of small-scale disturbances, such as monsoon, are understudied in tropical regions. The storms associated with monsoon events not only modify the local macroalgal community structure, but also reveal the continuation of short-term recolonisation. Thus, this study aims to determine the variation in species, assemblage and cover of macroalgae during the monsoonal cycle from 2015 to 2016. This paper presents data on the spatial and temporal distribution of benthic macroalgae along the coastline of Johor, Malaysia. The information is presented as raw and partially-processed data, which summarises the cover and frequency of macroalgae at the respective study sites. This paper describes an important set of data that can be used further for in-situ experiments on the effects of environmental disturbances towards pioneer and climax species in tropical areas. This study provides a description of the east coast shore of Peninsular Malaysia, specifically in Johor coast in 2015-2016. The spatial and temporal distribution and abundance of a total of 41 taxa were assessed at four monsoon-exposed locations. These data provide a comprehensive baseline against disturbance and recolonisation of macroalgal community can be effectively and objectively evaluated.

Control Allocation-Based Robust Tracking Control for Overactuated Surface Vessels Subject to Time-Varying Full-State Constraints

In this paper, we propose a robust tracking control scheme for trajectory tracking of overactuated marine surface vessels subject to environmental disturbances and asymmetric time-varying full-state constraints. The proposed robust control scheme is based on the unified barrier function technique that converts the original constrained dynamic positioning system into an equivalent nonconstrained one. In contrast to barrier Lyapunov function-based methods, the unbreakable requirement on the constraints is less restrictive, and the resultant controller is much simpler in this paper. The effect of environmental disturbances is compensated by a double-layer adaptive sliding mode disturbance observer. On the basis of the proposed adaptive disturbance observer, unknown lumped uncertainty can be estimated in finite time without knowing the upper bounds of the derivative of the lumped uncertainty. Since the surface vessel is overactuated, a control allocation scheme is required to distribute the generalized force signal to the actuators. The enhanced redistributed pseudoinverse algorithm is employed to ensure that the generalized force can be redistributed among the redundant actuators. Lastly, a simulation study is carried out on a dynamic positioning ship to verify the effectiveness of the proposed control method.

Characterization of surface structures by using interferometry under challenging environmental conditions

Surface data contains not only information about functionality of a product but also gives hints about the environmental conditions, like processing parameters or vibration. There are different methods to obtain such information and white light interferometers are accepted to be one of the most powerful tools for surface metrology. Besides other metrological characteristics, its vertical resolution in the level of nanometer enables the acquisition of important details in topography. But at the same time, effects of environmental factors like uncontrolled movement or vibrations can be seen in the measurement data if some precautions are not taken. In this paper a new method which reduces the effects of environmental disturbances is described.

A Multiple-Output Hybrid Ship Trajectory Predictor With Consideration for Future Command Assumption

Onboard sensors contribute to data-driven understanding of complex and nonlinear ship dynamics in real time. By using sensors, precise ship trajectory prediction plays a key role in intelligent collision avoidance. A hybrid predictor makes prediction based on a mathematical model of which error is compensated by a black-box model. A Multiple-output Hybrid Predictor (MHP), which makes a long-horizon prediction at a time based on onboard sensor data, was developed in the previous study. However, it cannot handle a time series of future command assumption. This limitation hinders an MHP from being applied to the evaluation of future command assumption in the predictive decision making. A novel architecture of MHP presented in this study converts a long time series of future command assumption into a fixed-length model-based-predicted vessel state; then, it is included in inputs of a black-box error compensator. This idea is robust to multidimensionality of commands and long control horizon. Assuming a low-fidelity vessel model and a limited data are available, simulation experiments are conducted. The effect of environmental disturbances and maneuverings on the prediction performance is examined comprehensively for the first time. The present study successfully incorporates a long time series of future command assumption in an MHP. It reduces the mean error by 81.8% compared to a model-based predictor and by 45.6% compared to a data-driven predictor under Beaufort wind force scale 4 wave, wind, and ocean current. Present study expands the application of MHP to the predictive decision making of future autonomous ships.

Experimental Warming Reduces Survival, Cold Tolerance, and Gut Prokaryotic Diversity of the Eastern Subterranean Termite, Reticulitermes flavipes (Kollar).

Understanding the effects of environmental disturbances on insects is crucial in predicting the impact of climate change on their distribution, abundance, and ecology. As microbial symbionts are known to play an integral role in a diversity of functions within the insect host, research examining how organisms adapt to environmental fluctuations should include their associated microbiota. In this study, subterranean termites [Reticulitermes flavipes (Kollar)] were exposed to three different temperature treatments characterized as low (15°C), medium (27°C), and high (35°C). Results suggested that pre-exposure to cold allowed termites to stay active longer in decreasing temperatures but caused termites to freeze at higher temperatures. High temperature exposure had the most deleterious effects on termites with a significant reduction in termite survival as well as reduced ability to withstand cold stress. The microbial community of high temperature exposed termites also showed a reduction in bacterial richness and decreased relative abundance of Spirochaetes, Elusimicrobia, and methanogenic Euryarchaeota. Our results indicate a potential link between gut bacterial symbionts and termite’s physiological response to environmental changes and highlight the need to consider microbial symbionts in studies relating to insect thermosensitivity.

Long-term monitoring of benthic communities reveals spatial determinants of disturbance and recovery dynamics on coral reefs

Coral reefs across the globe are facing threats from a variety of anthropogenic disturbances. Consequently, the proportional representation of live scleractinian corals in the benthic community has declined substantially in many regions. In contrast, parts of the reef ecosystem around Mo’orea (French Polynesia) have displayed remarkable rebound potential. Nevertheless, detailed studies of when, where, and to what extent reefs have been disturbed and subsequently recovered in the different reef habitats are lacking. Using long-term monitoring data (2004-2018), we reveal that the spatiotemporal dynamics of benthic communities differ markedly between the contiguous inner (fringing and barrier) and outer (fore) reefs. Coral communities on inner reefs vary spatially but were remarkably stable over 15 yr, exhibiting consistent levels of coral and algal cover, with no evidence for disturbance-driven regimes or community transitions. In contrast, the outer reefs showed marked declines in coral cover following consecutive acute disturbances, but coral recovered rapidly thereafter. Nevertheless, community composition changed significantly, with Pocillopora replacing Acropora as the dominant genus at several sites, indicating a more subtle but potentially critical transition into an alternative state defined by the prevalence of a single, fast-growing genus. Inner reef stability and outer reef recovery provide evidence that the effects of environmental disturbances and chronic anthropogenic stressors can manifest in fundamentally different ways, depending on prevailing conditions. Our results suggest important ecological and physical links between inner and outer reef systems that influence the observed dynamics, emphasizing that reef ecosystem management and conservation strategies need to consider all habitats.

Robustness, sensitivity and reproducibility of eDNA metabarcoding as an environmental biomonitoring tool in coastal salmon aquaculture – An inter-laboratory study

Environmental DNA metabarcoding of benthic bacterial communities emerged as a very powerful technology to assess environmental disturbance effects of coastal salmon aquaculture. A prerequisite for the implementation of this approach into compliance monitoring regulations is its robustness and reproducibility of obtained results. In the framework of regular compliance monitoring of a Scottish salmon farm, we therefore collected sediment samples along a transect from the salmon cages to reference sites in duplicates (biological replicates). Aliquots of both biological replicate samples were then processed by two different laboratories using independently the same eDNA metabarcoding protocol (technical replicates). Measures of alpha diversity and beta diversity, as well as taxonomic profiles of benthic bacterial communities were highly congruent among technical replicates, which even showed less variations then the biological replicates that were processed within each laboratory. Both technical replicate datasets identified the same bacterial indicator taxon groups and ASVs that are characteristic for the environmental quality (EQ) categories to which each of the samples was assigned based on traditional macroinvertebrate biomonitoring of the same samples. In a supervised machine learning (SML) approach, we could classify all individual samples from one technical replicate dataset into the correct EQ category using all samples of the other technical replicate dataset as a training dataset for the SML algorithm. We conclude that eDNA metabarcoding is sufficiently robust that different laboratories come to the same conclusions regarding officially regulated action criteria for environmental impact assessments in salmon aquaculture.

Time Series Analysis of Forest Dynamics at the Ecoregion Level

Forecasting of forest dynamics at a large scale is essential for land use management, global climate change and biogeochemistry modeling. We develop time series models of the forest dynamics in the conterminous United States based on forest inventory data collected by the US Forest Service over several decades. We fulfilled autoregressive analysis of the basal forest area at the level of US ecological regions. In each USA ecological region, we modeled basal area dynamics on individual forest inventory pots and performed analysis of its yearly averages. The last task involved Bayesian techniques to treat irregular data. In the absolute majority of ecological regions, basal area yearly averages behave as geometric random walk with normal increments. In California Coastal Province, geometric random walk with normal increments adequately describes dynamics of both basal area yearly averages and basal area on individual forest plots. Regarding all the rest of the USA’s ecological regions, basal areas on individual forest patches behave as random walks with heavy tails. The Bayesian approach allowed us to evaluate forest growth rate within each USA ecological region. We have also implemented time series ARIMA models for annual averages basal area in every USA ecological region. The developed models account for stochastic effects of environmental disturbances and allow one to forecast forest dynamics.

Breaking ecological barriers: Anthropogenic disturbance leads to habitat transitions, hybridization, and high genetic diversity

Genetic diversity is expected to erode in disturbed habitats through strong selection, local extinctions, and recolonization associated with genetic bottlenecks and restricted gene flow. Despite this general prediction and over three decades of population genetics studies, our understanding of the long-term effect of environmental disturbance on local and regional genetic diversity remains limited. We conducted a population genetic survey of the microcrustacean Daphnia across a landscape subject to anthropogenic stressors from a century of industrial mining. At the local scale we found moderate genetic diversity (i.e., low clonal diversity), characteristic of habitat-specific selective sweeps and local extinctions, but high diversity and strong genetic structure at the regional scale despite the shared watershed of many lakes and exceptional dispersal ability of daphniids. Many habitats experienced changes in species assemblages, with the obligate asexual Daphnia pulex lineages—known only to inhabit ponds—dominating disrupted urban lakes. This habitat transition (pond to lake) was likely facilitated by the disruption of ecological barriers maintaining the genomic separation of these young species. Thus, disrupted habitats can exhibit complex and unexpected genetic patterns of local extinctions and recolonizations, followed by habitat transitions, hybridization and potential speciation events that are difficult to predict and should not be underestimated.