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Invasive species have substantial ecological and economic costs and removing them can require large investments by management agencies. Optimal spatial allocation of removal effort is critical for efficient and effective management of invasive species. Using a series of ecologically informed model simulations, we evaluated and compared different spatially explicit removal strategies for invasive rusty crayfish (Faxonius rusticus) in the John Day River, USA. We assessed strategies in terms of their performance on three likely management objectives: suppression (minimise overall population abundance), containment (minimise the spatial extent of invasion) and prevention (minimise spread into a specific area). We developed five spatial removal strategies to achieve those objectives, denoted as: Target Abundance (removal at locations with the highest population abundance), Target Growth (removal at locations with the highest population growth), Target Edges (removal at the most distant locations in the river), Target Downstream (removal at the most downstream invaded segments on the Mainstem), and Target Random (removal at randomly selected locations). Each strategy was assessed at various effort levels, referring to the number of spatial segments in the river in which removals were conducted, after seven years of management. We identified the alternative that best achieved each objective, based on decision criteria for risk-neutral and risk-averse decision-makers and further evaluated strategies based on Pareto efficiency, which identifies the set of alternatives for which an improvement on one objective cannot be had without a decline in performance on another. We found that Target Abundance and Target Growth strategies best achieved the suppression objective, for risk neutral and risk averse decision-makers, respectively and Target Downstream was always best in achieving the prevention objective across both types of decision-makers. No single strategy consistently performed best in terms of the containment objective. In terms of all three objectives, Target Downstream was consistently Pareto efficient across all levels of management effort and both decision criteria. The modelling framework we provided is adaptable to a variety of riverine invasive species to help assess and compare spatial management strategies.

Context-dependency is prevalent in nature, challenging our understanding and prediction of the potential ecological impacts of non-native species (NNS). The presence of a top predator, for example, can modify the foraging behaviour of an intermediate consumer, by means of non-consumptive effects. This raises the question of whether the fear of predation might modulate consumption rates of NNS, thus shaping the magnitude of ecological impacts. Here, we quantified the functional feeding responses of three non-native crayfish species – red swamp crayfish Procambarus clarkii, rusty crayfish Faxonius rusticus and virile crayfish Faxonius virilis – compared to the native analogue signal crayfish Pacifastacus leniusculus, considering the predation risk imposed by a top fish predator, the globally invasive largemouth bass Micropterus salmoides. We applied the comparative functional response (FR) approach using snails as prey and exposing crayfish to water containing predator and dietary chemical cues or not. All crayfish species presented a destabilising Type II FR, regardless of the presence of chemical cues. Predation risk resulted in significantly longer handling times or lower attack rates in non-native crayfish; however, no significant differences were observed in signal crayfish. We estimated per capita impacts for each species using the functional response ratio (FRR; attack rate divided by handling time). The FRR metric was lower for all crayfish species when exposed to predation risk. Rusty crayfish demonstrated the highest FRR in the absence of chemical cues, followed by signal crayfish, virile crayfish and red swamp crayfish. By contrast, the FRR of signal crayfish was nearly twice that of rusty crayfish and virile crayfish and ten times greater than red swamp crayfish when chemical cues were present. The latter result agrees with the well-recognised ecological impacts of signal crayfish throughout its globally-introduced range. This study demonstrates the importance of considering the non-consumptive effects of predators when quantifying the ecological impacts of intermediate non-native consumers on prey. The direction and magnitude of the modulating effects of predators have clear implications for our understanding of NNS impacts and the prioritisation of management actions.

How scientists communicate can influence public viewpoints on invasive species. In the scientific literature, some invasion biologists adopt neutral language, while others use more loaded language, for example by emphasizing the devastating impacts of invasive species and outlining consequences for policy and practice. An evaluation of the use of language in the invasion biology literature does not exist, preventing us from understanding which frames are used and whether there are correlations between message framing in scientific papers and local environmental impacts associated with invasive species. Thus, we conducted a systematic literature review of 278 peer-reviewed articles published from 2008–2018 to understand communication styles adopted by social and natural scientists while reporting on aquatic non-native species research. Species-centered frames (45%) and human-centered frames (55%) were adopted to nearly equal degrees. Negative valence was dominant in that 81.3% of articles highlighted the negative risks and impacts of invasive species. Additionally, the use of terminology was found to broadly align with the stage of invasion, in that “invasive” was most commonly used except when the research was conducted at early stages of invasion, when “non-native” was most commonly used. Terminology use therefore enables readers of scientific papers to infer the status and severity of ongoing invasions. Given that science communication within the peer-reviewed literature affects public understanding of research outcomes, these findings provide an important point of reflection for researchers.

Abstract Background Altering the natural flow regime, an essential component of healthy fluvial systems, through hydropower operations has the potential to negatively impact freshwater fish populations. Establishing improved management of flow regimes requires better understanding of how fish respond to altered flow components, such as flow magnitude. Based on the results of a recent systematic map on the impacts of flow regime changes on direct outcomes of freshwater or estuarine fish productivity, evidence clusters on fish abundance and biomass responses were identified for full systematic review. The primary goal of this systematic review is to address one of those evidence clusters, with the following research question: how do changes in flow magnitude due to hydropower operations affect fish abundance and biomass? Methods This review follows the guidelines of the Collaboration for Environmental Evidence. It examined commercially published and grey literature originally identified during the systematic map process and a systematic search update. All articles were screened using an a priori eligibility criteria at two stages (title and abstract, and full-text) and consistency checks were performed at all stages. All eligible articles were assessed for study validity and specifically designed data extraction and study validity tools were used. A narrative synthesis included all available evidence and meta-analysis using the standardized mean difference (Hedges’ g) was conducted where appropriate. Review findings A total of 133 studies from 103 articles were included in this systematic review for data extraction and critical appraisal. Most studies were from North America (60%) and were conducted at 146 different hydropower dams/facilities. Meta-analysis included 268 datasets from 58 studies, separated into three analyses based on replication type [temporal (within or between year replication) or spatial]. Fish abundance (226 datasets) and biomass (30 datasets) had variable responses to changes in flow magnitude with estimated overall mean effect sizes ranging from positive to negative and varying by study design and taxa. In studies with temporal replication, we found a detectable effect of alterations to the direction of flow magnitude, the presence of other flow components, sampling methods, season, and fish life stage. However, we found no detectable effect of these moderators for studies with spatial replication. Taxonomic analyses indicated variable responses to changes in flow magnitude and a bias towards salmonid species. Conclusions This synthesis did not find consistent patterns in fish abundance or biomass responses to alterations or changes in flow magnitude. Fish responses to flow magnitude alterations or changes were highly variable and context dependent. Our synthesis suggests that biotic responses may not be generalizable across systems impacted by hydroelectric power production and operations, where specific features of the system may be highly influential. Site-specific and adaptive management may be necessary. To improve study validity and interpretability, studies with long-term continuous monitoring, and both temporal and spatial replication are needed. When this gold standard is unfeasible, studies should strive, at minimum, to maximize replication within both intervention and comparator groups for either temporal or spatial designs. To further address knowledge gaps, studies are needed that focus on non-salmonids, multiple seasons, and systems outside of North America.

Abstract River scientists strive to understand how streamflow regimes vary across space and time because it is fundamental to predicting the impacts of climate change and human activities on riverine ecosystems. Here we tested whether flow periodicity differs between rivers that are regulated or unregulated by large dams, and whether dominant periodicities change over time in response to dam regulation. These questions were addressed by calculating wavelet power at different timescales, ranging from 6 hr to 10 years, across 175 pairs of dam‐regulated and unregulated USGS gages with long‐term discharge data, spanning the conterminous United States. We then focused on eight focal reservoirs with high‐quality and high‐frequency data to examine the spectral signatures of dam‐induced flow alteration and their time‐varying nature. We found that regulation by dams induces changes not only in flow magnitude and variability, but also in the dominant periodicities of a river's flow regime. Our analysis also revealed that dams generally alter multi‐annual and annual periodicity to a higher extent than seasonal or daily periodicity. Based on the focal reservoirs, we illustrate that alteration of flow periodicity is time varying, with dam operations (e.g., daily peaking vs. baseload operation), changes in dam capacity, and environmental policies shifting the relative importance of periodicities over time. Our analysis demonstrates the pervasiveness of human signatures now characterizing the U.S. rivers' flow regimes, and may inform the restoration of environmental periodicity downstream of reservoirs via controlled flow releases—a critical need in light of new damming and dam retrofitting for hydropower globally.

Unselective fishing involves activities that target the entire assemblage rather than specific fish species, size classes, or trophic levels. This common fishing approach has been in practice for decades in inland waters in China but its implications for biodiversity remain unclear. We addressed this issue by studying fish assemblages in freshwater lakes (five fishing lakes, one reference lake, and a total of 51 sampling sites) between pre- and post-fishing time-periods in Eastern China during 2017–2019. The effects of lake, fishing period, and their interactions on fish abundance, biomass, and diversity indices were assessed. Multivariate analysis was conducted to test for differences in fish assemblages among lakes and between fishing periods. After the implementation of fishing activities, significant reductions in fish species richness, abundance, biomass, and all three life-history strategies (opportunistic, equilibrium, and periodic) were observed in fishing lakes, whereas opposite trends were observed in the reference lake. Compositional similarity of fish assemblages among fishing lakes increased over the three-year monitoring period. Our results suggest that unselective fishing reduces fish diversity and homogenizes fish assemblage structure in lakes. These findings have important implications for protecting both biodiversity and fisheries in inland waters in China and are applicable to other countries or regions that rely on fish as a major food source.

Abstract Trait‐based models of ecological communities and ecosystem functioning often fail to account for intraspecific variation in functional traits, assuming that intraspecific variability is negligible compared with interspecific variability. However, this assumption remains poorly tested across vertebrate animals where past studies routinely describe species according to mean trait values without explicit consideration of individual trait variability. We assessed nine functional traits for 4254 individuals belonging to 15 freshwater fish species from 11 families in northern Australia, including body elongation, body shape, caudal peduncle throttle, eye size, eye position, gape shape, gape size, mouth position, and pectoral fin length. We quantified the extent and geography of intraspecific trait variability and its relationship with riverine hydrologic regimes using a structured sampling design. Using a combination of single‐ and multi‐trait analyses, we demonstrate that intraspecific trait variability can contribute up to 70% of the total trait variability depending on the attribute considered and averaged 31% across all traits. The magnitude of intraspecific trait variability also varied across the hydrological permanency gradient. Fish assemblages in intermittent streams subjected to frequent environmental disturbance had high intraspecific trait variability, most likely due to strong abiotic filters limiting interspecific divergence. Conversely, assemblages in perennial rivers with less harsh environmental filters but with a larger pool of species expressed lower intraspecific trait variability: This is most likely due to stronger resource competition (biotic filter), which promotes specialization of resource use and, consequently, interspecific divergence. Our study provides the first evidence of intraspecific trait variability driven by a disturbance gradient for an animal group and points to the need for additional research into the functional importance of intraspecific variability in animal ecology. A better understanding of the patterns, drivers, and implications of intraspecific trait variability will help guide mechanistic‐based predictions of the effects of environmental changes on community assemblage and ecosystem processes.

Freshwater ecosystems are facing a deepening biodiversity crisis. Developing robust indicators to assess ecological integrity across large spatial scales and identifying the specific threats and pathways of impairment are thus critically needed if we are to inform freshwater conservation strategies. Here we present the first comprehensive threat assessment across the Colorado River Basin – one of the largest and most endangered river basins in North America – using a spatial framework accounting for the wide range of human activities (land uses, transportation infrastructure, exploitative activities, water withdrawals), pathways (local footprint, overland runoff, upstream cumulative effects), and spatial extent of influence (valley bottom, catchment and river network) known to affect the ecological integrity of riverine ecosystems. We quantified and mapped 69 individual threat indices with geospatial tools for each permanent, ephemeral, and intermittent stream segment within the Basin, encompassing a total of >1,067,700 river kilometers. We further aggregated these indices into components of water quality (diffuse and point-source pollution), hydrology (flow regulation/uses and climate change), and physical system (connectivity and geomorphology). To demonstrate the potential of our framework to inform spatial planning decision processes, we examined the typical combinations of threats experienced by different hydrologic areas and stream segment types, identified candidate watersheds for habitat restoration and enhancement where hotspots of biodiversity and threat overlapped, and assessed the associations between threat indices and in situ measurements of ecological integrity describing a suite of biological (benthic macroinvertebrate, fish), chemical (total nitrogen load, water conductivity), hydrological (flow alteration) and physical indicators (streambed stability, instream habitat complexity). Our assessment highlights clear disparities in term of overall degree of threat that result from different combinations and contributions of individual stressors, with different priorities emerging for perennial versus intermittent or ephemeral stream segments, and between the upper and lower parts of the Basin. Importantly, we showed that our threat indices were generally correlated with biological, chemical, hydrological and physical indicators of ecological integrity they were intended to capture. In addition to its implications for the conservation and management of the highly imperiled Colorado River Basin, our case study illustrates how multi-faceted threat mapping can be used to assess the ecological integrity of riverine ecosystems in the absence of spatially extensive in situ measurements.

Prevention of aquatic invasive species is a fundamental management challenge. With hundreds of millions of people participating in fishing trips each year, understanding angler movements that transmit invasive species can provide critical insight into the most effective locations and scales at which to apply preventative measures. Recent evidence suggests that mobile technologies provide new opportunities to understand different types of angler movement behaviour beyond what is possible with infrequently and sparsely conducted in-person boat surveys and mail questionnaires. Here we capitalise on data provided by ReelSonar’s iBobber, a sonar-enabled bobber with over 5 M recorded fishing locations, globally. By quantifying geographic patterns of fishing activities and assessing how these patterns change seasonally, we explore angler behaviour across the entire continental United States in terms of fishing frequency and distance travelled between sites and characterise the attributes of fished ecosystems. We found that iBobber users (anglers) undertook 66,918 trips to 20,049 different water-bodies over a two-year period. Anglers who use iBobber were more likely to visit larger, deeper and more urbanised water-bodies and these water-bodies were over five times more likely to be a reservoir compared to a lake. Inter-water-body travel road distances averaged 93 km (SD = 277 km; range < 1–300 km) and nearly half of these movements occurred over a timespan of two days or less, a timeframe that we show falls well within the desiccation tolerance window of many prevalent plant and animal invasive species. Our study offers novel insight into spatiotemporal patterns of angler behaviour well beyond the geographical and temporal extent of conventional ground-collected approaches and carries important implications for predicting and preventing future transmission of aquatic invasive species via recreational fishing.

Abstract Background There is growing evidence of the potential negative consequences of altered flow regimes, in terms of magnitude, frequency, timing, duration or season pattern, on fluvial ecosystems and the fisheries they support. The scientific and policy communities have acknowledged the need for a better understanding of the effects of flow alteration on fish productivity. We conducted a systematic map to provide an overview of the existing literature base on the effects of flow-regime changes on direct outcomes of freshwater or estuarine fish productivity in temperate regions to inform stakeholders and policy makers. Methods To identify relevant articles for inclusion in this systematic map, we searched six bibliographic databases, 29 organizational websites, one search engine, and 297 reviews, and solicited grey literature through relevant sources. We screened articles at title and abstract, then by full-text using predefined inclusion criteria. Included studies were coded for key variables of interest, along with a very basic critical appraisal for internal validity (i.e., susceptibility to bias). The quantity and characteristics of the available evidence, knowledge gaps and subtopics with sufficient coverage for full systematic reviewing are reported in a narrative synthesis. The distribution and frequency of examined effects of flow-regime changes on fish productivity outcomes are presented in visual heatmaps. Review findings A total of 1368 studies from 1199 articles were included in the systematic map database and used to identify a number of interesting themes in the evidence base: (1) large evidence bases were found in temperate regions of United States of America (USA), Canada, and Australia; (2) most studies either used a temporal or spatial trend design i.e., lacking a ‘true’ before intervention time period, or no intervention control sites; (3) the most studied causes of altered flow regime were natural (e.g., floods, droughts, climate change), hydroelectric facilities (hydro), and dams with no hydro; and (4) there were clear clusters of studies evaluating effects of changes in magnitude and surrogate measures (e.g., velocity, water depth) on fish productivity outcomes, in particular abundance and diversity metrics. A number of potential knowledge gaps were identified: including geographic (Northern Africa, and possibly parts of Asia), causes of altered flow regime (restoration, land-use change, and water abstraction/extraction/diversion), interventions (flow duration, frequency, rate of change, or timing), outcomes (population viability) and specific intervention/cause/outcome groups (e.g., changes in flow magnitude due to hydro or natural causes and fish survival, performance, and reproduction). A few aspects in methodology were also identified across studies, primarily a lack of true comparators (e.g., temporal or spatial trend designs). Conclusions This map suggests subtopics warranting future evidence synthesis include, examinations into how changes in flow magnitude affects: (1) fish abundance for dams with no hydro causes; (2) fish abundance, diversity/richness, migration, and growth for hydro causes; and (3) fish abundance, diversity/richness, growth, community structure, recruitment, and migrating fish abundance for natural causes. More comprehensive evidence is needed to understand how: (1) fish productivity metrics are affected by changes in flow regime due to restoration, land-use change, and water withdrawal/diversion activities; (2) how fish productivity is affected by changes to components of flow regime other than magnitude (e.g., flow duration, frequency); and (3) changes in flow magnitude due to hydro or natural causes affect fish survival, performance, and reproduction; and (4) changes in flow regime (all causes, all interventions) affect population viability.

Abstract Management strategies to address the challenges associated with invasive species are critical for effective conservation. An increasing variety of mathematical models offer insight into invasive populations, and can help managers identify cost effective prevention, control, and eradication actions. Despite this, as model complexity grows, so does the inaccessibility of these tools to conservation practitioners making decisions about management. Here, we seek to narrow the science‐practice gap by reviewing invasive species management models (ISMMs). We define ISMMs as mechanistic models used to explore invasive species management strategies, and include reaction‐advection–diffusion models, integrodifference equations, gravity models, particle transport models, nonspatial and spatial discrete‐time population growth models, cellular automata, and individual‐based models. For each approach, we describe the model framework and its implementation, discuss strengths and weaknesses, and give examples of conservation applications. We conclude by discussing how ISMMs can be used in concert with adaptive management to address scientific uncertainties impeding action and with multiple objective decision processes to evaluate tradeoffs among management objectives. We undertook this review to support more effective decision‐making involving invasive species by providing conservation practitioners with the information they need to identify tools most useful for their applications.

Abstract Mining activities have significantly affected the Neotropical freshwater ichthyofauna, the most diverse in the world. However, no study has systematized knowledge on the subject. In this review, we assembled information on the main impacts of mining of crude oil, gold, iron, copper, and bauxite on aquatic ecosystems, emphasizing Neotropical freshwater fishes. The information obtained shows that mining activities generate several different disturbances, mainly via input of crude oil, metals and other pollutants, erosion and siltation, deforestation, and road construction. Mining has resulted in direct and indirect losses of fish diversity in several Neotropical waterbodies. The negative impacts on the ichthyofauna may change the structure of communities, compromise entire food chains, and erode ecosystem services provided by freshwater fishes. Particularly noteworthy is that mining activities (legal and illegal) are widespread in the Neotropics, and often located within or near protected areas. Actions to prevent and mitigate impacts, such as inspection, monitoring, management, and restoration plans, have been cursory or absent. In addition, there is strong political pressure to expand mining; if – or when – this happens, it will increase the potential of the activity to further diminish the diversity of Neotropical freshwater fishes.

Abstract Resource managers face mounting challenges when it comes to the implementation of climate change adaptation strategies. Novel adaptation strategies, such as managed relocation, frequently entail embracing substantial risk of unintended harm to the focal ecosystems, in an effort to alleviate serious threats to biological diversity (e.g. extinction). Assessing ecological risks associated with different adaptation strategies is consistently called for, but the process for doing so is often undefined. Here, we describe a collaboration amongst university researchers, agency scientists and resource managers to create a set of ecological risk assessment protocols for managed relocation decision support. These protocols are designed to foster a rigorous assessment of ecological risk, while simultaneously being flexible and easy to use. We describe a collaborative process through which we developed a structure for assessing risk that includes a suite of 17 risk categories aggregated into six overarching groups, which is placed within a broader decision context for managed relocation (e.g. evaluating feasibility, social acceptability). Our risk scoring includes both scaled estimates of risk and perceived confidence in those estimates. Because of differences in the importance of risk categories, we do not recommend a quantitative summary across risk areas, but suggest decision makers make decisions based on three criteria: overall confidence that a proposed action can be confidently evaluated; low overall level or risk across categories; and no single risk category that is highly likely to result in severe adverse outcomes.

Dams and diversions are a primary threat to freshwater fish biodiversity, including the loss of species and restructuring of communities, often resulting in taxonomic homogenization (increased similarity) over time. Mitigating these impacts requires a strong scientific understanding of both patterns and drivers of fish diversity. Here, we test whether different components of fish biodiversity have changed in response to major dam construction, and whether these patterns are predictable as a function of key environmental factors in the Gan River Basin, China. The results showed that total and native species alpha diversity have declined from the historical period (pre-dam) to the current period (post-dam). A total of 29 native species are lost, while 6 alien species were gained over time. We found evidence for fish faunal homogenization in the Gan River Basin, with a slight (1%) increase in taxonomic similarity among river basins from the historical period to the current period. Additionally, we revealed significant associations between drainage length, drainage area, and average air temperature, and alpha and beta fish diversity. This study provides new insight into the patterns and drivers of fish biodiversity change in the broader Yangtze River Basin and helps inform management efforts seeking to slow, and even reverse, current trajectories of biodiversity change.

Abstract 1. Around the globe, instream infrastructures such as dams, weirs, and culverts associated with roads are wide‐spread and continue to be constructed. There is limited documentation of smaller infrastructure because of mixed regulation and laws related to instream construction, as well as difficulty in documentation because of their size and frequency in waterscapes. 2. We reviewed evidence of different methods used to quantify environmental and ecological responses (positive, negative, or neutral) to dams, weirs, and culverts. 3. Most studies (78% of 87) in our review evaluated dams or weirs, and more than half evaluated environmental or ecological responses at more than one of these structures. More than half of the studies used spatial (disturbed–undisturbed in the same or a different catchment) rather than temporal (before–after construction or before–after destruction) comparative methods. Evaluations also tended to focus on ecological variables, most specifically on fish community responses (just over a quarter) to infrastructure. 4. More than half (58%) of the evaluations at dams, weirs, or culverts reported negative environmental or ecological responses. Discrepancies in responses recorded for different infrastructure types could be partially explained by the focus on ecological responses in reviewed studies and related metrics used for evaluations (e.g. biotic groups, richness, and abundance), the imbalance of studies at different infrastructure types, and discrepancies in spatial and temporal scales of evaluations compared to those at which the variables respond to infrastructure. 5. Despite the abundance of road culverts greatly exceeding the number of small or large dams worldwide, they were evaluated in only 22% of studies that we reviewed. Our findings underscore the need for studies to not only better understand local but also cumulative impacts of these smaller infrastructure, as these could be greater than those caused by large infrastructure depending on their location, density, and type, among other factors. Such studies are needed to inform infrastructure planning and watershed management.

In an era of global change, the process of biotic homogenisation by which regional biotas become more similar through time has attracted considerable attention from ecologists. Here, a retrospective look at the literature is taken and the question asked how comprehensive is the understanding of this global phenomenon? The goal is to identify potential areas for additional and future enquiries to advance this research frontier and best ensure the long-term preservation of biological diversity across the world. Six propositions are presented here to; (1) broaden our geographic and taxonomic understanding, (2) diversify the spatial and temporal scales of inquiry, (3) reconcile past and embrace new approaches to quantification, (4) improve our knowledge of the underlying drivers, (5) reveal the conservation implications and (6) forecast future homogenisation. It is argued that significant progress in the understanding of the causes, consequences and conservation implication of biotic homogenisation will come by integrating concepts and approaches from ecology, evolution and conservation across a hierarchy of spatial and temporal scales.

Human and environmental water needs can come into conflict in dam-regulated river systems. Here, Chen and Olden investigate the potential for the use of fish–flow modeling to make recommendations for the management of native and nonnative fish species whilst providing water for society.

Abstract We led a curriculum vitae (CV) clinic aimed at student participants attending the 28th International Congress for Conservation Biology (ICCB 2017) in Cartagena, Colombia. The CV Clinic was a pilot program consisting of resources to assist with developing an effective CV and involving preconference and at‐conference reviews of student attendees' CVs. Here, we explore our experiences in organizing the CV Clinic as well as nonparticipant and participant perceptions of the clinic. We used an online standardized interview form to gather qualitative data on nonparticipant and participant perceptions of the CV Clinic, and to explore how such a CV Clinic program could best align with student needs. Most respondents who submitted their CV for review ahead of ICCB 2017 (n = 9) found the template and guidance useful. Half of the respondents who did not participate in the CV Clinic perceived the clinic as duplicating services provided by their academic institutions. Both participant and nonparticipant respondents perceived value in such a CV Clinic, but also believed that adjustments could be made to make the CV review part of a broader professional development program lead by Society for Conservation Biology (SCB). Key lessons learned from the CV Clinic include the need to: (a) document and evaluate professional development initiatives within SCB; (b) better understand and account for the diversity of student needs before program creation; and (c) pilot and evaluate appropriateness of different locations, frequency, and duration of professional development programs.

Globalization facilitates the spread of invasive alien species, while environmental change can ease invasion. Here, Early et al. identify vulnerable regions globally and evaluate capacity in vulnerable countries to prevent invasions arising from sources such as air travel, horticulture, and pet trade.

Shifts in wildflower phenology in response to climate change are well documented in the scientific literature. The majority of studies have revealed phenological shifts using in-situ observations, some aided by citizen science efforts (e.g., National Phenology Network). Such investigations have been instrumental in quantifying phenological shifts but are challenged by the fact that limited resources often make it difficult to gather observations over large spatial scales and long-time frames. However, recent advances in finer scale satellite imagery may provide new opportunities to detect changes in phenology. These approaches have documented plot level changes in vegetation characteristics and leafing phenology, but it remains unclear whether they can also detect flowering in natural environments. Here, we test whether fine-resolution imagery (

Human activities create threats that have consequences for freshwater ecosystems and, in most watersheds, observed ecological responses are the result of complex interactions among multiple threats and their associated ecological alterations. Here we discuss the value of considering multiple threats in research and management, offer suggestions for filling knowledge gaps, and provide guidance for addressing the urgent management challenges posed by multiple threats in freshwater ecosystems. There is a growing literature assessing responses to multiple alterations, and we build off this background to identify three areas that require greater attention: linking observed alterations to threats, understanding when and where threats overlap, and choosing metrics that best quantify the effects of multiple threats. Advancing science in these areas will help us understand existing ecosystem conditions and predict future risk from multiple threats. Because addressing the complex issues and novel ecosystems that arise from the interaction of multiple threats in freshwater ecosystems represents a significant management challenge, and the risks of management failure include loss of biodiversity, ecological goods, and ecosystem services, we also identify actions that could improve decision-making and management outcomes. These actions include drawing insights from management of individual threats, using threat attributes (e.g., causes and spatio-temporal dynamics) to identify suitable management approaches, testing management strategies that are likely to be successful despite uncertainties about the nature of interactions among threats, avoiding unintended consequences, and maximizing conservation benefits. We also acknowledge the broadly applicable challenges of decision-making within a socio-political and economic framework, and suggest that multidisciplinary teams will be needed to innovate solutions to meet the current and future challenge of interacting threats in freshwater ecosystems.

Abstract A contemporary challenge in ecology is assessing the ecosystem effects of multispecies introductions. Quantifying shifts in body sizes, a common trait with which many per capita rates of ecosystems functioning scales, provide an important way forward. Evidence suggests that freshwater fish introductions have altered species‐level body size distributions globally, but it is difficult to interpret their functional consequences because animals contribute to ecosystem functioning at the individual level at smaller spatial scales. In this study, we determine whether these macroecological patterns hold for individual size distributions (ISDs) at local scales. We use a comprehensive dataset of fish communities in a highly invaded dryland river to (1) compare the statistical moments of ISDs between native and non‐native pools and (2) relate biological and environmental covariates to the univariate moments of local ISDs and the multivariate community structure of local fish assemblages. We found that ISDs of native and non‐native pools were significantly different when data were pooled across sites. Non‐natives had smaller mean body size than natives across all guilds and within invertivore and omnivore guilds, but were significantly larger within the invertivore–piscivore guild. Moreover, differences in the variance of size distributions were often relatively greater than differences in the mean. By modeling ISDs at the site level as a function of biological and environmental covariates, we found that non‐native dominance within sites had similar effects on ISDs as expected from differences between species pools. However, neither biological nor environmental predictors explained significant community‐level variation when size and trophic structure were considered simultaneously. Shifts in size distributions can have multiple ecological consequences, and our results provide a baseline for generating size‐based predictions of non‐native species’ roles in ecosystem functioning. However, these size‐based predictions should be considered alongside other important trait distributions such as trophic structure, which had no consistent relationship with non‐native dominance in this study.

Abstract Despite significant progress in recent years, understanding the rules governing the assembly of natural communities is still challenging and knowledge of how the integration of nonnative species may disrupt community structure and function is needed. To address this challenge, we collated stable isotope data for 159 freshwater fish communities around the world with and without nonnative species and quantified spatial variation in both community isotopic functional diversity and intraspecific variation in species niches. Using a null model and partial least squares path analysis, we then evaluated how the interplay between abiotic (historical, energetic, climatic, habitat size) and biotic (niche segregation) factors shape community structure and functional diversity, and how these relationships have changed, and with what consequences, in the presence of nonnative species. We found that niche partitioning is a primary force underlying the structure and functional redundancy of native fish communities, which may be governed by a synergism between contemporary climate, productivity and habitat size. We also found evidence of a legacy of historical climate on functional diversity, independent from species richness. By contrast, path models of communities containing nonnative species demonstrated lower explanatory power and had no clear association with any of the abiotic or biotic factors. In conclusion, we demonstrated that strong spatial patterns in community structure and functional diversity of freshwater fish communities exist at the global scale, underlined by the complex interplay between external and internal filters, but that these patterns may be blurred by anthropogenic species introductions. Our results further highlighted the importance of accounting for realized species niches and species status (i.e., native and nonnative) when investigating questions related to the assembly and functional diversity of multitrophic communities.

Abstract Non‐native species are widely regarded as threats to ecosystem structure and function; however, these species may also provide benefits to ecosystems that have lost former functions to environmental degradation. This study evaluated whether non‐native species provide prey resources or induce trophic cul‐de‐sacs (by diverting basal energy away from higher trophic levels) in developed ecosystems where native prey are in decline. We used stable isotopes of 13C, 15N, and 2H to assess whether non‐native Chinese Mystery snail (Bellamya chinensis) provides a prey resource to consumers, and maintains the integration of benthic resources into food webs of lakes subjected to lakeshore development. Regardless of Bellamya presence, consumers in undeveloped lakes were supported primarily by benthic resources, and lakeshore development dramatically reduced consumer reliance on these resources. This was at least partly due to a reduction in the availability of native snails, a high‐quality prey item, to the dominant littoral consumer, molluscivorous pumpkinseed sunfish (Lepomis gibbosus). In developed lakes with non‐native Bellamya, generalist yellow perch (Perca flavescens) and piscivorous largemouth bass (Micropterus salmoides) consumed benthic resources in proportions similar to undeveloped lakes, and pumpkinseed sunfish consumed Bellamya in higher proportions than in undeveloped lakes. Thus, Bellamya provided a prey substitute in developed lakes where native snail populations were depressed; and Bellamya's influence extended to higher trophic‐level consumers. Our study provides evidence that non‐native species can ameliorate some effects of environmental degradation, and we suggest that future research considers how the effects of non‐native species, either positive or negative, may vary across human‐modified landscapes.

Molecular genetic approaches are playing an increasing role in conservation science by identifying biodiversity that may not be evident by morphology-based taxonomy and systematics. So-called cryptic species are particularly prevalent in freshwater environments, where isolation of dispersal-limited species, such as crayfishes, within dendritic river networks often gives rise to high intra- and inter-specific genetic divergence. We apply here a multi-gene molecular approach to investigate relationships among extant species of the crayfish genus Pacifastacus, representing the first comprehensive phylogenetic study of this taxonomic group. Importantly, Pacifastacus includes both the widely invasive signal crayfish Pacifastacus leniusculus, as well as several species of conservation concern like the Shasta crayfish Pacifastacus fortis. Our analysis used 83 individuals sampled across the four extant Pacifastacus species (omitting the extinct Pacifastacus nigrescens), representing the known taxonomic diversity and geographic distributions within this genus as comprehensively as possible. We reconstructed phylogenetic trees from mitochondrial (16S, COI) and nuclear genes (GAPDH), both separately and using a combined or concatenated dataset, and performed several species delimitation analyses (PTP, ABGD, GMYC) on the COI phylogeny to propose Primary Species Hypotheses (PSHs) within the genus. All phylogenies recovered the genus Pacifastacus as monophyletic, within which we identified a range of six to 21 PSHs; more abundant PSHs delimitations from GMYC and ABGD were always nested within PSHs delimited by the more conservative PTP method. Pacifastacus leniusculus included the majority of PSHs and was not monophyletic relative to the other Pacifastacus species considered. Several of these highly distinct P. leniusculus PSHs likely require urgent conservation attention. Our results identify research needs and conservation priorities for Pacifastacus crayfishes in western North America, and may inform better understanding and management of P. leniusculus in regions where it is invasive, such as Europe and Japan.

Whether a species niche is conserved or shifts across space and time is a question of heightened interest in ecology and evolution. Considerable scientific inquiry into this topic has used invasive species to evaluate conservatism of the Grinnellian climatic niche while generally neglecting the Eltonian functional niche. By contrast, we report here on the first simultaneous reciprocal comparison of both the Grinnellian and Eltonian niches for the globally invasive signal crayfish Pacifastacus leniusculus between its native (Pacific Northwest of North America) and non‐native ranges (Japan). Using multivariate statistics and the Maxent machine‐learning algorithm, we found strong evidence for a climatic niche shift between geographic regions for P. leniusculus. Pacifastacus leniusculus shifted from warmer temperatures with strong precipitation seasonality in western North America to cooler temperatures with less precipitation seasonality in Japan. However, analysis of stable isotopes of carbon and nitrogen revealed conservatism of the functional niche of P. leniusculus between multiple lakes in the native and non‐native ranges. We found that trophic position and niche width of P. leniusculus were equivalent between regions, and that niche attributes including reliance on autochthonous or allochthonous energy sources and ontogenetic shifts were comparable regardless of origin. Our finding of functional niche conservatism contrasts with the results of some recent studies evaluating the Grinnellian niche for invasive species, as well as our own climatic niche comparison, and raises the question of whether Grinnellian or Eltonian niches are more prone to shifts or conservatism. We hypothesize that the Grinnellian niche may be more labile than the Eltonian niche in general, but argue that resolving this question will require more reciprocal comparisons of Eltonian niches to keep pace with the recent increase in Grinnellian niche studies.