Opinion: Is CRISPR-based gene drive a biocontrol silver bullet or global conservation threat?

General science-technology orientation, specific benefit-risk assessment frame, and public acceptance of gene drive biotechnology

With limited understanding of most new biotechnologies, how do citizens form their opinion and what factors influence their attitudes about these innovations? In this study, we use gene drive biotechnology in agricultural pest management as an example and theoretically propose that given low levels of knowledge and awareness, citizens' acceptance of, or opposition to, gene drive is significantly shaped by two predisposition factors: individuals' general orientation toward science and technology, and their specific benefit-risk assessment frame. Empirically, we employ data collected from a recent US nationally representative public opinion survey (N = 1220) and conduct statistical analyses to test the hypotheses derived from our theoretical expectations. Our statistical analyses, based on various model specifications and controlling for individual-level covariates and state-fixed effects, show that citizens with a more favorable general orientation toward science and technology are more likely to accept gene drive. Our data analyses also demonstrate that citizens' specific gene drive assessment frame-consisting of a potential benefit dimension and a potential risk dimension, significantly shapes their attitudes as well-specifically, people emphasizing more on the benefit dimension are more likely to accept gene drive, whereas those who place more importance on the risk dimension tend to oppose it. We discuss contributions of our study and make suggestions for future research in the conclusion.

Genetics of flight in spongy moths (Lymantria dispar ssp.): functionally integrated profiling of a complex invasive trait

BACKGROUND

Flight can drastically enhance dispersal capacity and is a key trait defining the potential of exotic insect species to spread and invade new habitats. The phytophagous European spongy moths (ESM, Lymantria dispar dispar) and Asian spongy moths (ASM; a multi-species group represented here by L. d. asiatica and L. d. japonica), are globally invasive species that vary in adult female flight capability-female ASM are typically flight capable, whereas female ESM are typically flightless. Genetic markers of flight capability would supply a powerful tool for flight profiling of these species at any intercepted life stage. To assess the functional complexity of spongy moth flight and to identify potential markers of flight capability, we used multiple genetic approaches aimed at capturing complementary signals of putative flight-relevant genetic divergence between ESM and ASM: reduced representation genome-wide association studies, whole genome sequence comparisons, and developmental transcriptomics. We then judged the candidacy of flight-associated genes through functional analyses aimed at addressing the proximate demands of flight and salient features of the ecological context of spongy moth flight evolution.

RESULTS

Candidate gene sets were typically non-overlapping across different genetic approaches, with only nine gene annotations shared between any pair of approaches. We detected an array of flight-relevant functional themes across gene sets that collectively suggest divergence in flight capability between European and Asian spongy moth lineages has coincided with evolutionary differentiation in multiple aspects of flight development, execution, and surrounding life history. Overall, our results indicate that spongy moth flight evolution has shaped or been influenced by a large and functionally broad network of traits.

CONCLUSIONS

Our study identified a suite of flight-associated genes in spongy moths suited to exploration of the genetic architecture and evolution of flight, or validation for flight profiling purposes. This work illustrates how complementary genetic approaches combined with phenotypically targeted functional analyses can help to characterize genetically complex traits.

Gene drives for invasive wasp control: Extinction is unlikely, with suppression dependent on dispersal and growth rates

Gene drives offer a potentially revolutionary method for pest control over large spatial extents. These genetic modifications spread deleterious variants through a population and have been proposed as methods for pest suppression or even eradication. We examined the influence of local dispersal, long-distance and/or human-mediated dispersal, and variation in population growth on the success of a gene drive for the control of invasive social wasps (Vespula vulgaris). Our simulations incorporated a spatially realistic environment containing variable habitat quality in New Zealand. Pest eradication was not observed, except in extreme and unrealistic scenarios of constant, widespread, and spatially intense releases of genetically modified individuals every year for decades. Instead, the regional persistence of genetically modified and wild-type wasps was predicted. Simulations using spatially homogeneous versus realistic landscapes (incorporating uninhabitable areas and dispersal barriers) showed little difference in overall population dynamics. Overall, little impact on wasp abundance was observed in the first 15 years after introduction. After 25 years, populations were suppressed to levels <95% of starting populations. Populations exhibited "chase dynamics" with population cycles in space, with local extinction occurring in some areas while wasps became abundant in others. Increasing the wasps' local dispersal distance increased the spatial and temporal variability of the occupied area and population suppression. Varying levels of human-associated long-distance dispersal had little effect on population dynamics. Increasing intrinsic population growth rates interacted with local dispersal to cause higher mean populations and substantially higher levels of variation in population suppression and the total amount of landscape occupied. Gene drives appear unlikely to cause a rapid and widespread extinction of this and probably other pests but could offer long-term and cost-effective methods of pest suppression. The predicted level of <95% pest suppression would substantially reduce the predation pressure and competitive interactions of this invasive wasp on native species. However, the predicted long-term persistence of genetically modified pests will influence the ethics and likelihood of using gene drives for pest control, especially given concerns that modified wasps would eventually be transported back to their home range.

Incorporating ecology into gene drive modelling

Gene drive technology, in which fast-spreading engineered drive alleles are introduced into wild populations, represents a promising new tool in the fight against vector-borne diseases, agricultural pests and invasive species. Due to the risks involved, gene drives have so far only been tested in laboratory settings while their population-level behaviour is mainly studied using mathematical and computational models. The spread of a gene drive is a rapid evolutionary process that occurs over timescales similar to many ecological processes. This can potentially generate strong eco-evolutionary feedback that could profoundly affect the dynamics and outcome of a gene drive release. We, therefore, argue for the importance of incorporating ecological features into gene drive models. We describe the key ecological features that could affect gene drive behaviour, such as population structure, life-history, environmental variation and mode of selection. We review previous gene drive modelling efforts and identify areas where further research is needed. As gene drive technology approaches the level of field experimentation, it is crucial to evaluate gene drive dynamics, potential outcomes, and risks realistically by including ecological processes.

How genomics can help biodiversity conservation

The availability of public genomic resources can greatly assist biodiversity assessment, conservation, and restoration efforts by providing evidence for scientifically informed management decisions. Here we survey the main approaches and applications in biodiversity and conservation genomics, considering practical factors, such as cost, time, prerequisite skills, and current shortcomings of applications. Most approaches perform best in combination with reference genomes from the target species or closely related species. We review case studies to illustrate how reference genomes can facilitate biodiversity research and conservation across the tree of life. We conclude that the time is ripe to view reference genomes as fundamental resources and to integrate their use as a best practice in conservation genomics.

Moving beyond narrow definitions of gene drive: Diverse perspectives and frames enable substantive dialogue among science and humanities teachers in the United States and United Kingdom

Gene drive is an emerging biotechnology with applications in global health, conservation and agriculture. Scientists are preparing for field trials, triggering debate about when and how to release gene-drive organisms. These decisions depend on public understandings of gene drive, which are shaped by language. While some studies on gene drive communication assume the need to persuade publics of expert definitions of gene drive, we highlight the importance of meaning-making in communication and engagement. We conducted focus groups with humanities and science teachers in the United Kingdom and United States to explore how different media framings stimulated discussions of gene drive. We found diversity in the value of these framings for public debate. Interestingly, the definition favoured by gene drive scientists was the least popular among participants. Rather than carefully curating language, we need opportunities for publics to make sense and negotiate the meanings of a technology on their own terms.

Bayesian network-based risk assessment of synthetic biology: Simulating CRISPR-Cas9 gene drive dynamics in invasive rodent management

Gene drive technology has been proposed to control invasive rodent populations as an alternative to rodenticides. However, this approach has not undergone risk assessment that meets criteria established by Gene Drives on the Horizon, a 2016 report by the National Academies of Sciences, Engineering, and Medicine. To conduct a risk assessment of gene drives, we employed the Bayesian network-relative risk model to calculate the risk of mouse eradication on Southeast Farallon Island using a CRISPR-Cas9 homing gene drive construct. We modified and implemented the R-based model "MGDrivE" to simulate and compare 60 management strategies for gene drive rodent management. These scenarios spanned four gene drive mouse release schemes, three gene drive homing rates, three levels of supplemental rodenticide dose, and two timings of rodenticide application relative to gene drive release. Simulation results showed that applying a supplemental rodenticide simultaneously with gene drive mouse deployment resulted in faster eradication of the island mouse population. Gene drive homing rate had the highest influence on the overall probability of successful eradication, as increased gene drive accuracy reduces the likelihood of mice developing resistance to the CRISPR-Cas9 homing mechanism.

Consensus and controversy in the discipline of invasion science

Approaches, values, and perceptions in invasion science are highly dynamic, and like in other disciplines, views among different people can diverge. This has led to debate in the field specifically surrounding the core themes of values, management, impacts, and terminology. Considering these debates, we surveyed 698 scientists and practitioners globally to assess levels of polarization (opposing views) on core and contentious topics. The survey was distributed online (via Google Forms) and promoted through listservs and social media. Although there were generally high levels of consensus among respondents, there was some polarization (scores of ≥0.39 [top quartile]). Relating to values, there was high polarization regarding claims of invasive species denialism, whether invasive species contribute to biodiversity, and how biodiversity reporting should be conducted. With regard to management, there were polarized views on banning the commercial use of beneficial invasive species, the extent to which stakeholders' perceptions should influence management, whether invasive species use alone is an appropriate control strategy, and whether eradication of invasive plants is possible. For impacts, there was high polarization concerning whether invasive species drive or are a side effect of degradation and whether invasive species benefits are understated. For terminology, polarized views related to defining invasive species based only on spread, whether species can be labeled as invasive in their native ranges, and whether language used is too xenophobic. Factor and regression analysis revealed that views were particularly divergent between people working on different invasive taxa (plants and mammals) and in different disciplines (between biologists and social scientists), between academics and practitioners, and between world regions (between Africa and the Global North). Unlike in other studies, age and gender had a limited influence on response patterns. Better integration globally and between disciplines, taxa, and sectors (e.g., academic vs. practitioners) could help build broader understanding and consensus.

Reflection on the Challenges, Accomplishments, and New Frontiers of Gene Drives

Ongoing pest and disease outbreaks pose a serious threat to human, crop, and animal lives, emphasizing the need for constant genetic discoveries that could serve as mitigation strategies. Gene drives are genetic engineering approaches discovered decades ago that may allow quick, super-Mendelian dissemination of genetic modifications in wild populations, offering hopes for medicine, agriculture, and ecology in combating diseases. Following its first discovery, several naturally occurring selfish genetic elements were identified and several gene drive mechanisms that could attain relatively high threshold population replacement have been proposed. This review provides a comprehensive overview of the recent advances in gene drive research with a particular emphasis on CRISPR-Cas gene drives, the technology that has revolutionized the process of genome engineering. Herein, we discuss the benefits and caveats of this technology and place it within the context of natural gene drives discovered to date and various synthetic drives engineered. Later, we elaborate on the strategies for designing synthetic drive systems to address resistance issues and prevent them from altering the entire wild populations. Lastly, we highlight the major applications of synthetic CRISPR-based gene drives in different living organisms, including plants, animals, and microorganisms.

Scalability of genetic biocontrols for eradicating invasive alien mammals

CRISPR-based gene drives offer novel solutions for controlling invasive alien species, which could ultimately extend eradication efforts to continental scales. Gene drives for suppressing invasive alien vertebrates are now under development. Using a landscape-scale individual-based model, we present the first estimates of times to eradication for long-lived alien mammals. We show that demography and life-history traits interact to determine the scalability of gene drives for vertebrate pest eradication. Notably, optimism around eradicating smaller-bodied pests (rodents and rabbits) with gene-drive technologies does not easily translate into eradication of larger-bodied alien species (cats and foxes).

Gene Drives in the U.K., U.S., and Australian Press (2015-2019): How a New Focus on Responsibility Is Shaping Science Communication

Gene drive is a controversial biotechnology for pest control. Despite a commitment from gene drive researchers to responsibility and the key role of the media in debates about science and technology, little research has been conducted on media reporting of gene drive. We employ metaphor and discourse analysis to explore how responsibility is reflected in the coverage of this technology in the U.S., U.K., and Australian press. The findings reveal a rhetorical strategy of trust-building by evoking the moral attributes of gene drive researchers. We discuss the implications of these findings for the communication of new technologies.

Evaluating unintended consequences of intentional species introductions and eradications for improved conservation management

Increasingly intensive strategies to maintain biodiversity and ecosystem function are being deployed in response to global anthropogenic threats, including intentionally introducing and eradicating species via assisted migration, rewilding, biological control, invasive species eradications, and gene drives. These actions are highly contentious because of their potential for unintended consequences. We conducted a global literature review of these conservation actions to quantify how often unintended outcomes occur and to elucidate their underlying causes. To evaluate conservation outcomes, we developed a community assessment framework for systematically mapping the range of possible interaction types for 111 case studies. Applying this tool, we quantified the number of interaction types considered in each study and documented the nature and strength of intended and unintended outcomes. Intended outcomes were reported in 51% of cases, a combination of intended outcomes and unintended outcomes in 26%, and strictly unintended outcomes in 10%. Hence, unintended outcomes were reported in 36% of all cases evaluated. In evaluating overall conservations outcomes (weighing intended vs. unintended effects), some unintended effects were fairly innocuous relative to the conservation objective, whereas others resulted in serious unintended consequences in recipient communities. Studies that assessed a greater number of community interactions with the target species reported unintended outcomes more often, suggesting that unintended consequences may be underreported due to insufficient vetting. Most reported unintended outcomes arose from direct effects (68%) or simple density-mediated or indirect effects (25%) linked to the target species. Only a few documented cases arose from more complex interaction pathways (7%). Therefore, most unintended outcomes involved simple interactions that could be predicted and mitigated through more formal vetting. Our community assessment framework provides a tool for screening future conservation actions by mapping the recipient community interaction web to identify and mitigate unintended outcomes from intentional species introductions and eradications for conservation.

Gene drives for vertebrate pest control: realistic spatial modelling of eradication probabilities and times for island mouse populations

Invasive alien species continue to threaten global biodiversity. CRISPR‐based gene drives, which can theoretically spread through populations despite imparting a fitness cost, could be used to suppress or eradicate pest populations. We develop an individual‐based, spatially explicit, stochastic model to simulate the ability of CRISPR‐based homing and X chromosome shredding drives to eradicate populations of invasive house mice (Mus muculus) from islands. Using the model, we explore the interactive effect of the efficiency of the drive constructs and the spatial ecology of the target population on the outcome of a gene‐drive release. We also consider the impact of polyandrous mating and sperm competition, which could compromise the efficacy of some gene‐drive strategies. Our results show that both drive strategies could be used to eradicate large populations of mice. Whereas parameters related to drive efficiency and demography strongly influence drive performance, we find that sperm competition following polyandrous mating is unlikely to impact the outcome of an eradication effort substantially. Assumptions regarding the spatial ecology of mice influenced the probability of and time required for eradication, with short‐range dispersal capacities and limited mate‐search areas producing ‘chase’ dynamics across the island characterized by cycles of local extinction and recolonization by mice. We also show that highly efficient drives are not always optimal, when dispersal and mate‐search capabilities are low. Rapid local population suppression around the introduction sites can cause loss of the gene drive before it can spread to the entire island. We conclude that, although the design of efficient gene drives is undoubtedly critical, accurate data on the spatial ecology of target species are critical for predicting the result of a gene‐drive release.

Gene drive and RNAi technologies: a bio-cultural review of next-generation tools for pest wasp management in New Zealand

There is a global need for novel, next-generation technologies and techniques to manage pest species. We review work on potential step-changing technologies for large landscape (>1000 hectares) pest management of social Vespula wasps. We also review Māori perspectives on these controls to gauge social and cultural acceptability to research, test and use of novel controls. Approaches discussed are the use of gene silencing (RNAi) and gene drives (CRISPR-Cas 9) involving genetic modification, which has potential for pest control but vary in feasibility, cost, benefits and off-target risks. RNAi may be better suited for wasp control in high-value cropping systems due to scaling inefficiencies. Gene drives offer potential for large-scale control but would require legislative and wide social deliberation due to their status as genetic modification. Both RNAi and gene drives will require consultation with tangata whenua. Māori interest groups agreed that exotic wasps must be controlled and expressed aversion to non-targeted traditional control methods. We present a diversity of opinions in parallel with scientific research underscoring the need for continued dialogue with Māori. Novel biotechnological controls must satisfy a broad range of social and cultural criteria, receive regulatory approval, along with being demonstrated as safe, selective, and cost-effective.

Rodent management and cereal production in Asia: Balancing food security and conservation

Rodents present a major problem for food security in Asia where smallholder farming families are particularly vulnerable. We review here recent developments in the biology and management of rodent pests in cereal cropping systems in Asia. The past decade has seen a strong focus on ecologically-based rodent management (EBRM), its adoption in field studies significantly increased rice yields (6-15%) and income (>15%) in seven Asian countries. EBRM principles have also been successfully applied to maize in China. We provide case studies on EBRM in Cambodia, on interactions between rodent pests and weeds, and on the importance of modified wetlands for biodiversity and rodent pest management. Knowledge on post-harvest impacts of rodents is increasing. One research gap is the assessment of human health impacts from a reduction of rodent densities in and around houses. We identify 10 challenges for the next decade. For example, the need for population modelling, a valuable tool missing from our toolbox to manage rodent pests in cereal systems. We also need to understand better the interactive effects of cropping intensification, conservation agriculture and climate change. Finally, new management approaches such as fertility control are on the horizon and need to be considered in the context of smallholder cereal farming systems and mitigating health risks from zoonotic diseases associated with rodents. © 2021 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

The status of fertility control for rodents-recent achievements and future directions

Management of overabundant rodents at a landscape scale is complex but often required to sustainably reduce rodent abundance below damage thresholds. Current conventional techniques such as poisoning are not species specific, with some approaches becoming increasingly unacceptable to the general public. Fertility control, first proposed for vertebrate pest management over 5 decades ago, has gained public acceptance because it is perceived as a potentially more species-specific and humane approach compared with many lethal methods. An ideal fertility control agent needs to induce infertility across one or more breeding seasons, be easily delivered to an appropriate proportion of the population, be species specific with minimal side-effects (behavioral or social structure changes), and be environmentally benign and cost effective. To date, effective fertility control of rodents has not been demonstrated at landscape scales and very few products have achieved registration. Reproductive targets for fertility control include disrupting the hormonal feedback associated with the hypothalamic-pituitary-gonadal axis, gonad function, fertilization, and/or early implantation. We review progress on the oral delivery of various agents for which laboratory studies have demonstrated efficacy in females and/or males and synthesize progress with the development and/or use of synthetic steroids, plant extracts, ovarian specific peptides, and immunocontraceptive vaccines. There are promising results for field application of synthetic steroids (levonorgestrel, quinestrol), chemosterilants (4-vinylcyclohexene diepoxide), and some plant extracts (triptolide). For most fertility control agents, more research is essential to enable their efficient and cost-effective delivery such that rodent impacts at a population level are mitigated and food security is improved.

The Promise of Genetics and Genomics for Improving Invasive Mammal Management on Islands

Invasive species are major contributors to global biodiversity decline. Invasive mammalian species (IMS), in particular, have profound negative effects in island systems that contain disproportionally high levels of species richness and endemism. The eradication and control of IMS have become important conservation tools for managing species invasions on islands, yet these management operations are often subject to failure due to knowledge gaps surrounding species- and system-specific characteristics, including invasion pathways and contemporary migration patterns. Here, we synthesize the literature on ways in which genetic and genomic tools have effectively informed IMS management on islands, specifically associated with the development and modification of biosecurity protocols, and the design and implementation of eradication and control programs. In spite of their demonstrated utility, we then explore the challenges that are preventing genetics and genomics from being implemented more frequently in IMS management operations from both academic and non-academic perspectives, and suggest possible solutions for breaking down these barriers. Finally, we discuss the potential application of genome editing to the future management of invasive species on islands, including the current state of the field and why islands may be effective targets for this emerging technology.

Autocatalytic-protection for an unknown locus CRISPR-Cas countermeasure for undesired mutagenic chain reactions

The mutagenic chain reaction (MCR) is a genetic tool to use a CRISPR-Cas construct to introduce a homing endonuclease, allowing gene drive to influence whole populations in a minimal number of generations (Esvelt et al., 2014; Gantz and Bier, 2015; Gantz and Bier, 2016). The question arises: if an active genetic terror event is released into a population, could we prevent the total spread of the undesired allele (Gantz, et al., 2015; Webber et al., 2015)? Thus far, effective protection methods require knowledge of the terror locus (Grunwald et al., 2019). Here we introduce a novel approach, an autocatalytic-Protection for an Unknown Locus (a-PUL), whose aim is to spread through a population and arrest and decrease an active terror event's spread without any prior knowledge of the terror-modified locus, thus allowing later natural selection and ERACR drives to restore the normal locus (Hammond et al., 2017). a-PUL, using a mutagenic chain reaction, includes (i) a segment encoding a non-Cas9 endonuclease capable of homology-directed repair suggested as Type II endonuclease Cpf1 (Cas12a), (ii) a ubiquitously-expressed gene encoding a gRNA (gRNA1) with a U4AU4 3'-overhang specific to Cpf1 and with crRNA specific to some desired genomic sequence of non-coding DNA, (iii) a ubiquitously-expressed gene encoding two gRNAs (gRNA2/gRNA3) both with tracrRNA specific to Cas9 and crRNA specific to two distinct sites of the Cas9 locus, and (iv) homology arms flanking the Cpf1/gRNA1/gRNA2/gRNA3 cassette that are identical to the region surrounding the target cut directed by gRNA1 (Khan, 2016; Zetsche et al., 2015). We demonstrate the proof-of-concept and efficacy of our protection construct through a Graphical Markov model and computer simulation.

Small nucleic acids and the path to the clinic for anti-CRISPR

CRISPR-based therapeutics have entered clinical trials but no methods to inhibit Cas enzymes have been demonstrated in a clinical setting. The ability to inhibit CRISPR-based gene editing or gene targeting drugs should be considered a critical step in establishing safety standards for many CRISPR-Cas therapeutics. Inhibitors can act as a failsafe or as an adjuvant to reduce off-target effects in patients. In this review we discuss the need for clinical inhibition of CRISPR-Cas systems and three existing inhibitor technologies: anti-CRISPR (Acr) proteins, small molecule Cas inhibitors, and small nucleic acid-based CRISPR inhibitors, CRISPR SNuBs. Due to their unique properties and the recent successes of other nucleic acid-based therapeutics, CRISPR SNuBs appear poised for clinical application in the near-term.

Climate Mismatch between Introduced Biological Control Agents and Their Invasive Host Plants: Improving Biological Control of Tropical Weeds in Temperate Regions

Simple Summary

Mismatched distributions between biological control agents and their host plants occur for a variety of reasons but are often linked to climate, specifically differences in their low-temperature tolerances. How to measure and use low-temperature tolerances of control agents to inform agent prioritization, selection for redistribution, or predict efficacy is vitally important, but has not been previously synthesized in a single source. We discuss causes of climate mismatches between agents and target weeds, the traditional and non-traditional approaches that could be used to decrease the degree of mismatch and improve control, and regulatory issues to consider when taking such approaches. We also discuss the variety of cold tolerance metrics, their measurement and ecological value, and the types of modeling that can be carried out to improve predictions about potential distributions of agents. We also briefly touch on molecular bases for cold tolerance and opportunities for improving cold tolerance of agents using modern molecular tools.

Abstract

Many weed biological control programs suffer from large-scale spatial variation in success due to restricted distributions or abundances of agents in temperate climates. For some of the world’s worst aquatic weeds, agents are established but overwintering conditions limit their survival in higher latitudes or elevations. The resulting need is for new or improved site- or region-specific biological control tools. Here, we review this challenge with a focus on low-temperature limitations of agents and propose a roadmap for improving success. Investigations across spatial scales, from global (e.g., foreign exploration), to local (selective breeding), to individual organisms (molecular modification), are discussed. A combination of traditional (foreign) and non-traditional (introduced range) exploration may lead to the discovery and development of better-adapted agent genotypes. A multivariate approach using ecologically relevant metrics to quantify and compare cold tolerance among agent populations is likely required. These data can be used to inform environmental niche modeling combined with mechanistic modeling of species’ fundamental climate niches and life histories to predict where, when, and at what abundance agents will occur. Finally, synthetic and systems biology approaches in conjunction with advanced modern genomics, gene silencing and gene editing technologies may be used to identify and alter the expression of genes enhancing cold tolerance, but this technology in the context of weed biological control has not been fully explored.

Synthetic threads through the web of life

CRISPR-Cas gene editing tools have brought us to an era of synthetic biology that will change the world. Excitement over the breakthroughs these tools have enabled in biology and medicine is balanced, justifiably, by concern over how their applications might go wrong in open environments. We do not know how genomic processes (including regulatory and epigenetic processes), evolutionary change, ecosystem interactions, and other higher order processes will affect traits, fitness, and impacts of edited organisms in nature. However, anticipating the spread, change, and impacts of edited traits or organisms in heterogeneous, changing environments is particularly important with "gene drives on the horizon." To anticipate how "synthetic threads" will affect the web of life on Earth, scientists must confront complex system interactions across many levels of biological organization. Currently, we lack plans, infrastructure, and funding for field science and scientists to track new synthetic organisms, with or without gene drives, as they move through open environments.

Designing gene drives to limit spillover to non-target populations

The prospect of utilizing CRISPR-based gene-drive technology for controlling populations has generated much excitement. However, the potential for spillovers of gene-drive alleles from the target population to non-target populations has raised concerns. Here, using mathematical models, we investigate the possibility of limiting spillovers to non-target populations by designing differential-targeting gene drives, in which the expected equilibrium gene-drive allele frequencies are high in the target population but low in the non-target population. We find that achieving differential targeting is possible with certain configurations of gene-drive parameters, but, in most cases, only under relatively low migration rates between populations. Under high migration, differential targeting is possible only in a narrow region of the parameter space. Because fixation of the gene drive in the non-target population could severely disrupt ecosystems, we outline possible ways to avoid this outcome. We apply our model to two potential applications of gene drives—field trials for malaria-vector gene drives and control of invasive species on islands. We discuss theoretical predictions of key requirements for differential targeting and their practical implications.

CRISPR-based gene drive is an emerging genetic engineering technology that enables engineered genetic variants, which are usually designed to be harmful to the organism carrying them, to be spread rapidly in populations. Although this technology is promising for controlling disease vectors and invasive species, there is a considerable risk that a gene drive could unintentionally spillover from the target population, where it was deployed, to non-target populations. We develop mathematical models of gene-drive dynamics that incorporate migration between target and non-target populations to investigate the possibility of effectively applying a gene drive in the target population while limiting its spillover to non-target populations (‘differential targeting’). We observe that the feasibility of differential targeting depends on the gene-drive design specification, as well as on the migration rates between the populations. Even when differential targeting is possible, as migration increases, the possibility for differential targeting disappears. We find that differential targeting can be effective for low migration rates, and that it is sensitive to the design of the gene drive under high migration rates. We suggest that differential targeting could be used, in combination with other mitigation measures, as an additional safeguard to limit gene drive spillovers.

Playing God and tampering with nature: popular labels for real concerns in synthetic biology

Public engagement in science with diverse cross-sections of the community is considered a critical aspect of responsible biotechnological innovation. While the research community shows willingness to engage with both ambivalent and supportive audiences about potentially disruptive technological advances, there is less enthusiasm for engaging with groups who hold deeply opposing views to such advances. 'Playing God' and 'tampering with nature' are popular examples of intrinsic objections often made in opposition to the development or use of novel genetic technologies. Historically appearing in arguments against the pursuit of genetically modified organisms in agriculture and food industries, intrinsic objections have previously been labelled by the science community as inconsistent, non-scientific, and vague. Now found in a range of innovation contexts, the domain of synthetic biology appears to attract such objections consistently. We present the findings from a large Australian study (N = 4593) which suggests 'playing God' objections and their variants can be multilayered and, at times, accompanied by meaningful information about risk perceptions. We use qualitative analysis of open-ended responses from an online survey to show how these objections are articulated in response to selected synthetic biology applications across environmental and health domains. Our research invites a rethink of how the synthetic biology community perceives, and engages with, people who express intrinsic objections. These people may additionally hold extrinsic concerns that may be potentially addressed, or at least reasonably considered, through dialogue. We offer some concluding remarks for engaging with publics who employ these types of arguments to communicate unease with aspects of technology development and use.

Modeling the impacts of a simple meiotic gene drive on small, homeostatic populations

Gene drives offer unprecedented control over the fate of natural ecosystems by leveraging non-Mendelian inheritance mechanisms to proliferate synthetic genes across wild populations. However, these benefits are offset by a need to avoid the potentially disastrous consequences of unintended ecological interactions. The efficacy of many gene-editing drives has been brought into question due to predictions that they will inevitably be thwarted by the emergence of drive-resistant mutations, but these predictions derive largely from models of large or infinite populations that cannot be driven to extinction faster than mutations can fixate. To address this issue, we characterize the impact of a simple, meiotic gene drive on a small, homeostatic population whose genotypic composition may vary due to the stochasticity inherent in natural mating events (e.g., partner choice, number of offspring) or the genetic inheritance process (e.g., mutation rate, gene drive fitness). To determine whether the ultimate genotypic fate of such a population is sensitive to such stochastic fluctuations, we compare the results of two dynamical models: a deterministic model that attempts to predict how the genetics of an average population evolve over successive generations, and an agent-based model that examines how stable these predictions are to fluctuations. We find that, even on average, our stochastic model makes qualitatively distinct predictions from those of the deterministic model, and we identify the source of these discrepancies as a dynamic instability that arises at short times, when genetic diversity is maximized as a consequence of the gene drive's rapid proliferation. While we ultimately conclude that extinction can only beat out the fixation of drive-resistant mutations over a limited region of parameter space, the reason for this is more complex than previously understood, which could open new avenues for engineered gene drives to circumvent this weakness.

Adequacy and sufficiency evaluation of existing EFSA guidelines for the molecular characterisation, environmental risk assessment and post-market environmental monitoring of genetically modified insects containing engineered gene drives

Advances in molecular and synthetic biology are enabling the engineering of gene drives in insects for disease vector/pest control. Engineered gene drives (that bias their own inheritance) can be designed either to suppress interbreeding target populations or modify them with a new genotype. Depending on the engineered gene drive system, theoretically, a genetic modification of interest could spread through target populations and persist indefinitely, or be restricted in its spread or persistence. While research on engineered gene drives and their applications in insects is advancing at a fast pace, it will take several years for technological developments to move to practical applications for deliberate release into the environment. Some gene drive modified insects (GDMIs) have been tested experimentally in the laboratory, but none has been assessed in small-scale confined field trials or in open release trials as yet. There is concern that the deliberate release of GDMIs in the environment may have possible irreversible and unintended consequences. As a proactive measure, the European Food Safety Authority (EFSA) has been requested by the European Commission to review whether its previously published guidelines for the risk assessment of genetically modified animals (EFSA, 2012 and 2013), including insects (GMIs), are adequate and sufficient for GDMIs, primarily disease vectors, agricultural pests and invasive species, for deliberate release into the environment. Under this mandate, EFSA was not requested to develop risk assessment guidelines for GDMIs. In this Scientific Opinion, the Panel on Genetically Modified Organisms (GMO) concludes that EFSA's guidelines are adequate, but insufficient for the molecular characterisation (MC), environmental risk assessment (ERA) and post-market environmental monitoring (PMEM) of GDMIs. While the MC,ERA and PMEM of GDMIs can build on the existing risk assessment framework for GMIs that do not contain engineered gene drives, there are specific areas where further guidance is needed for GDMIs.

Can CRISPR gene drive work in pest and beneficial haplodiploid species?

Gene drives based on CRISPR/Cas9 have the potential to reduce the enormous harm inflicted by crop pests and insect vectors of human disease, as well as to bolster valued species. In contrast with extensive empirical and theoretical studies in diploid organisms, little is known about CRISPR gene drive in haplodiploids, despite their immense global impacts as pollinators, pests, natural enemies of pests, and invasive species in native habitats. Here, we analyze mathematical models demonstrating that, in principle, CRISPR homing gene drive can work in haplodiploids, as well as at sex-linked loci in diploids. However, relative to diploids, conditions favoring the spread of alleles deleterious to haplodiploid pests by CRISPR gene drive are narrower, the spread is slower, and resistance to the drive evolves faster. By contrast, the spread of alleles that impose little fitness cost or boost fitness was not greatly hindered in haplodiploids relative to diploids. Therefore, altering traits to minimize damage caused by harmful haplodiploids, such as interfering with transmission of plant pathogens, may be more likely to succeed than control efforts based on introducing traits that reduce pest fitness. Enhancing fitness of beneficial haplodiploids with CRISPR gene drive is also promising.

Evaluating the probability of CRISPR-based gene drive contaminating another species

The probability D that a given clustered regularly interspaced short palindromic repeats (CRISPR)-based gene drive element contaminates another, nontarget species can be estimated by the following Drive Risk Assessment Quantitative Estimate (DRAQUE) Equation: D = h y b + t r a n s f × e x p r e s s × c u t × f l a n k × i m m u n e × n o n e x t i n c t with hyb = probability of hybridization between the target species and a nontarget species; transf = probability of horizontal transfer of a piece of DNA containing the gene drive cassette from the target species to a nontarget species (with no hybridization); express = probability that the Cas9 and guide RNA genes are expressed; cut = probability that the CRISPR-guide RNA recognizes and cuts at a DNA site in the new host; flank = probability that the gene drive cassette inserts at the cut site; immune = probability that the immune system does not reject Cas9-expressing cells; nonextinct = probability of invasion of the drive within the population. We discuss and estimate each of the seven parameters of the equation, with particular emphasis on possible transfers within insects, and between rodents and humans. We conclude from current data that the probability of a gene drive cassette to contaminate another species is not insignificant. We propose strategies to reduce this risk and call for more work on estimating all the parameters of the formula.

Interventions to help coral reefs under global change-A complex decision challenge

Climate change is impacting coral reefs now. Recent pan-tropical bleaching events driven by unprecedented global heat waves have shifted the playing field for coral reef management and policy. While best-practice conventional management remains essential, it may no longer be enough to sustain coral reefs under continued climate change. Nor will climate change mitigation be sufficient on its own. Committed warming and projected reef decline means solutions must involve a portfolio of mitigation, best-practice conventional management and coordinated restoration and adaptation measures involving new and perhaps radical interventions, including local and regional cooling and shading, assisted coral evolution, assisted gene flow, and measures to support and enhance coral recruitment. We propose that proactive research and development to expand the reef management toolbox fast but safely, combined with expedient trialling of promising interventions is now urgently needed, whatever emissions trajectory the world follows. We discuss the challenges and opportunities of embracing new interventions in a race against time, including their risks and uncertainties. Ultimately, solutions to the climate challenge for coral reefs will require consideration of what society wants, what can be achieved technically and economically, and what opportunities we have for action in a rapidly closing window. Finding solutions that work for coral reefs and people will require exceptional levels of coordination of science, management and policy, and open engagement with society. It will also require compromise, because reefs will change under climate change despite our best interventions. We argue that being clear about society's priorities, and understanding both the opportunities and risks that come with an expanded toolset, can help us make the most of a challenging situation. We offer a conceptual model to help reef managers frame decision problems and objectives, and to guide effective strategy choices in the face of complexity and uncertainty.

The potential for a CRISPR gene drive to eradicate or suppress globally invasive social wasps

CRISPR gene drives have potential for widespread and cost-efficient pest control, but are highly controversial. We examined a potential gene drive targeting spermatogenesis to control the invasive common wasp (Vespula vulgaris) in New Zealand. Vespula wasps are haplodiploid. Their life cycle makes gene drive production challenging, as nests are initiated by single fertilized queens in spring followed by several cohorts of sterile female workers and the production of reproductives in autumn. We show that different spermatogenesis genes have different levels of variation between introduced and native ranges, enabling a potential 'precision drive' that could target the reduced genetic diversity and genotypes within the invaded range. In vitro testing showed guide-RNA target specificity and efficacy that was dependent on the gene target within Vespula, but no cross-reactivity in other Hymenoptera. Mathematical modelling incorporating the genetic and life history traits of Vespula wasps identified characteristics for a male sterility drive to achieve population control. There was a trade-off between drive infiltration and impact: a drive causing complete male sterility would not spread, while partial sterility could be effective in limiting population size if the homing rate is high. Our results indicate that gene drives may offer viable suppression for wasps and other haplodiploid pests.

Keeping crispr in check: diverse mechanisms of phage-encoded anti-crisprs

CRISPR-Cas represents the only adaptive immune system of prokaryotes known to date. These immune systems are widespread among bacteria and archaea, and provide protection against invasion of mobile genetic elements, such as bacteriophages and plasmids. As a result of the arms-race between phages and their prokaryotic hosts, phages have evolved inhibitors known as anti-CRISPR (Acr) proteins to evade CRISPR immunity. In the recent years, several Acr proteins have been described in both temperate and virulent phages targeting diverse CRISPR-Cas systems. Here, we describe the strategies of Acr discovery and the multiple molecular mechanisms by which these proteins operate to inhibit CRISPR immunity. We discuss the biological relevance of Acr proteins and speculate on the implications of their activity for the development of improved CRISPR-based research and biotechnological tools.

Genetic Biocontrol for Invasive Species

Invasive species are increasingly affecting agriculture, food, fisheries, and forestry resources throughout the world. As a result of global trade, invasive species are often introduced into new environments where they become established and cause harm to human health, agriculture, and the environment. Prevention of new introductions is a high priority for addressing the harm caused by invasive species, but unfortunately efforts to prevent new introductions do not address the economic harm that is presently manifested where invasive species have already become established. Genetic biocontrol can be defined as the release of organisms with genetic methods designed to disrupt the reproduction of invasive populations. While these methods offer the potential to control or even eradicate invasive species, there is a need to ensure that genetic biocontrol methods can be deployed in a way that minimizes potential harm to the environment. This review provides an overview of the state of genetic biocontrol, focusing on several approaches that were the subject of presentations at the Genetic Biocontrol for Invasive Species Workshop in Tarragona, Spain, March 31st, 2019, a workshop sponsored by the OECD’s Co-operative Research Program on Biological Resource Management for Sustainable Agricultural Systems. The review considers four different approaches to genetic biocontrol for invasive species; sterile-release, YY Males, Trojan Female Technique, and gene drive. The different approaches will be compared with respect to the efficiency each affords as a genetic biocontrol tool, the practical utility and cost/benefits associated with implementation of the approach, and the regulatory considerations that will need to be addressed for each. The opinions expressed and arguments employed in this publication are the sole responsibility of the authors and do not necessarily reflect those of the OECD or of the governments of its Member countries.

Gene technologies in weed management: a technical feasibility analysis

With the advent of new genetic technologies such as gene silencing and gene drive, efforts to develop additional management tools for weed management is gaining significant momentum. These technologies promise novel ways to develop sustainable weed control options because gene silencing can switch-off genes mediating adaptation (e.g. growth, herbicide resistance), and gene drive can be used to spread modified traits and to engineer wild populations with reduced fitness. However, applying gene silencing and/or gene drive is expected to be inherently complex as their application is constrained by several methodological and technological difficulties. In this review we explore the challenges of these technologies, and discuss strategies and resources accessible to accelerate the development of gene-tech based tools for weed management. We also highlight how gene technologies can be integrated into existing management tactics such as classical biological control, and their possible interactions.

How to better predict long-term benefits and risks in weed biocontrol: an evolutionary perspective

Classical biological control (also called importation biological control) of weeds has a remarkable track record for efficiency and safety, but further improvement is still needed, particularly to account for potential evolutionary changes after release. Here, we discuss the increasing yet limited evidence of post-introduction evolution and describe approaches to predict evolutionary change. Recent advances include using experimental evolution studies over several generations that combine -omics tools with behavioral bioassays. This novel approach in weed biocontrol is well suited to explore the potential for rapid evolutionary change in real-time and thus can be used to estimate more accurately potential benefits and risks of agents before their importation. We outline this approach with a chrysomelid beetle used to control invasive common ragweed.

Gridlock and beltways: the genetic context of urban invasions

The rapid expansion of urban land across the globe presents new and numerous opportunities for invasive species to spread and flourish. Ecologists historically rejected urban ecosystems as important environments for ecology and evolution research but are beginning to recognize the importance of these systems in shaping the biology of invasion. Urbanization can aid the introduction, establishment, and spread of invaders, and these processes have substantial consequences on native species and ecosystems. Therefore, it is valuable to understand how urban areas influence populations at all stages in the invasion process. Population genetic tools are essential to explore the driving forces of invasive species dispersal, connectivity, and adaptation within cities. In this review, we synthesize current research about the influence of urban landscapes on invasion genetics dynamics. We conclude that urban areas are not only points of entry for many invasive species, they also facilitate population establishment, are pools for genetic diversity, and provide corridors for further spread both within and out of cities. We recommend the continued use of genetic studies to inform invasive species management and to understand the underlying ecological and evolutionary processes governing successful invasion.

Transforming ecology and conservation biology through genome editing

As the conservation challenges increase, new approaches are needed to help combat losses in biodiversity and slow or reverse the decline of threatened species. Genome-editing technology is changing the face of modern biology, facilitating applications that were unimaginable only a decade ago. The technology has the potential to make significant contributions to the fields of evolutionary biology, ecology, and conservation, yet the fear of unintended consequences from designer ecosystems containing engineered organisms has stifled innovation. To overcome this gap in the understanding of what genome editing is and what its capabilities are, more research is needed to translate genome-editing discoveries into tools for ecological research. Emerging and future genome-editing technologies include new clustered regularly interspaced short palindromic repeats (CRISPR) targeted sequencing and nucleic acid detection approaches as well as species genetic barcoding and somatic genome-editing technologies. These genome-editing tools have the potential to transform the environmental sciences by providing new noninvasive methods for monitoring threatened species or for enhancing critical adaptive traits. A pioneering effort by the conservation community is required to apply these technologies to real-world conservation problems.

Regulation of GM Organisms for Invasive Species Control

Invasive species can cause significant harm to the environment, agriculture, and human health, but there are often very limited tools available to control their populations. Gene drives (GD) have been proposed as a new tool which could be used to control or eliminate such species. Here, GD describes a variety of molecular biology applications which all enable the introduction of genetic elements at a higher than expected frequency. These elements can change the genotypes in target populations rapidly with consequences either for (intrinsic) fitness or host-parasite interaction, or both. Beneficial applications are foreseen for human and animal health, agriculture, or nature conservation. This rapidly developing technology is likely to have major impacts in the fight against various diseases, pests, and invasive species. The majority of GD applications involve genetic engineering and novel traits. Therefore, applicants and GMO regulators need to interact to achieve the benefits in innovation while cautiously avoiding unacceptable risks. The release into the environment may include transboundary movement and replacement of target populations, with potential impact on human/animal health and the environment. This article summarizes knowledge-based discussions to identify information gaps and analyzes scenarios for responsible introduction of GD organisms into the environment. It aims to connect the latest scientific developments with regulatory approaches and decision-making.

Public views about editing genes in wildlife for conservation

Developments in CRISPR-based gene-editing technologies have generated a growing number of proposals to edit genes in wildlife to meet conservation goals. As these proposals have attracted greater attention, controversies have emerged among scientists and stakeholder groups over potential consequences and ethical implications of gene editing. Responsible governance cannot occur without consulting broader publics, yet little effort has been made to systematically assess public understandings and beliefs in relation to this new area of applied genetic engineering. We analyzed data from a survey of U.S. adults (n = 1600), collected by YouGov, and that examined respondents' concerns about gene editing in animal and plant wildlife and how those concerns are shaped by cultural dispositions toward science and beliefs about the appropriateness of intervening in nature at the genetic level. On average, respondents perceived more risk than benefit in using these tools. Over 70% agreed that gene editing in wildlife could be "easily used for the wrong purposes." When evaluating the moral acceptability of gene editing in wildlife, respondents evaluated applications to improve survival in endangered wildlife as more morally acceptable than applications to decrease abundance in a population or eliminate a population. Belief in the authority of scientific knowledge was positively related to favorable views of the benefits, risks, and moral acceptability of editing genes in wildlife. The belief that editing genes in wildlife inappropriately intervenes in nature predicted relatively more concern about risks and moral acceptability and skepticism about benefits. Given high levels of concern and skepticism about gene editing in wildlife for conservation among the U.S. public, a take-it-slow approach to making decisions about when or whether to use these tools is advisable. Early opinions, including those uncovered in this study, are likely to be provisional. Thus, consulting the public should be an ongoing process.

Assisted Evolution in Astrobiology-Convergence of Ecology and Evolutionary Biology within the Context of Planetary Colonization

In ecology and conservation biology, the concept of assisted evolution aims at the optimization of the resilience of organisms and populations to changing environmental conditions. What has hardly been considered so far is that this concept is also relevant for future astrobiological research, since in artificial extraterrestrial habitats (e.g., plants and insects in martian greenhouses) novel environmental conditions will also affect the survival and performance of organisms. The question therefore arises whether and how space-relevant organisms can be artificially adapted to the desired circumstances in advance. Based on several adaptation and acclimatization strategies in wild ecosystems of Earth, I discuss which methods can be considered for assisted evolution in the context of astrobiological research. This includes enhanced selective breeding, induction of epigenetic inheritance, and genetic engineering, as well as possible problems of these applications. This short overview article aims to stimulate an emerging discussion as to whether humans, which are already prominent drivers of Earth's evolution, should consider such interventions for future planetary colonization as well.

Gene drives in plants: opportunities and challenges for weed control and engineered resilience

Plant species, populations and communities are under threat from climate change, invasive pathogens, weeds and habitat fragmentation. Despite considerable research effort invested in genome engineering for crop improvement, the development of genetic tools for the management of wild plant populations has rarely been given detailed consideration. Gene drive systems that allow direct genetic management of plant populations via the spread of fitness-altering genetic modifications could be of great utility. However, despite the rapid development of synthetic tools and their enormous promise, little explicit consideration has been given to their application in plants and, to date, they remain untested. This article considers the potential utility of gene drives for the management of wild plant populations, and examines the factors that might influence the design, spread and efficacy of synthetic drives. To gain insight into optimal ways to design and deploy synthetic drive systems, we investigate the diversity of mechanisms underlying natural gene drives and their dynamics within plant populations and species. We also review potential approaches for engineering gene drives and discuss their potential application to plant genomes. We highlight the importance of considering the impact of plant life-history and genetic architecture on the dynamics of drive, investigate the potential for different types of resistance evolution, and touch on the ethical, regulatory and social challenges ahead.

Population Genomic Approaches for Weed Science

Genomic approaches are opening avenues for understanding all aspects of biological life, especially as they begin to be applied to multiple individuals and populations. However, these approaches typically depend on the availability of a sequenced genome for the species of interest. While the number of genomes being sequenced is exploding, one group that has lagged behind are weeds. Although the power of genomic approaches for weed science has been recognized, what is needed to implement these approaches is unfamiliar to many weed scientists. In this review we attempt to address this problem by providing a primer on genome sequencing and provide examples of how genomics can help answer key questions in weed science such as: (1) Where do agricultural weeds come from; (2) what genes underlie herbicide resistance; and, more speculatively, (3) can we alter weed populations to make them easier to control? This review is intended as an introduction to orient weed scientists who are thinking about initiating genome sequencing projects to better understand weed populations, to highlight recent publications that illustrate the potential for these methods, and to provide direction to key tools and literature that will facilitate the development and execution of weed genomic projects.

Genetically Engineering Wild Mice to Combat Lyme Disease: An Ecological Perspective

Genetic engineering of wild populations has been proposed for reducing human diseases by altering pathogens’ hosts. For example, CRISPR-based genome editing may be used to create white-footed mice (Peromyscus leucopus) that are resistant to the Lyme disease spirochete vectored by blacklegged ticks (Ixodes scapularis). Toward this goal, academic researchers are developing Lyme-resistant and tick-resistant white-footed mice, which are a primary pathogen reservoir for Lyme disease in the United States. If field trials on small, experimental islands are successful, the project would scale up to the larger islands of Nantucket and Martha's Vineyard, Massachusetts, and possibly to the mainland, most likely with a local gene drive to speed the traits’ proliferation, pending approvals from relevant constituents. Despite considerable publicity, this project has yet to be evaluated by independent professional ecologists. In the present article, I discuss key ecological and evolutionary questions that should be considered before such genetically engineered mice are released into natural habitats.

Does the U.S. public support using gene drives in agriculture? And what do they want to know?

Gene drive development is progressing more rapidly than our understanding of public values toward these technologies. We analyze a statistically representative survey (n = 1018) of U.S. adult attitudes toward agricultural gene drives. When informed about potential risks, benefits, and two previously researched applications, respondents' support/opposition depends heavily (+22%/-19%) on whether spread of drives can be limited, non-native versus native species are targeted (+12%/-9%), or the drive replaces versus suppresses target species (±2%). The one-fifth of respondents seeking out non-GMO-labeled food are more likely to oppose drives, although their support exceeds opposition for limited applications. Over 62% trust U.S. universities and the Department of Agriculture to research gene drives, with the private sector and Department of Defense viewed as more untrustworthy. Uncertain human health and ecological effects are the public's most important concerns to resolve. These findings can inform responsible innovation in gene drive development and risk assessment.

Conservation through the lens of (mal)adaptation: Concepts and meta-analysis

Evolutionary approaches are gaining popularity in conservation science, with diverse strategies applied in efforts to support adaptive population outcomes. Yet conservation strategies differ in the type of adaptive outcomes they promote as conservation goals. For instance, strategies based on genetic or demographic rescue implicitly target adaptive population states whereas strategies utilizing transgenerational plasticity or evolutionary rescue implicitly target adaptive processes. These two goals are somewhat polar: adaptive state strategies optimize current population fitness, which should reduce phenotypic and/or genetic variance, reducing adaptability in changing or uncertain environments; adaptive process strategies increase genetic variance, causing maladaptation in the short term, but increase adaptability over the long term. Maladaptation refers to suboptimal population fitness, adaptation refers to optimal population fitness, and (mal)adaptation refers to the continuum of fitness variation from maladaptation to adaptation. Here, we present a conceptual classification for conservation that implicitly considers (mal)adaptation in the short-term and long-term outcomes of conservation strategies. We describe cases of how (mal)adaptation is implicated in traditional conservation strategies, as well as strategies that have potential as a conservation tool but are relatively underutilized. We use a meta-analysis of a small number of available studies to evaluate whether the different conservation strategies employed are better suited toward increasing population fitness across multiple generations. We found weakly increasing adaptation over time for transgenerational plasticity, genetic rescue, and evolutionary rescue. Demographic rescue was generally maladaptive, both immediately after conservation intervention and after several generations. Interspecific hybridization was adaptive only in the F1 generation, but then rapidly leads to maladaptation. Management decisions that are made to support the process of adaptation must adequately account for (mal)adaptation as a potential outcome and even as a tool to bolster adaptive capacity to changing conditions.

Climate vulnerability assessment for Pacific salmon and steelhead in the California Current Large Marine Ecosystem

Major ecological realignments are already occurring in response to climate change. To be successful, conservation strategies now need to account for geographical patterns in traits sensitive to climate change, as well as climate threats to species-level diversity. As part of an effort to provide such information, we conducted a climate vulnerability assessment that included all anadromous Pacific salmon and steelhead (Oncorhynchus spp.) population units listed under the U.S. Endangered Species Act. Using an expert-based scoring system, we ranked 20 attributes for the 28 listed units and 5 additional units. Attributes captured biological sensitivity, or the strength of linkages between each listing unit and the present climate; climate exposure, or the magnitude of projected change in local environmental conditions; and adaptive capacity, or the ability to modify phenotypes to cope with new climatic conditions. Each listing unit was then assigned one of four vulnerability categories. Units ranked most vulnerable overall were Chinook (O. tshawytscha) in the California Central Valley, coho (O. kisutch) in California and southern Oregon, sockeye (O. nerka) in the Snake River Basin, and spring-run Chinook in the interior Columbia and Willamette River Basins. We identified units with similar vulnerability profiles using a hierarchical cluster analysis. Life history characteristics, especially freshwater and estuary residence times, interplayed with gradations in exposure from south to north and from coastal to interior regions to generate landscape-level patterns within each species. Nearly all listing units faced high exposures to projected increases in stream temperature, sea surface temperature, and ocean acidification, but other aspects of exposure peaked in particular regions. Anthropogenic factors, especially migration barriers, habitat degradation, and hatchery influence, have reduced the adaptive capacity of most steelhead and salmon populations. Enhancing adaptive capacity is essential to mitigate for the increasing threat of climate change. Collectively, these results provide a framework to support recovery planning that considers climate impacts on the majority of West Coast anadromous salmonids.

The potential of genomics for restoring ecosystems and biodiversity

Billions of hectares of natural ecosystems have been degraded through human actions. The global community has agreed on targets to halt and reverse these declines, and the restoration sector faces the important but arduous task of implementing programmes to meet these objectives. Existing and emerging genomics tools offer the potential to improve the odds of achieving these targets. These tools include population genomics that can improve seed sourcing, meta-omics that can improve assessment and monitoring of restoration outcomes, and genome editing that can generate novel genotypes for restoring challenging environments. We identify barriers to adopting these tools in a restoration context and emphasize that regulatory and ethical frameworks are required to guide their use.