Brian C Verrelli
email: bverrelli@vcu.edu

Marina Alberti

Simone Des Roches

Nyeema C Harris

Andrew P Hendry

Marc T J Johnson

Amy M Savage

Anne Charmantier

Kiyoko M Gotanda

Lynn Govaert

Lindsay S Miles

L Ruth Rivkin

Kristin M Winchell

Kristien I Brans

Cristian Correa

Sarah E Diamond

Ben Fitzhugh

Nancy B Grimm

Sara Hughes

John M Marzluff

Jason Munshi- South

Carolina Rojas

James S Santangelo

Christopher J Schell

Jennifer A Schweitzer

Marta Szulkin

Mark C Urban

Yuyu Zhou

Carly Ziter

Verrelli et al: A global horizon scan for urban evolutionary ecology

Keywords: urbanization, urban ecology, urban evolution, sustainability, socio-political, climate change

Research on the evolutionary ecology of urban areas reveals how human-induced evolutionary changes affects biodiversity and essential ecosystem services. In a rapidly urbanizing world imposing many selective pressures, a time-sensitive goal is to identify the emergent issues and research priorities that affect the ecology and evolution of species within cities. Here, we report the results of a horizon scan of research questions in urban evolutionary ecology submitted by 100 interdisciplinary scholars. We identified 30 top questions organized into six themes that highlight priorities for future research. These research questions will require methodological advances and interdisciplinary collaborations, with continued revision as the field of urban evolutionary ecology expands with the rapid growth of cities.

Emerging challenges in urban evolutionary ecology

Urbanization (see Glossary) is altering ecosystems at a global scale, and challenging the future persistence of biodiversity [START_REF] Mckinney | Urbanization as a major cause of biotic homogenization[END_REF][START_REF] Mcdonald | The implications of current and future urbanization for global protected areas and biodiversity conservation[END_REF][START_REF] Alberti | Eco-evolutionary dynamics in an urbanizing planet[END_REF]. Specifically, demographic predictions suggest that by 2050, urban areas will be home to two-thirds of the human population [START_REF]World Urbanization Prospects: The 2018 Revision (ST/ESA/SER.A/420)[END_REF]. With this rapid urbanization, habitats will be irrevocably changed and natural resource extraction will accelerate. These impacts create complex ecoevolutionary dynamics that emerge at the intersection of social, political, and cultural systems and technological infrastructure within and among urban areas [START_REF] Alberti | The complexity of urban eco-evolutionary dynamics[END_REF][START_REF] Des Roches | Socio-eco-evolutionary dynamics in cities[END_REF]. The field of urban evolutionary ecology has received increasing attention from diverse disciplines to address not only how urbanization changes fundamental evolutionary and ecological processes, but also how a more integrated research agenda on evolutionary ecology can reveal the potential feedback of these changes on human and ecosystem health across spatial and temporal scales [START_REF] Johnson | Evolution of life in urban environments[END_REF][START_REF] Schell | The ecological and evolutionary consequences of systemic racism in urban environments[END_REF][START_REF] Szulkin | Urban evolutionary biology[END_REF]. Because cities share environmental properties that are distinct from other ecosystems, they also provide an ideal system for answering outstanding questions in evolutionary ecology.

Multiple reviews of urban evolutionary ecology research call for developing a shared agenda and guidelines for collaborative initiatives in funding and policy [START_REF] Des Roches | Socio-eco-evolutionary dynamics in cities[END_REF][START_REF] Rivkin | A roadmap for urban evolutionary ecology[END_REF][START_REF] Diamond | Evolution in cities[END_REF]. Timing is important, as the results of these guidelines will not only shed light on current issues in urban ecosystems, but also provide a forward-looking perspective from this burgeoning field relevant to addressing and solving urban problems emerging now and in the future. The current study applied a formalized horizon scanning protocol (Box 1), which used a survey of interdisciplinary expert opinions (Box 2) to identify future challenges ranging across a spectrum of technological, environmental, and socio-political dimensions. Here, we present the six broad themes in urban evolutionary ecology (Figure 1) that encompass the 30 top questions that emerged from the horizon scan (Table 1 & Figure 2).

Fundamental processes and mechanisms

Studies increasingly show that cities across the globe are altering fundamental ecological and evolutionary processes. While studied primarily in isolation, these processes may interact in complex ways within cities, creating unique selection pressures and eco-evolutionary feedbacks [START_REF] Alberti | The complexity of urban eco-evolutionary dynamics[END_REF]. For example, plant-herbivore and predator-prey interactions [START_REF] Miles | Urbanization shapes the ecology and evolution of plant-arthropod herbivore interactions[END_REF][START_REF] Brans | Cryptic eco-evolutionary feedback in the city: Urban evolution of prey dampens the effect of urban evolution of the predator[END_REF] are altered by urbanization, leading to phenotypic changes in traits ranging from morphological, behavioral, physiological, and life history [START_REF] Gotanda | Human influences on antipredator behaviour in Darwin's finches[END_REF][START_REF] Santangelo | Predicting the strength of urban-rural clines in a Mendelian polymorphism along a latitudinal gradient[END_REF]. Urban environments likely also modify sexual selection and thus generate novel mating strategies and preferences [START_REF] Halfwerk | Adaptive changes in sexual signalling in response to urbanization[END_REF], which could further shape population dynamics and interactions with other species. However, it is unclear whether these traits are either exaptations or novel adaptations to the urban environment [START_REF] Rivkin | A roadmap for urban evolutionary ecology[END_REF][START_REF] Mcdonnell | Adaptation and adaptedness of organisms to urban environments[END_REF]. In fact, although most adaptations arise from selection on standing genetic variation [START_REF] Barrett | Adaptation from standing genetic variation[END_REF], we know little about how cities influence novel mutation or their long-term effects on organism health [START_REF] Marchetti | A return to the origin of the EMGS: Rejuvenating the quest for human germ cell mutagens and determining the risk to future generations[END_REF], despite the importance of mutation in contributing to evolutionary potential.

Understanding the role of urbanization for evolutionary ecology requires disentangling how landscape changes, temporal change in human-nature interactions, and past ecological and evolutionary legacies influence present-day dynamics. Over longer time periods, organismal changes in response to evolutionary processes altered by humans may ultimately lead to speciation, although it is unknown how common speciation is in cities or the conditions that may favor it in urban areas [START_REF] Halfwerk | How should we study urban speciation?[END_REF]. Anthropogenic habitat modification has altered ecological and evolutionary processes for at least the last 50,000 years, resulting in species that rely on anthropogenic resources [START_REF] Sullivan | Human behaviour as a long-term ecological driver of non-human evolution[END_REF], including commensals and domesticated species [START_REF] Ravinet | Signatures of human-commensalism in the house sparrow genome[END_REF]. In fact, domesticated animals, such as pet cats (Felis catus), have severely negative effects on endemic wildlife [START_REF] Legge | We need to worry about Bella and Charlie: the impacts of pet cats on Australian wildlife[END_REF], yet the long-term evolutionary consequences of these predator-prey interactions in cities are not well-studied. Studies of these organisms can give us a glimpse into the process of organismal change across anthropogenic environments, in some cases leading to populations that are reproductively isolated from their non-urban counterparts [START_REF] Booth | Host association drives genetic divergence in the bed bug, Cimex lectularius[END_REF].

Another focus is the extent to which urbanization has increased or decreased natural connectivity within and among ecosystems, and whether the resulting evolutionary effects can be generalized across cities and taxa [START_REF] Miles | Gene flow and genetic drift in urban environments[END_REF]. It is unclear how urban drivers (e.g., social, environmental, ecological, and technological) interact to alter population connectivity, and what impact this has on population size and genetic diversity [START_REF] Gustafson | Genetic source-sink dynamics among naturally structured and anthropogenically fragmented puma populations[END_REF], as maintained by source-sink dynamics between urban and nonurban areas [START_REF] Tassone | Evolutionary stability, landscape heterogeneity, and human land-usage Verrelli et al: A global horizon scan for urban evolutionary ecology 20 shape population genetic connectivity in the Cape Floristic Region biodiversity hotspot[END_REF].

Lastly, incorporating human-mediated gene flow into general models of evolutionary ecology is critical for understanding demography, genetic diversity, and ultimately evolutionary potential [28].

Spatial and temporal scales of drivers and responses

The fast development of cities and their fine-scaled heterogeneity [START_REF] Zhou | Shifting concepts of urban spatial heterogeneity and their implications for sustainability[END_REF] can lead to local selection pressures that create rapid and microgeographic adaptations. This premise suggests that cities are hotspots for evolution, with the potential for novel species interactions that further drive rapid ecological and evolutionary change [START_REF] Miles | Gene flow and genetic drift in urban environments[END_REF][START_REF] Gallo | Urbanization alters predator-avoidance behaviours[END_REF]. However, the extent to which cities alter ecological niches and increase evolutionary potential [28,[START_REF] Alberti | Global urban signatures of phenotypic change in animal and plant populations[END_REF] is an empirical question that, once answered, could uncover the scale dependency of both drivers and responses.

The extent to which urban ecological and evolutionary dynamics occurring at various spatial and temporal scales are species-and city-specific is still relatively unknown. Variable patterns (e.g., spatial and temporal) of urbanization can reduce or increase colonization rates, genetic drift, and gene flow, which might determine the relative contribution of adaptive evolution and species-sorting shaping local communities [START_REF] Alberti | The complexity of urban eco-evolutionary dynamics[END_REF]. For example, high human-mediated dispersal of some species may counteract local adaptation to cities, whereas others may adapt quickly at fine scales [START_REF] Combs | Urban rat races: spatial population genomics of brown rats (Rattus norvegicus) compared across multiple cities[END_REF][START_REF] Johnson | Contrasting the effects of natural selection, genetic drift and gene flow on urban evolution in white clover (Trifolium repens)[END_REF]. In addition, factors such as age, history, and the pace of urban development may determine the magnitude of evolutionary responses, such as the strength and direction of selection [START_REF] Ossola | Valuing the role of time in urban ecology[END_REF][START_REF] Wei | Long-term urbanization impacts the eastern golden frog (Pelophylax plancyi) in Shanghai City: Demographic history, genetic structure, and implications for amphibian conservation in intensively urbanizing environments[END_REF]. Empirical studies that collect comparable data within and among cities with similar and different histories are necessary to relate cities' spatial and temporal heterogeneity to evolutionary responses [START_REF] Santangelo | Global urban environmental change drives adaptation in white clover[END_REF].

Evolution in natural systems can dampen ecological variation in time and space [START_REF] Kinnison | Cryptic eco-evolutionary dynamics: Cryptic eco-evolutionary dynamics[END_REF][START_REF] Urban | Evolutionary origins for ecological patterns in space[END_REF]. For example, adaptive evolution can dampen population cycling through time, and local adaptation to harsh environments can homogenize population abundances across spatially heterogeneous landscapes. However, the extent to which evolution stabilizes and homogenizes temporal and spatial heterogeneity in the urban environment is unexplored, although such dampening mechanisms could be counted as an important service to humans when they buffer adverse ecosystem impacts that occur in time or space.

Although ecological features can be homogenized across cities globally [START_REF] Santangelo | Global urban environmental change drives adaptation in white clover[END_REF][START_REF] Groffman | Ecological homogenization of residential macrosystems[END_REF], it is unclear whether selective pressures within cities are similar and if convergence in the evolutionary responses across cities is predictable.

Sustainability, health, and well-being

Cities are an important frontier in achieving future global biodiversity and sustainability goals [START_REF] Arneth | Post-2020 biodiversity targets need to embrace climate change[END_REF]. In particular, the United Nations Sustainable Development Goals (SDGs), specifically SDG 11 for sustainable cities and communities, provides an opportunity to link urban evolutionary ecology research with policies to mitigate environmental crises and promote ecosystem health [START_REF]World Urbanization Prospects: The 2018 Revision (ST/ESA/SER.A/420)[END_REF]. For example, cities could serve as reservoirs for biodiversity that benefit people and nature while also supporting ecosystem functions, such as decomposition, nutrient recycling, and carbon storage. These processes involve both ecological and evolutionary mechanisms that underpin ecosystem services such as urban sanitation, water purification, microclimate modulation, and pollinationall indispensable to well-being [START_REF] Otto | Social tipping dynamics for stabilizing Earth's climate by 2050[END_REF].

Research that integrates evolutionary ecology with urban development creates a direct link between urban eco-evolutionary dynamics and human and ecosystem health. As the COVID-19 pandemic demonstrates, the concentration of humans in cities and the interconnectedness of cities can facilitate the spread and evolution of certain diseases [START_REF] Nuñez | Invasion science and the global spread of SARS-CoV-2[END_REF], and pose an immense challenge to sustainable global health systems. It is imperative to understand how social heterogeneity and the design of urban landscapes influences the spread of diseases and their vectors, as well as other established health risks such as urban heat and elevated pollution [START_REF] Douglas | Urban ecology and urban ecosystems: understanding the links to human health and well-being[END_REF]. Urban greening can help cool cities and reduce pollution-related health issues [START_REF] Mei | Air pollution, human health and the benefits of trees: a biomolecular and physiologic perspective[END_REF], while also maintaining biodiversity and ecosystem functioning [START_REF] Lepczyk | Biodiversity in the city: Fundamental questions for understanding the ecology of urban green spaces for biodiversity conservation[END_REF]. Related, rewilding projects typically focus on ecological processes, yet more research is needed to investigate how they influence evolutionary processes and their effects on ecology and human health. For example, green spaces can reduce gene flow in species, which are well-suited for urban environments (e.g., brown rats, Rattus norvegicus) and that spread human pathogens [START_REF] Byers | Using genetic relatedness to understand heterogeneous distributions of urban rat-associated pathogens[END_REF].

Another link between urban evolutionary ecology and ecosystem health may be through the understudied world of urban microbiomes. While some soil microbial taxa show reduced abundance and richness in response to urbanization [START_REF] Schmidt | Urbanization erodes ectomycorrhizal fungal diversity and may cause microbial communities to converge[END_REF], this effect is not universal [START_REF] Reese | Urban stress is associated with variation in microbial species compositionbut not richnessin Manhattan[END_REF]. Signatures of urbanization have also been detected in animal microbial communities [START_REF] Danko | A global metagenomic map of urban microbiomes and antimicrobial resistance[END_REF], while human microbiomes are known to be less diverse in cities than in rural habitats, with possible repercussions for human autoimmune disorders [START_REF] Blaser | The microbiome revolution[END_REF].

However, it is unclear how cities impose selection on humans and other species that is mediated through the microbiome. Research into the influence of urban pollution on local microbial adaptation is needed to understand how to manage, or potentially rewild [START_REF] Mills | Urban habitat restoration provides a human health benefit through microbiome rewilding: the Microbiome Rewilding Hypothesis[END_REF], a range of urban microbial communities for ecosystem health.

Impacts and interactions with climate change

Synergistic effects of urbanization and climate change simultaneously impact organisms, including humans, with complex feedbacks between the two. For example, extreme weather events are exacerbated by both climate change [START_REF] Aghakouchak | Climate extremes and compound hazards in a warming world[END_REF] and urbanization [START_REF] Yang | Contribution of urbanization to the increase of extreme heat events in an urban agglomeration in east China[END_REF], with little understanding of whether the effects will be additive or multiplicative [START_REF] Lahr | Getting ahead of the curve: cities as surrogates for global change[END_REF][START_REF] Avilés-Rodríguez | Phenotypic response to a major hurricane in Anolis lizards in urban and forest habitats[END_REF]. As these intensifying disturbances become more common, they are likely to influence genetic diversity [START_REF] Schmidt | Continent-wide effects of urbanization on bird and mammal genetic diversity[END_REF] and exert strong selective pressures on urban organisms [START_REF] Johnson | Evolution of life in urban environments[END_REF].

Thus, understanding the resulting short-and long-term ecological resilience of urban communities to increasingly frequent extreme weather events will require investigations focused on urban long-term studies.

We especially point to the need for research on the evolution of urban pests and diseases, as well as their interactions with hosts and vectors. For example, the invasive Asian tiger mosquito (Aedes albopictus), a known vector of chikungunya and dengue viruses [START_REF] Benedict | Spread of the tiger: Global risk of invasion by the mosquito Aedes albopictus[END_REF], is predicted to invade all European countries because it benefits from warming conditions and is well-adapted to the urban environment.

Research might ask which invasive species possess adaptations for warmer urban conditions, and assess the evolutionary potential for novel adaptation to those conditions. Insight sought through historical and archeological analyses could likewise explore novel ecological and evolutionary relationships between humans, pests and diseases during past eras of rapid climate change [START_REF] Penny | Historical socioecological transformations in the global tropics as an Anthropocene analogue[END_REF]. Such retrospective and contemporary research could then inform scenarios and models to better anticipate the evolution and spread of pests and diseases in the urban matrix under various projections of future climate conditions.

Most studies of evolutionary ecology in cities focus on terrestrial organisms, yet changes are also likely in aquatic organisms, particularly in response to: changing flow patterns in urban streams [START_REF] Kern | Urbanization drives contemporary evolution in stream fish[END_REF]; changing temperature in urban streams, ponds, and lakes [START_REF] Brans | Urban hot-tubs: Local urbanization has profound effects on average and extreme temperatures in ponds[END_REF]; and rising sea levels in coastal areas [START_REF] Tully | The invisible flood: The chemistry, ecology, and social implications of coastal saltwater intrusion[END_REF].

The last has been the least studied and is therefore emphasized here. In particular, rising sea levels will lead to inundation farther inland and therefore increased salinization of coastal wetlands. It will be important to determine the extent to which freshwater resident species are able to adapt to those changing conditions. For example, species that have developed adaptations to increased road salt [START_REF] Hintz | A review of the species, community, and ecosystem impacts of road salt salinisation in fresh waters[END_REF] might also have a tolerance to increased sea-water inundation.

Politics, governance, culture, their interactions, and their ethical considerations

Political systems and governance arrangements guide urban growth and development in highly variable ways [START_REF] Elmqvist | Sustainability and resilience for transformation in the urban century[END_REF][START_REF] Hughes | Just urban transitions: Toward a research agenda[END_REF] that can shape urban evolutionary ecology. These arrangements can determine the spatial distribution of environmental burdens and access to amenities, exacerbating social and economic inequity and oppression [START_REF]Global Environment for Cities-GEO for Cities: Towards Green and Just Cities[END_REF]. For example, housing and land-use policies have resulted in green spaces being disproportionately located in affluent and primarily white areas within many global cities [START_REF] Schell | The ecological and evolutionary consequences of systemic racism in urban environments[END_REF][START_REF] Kronenberg | Environmental justice in the context of urban green space availability, accessibility, and attractiveness in postsocialist cities[END_REF][START_REF] Venter | Green Apartheid: Urban green infrastructure remains unequally distributed across income and race geographies in South Africa[END_REF]. Thus, investigations into how institutionally-entrenched distributions of urban land-use inequities may influence ecological properties (e.g., resource distribution or microclimates) and evolutionary change are a high research priority.

Another focus is understanding urban ecological and evolutionary dynamics in cultural contexts across space and time. Specifically, the historical characteristics of place, people, culture, and history might shape present ecological and evolutionary processes [START_REF] Tuckett | Domestication and feralization influence the distribution and phenotypes of escaped ornamental fish[END_REF], and offer input to models that make more realistic future predictions [START_REF] Larmuseau | A historical-genetic reconstruction of human extra-pair paternity[END_REF]. We must also differentiate between biological evolution and cultural evolution as they encompass different traits, underlying mechanisms and units of inheritance, such that cultural evolution can proceed at faster rates than biological evolution [START_REF] Milot | Selection on humans in cities[END_REF]. For example, increasing economic prosperity in cities often results in changing nutritional landscapes that produce greater quantities of urban food waste. Such waste can, in turn, influence wildlife behavior and population structure when animals expand into urban habitats and alter their feeding behaviors and diets [START_REF] Lee | Animal cognition in an urbanised world[END_REF]. While urban evolutionary dynamics have generally been understood according to biological traits, integrating cultural niche construction into urban evolutionary models is needed to conceptualize urban ecosystems from historical and contemporary perspectives [START_REF] Marzluff | Urban evolutionary ecology[END_REF][START_REF] Riede | Niche construction theory and human biocultural evolution[END_REF].

Although ethics can directly influence research decisions in urban evolutionary ecology, there is also the potential for ethical considerations to play a role in urban eco-evolutionary outcomes. One oftenoverlooked consideration is the moral responsibility of researchers and the role of empathy. For example, how pro-environmental behaviors have developed over time to influence policy that shapes urban evolutionary ecology could be thought of as a moral and motivational dilemma [START_REF] Turaga | Pro-environmental behavior: Rational choice meets moral motivation[END_REF]. However, decisions tied to urban areassuch as the magnitude of recycling and composting, programs such as food sharing or needle exchange, or the distribution of services such as homeless care, community clinics, or street cleanlinessmay have downstream implications for organisms by altering the adaptive landscape. For example, urban waste recycling practices generate potentially unique pollutants, such as microplastics, with yet unknown long-term selective pressures linked to water, air, and soil [START_REF] Yang | Waste management, informal recycling, environmental pollution and public health[END_REF]. Interdisciplinary collaborations will help inform how political, institutional, social, cultural, and ethical factors are not only considered in research, but how they play a direct role in shaping how processes of urban evolutionary ecology unfold and interact.

Innovation in technology and methodology

Advancements in technology and methodology provide unprecedented capacity to enable real-time monitoring and data analysis for previously unanswered questions in urban evolutionary ecology.

Genomic, transcriptomic, and epigenomic tools have not only provided insights into the effects of urbanization on evolution [START_REF] Campbell-Staton | Parallel selection on thermal physiology facilitates repeated adaptation of city lizards to urban heat islands[END_REF][START_REF] Miles | Ovarian transcriptomic analyses in the urban human health pest, the Western black widow spider[END_REF][START_REF] Perrier | Adaptation genomics in urban environments[END_REF][START_REF] Watson | Urbanization is associated with modifications in DNA methylation in a small passerine bird[END_REF], they have also provided the raw materials for downstream experiments. One example is how genetic technology has been tested for pest control of disease-carrying organisms [START_REF] Kyrou | A CRISPR-Cas9 gene drive targeting doublesex causes complete population suppression in caged Anopheles gambiae mosquitoes[END_REF][START_REF] Buchthal | Mice against ticks: an experimental community-guided effort to prevent tick-borne disease by altering the shared environment[END_REF], where manipulating genetic material could shift the evolution and adaptive landscape of endangered native organisms and their communities [START_REF] Kumar | CRISPR-based genome editing in wheat: a comprehensive review and future prospects[END_REF]. Another example comes from the expected increase of autonomous systems and robotics deployed in urban areas in the coming decades [START_REF] Goddard | A global horizon scan of the future impacts of robotics and autonomous systems on urban ecosystems[END_REF], leading to applications such as weed and pest control that may enhance or hinder plant-pollinator systems [START_REF] Potts | Robotic bees for crop pollination: Why drones cannot replace biodiversity[END_REF]. With the introduction of new artificial agents come unknown consequences, and the need to characterize the selection regimes that emerge as a natural response [START_REF] Gulsrud | Rage against the machine'? The opportunities and risks concerning the automation of urban green infrastructure[END_REF].

A related emerging issue is the abundance of databoth in volume and typesnewly generated to describe urban ecosystems. One solution may be through smart city approaches, which have traditionally focused on enhancing economic efficiency and quality of life for humans [START_REF] Bibri | On the sustainability of smart and smarter cities in the era of big data: an interdisciplinary and transdisciplinary literature review[END_REF]. For example, by integrating evolutionary ecology with engineering and social science in the design and connectivity of green infrastructure [START_REF] Maclvor | Phylogenetic ecology and the greening of cities[END_REF][START_REF] Zohrabi | Towards sustainable food security: an interdisciplinary approach[END_REF], we can increase gene flow and population connectivity while also attaining sustainable development goals in enhancing nature's contribution to people within cities. Just as the growing field of 'precision medicine' is using artificial intelligence (AI) methodology to find unique patterns among human genomes, environments, behavior, and social context [START_REF] Álvarez-Machancoses | On the role of artificial intelligence in genomics to enhance precision medicine[END_REF], the same AI approaches can make sense of complex systems in cities composed of variable environments in space and time, pollutants/mutagens, genomic structures and phylogenetic relationships. For example, these approaches can be used to monitor biodiversity from environmental DNA as well as predict epidemics from wastewater [START_REF] Goddard | A global horizon scan of the future impacts of robotics and autonomous systems on urban ecosystems[END_REF]. The future challenge largely rests in finding ways of translating the massive amounts of data into impactful and just strategies for management (of species, communities, soil, crops, urban ecosystems), application (education, infrastructure), and implementation (policies) that will feed back on nature within cities.

Concluding remarks

In this first horizon scan for urban evolutionary ecology research, a core team of diverse researchers prioritized over 700 research questions into 30 key questions and grouped them into six major themes.

These themes highlight the important topics and breadth of research directions that are priorities for future investigation. For example, fundamental processes such as species interactions and mutation rates might be uniquely affected within and among urbanized areas. Additionally, eco-evolutionary feedbacks could have applied implications in the context of climate change and sustainability given the global extent of rapid urbanization and its local and regional impacts [START_REF]Global Environment for Cities-GEO for Cities: Towards Green and Just Cities[END_REF]. We anticipate that innovations in technology and methodology in addressing large and diverse datasets will emerge from these research directions. In addition, it will be vital to not only integrate ethical considerations into these research areas, but also to evaluate how social and political biases associated with race, culture, and religion directly feed back into urban evolutionary ecology outcomes.

Because cities are globally distributed across diverse cultures and histories, this study is a reminder of the need for international collaborations to rebalance our perspective [START_REF] Hughes | Just urban transitions: Toward a research agenda[END_REF]. For example, regions of China and the former Soviet republics are urbanizing rapidly, yet knowledge of the ecological and evolutionary dynamics of those landscapes is limited [START_REF] Jiang | Urban pluvial flooding and stormwater management: A contemporary review of China's challenges and "sponge cities" strategy[END_REF]. Collaboration between scholars from the Global South and Global North is necessary, and evolutionary ecologists in the North (especially Englishlanguage writers) need to take better stock of research conducted in other parts of the world and published in other languages [START_REF] Khelifa | A solution for breaking the language barrier[END_REF]. Because cities are best viewed as social-ecological-technological systems [START_REF] Markolf | Interdependent infrastructure as linked social, ecological, and technological systems (SETSs) to address lock-in and enhance resilience[END_REF], interdisciplinary collaborations will help address fundamental questions in urban evolutionary ecology while ensuring that cities develop in ways that benefit both humans and other organisms.

There are multiple challenges to realizing these research priorities. Accounting for heterogeneity among cities is one such challenge, as are the needs to consider historical contexts and socio-political, economic, and racist legacies, even when studying evolutionary ecology. This means confronting financial, social, and geographic barriers to research, particularly in regions with limited resources and infrastructure. Horizon scans are designed to prioritize future research directions, yet we also must recognize research of high importance today. For example, this scan highlighted current global issues, such as social injustice and the COVID-19 pandemic, and their potential scaled effects on urban evolutionary ecology. In this respect, we recognize the need to constantly revise these research priorities to changes in the global landscape.

Despite the challenge, research in urban evolutionary ecology offers opportunities for advancing fundamental and applied science. First, the concentration of diverse people and non-human biota in urban-built environments facilitates new collaborations to incorporate insights from disciplines across the life and social sciences, as well as physical sciences (e.g., climate scholars) and humanities (e.g., architects and historians) [START_REF] Des Roches | Socio-eco-evolutionary dynamics in cities[END_REF][START_REF] Schell | The ecological and evolutionary consequences of systemic racism in urban environments[END_REF][START_REF] Mcphearson | Advancing urban ecology toward a science of cities[END_REF]. Second, while frequent and ongoing management actions in cities provide challenges to urban research [START_REF] Aronson | Biodiversity in the city: key challenges for urban green space management[END_REF], cities may also offer future opportunities for designing field manipulations that are challenging in natural areas. For example, new parks might alternate between connected and unconnected patches to test hypotheses about connectivity without needing to alter rural habitats. Third, research in cities offers the potential of new-found socio-ecological, and not just biological discoveries, to enhance human well-being and improve socio-political issues in urban settings where the majority of people are projected to reside in the coming decades [START_REF] Kardan | Neighborhood greenspace and health in a large urban center[END_REF]. Ultimately, these opportunities could expose city dwellers to the excitement of evolutionary ecology, such as through community science activities, and encourage them to pursue careers in these disciplines.

Box 1. Horizon scan protocol

Our horizon scan used a modified Delphi technique [START_REF] Mukherjee | The Delphi technique in ecology and biological conservation: applications and guidelines[END_REF], consistent with previous horizon scans [START_REF] Ricciardi | Invasion science: A horizon scan of emerging challenges and opportunities[END_REF][START_REF] Sutherland | A horizon scan of global biological conservation issues for 2022[END_REF].

The main objective of this technique is to conduct iterative evaluations of survey responses (Figure I).

From an international research network on urban eco-evolutionary dynamics (see "Acknowledgements"), 24 individuals established the "core" group, with an additional five invited from outside this network to balance backgrounds in ecology, evolutionary biology, environmental science, anthropology, urban planning, policy, and sustainability. The core group (29 authors here) oversaw the horizon-scanning protocol, which generated the survey, identified survey participants, evaluated the survey responses, and provided synthesis for a publication. The survey (Table S1) was designed for participants to provide questions in ecology and evolutionary biology in urban areas for future research directions. The survey also collected voluntary demographic information, anonymized through statistical aggregation, so that responses could not be tied to individual participants.

In September 2020, the survey was emailed to 420 potential participants from 33 countries representing six continents, with responses from 100 participants from 25 countries (Table S2). Our protocol (Figure I) identified potential survey participants from review of the literature on urban ecology and evolutionary biology, with care taken to balance diversity in demographics (e.g., career stage, geography, and discipline) when possible. The 100 respondents provided over 700 questions, which were curated for clarity (e.g., redundancies removed) by a team of seven core individuals. A curated list of 75 questions was presented to the 29 core participants via email to score from 1 (highest) to 5 (lowest) for each of "novelty" and "importance" in urban ecology and evolutionary biology. Input on "novelty" reflected areas not investigated or not thoroughly (e.g., across diverse taxa, geographic areas), whereas, "importance" reflected areas that while possibly not novel, are highly valued in the literature and need attention. A three-day virtual workshop was held in November 2020 for several rounds of small break-out groups and anonymous voting among the 29 core participants in discussing and editing the submitted questions to reach a consensus. A list of 30 questions emerged that were ranked 1-30 by each core participant post-workshop. Consistent with previous horizon scans, the median rank for each question was used to determine the final list (Table 1 & Figure 2). After the final ranking, feedback was collected from the core participants to bin and summarize the questions into "themes" that focused the research directions.

Box 2. Backgrounds of survey participants

The demographic and disciplinary backgrounds of the 100 survey participants are likely to influence their responses. Although the number of countries from Europe was more represented compared to other continents, more than half of the survey participants came from North America (Table S2). Six countries and 12% of survey participants are from the Global South. Although this sample is geographically biased with respect to total population distribution, it does reflect the distribution of current researchers [START_REF] Goddard | A global horizon scan of the future impacts of robotics and autonomous systems on urban ecosystems[END_REF]; researchers from the Global North dominate the field of urban ecology [START_REF] Dobbs | Urban ecosystem services in Latin America: mismatch between global concepts and regional realities?[END_REF]. Although survey participants may reflect the current research domain, they do not represent the overall urban landscape, especially in developing nations. This potential bias could influence the core participants' opinions of research at local scales. For example, while the theme on innovations in technology and methodology discusses research likely to be impactful at a global scale, how it may solve specific problems between and even within areas of North America and Africa was not discussed. Future research directions and their alignment with challenges across socio-political structures needs to involve greater representation in decision-making [START_REF] Schell | The ecological and evolutionary consequences of systemic racism in urban environments[END_REF], as discussed in our concluding remarks. Our horizon scan prioritized this issue, as the top-ranked question was focused on social inequalities and their impact on eco-evolutionary dynamics within cities (Table 1 & Figure 2).

The high variance associated with the ranked questions (Figure 2) reflects the diverse disciplinary backgrounds of survey participants. It is not surprising that just over 90% of the participants used the words "ecology" or "evolution" to describe their expertise (Table S3). However, while a very small number of participants used additional descriptors for "evolution" (e.g., "evolutionary geneticist"), over half of the participants who used "ecologist" used at least one, and some as many as three additional descriptors (e.g., "urban/wetland/ecosystem ecologist"). Finally, while 22% of the participants used the word "urban" to define their expertise, the vast majority of this latter group describe themselves as "urban ecologists/evolutionary ecologists", and never as "urban evolutionary biologists" alone (Figure S1). These results reflect a growing and emerging discipline previously dominated by urban ecologists [START_REF] Rivkin | A roadmap for urban evolutionary ecology[END_REF]. Just as evolutionary biologists, who were not initially focused on urban ecosystems, have entered the field more recently, we anticipate further diversification of the fieldwith other disciplines, such as engineering, social sciences, and medicine, pursuing the research directions outlined here. What are the effects of urbanization on somatic and gametic mutation rates, and how do we mitigate elevated mutation rates in cities?

Under what conditions will urbanization promote or impede speciation, and how does urbanization impact speciation rates?

How does urbanization influence the (co)evolution of species interactions, and do species interactions exacerbate or ameliorate selective pressures associated with urbanization?

To what extent has urbanization led to the evolution of new commensal species, including those that are selfdomesticating?

How can cities enhance global eco-evolutionary potential by altering intraspecific and interspecific interactions?

How do urban areas act as genetic sources or sinks in preserving biodiversity?

How is sexual selection altered by urbanization?

Spatial & temporal scales of drivers and responses (Scales)

What is the relative importance of evolution in cities in affecting the magnitude and direction of ecological dynamics and patterns, especially compared to non-evolutionary drivers in cities?

6

What is the spatial and temporal scale of eco-evolutionary dynamics, including in deep time, and how does it differ between urban habitats compared to other non-urban habitats?

8

How does rapid evolution differ between established and newly-developing cities?

What are the relative strengths of individual and interactive effects of drivers of evolution in cities, both genetic and cultural, and do they vary among taxa and across cities?

How does heterogeneity both within the urban environment and between urban and non-urban environments influence eco-evolutionary dynamics?

To what extent can eco-evolutionary signatures that we observe in cities tell us about eco-evolutionary trends at the global scale?

Sustainability, health, & wellbeing (Sustainability)

How do pathogens that cause human disease adapt to the urban environment and how does rewilding and restoration alter our ability to fight disease outbreaks? 2 How can we harness urban microbiomes for human wellbeing, for improved soil health and productivity, and to create more sustainable approaches to inform eco-evolutionary dynamics in terrestrial and aquatic systems? To what extent does variation among political systems and governance predict evolutionary responses to, and biodiversity of, urban environments? 3 How does both biological and cultural evolution in humans differ in the past, present, and in the future, and how does that human evolution feed back to affect the development of cities and cultures? 7 How does expanding/enhancing empathy for nature and blue-green infrastructure alter eco-evolutionary processes in urban environments? How do human diets and behavior impact food webs in urban environments that alter eco-evolutionary dynamics?

How can we more effectively collaborate across disciplines and with communities to incorporate ethics and human cultural sensitivity into the study of urban evolutionary ecology and the implementation and dissemination of research findings? What role or responsibility do we have as humans for seeking to influence urban eco-evolutionary outcomes? What role does human society and culture, underpinning the preference and artificial selection for novel traits in pets and ornamentals, have on evolutionary ecology within and among cities?

Innovation in technology & methodology (Technology)

What role do genetic manipulations, including genetic engineering, gene editing, and artificial selection, have on the evolution of organisms including humans, and their impact on society and the urban environment? 4

Will there be synthetic organisms (e.g., drones, robots) that are capable of adapting to the urban environment independent of humans, and if so, how will they reshape the natural environment? How can automated, high-throughput data collection in cities be used as input to artificial intelligence (AI) to enable discovery and implementation of nature-based solutions?

How can mathematical theory and data synthesis be used to predict urban eco-evolutionary feedbacks? Figure 1. Emerging research themes in urban evolutionary ecology. Six themes were identified that summarized the 30 questions ranked by core participants (see Box 1 for methods). Keywords reflecting the questions are shown circling a visual reflection of each of the six themes (see Table 1 for the list of questions and their theme names).

Figure 2. Rank and variance of questions with their themes for research in urban evolutionary ecology.

Boxplots reflect the median ranks of the 30 questions by the 29 core participants (see Table 1). Box limits indicate the 25th and 75th percentiles, whiskers extend 1.5 times the interquartile range from the 25th and 75th percentiles, and outliers are represented by dots.

• The impact of urbanization on biodiversity has been well-documented, yet research into the complex dynamics of ecological and evolutionary processes in urban areas is still in its infancy.

• When novel research challenges emerge, a horizon scan exercise is an integrated approach that brings together global interdisciplinary-minded individuals to identify future research questions that can influence new collaborations and funding agenda.

• Our horizon scan identified 30 questions for future research in urban evolutionary ecology covering themes in fundamental ecological and evolutionary processes, temporal and spatial scales, sustainability, climate change, socio-political and ethical considerations, and innovation in technology. S3), we examined the number of individuals using any form of the the word "ecology" (eco), "evolution" (evo), or "urban". For example, 31 individuals used the word "ecology" without "evolution" or "urban", whereas, only 6 individuals used the words "ecology", "evolution", and "urban".

Figure I .

 I Figure I. Protocol summary for identifying and reviewing questions for the horizon scan exercise.

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  How can eco-evolutionary understanding contribute to the implementation of the Sustainable Development Goals (SDGs), and how will the SDGs influence eco-evolutionary dynamics in cities in different global contexts? change and urbanization interact to alter eco-evolutionary dynamics in terms of extreme weather effects on biodiversity and societal consequences in the past and future? 5What is the effect of urbanization on ecology and evolution in aquatic environments, especially in the context of artificial aquatic infrastructure such as harbors and submersion of cities due to rising sea levels? magnitude of effect of social inequality and systemic oppression in driving ecological and evolutionary dynamics in cities, and how do we ethically and empirically quantify and test this?

1

 1

Figure 1

 1 Figure 1

Figure 2

 2 Figure 2

Figure I

 I Figure I

Figure S1 .

 S1 Figure S1. Intersection of keywords reflecting reported expertise of survey respondents. From the keywords provided by 94 of the 100 respondents (see TableS3), we examined the number of individuals using any form of the the word "ecology" (eco), "evolution" (evo), or "urban". For example, 31 individuals used the word "ecology" without "evolution" or "urban", whereas, only 6 individuals used the words "ecology", "evolution", and "urban".

Table 1 . Ranked questions and their themes for research in urban evolutionary ecology. 408

 1

	Themes	Questions	Rank
	Fundamental
	processes &
	mechanisms
	(Processes)

Table S3 . Keywords provided by survey participants in response to how they would describe their professional/research expertise (94 reporting of 100 respondents).

 S3

		plant geneticist ecologist	quantitative geneticist	population geneticist
		evolutionary biologist ecologist	ecologist	population genetics
	Participant	keyword (1) household ecology ecologist archaeologist ecologist and ecophysiologist	keyword (2) cities anthropologist	rapid evolution keyword (3) social scientist
	1	ecologist conservation biologist environmental engineer	science policy evolutionary biologist	animal behaviour urban ecologist
	2	evolutionary biolgy evolutionary biology evolutionary biologist	genetics population genomics	animal behaviour urban ecology
	3	insect ecophysiologist urban ecology evolutionary ecologist	evolutionary ecologist urban biodiversity	behavioral ecologist urban environmental planning
	4	molecular ecologist urban evolutionary biologist evolutionary ecologist	population geneticist urban biologist	behavioral ecologist urban evolutionary ecologist
	5	ecologist ecologist evolutionary ecologist	ecophysiologist forester	behavioural ecologist urban planning
	6	ecologist ecosystems ecologist historical ecologist	microbiologist urban ecologist	biochemist wetland ecologist
	7	evolutionary ecology evolutionary biologist plant evolutionary biologist	population genomics ecologist	biodiversity wildlands manager
	8	landscape ecology ornithologist urban ecology	anthropology/archaeology urban ecologist	climate change wildlife scientist
	9	ecologist ethologist urban ecology	urban design urban ecologist	community scientist zoologist
		population geneticist evolutionary biologist	evolutionary biologist behavioural ecologist	computational biologist
		contemporary evolution urban wildlife planner	eco-evolutionary dynamics biologist	conservation genetics
		evolutionary ecologist population biologist	invertebrate zoologist ecologist	data science
		ecologist ecologist	species interactions entomologist	dispersal
		genetics/ genomics behavioural ecologist	molecular biology evolutionary biologist	ecology
		plant ecologist botanist landscape ecologist ecologist ecologist evolutionary ecologist evolutionary ecologist evolutionary ecologist ecology	plant ecophysiologist evolutionary biologist urban ecologist evolutionary biologist environmental science evolutionary biologist biologist evolutionary biologist evolutionary biology	ecosystem processes ecosystem service ecosystem services empirical
		ecologist ecologist	biostatistician insects	entomologist
		community ecologist ecologist	global change ecologist interdisciplinary	evolutionary ecologist
		ecologist urban ecologist	behavioral ecologist landscape ecologist	evolutionary ecologist
		population geneticist landscape ecologist	human evolution landscape geneticist	evolutionary ecologist
		urban ecologist ecologist	ecotoxicologist lepidopterist	evolutionary ecologist
		urban ecologist archaeologist	landscape ecologist modeler	geography
		ecologist restoration ecologist	evolutionary biologist plant ecology	global change
		ecologist evolutionary biologist	landscape geneticist population genetics	herpetologist
		community ecologist evolutionary geneticist	applied ecologist protistologist	insect biologist
		environmental scientist evolutionary ecologist	landscape ecologist quantitative geneticist	land change dynamics
		ecologist geographer	urban ecologist remote sensing	landscape ecologist
		ecologist forester	community ecology socio-ecologist	landscape ecology
		evolutionary ecologist evolutionary ecologist	species interactions theoretician	mutualism
		evolutionary ecologist evolutionary ecologist	quantitative geneticist urban evolutionary biology	ornithologist
		anthropology evolutionary ecologist	hazards/ disasters urban evolutionary ecologist	philosophy
		animal ecologist environmental policy	evolutionary ecologist urban politics	physiologist
		evolutionary biologist ecologist	botanist	plant
		quantitative geneticist ecologist	population geneticist	plant
		evolutionary ecologist ecologist	botanist	plant-insect
		evolutionary ecology ecologist	community ecology	plant-insect interactions
			5 6

Acknowledgments

There is not a separate section for "Outstanding Questions" for our submission. In accordance with a standard "horizon scan", the main objective of our study is to collect recommendations and analyze questions for future research. This list of questions can be found in Table 1.

Author response: Thank you for seeing this. The continent names are now appropriately justified.

Reviewers' Comments:

Reviewer #3: Verrelli et al. present a horizon scan of urban evolutionary ecology and address key questions for the future of urban evolutionary ecology. The revisions to the methodology address much of the reviewers questions. However, I do not agree with the authors' decision to not publish the survey. The original survey that was sent out to the 420 participants (e.g., how the open-ended questions were asked, the demographic questions and possible responses) should be published in the supplementary material, as is common in publications that utilize survey methodology. Many horizon scans minimally publish this information, as well as the responses (e.g., your 709 questions), and each step of distilled responses (e.g., your 75 questions), all of which are needed here.

Author response:

We have made the survey questions that were analyzed available in Supplementary Information Table S1, which is now cited in Box 1 (line 352).

Other points:

1. "novelty" and "importance" are still not defined in Box 1.

Author response:

We have now provided a sentence to clarify in Box 1 (line 363): "Input on "novelty" reflected questions not investigated or not thoroughly (e.g., across diverse taxa, geographic areas), whereas, "importance" reflected questions that while possibly not novel, are highly valued in the literature and need attention." 2. rewilding vs. urban greening. This has been clarified in the text, but the Figure still has "rewilding". I see that the question specifically addresses rewilding and restoration, so leaving "rewilding" in the figure works, but I would argue that urban greening as a whole is more impactful on urban ecological and evolutionary processes as rewilding is a very small part of urban greenspace design, management, etc.

Response to Reviewers

Also, not to be too picky, but the picture you chose for this is a designed garden, not a "rewilding", so this also confuses your point.

Author response: We agree that "rewilding" may currently be a "very small part of urban greenspace design" as the reviewer says here; however, we note that in looking forward on the "horizon" (i.e., not current research), our review of the questions submitted found several focused on novel ways to "rewild" urban areas. One example is the microbiome research we noted as a novel direction in rewilding. Lastly, we will note that the picture provided for "rewilding" in Figure 1 can indeed be an example of "rewilding". For example, although it may be a garden design, the intention here (as we noted in the text) could be to design urban spaces that "rewild" areas for pollinators in new ecological interactions within cities.

3. still not following the empathy argument -particularly where it comes to "moral responsibility of researchers" as your examples are not specific to research fields, but to policy and management actions.

Author response: We have several individuals within our core group who participate in socio-cultural research in urban areas and its impact on eco-evolutionary outcomes. This growing literature (as cited) and our review of it shows that humans often make decisions that come from "moral and motivational" perspectives, as we note. That is, the "moral dilemma" as we point out is whether researchers make decisions in urban areas that consider not just research outcomes but socio-cultural impacts they have, and downstream, how these decisions can affect eco-evolutionary outcomes. We previously provided specific examples in the text in this theme that are not just policy-or management-related but also related to the "adaptive landscape" to help explain what these eco-evolutionary outcomes related to moral decisions could be in the future. [START_REF]World Urbanization Prospects: The 2018 Revision (ST/ESA/SER.A/420)[END_REF]. Line 281 -while I whole-heartedly agree with this paragraph, I argue one way to address these issues is to start at the top -with the author list. Inviting scientists from institutions in these underrepresented regions into these types of working groups and co-authoring is key to incorporating diverse sociopolitical, cultural and scientific perspectives.

Author response:

We completely agree that incorporating diversity from ethnic, geographic, and discipline perspectives at the top is the way to go. This point is reflected in this noted paragraph in the concluding remarks of "…this study is a reminder of the need for international collaborations to rebalance our perspective" and "Collaboration between scholars from the Global South and Global North is necessary". Additionally, in Box 2 we also discuss specifically the inherent bias of survey and core participants in horizon scans when current research groups do not match the current landscape, something pointed out by other horizon scans too (and which we cited). In this respect, to the best of our ability, our recruitment for the core group over many months did prioritize diversity in all three of these areas of ethnicity, geography, and discipline consistent with whom is currently conducting urban eco-evo research across career stages. In fact, our consortium and this horizon scan has built new bridges and brought in new students from backgrounds with which we had previously not interacted. Thus, these movements bring new hope and we strongly embrace future opportunities with those in the field as diversity continues to grow with this expanding discipline.