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Denitrification causes loss of available nitrogen from soil systems, thereby reducing crop productivity and increasing reliance on agrochemicals. The dynamics of denitrification and denitrifying communities are thought to be altered by land management practices, which affect the physicochemical properties of the soil. In this study, we look at the effects of long-term tillage and fertilization regimes on arable soils following 16 years of treatment in a factorial field trial. By studying the bacterial community composition based on 16S rRNA amplicons, absolute bacterial abundance and diversity of denitrification functional genes (nirK, nirS and nosZ), under conditions of minimum/conventional tillage and organic/synthetic mineral fertilizer, we tested how specific land management histories affect the diversity and distribution of both bacteria and denitrification genes. Bacterial and denitrifier communities were largely unaffected by land management history and clustered predominantly by spatial location, indicating that the variability in bacterial community composition in these arable soils is governed by innate environmental differences and Euclidean distance rather than agricultural management intervention.

In response to environmental stimuli, including variation in the presence of conspecifics, genotypes show highly plastic responses in behavioral and physiological traits influencing reproduction. Although extensively documented in males, such female responses are rather less studied. We expect females to be highly responsive to environmental variation and to differentially allocate resources to increase offspring fitness, given the major contribution of mothers to offspring number, size, and developmental conditions. Using Drosophila melanogaster, we (a) manipulate exposure to conspecific females, which mothers could use to anticipate the number of potential mates and larval density, and; (b) test how this interacts with the spatial distribution of potential oviposition sites, with females from higher densities expected to prefer clustered resources that can support a larger number of larvae. We found that high density females were slower to start copulating and reduced their copulation duration, the opposite effect to that observed in males. There was a parallel, perhaps related, effect on egg production: females previously housed in groups laid fewer eggs than those housed in solitude. Resource patchiness also influenced oviposition behavior: females preferred aggregated substrate, which attracted more females to lay eggs. However, we found no interaction between prior housing conditions and resource patchiness, indicating that females did not perceive the value of different resource distributions differently when exposed to environments that could signal expected levels of larval competition. We show that, although exposure to consexual competition changes copulatory behaviors of females, the distribution of oviposition resources has a greater effect on oviposition decisions., When choosing how many eggs to produce, female fruit flies must consider the physical environment and the likely level of competition their offspring will face. Females raised with other females were slower to mate, mated for less time, and laid fewer eggs. However, when choosing where to lay, patchiness of laying sites had a greater impact than social environment: clustered resources attracted more females, who laid on more of the available patches.

Many species advertise their unique identity to conspecifics using dedicated individuality signals: one familiar example is human faces. But how unique in the global population do these signals need to be? While human faces are highly variable, each person interacts with many fewer individuals than are found in the total population. This raises the question of how evolutionary mechanisms drive up population-wide diversity when selection occurs at such a local level. We use an individual-based model in which individuals broadcast their identity and quality in separate, genetically-coded signals. Mimicking, for example, scent marking mammal species, females in the model assess males using the quality signal, then attempt to relocate the highest quality male using his identity signal. We ask how population fragmentation affects genetic diversity in the individual identity-signalling region under sexual selection, predicting one of two opposing outcomes: 1) divided populations evolve fewer signal variants globally, since repetition of signals is not costly when individuals interact only with local conspecifics, or 2) stochasticity in mutation and selection cause divergence among subpopulations, increasing the global number of signal variants. We show that local selection drives up global genetic diversity substantially in fragmented populations, even with extremely low rates of dispersal. Because new signal variants arise by mutation and then sweep through their subpopulation, a fragmented population has more global signal variation. This result furthers our understanding of how high levels of diversity in individuality signals are maintained.

Archaeological evidence suggests that important shifts were taking place in the character of human social behaviours 300,000 to 30,000 years ago. New artefact types appear and are disseminated with greater frequency. Transfers of both raw materials and finished artefacts take place over increasing distances, implying larger scales of regional mobility and more frequent and friendlier interactions between different communities. Whilst these changes occur during a period of increasing environmental variability, the relationship between ecological changes and transformations in social behaviours is elusive. Here, we explore a possible theoretical approach and methodology for understanding how ecological contexts can influence selection pressures acting on intergroup social behaviours. We focus on the relative advantages and disadvantages of intergroup tolerance in different ecological contexts using agent-based modelling (ABM). We assess the relative costs and benefits of different ‘tolerance’ levels in between-group interactions on survival and resource exploitation in different environments. The results enable us to infer a potential relationship between ecological changes and proposed changes in between-group behavioural dynamics. We conclude that increasingly harsh environments may have driven changes in hormonal and emotional responses in humans leading to increasing intergroup tolerance, i.e. transformations in social behaviour associated with ‘self-domestication’. We argue that changes in intergroup tolerance is a more parsimonious explanation for the emergence of what has been seen as ‘modern human behaviour’ than changes in hard aspects of cognition or other factors such as cognitive adaptability or population size. Supplementary Information The online version contains supplementary material available at 10.1007/s10816-020-09503-5.

In response to environmental stimuli, including variation in the presence of conspecifics, animals show highly plastic responses in behavioural and physiological traits influencing reproduction. These responses have been extensively documented in males, but equivalent study of females is so far lacking. We expect females to be highly responsive to environmental variation, with significant impacts on fitness given females’ direct impact on offspring number, size, and developmental conditions. Using Drosophila melanogaster as a model, we manipulate (a) exposure to conspecific females, expected to influence their expectation of number of potential mates and larval density for their own offspring, and (b) test how prior consexual population density interacts with the spatial distribution of potential oviposition sites, with females expected to prefer clustered food resources that can support a larger number of eggs and larvae. After exposure to competition, females were slower to start copulating and reduced their copulation duration – the opposite effect to that observed in males previously exposed to rivals. There was a parallel and perhaps related effect on egg production, with females previously housed in groups laying fewer eggs than those that were housed in solitude. The spatial distribution of resources also influenced oviposition behaviour: females clearly preferred aggregated patches of substrate, being more likely to lay, and laying on more of the available patches, in the clustered environment. However, we found no significant interaction between prior housing conditions and resource patchiness, indicating that females did not perceive the value of different resource distributions differently when they were expecting either high or low levels of larval competition. While exposure to consexual competition influences copulatory behaviours, it is the distribution of oviposition resources that has a greater impact on oviposition decisions.

Increasingly imperative objectives in ecology are to understand and forecast population dynamic and evolutionary responses to seasonal environmental variation and change. Such population and evolutionary dynamics result from immediate and lagged responses of all key life-history traits, and resulting demographic rates that affect population growth rate, to seasonal environmental conditions and population density. However, existing population dynamic and eco-evolutionary theory and models have not yet fully encompassed within-individual and among-individual variation, covariation, structure and heterogeneity, and ongoing evolution, in a critical life-history trait that allows individuals to respond to seasonal environmental conditions: seasonal migration. Meanwhile, empirical studies aided by new animal-tracking technologies are increasingly demonstrating substantial within-population variation in the occurrence and form of migration versus year-round residence, generating diverse forms of 'partial migration' spanning diverse species, habitats and spatial scales. Such partially migratory systems form a continuum between the extreme scenarios of full migration and full year-round residence, and are commonplace in nature. Here, we first review basic scenarios of partial migration and associated models designed to identify conditions that facilitate the maintenance of migratory polymorphism. We highlight that such models have been fundamental to the development of partial migration theory, but are spatially and demographically simplistic compared to the rich bodies of population dynamic theory and models that consider spatially structured populations with dispersal but no migration, or consider populations experiencing strong seasonality and full obligate migration. Second, to provide an overarching conceptual framework for spatio-temporal population dynamics, we define a 'partially migratory meta-population' system as a spatially structured set of locations that can be occupied by different sets of resident and migrant individuals in different seasons, and where locations that can support reproduction can also be linked by dispersal. We outline key forms of within-individual and among-individual variation and structure in migration that could arise within such systems and interact with variation in individual survival, reproduction and dispersal to create complex population dynamics and evolutionary responses across locations, seasons, years and generations. Third, we review approaches by which population dynamic and eco-evolutionary models could be developed to test hypotheses regarding the dynamics and persistence of partially migratory meta-populations given diverse forms of seasonal environmental variation and change, and to forecast system-specific dynamics. To demonstrate one such approach, we use an evolutionary individual-based model to illustrate that multiple forms of partial migration can readily co-exist in a simple spatially structured landscape. Finally, we summarise recent empirical studies that demonstrate key components of demographic structure in partial migration, and demonstrate diverse associations with reproduction and survival. We thereby identify key theoretical and empirical knowledge gaps that remain, and consider multiple complementary approaches by which these gaps can be filled in order to elucidate population dynamic and eco-evolutionary responses to spatio-temporal seasonal environmental variation and change.

Conjugative plasmids are widespread and play an important role in bacterial evolution by accelerating adaptation through horizontal gene transfer. However, explaining the long-term stability of plasmids remains challenging because segregational loss and the costs of plasmid carriage should drive the loss of plasmids though purifying selection. Theoretical and experimental studies suggest two key evolutionary routes to plasmid stability: First, the evolution of high conjugation rates would allow plasmids to survive through horizontal transmission as infectious agents, and second, compensatory evolution to ameliorate the cost of plasmid carriage can weaken purifying selection against plasmids. How these two evolutionary strategies for plasmid stability interact is unclear. Here, we summarise the literature on the evolution of plasmid stability and then use individual based modelling to investigate the evolutionary interplay between the evolution of plasmid conjugation rate and cost amelioration. We find that, individually, both strategies promote plasmid stability, and that they act together to increase the likelihood of plasmid survival. However, due to the inherent costs of increasing conjugation rate, particularly where conjugation is unlikely to be successful, our model predicts that amelioration is the more likely long-term solution to evolving stable bacteria-plasmid associations. Our model therefore suggests that bacteria-plasmid relationships should evolve towards lower plasmid costs that may forestall the evolution of highly conjugative, ‘infectious’ plasmids.

Evidence of care for the ill and injured amongst Neanderthals, inferred through skeletal evidence for survival from severe illness and injury, is widely accepted. However, healthcare practices have been viewed primarily as an example of complex cultural behaviour, often discussed alongside symbolism or mortuary practices. Here we argue that care for the ill and injured is likely to have a long evolutionary history and to have been highly effective in improving health and reducing mortality risks. Healthcare provisioning can thus be understood alongside other collaborative ‘risk pooling’ strategies such as collaborative hunting, food sharing and collaborative parenting. For Neanderthals in particular the selective advantages of healthcare provisioning would have been elevated by a variety of ecological conditions which increased the risk of injury as well their particular behavioural adaptations which affected the benefits of promoting survival from injury and illness. We argue that healthcare provisioning was not only a more significant evolutionary adaptation than has previously been acknowledged, but moreover may also have been essential to Neanderthal occupation at the limits of the North Temperate Zone.

Community profiling is one of the most utilised tools in microbial ecology today. The relationships between microbial communities and their environment affect ecosystem function in fields spanning from medicine to agriculture; and understanding the community dynamics of a microbial community is key to understanding the complex effects of human intervention. In this study, we look at the effects of long-term tillage and fertilization regimes in soils from an agricultural block-designed field trial set up in 2001. By studying the microbial community composition, absolute microbial abundance and diversity of denitrification functional genes in the context of environmental data, we were able to address the question of how specific land management histories affect the diversity and distribution of bacteria and denitrification genes within agricultural soils. It was found that microbial communities appear to be largely unaffected by land management history, and cluster predominantly by spatial location within the field, despite lack of significant environmental variation. In this well-established agricultural field trial, Euclidean distance is the major identifiable determinant of microbial community dissimilarity (as well as dissimilarity in microbial abundance). That ecological drift, rather than physicochemical factors can be the major determinant of genetic potential may have consequences for attempts to understand nutrient availability in agricultural systems. Additionally, the overwhelming variation caused by spatial distance indicates that block designed experiments may not always have sufficient statistical power to identify any effects of human treatment.

Dispersal and migration are superficially similar large-scale movements, but which appear to differ in terms of inter-individual behavioural synchronization. Seasonal migration is a striking example of coordinated behaviour, enabling animal populations to track spatio-temporal variation in ecological conditions. By contrast, for dispersal, while social context may influence an individual's emigration and settlement decisions, transience is believed to be mostly a solitary behaviour. Here, we review differences in drivers that may explain why migration appears to be more synchronized than dispersal. We derive the prediction that the contrast in the importance of behavioural synchronization between dispersal and migration is linked to differences in the selection pressures that drive their respective evolution. Although documented examples of collective dispersal are rare, this behaviour may be more common than currently believed, with important consequences for eco-evolutionary dynamics. Crucially, to date, there is little available theory for predicting when we should expect collective dispersal to evolve, and we also lack empirical data to test predictions across species. By reviewing the state of the art in research on migration and collective movements, we identify how we can harness these advances, both in terms of theory and data collection, to broaden our understanding of synchronized dispersal and its importance in the context of global change.

Summary Identifying how microbes are able to manipulate, survive, and thrive in complex multispecies communities has expanded our understanding of how microbial ecosystems impact human health and the environment. The ability of bacteria to negatively affect neighbors, through explicit toxin delivery systems, provides them with an opportunity to manipulate the composition of growing microbial communities. Contact-dependent inhibition (CDI) systems (a Type Vb secretion system) are a distinct subset of competition systems whose contribution to shaping the development of spatially structured bacterial communities are yet to be fully understood. Here, we compare the impact of different CDI systems, at both the single-cell and population level, to determine the key drivers of CDI-mediated competition within spatially structured bacterial populations. Through an iterative approach using both an Escherichia coli experimental system and computational modeling, we show that CDI systems have subtle and system-specific effects at the single-cell level, generating single-cell-wide boundaries between CDI-expressing inhibitor cells and their neighboring targets. Despite the subtle effects of CDI at a single-cell level, CDI systems greatly diminished the ability of susceptible targets to expand their range during colony growth. The inoculum density of the population, together with the CDI system-specific variables of the speed of inhibition after contact and biological cost of CDI, strongly affects CDI-mediated competition. In contrast, the magnitude of the toxin-induced growth retardation of target cells only weakly impacts the composition of the population. Our work reveals how distinct CDI systems can differentially affect the composition and spatial arrangement of bacterial populations., Highlights • CDI causes subtle growth inhibition in a subset of contacted target cells • Model describes and predicts observed effects on spatial distribution of strains • CDI facilitates success of inhibitor strain increasing population patch size • A CDI system’s inhibition rate dominates toxicity in driving competition outcome, Bottery et al. use an interdisciplinary approach to analyze contact-dependent inhibition in bacteria. CDI-dependent growth rate reduction is subtle but facilitates increased patch size for inhibitor cells in competitions on solid media. Of the variables impacting outcome, it is striking that the CDI system’s inhibition rate dominates toxicity.

Improving our capacity for predicting range shifts requires improved theory exploring the interplay between ecological and evolutionary processes and the (changing) environment. We introduce an individual-based model incorporating simple stage structure and genetically determined resource allocation rules. Population dynamics are mediated by the resources available and the individual's genetics, and density dependence emerges solely as a consequence of resource levels decreasing as population density increases. Running the model for a set of stylised range-expansion scenarios reveals the extent to which eco-evolutionary processes can matter: spatial assortment of individuals possessing effective range expansion strategies (higher dispersal propensity, semelparity rather than iteroparity) can substantially accelerate range advance, and this is more important than the contribution of novel mutations arising during range expansion. In simulations of range expansion there is a greater risk of extinction when all individuals are given the mean strategy evolved in a stationary range. Additionally, our results demonstrate that the erosion of inter-individual variability during a range-shift can depress population abundance for lengthy periods, even after the climate has stabilised. Our theoretical results highlight the importance of accounting for inter-individual variability in future predictive modelling of species' responses to environmental change.

Postcopulatory sexual selection arising from female multiple mating leads to the evolution of ejaculates that maximize a male's reproductive success under sperm competition. Where the risk of sperm competition is variable, optimal fitness may be achieved by plastically altering ejaculate characteristics in response to the prevailing sperm competition environment. In the model species Drosophila melanogaster, males expecting to encounter sperm competition mate for longer and transfer more accessory proteins and sperm. Here we show that after being housed with a single rival for one week, the seminal vesicles of male D. melanogaster contain a significantly greater proportion of live sperm than those of males maintained alone, indicating adaptive adjustment of sperm quality in response to the perceived risk of sperm competition. This effect is due to an increase in the number of live sperm produced, indicating that males upregulate sperm production in response to the presence of rivals. Our data suggest that males show plasticity in the rate of spermatogenesis that is adaptive in the context of a fluctuating sperm competition environment.

Aim: As the global climate is changing rapidly, there is a need to make conservation decisions to facilitate species' persistence under climate change. Models employed to make predictions regarding the impacts of climate change on species' distributions, and ultimately persistence, typically assume that interannual variability in environmental conditions is independent between years. However, the colour of environmental noise has been shown to affect extinction risk in populations occupying spatially static environments, and should therefore affect persistence during climate change. This study aims to investigate the importance of noise colour for extinction risk during climate-induced range shifts. Methods: We use a spatially explicit coupled map lattice with a latitudinal gradient in climatic suitability, together with time series of environmental noise, to simulate periods of directional climate change and investigate the effects of noise colour on extinction risk and range size. Results: Extinction risk increases with reddening of the environmental noise, and this effect is particularly pronounced over short time frames when climate change is rapid. Main conclusions: Given that management decisions are typically made over such short time frames, and the rapid rates of climate change currently being experienced, we highlight the importance of incorporating realistic time series of environmental noise into models used for conservation planning under climate change.

Conjugative plasmids play a vital role in bacterial adaptation through horizontal gene transfer. Explaining how plasmids persist in host populations however is difficult, given the high costs often associated with plasmid carriage. Compensatory evolution to ameliorate this cost can rescue plasmids from extinction. In a recently published study we showed that compensatory evolution repeatedly targeted the same bacterial regulatory system, GacA/GacS, in populations of plasmid-carrying bacteria evolving across a range of selective environments. Mutations in these genes arose rapidly and completely eliminated the cost of plasmid carriage. Here we extend our analysis using an individual based model to explore the dynamics of compensatory evolution in this system. We show that mutations which ameliorate the cost of plasmid carriage can prevent both the loss of plasmids from the population and the fixation of accessory traits on the bacterial chromosome. We discuss how dependent the outcome of compensatory evolution is on the strength and availability of such mutations and the rate at which beneficial accessory traits integrate on the host chromosome.

Theoretical predictions for biodiversity patterns are typically derived under the assumption that ecological systems have reached a dynamic equilibrium. Yet, there is increasing evidence that various aspects of ecological systems, including (but not limited to) species richness, are not at equilibrium. Here, we use simulations to analyse how biodiversity patterns unfold through time. In particular, we focus on the relative time required for various biodiversity patterns (macroecological or phylogenetic) to reach equilibrium. We simulate spatially explicit metacommunities according to the Neutral Theory of Biodiversity (NTB) under three modes of speciation, which differ in how evenly a parent species is split between its two daughter species. We find that species richness stabilizes first, followed by species area relationships (SAR) and finally species abundance distributions (SAD). The difference in timing of equilibrium between these different macroecological patterns is the largest when the split of individuals between sibling species at speciation is the most uneven. Phylogenetic patterns of biodiversity take even longer to stabilize (tens to hundreds of times longer than species richness) so that equilibrium predictions from neutral theory for these patterns are unlikely to be relevant. Our results suggest that it may be unwise to assume that biodiversity patterns are at equilibrium and provide a first step in studying how these patterns unfold through time.

Individual recognition is a taxonomically widespread ability that underlies a diverse suite of behaviors including the identification of individual nest-mates, agonistic opponents, and mating partners. However, as yet relatively little is known about the circumstances under which the requisite signal diversity can evolve. Here, we develop a model describing a novel mechanism of individual identity evolution via sexual selection. Females choose among a subset of males, but can select the most attractive male only when he bears a unique identity signal. This mimics a species in which mate assessment and choice are temporally separate, such as when females observe males in direct conflict and must subsequently locate the winner. When females in our model are choosy at least 10% of the time, diversity at individuality signaling loci evolves as a by-product of selection on male attractiveness more rapidly than does diversity at equivalent loci evolving only under neutral processes. Even at lower discrimination rates, drifting signal diversity gives the female choice mechanism sufficient traction to drive up average male attractiveness. The mechanism we describe here can significantly increase signal diversity at even low rates of discrimination by females.

1. Understanding the causes and consequences of dispersal remains a central topic in ecology and evolution. However, a mismatch exists between our empirical understanding of the complexity of dispersal and our representation of dispersal in models. While the empirical literature is replete with examples of condition dependence at the emigration, movement and settlement phases, models rarely incorporate realism or complexity to this degree. Nor do models often include the different costs associated with dispersal, which can themselves be linked to one or more of the three key phases. 2. Here, we propose that by explicitly accounting for emigration, movement and settlement (and the multiple costs associated with each) we can substantially improve our understanding of both the dispersal process itself and how dispersal traits trade off against other life-history characteristics. We explore some of these issues conceptually, before presenting illustrative results gained from a flexible individual-based model which incorporates considerable dispersal complexity. 3. These results emphasise the nonlinear interplay between the different dispersal stages. For example, we find that investment in movement ability (at a cost to fecundity) depends upon the propensity to emigrate (and vice versa). However, owing to selection acting at the metapopulation level as well as at the individual level, the relationship between the two is not straightforward. Importantly, the shape of the trade-off between movement ability and reproductive potential can strongly influence the joint evolution of dispersal parameters controlling the degree of investment in safer movement, the probability of emigration and the straightness of movement. 4. Our results highlight that the joint evolution of dispersal characteristics can have major implications for spatial population dynamics and we argue that, in addition to increasing our fundamental biological understanding, a new generation of dispersal modelling, which exploits recent empirical advances, can substantially improve our ability to predict and manage the response of species to environmental change.

Dispersal costs can be classified into energetic, time, risk and opportunity costs and may be levied directly or deferred during departure, transfer and settlement. They may equally be incurred during life stages before the actual dispersal event through investments in special morphologies. Because costs will eventually determine the performance of dispersing individuals and the evolution of dispersal, we here provide an extensive review on the different cost types that occur during dispersal in a wide array of organisms, ranging from micro-organisms to plants, invertebrates and vertebrates. In general, costs of transfer have been more widely documented in actively dispersing organisms, in contrast to a greater focus on costs during departure and settlement in plants and animals with a passive transfer phase. Costs related to the development of specific dispersal attributes appear to be much more prominent than previously accepted. Because costs induce trade-offs, they give rise to covariation between dispersal and other life-history traits at different scales of organismal organisation. The consequences of (i) the presence and magnitude of different costs during different phases of the dispersal process, and (ii) their internal organisation through covariation with other life-history traits, are synthesised with respect to potential consequences for species conservation and the need for development of a new generation of spatial simulation models.

The adverse influence of habitat degradation on the survival of populations may sometimes be amplified by rapid evolution over ecological timescales. This phenomenon of "evolutionary suicide" has been described in theoretical as well as empirical studies. However, no studies have suggested that habitat improvement could possibly also trigger an evolutionary response that would result in a decline in population size. We use individual-based simulations to demonstrate the potential for such a paradoxical response. An increase in the quality, size, or stability of only a fraction of the habitat patches in a metapopulation may result in an evolutionary decline in the dispersal propensity of individuals, followed by a decrease in recolonization, a reduction in the number of patches occupied, a decline in overall population size, and even extinction. Thus, well-intended conservation efforts that ignore potential evolutionary consequences of habitat management may increase the extinction risk of populations.

Summary 1. Models that represent space as a lattice have a critical function in theoretical and applied ecology. Despite their significance, there is a dearth of appropriate theoretical developments for the description of dispersal across such lattices. 2. We present a series of methods for approximating continuous dispersal in discrete landscapes (denoted as centroid-to-centroid, centroid-to-area, area-to-centroid and area-to-area dispersal). We describe how these methods can be extended to incorporate different conditions at the boundary of the simulation arena and a framework for approximating continuous dispersal between irregularly shaped patches. 3. Each approximation method was tested against a baseline of continuous Gaussian dispersal in a periodic simulation arena. The residence probabilities for an individual dispersing in each time step according to a Gaussian kernel across grids of three differing resolutions were calculated over a number of dispersal steps. In addition, the steady-state asymptotic properties for the transition matrices for each approximation method and cell resolution were calculated and compared against the uniform expectation under continuous dispersal. 4. All four methods described in this article provide a reasonable approximation to the continuous baseline (

Marine reserves are used as a management tool to ensure sustainability of fish stocks. Using an individual-based model, we compare the evolutionary effect of a reserve located on a nursery ground, spawning ground, feeding ground, or in a year-round habitat for sedentary species. We model the evolution of life-history traits, specifically size at maturation and site fidelity. Within species, individuals will differ in the time spent within a reserve depending on their patterns of movement and migration. We predict that the evolutionary effect of fishing depends not only on the survival probability but also on the life-history stages primarily affected by high harvest mortality. Protection against evolution to small maturation size is most effective where a reserve protects a sedentary population or protects the feeding grounds of a population. We also find that protection of the feeding ground of an anadromous stock such as Atlantic salmon may lead to local adaptation enhanced by evolution of higher site fidelity, similar to protection of a sedentary species.

Most attempts to identify the processes that structure natural communities have focused on conspicuous macroorganisms whereas the processes responsible for structuring microbial communities remain relatively unknown. Two main theories explaining these processes have emerged; niche theory, which highlights the importance of deterministic processes, and neutral theory, which focuses on stochastic processes. We examined whether neutral or niche-based mechanisms best explain the composition and structure of communities of a functionally important soil microbe, the arbuscular mycorrhizal (AM) fungi. Using molecular techniques, we surveyed AM fungi from 425 individual plants of 28 plant species along a soil pH gradient. There was evidence that both niche and neutral processes structured this community. Species abundances fitted the zero-sum multinomial distribution and there was evidence of dispersal limitation, both indicators of neutral processes. However, we found stronger support that niche differentiation based on abiotic soil factors, primarily pH, was structuring the AM fungal community. Host plant species affected AM fungal community composition negligibly compared to soil pH. We conclude that although niche partitioning was the primary mechanism regulating the composition and diversity of natural AM fungal communities, these communities are also influenced by stochastic-neutral processes. This study represents one of the most comprehensive investigations of community-level processes acting on soil microbes; revealing a community that although influenced by stochastic processes, still responded in a predictable manner to a major abiotic niche axis, soil pH. The strong response to environmental factors of this community highlights the susceptibility of soil microbes to environmental change.

Miethe, T., Dytham, C., Dieckmann, U., and Pitchford, J. W. 2010. Marine reserves and the evolutionary effects of fishing on size at maturation. – ICES Journal of Marine Science, 67: 412–425. Size-selective fishing may induce rapid evolutionary changes in life-history traits such as size at maturation. A major concern is that these changes will reduce population biomass and detrimentally affect yield and recruitment. Although marine reserves have been proposed as a tool for fisheries management, their evolutionary implications have as yet attracted little scrutiny. A simple model is used to investigate whether marine reserves can be expected to mitigate the evolutionary impacts of fishing on maturation size. The adaptive dynamics of size at maturation are analysed based on a stage-structured population model including size-selective fishing and marine reserves with different retention rates. As has been shown before, imposing greater fishing mortality on the largest individuals promotes an evolutionary change towards smaller maturation size. In the model, protecting part of a fish stock using a marine reserve can prevent such fisheries-induced evolution, and this protection critically depends on the type and extent of movement between the reserve and the fished area. Specifically, although the frequent movement of large adults increases catches of large adult fish outside a marine reserve, it also reduces the reserve's effectiveness in preventing fisheries-induced evolution. In contrast, when there is exchange between protected and fished areas through juvenile export alone, a marine reserve can effectively prevent evolution towards smaller maturation size, but does so at the expense of reducing the yield of large adult fish. Differences in the movement behaviour of successive life stages need to be considered for marine reserves, to help make fisheries more sustainable evolutionarily.

Evolutionary processes play an important role in shaping the dynamics of range expansions, and selection on dispersal propensity has been demonstrated to accelerate rates of advance. Previous theory has considered only the evolution of unconditional dispersal rates, but dispersal is often more complex. For example, many species emigrate in response to crowding. Here, we use an individual-based model to investigate the evolution of density dependent dispersal into empty habitat, such as during an invasion. The landscape is represented as a lattice and dispersal between populations follows a stepping-stone pattern. Individuals carry three 'genes' that determine their dispersal strategy when experiencing different population densities. For a stationary range we obtain results consistent with previous theoretical studies: few individuals emigrate from patches that are below equilibrium density. However, during the range expansion of a previously stationary population, we observe evolution towards dispersal strategies where considerable emigration occurs well below equilibrium density. This is true even for moderate costs to dispersal, and always results in accelerating rates of range expansion. Importantly, the evolution we observe at an expanding front depends upon fitness integrated over several generations and cannot be predicted by a consideration of lifetime reproductive success alone. We argue that a better understanding of the role of density dependent dispersal, and its evolution, in driving population dynamics is required especially within the context of range expansions.

West, C. D., Dytham, C., Righton, D., and Pitchford, J.W. 2009. Preventing overexploitation of migratory fish stocks: the efficacy of marine protected areas in a stochastic environment. – ICES Journal of Marine Science, 66: 1919–1930. Marine protected areas (MPAs) have been widely proposed for protecting overexploited fish populations. It has been suggested that fisheries may be enhanced by spillover of individuals from MPAs into fishing grounds. However, traditional spillover studies fail to account for the seasonal migrations of many populations. Most fisheries models also fail to include the stochasticity inherent in marine environments explicitly. Here we assess MPA efficacy using a simple population model simulating the migration of fish populations between a spawning ground MPA and a fishery. Including realistic environmental stochasticity in our model allows the population to deviate from, and shift between, positive stable equilibria, something that is impossible in a deterministic analysis. This deviation may result in population collapse in cases where deterministic analysis predicts population persistence. We show that, although effective at low migration levels, the ability of MPAs to protect stocks from collapse generally decreases as migration increases. However, an MPA provides greater protection and greater expected fisheries yield than a system without an MPA, irrespective of migration level. Combining MPAs with a harvest control rule may further increase protection and yield. We therefore argue that MPAs can play a role in the protection of migratory species.

Predictive population models designed to assist managers and policy makers require an explicit treatment of inherent uncertainty and variability. These are particular concerns when modelling non-native and reintroduced species, when data have been collected within one geographical or ecological context but predictions are required for another, or when extending models to predict the consequences of environmental change (e.g., climate or land-use). We present an aspatial, probabilistic framework of hierarchical process models for predicting population growth even when data are sparse or of poor quality. Insight into the factors affecting population dynamics in real landscapes can be provided and Kullback–Leibler distances are used to compare the relative output of models. This flexible yet robust framework gives easily interpretable results, allowing managers as well as modellers to invalidate anomalous models and apply others to real-life scenarios. We illustrate the framework’s power with a meta-analysis of European wild boar (Sus scrofa) data. We test hypotheses about the effect of geographic region, hunting and mast years on wild boar population growth, to build models of wild boar dynamics for the UK. The framework quantifies the importance of hunting pressure as a driver of population growth, and confirms that reproductive success is greatly decreased in poor mast years, suggesting that the key to predicting wild boar dynamics is to ascertain local hunting pressure and to better understand changing food availability. Geography had no significant effect, indicating that it is not a good proxy for modelling the impact of change in climate or land-use on wild boar populations at the European scale. We use the framework to predict population abundance 9 years after an isolated population of wild boar established in the UK; in a comparison with the only field data and two independent modelling exercises, our framework provides the most robust and informative results.

We investigated whether signals of known dispersal processes and habitat patch turnover could be detected in a snapshot of the distribution of the tansy leaf beetle Chrysolina graminis among patches of its host plant tansy Tanacetum vulgare. Beetle occupancy in 1305 patches was analysed using autologistic generalised additive models (GAMs). These model spatial autocorrelation with an autocovariate calculated as the distance-weighted rate of occupancy among neighbouring patches. The autocovariate that best explained beetle occupancy was one which represented the active search for patches during beetle dispersal, included a distance weight that closely matched a previously fitted dispersal kernel and had neighbourhood sizes encompassing ∼ 95% of known dispersal distances. Autocovariates distinguishing between neighbours on the same and opposite riverbanks outperformed those that did not, revealing the river as a barrier to dispersal. Differentiating between up and downstream autocorrelation did not improve model fit, as is consistent with the beetle's lack of directional bias in dispersal. Habitat connectivity (the extent to which it was surrounded by other patches) did not appear to affect beetle occupancy in the field, while positive effects were found for distributions simulated from the GAM. We argue that this reflects a non-equilibrium distribution driven by slow responses to high rates of habitat patch turnover due to limited dispersal ability. Our findings suggest that presence/absence snapshots can reveal patterns of dispersal and be used to test whether species' ranges are at equilibrium. Such information is important for effective conservation so the possibility of inferring these patterns from distribution data is an appealing one.

Dispersal is a key component of a species's ecology and will be under different selection pressures in different parts of the range. For example, a long-distance dispersal strategy suitable for continuous habitat at the range core might not be favoured at the margin, where the habitat is sparse. Using a spatially explicit, individual-based, evolutionary simulation model, the dispersal strategies of an organism that has only one dispersal event in its lifetime, such as a plant or sessile animal, are considered. Within the model, removing habitat, increasing habitat turnover, increasing the cost of dispersal, reducing habitat quality or altering vital rates imposes range limits. In most cases, there is a clear change in the dispersal strategies across the range, although increasing death rate towards the margin has little impact on evolved dispersal strategy across the range. Habitat turnover, reduced birth rate and reduced habitat quality all increase evolved dispersal distances at the margin, while increased cost of dispersal and reduced habitat density lead to lower evolved dispersal distances at the margins. As climate change shifts suitable habitat poleward, species ranges will also start to shift, and it will be the dispersal capabilities of marginal populations, rather than core populations, that will influence the rate of range shifting.

Selecting suitable nature reserves is a continuing challenge in conservation, particularly for target groups that are time-consuming to survey, species rich, and extinction prone. One such group is the parasitoid Hymenoptera, which have been excluded from conservation planning. If basic characteristics of habitats or vegetation could be used as reliable surrogates of specific target taxa, this would greatly facilitate appropriate reserve selection. We identified a range of potential habitat indicators of the species richness of pimpline parasitoid communities (Hymenoptera: Ichneumonidae: Pimplinae, Diacritinae, Poemeniinae) and tested their efficiency at capturing the observed diversity in a group of small woodlands in the agricultural landscape of the Vale of York (United Kingdom). Eight of the 18 vegetation-based reserve-selection strategies were significantly better at parasitoid species inclusion than random selection of areas. The best strategy maximized richness of tree species over the entire reserve network through complementarity. This strategy omitted only 2–3 species more (out of 38 captured in the landscape as a whole) than selections derived from the parasitoid survey data. In general, strategies worked equally well at capturing species richness and rarity. Our results suggest that vegetation data as a surrogate for species richness could prove an informative tool in parasitoid conservation, but further work is needed to test how broadly applicable these indicators may be. Resumen: La seleccion de reservas naturales adecuadas es un reto permanente en la conservacion, particularmente para grupos cuyos muestreos consumen mucho tiempo, que son ricos en especies y que estan propensos a la extincion. Uno de esos grupos es el de los Hymenoptera parasitoides, que han sido excluidos de la planificacion de la conservacion. Si las caracteristicas basicas de los habitats o de la vegetacion pudieran ser utilizadas como sustitutos confiables de taxa especificos, la seleccion de reservas adecuadas se facilitaria enormemente. Identificamos una gama de indicadores potenciales de habitat para la riqueza de especies de comunidades de parasitoides (Hymenoptera: Ichneumonidae: Pimplinae, Diacritinae, Poemeniinae) y probamos su eficiencia en la captura de la diversidad observada en un grupo de bosques pequenos en el paisaje agricola del Vale de York (R. U.). Ocho de las 18 estrategias para la seleccion de reservas basadas en vegetacion fueron significativamente mejores para la inclusion de especies de parasitoides que la seleccion aleatoria de areas. La mejor estrategia maximizo la riqueza de especies de arboles en toda la red de reservas mediante la complementariedad. Esta estrategia omitio solo 2–3 especies mas (de 38 registradas en todo el paisaje) que las selecciones derivadas de los datos del muestreo de parasitoides. En general, las estrategias funcionaron bien tanto para la captura de especies como de rareza. Nuestros resultados sugieren que los datos de vegetacion como un sustituto de la riqueza de especies podrian ser una herramienta informativa para la conservacion de parasitoides, pero se requiere mas trabajo para probar la amplitud de la aplicacion de estos indicadores.

Size-selective fishing mortality may induce evolutionary changes to smaller size at maturation in fish stocks. Marine reserves can be a useful management tool dealing with the ecological and evolutionary effects of fisheries. We examine the effect of size-selective harvesting and the implementation of marine reserves on the evolution of size at maturation using individual-based models. The mobility of individual fish is included as an evolving trait to account for possible behavioural changes in dispersal patterns. The evolutionary change in maturation size can be prevented inside the reserve, leading to higher abundance there. The results show the benefit of reserves on yield, especially at intermediate movement probability. Reserve implementation may cause mobility of individuals to decrease, increasing the possibility of local adaptation in maturation strategy. Evolutionary changes in mobility through marine reserve implementation increase the protection from evolution to small maturation size within the reserve, but may lead to overestimation of yield benefits due to reduced spill-over.

Predicted future climate change will alter species' distributions as they attempt to track the most suitable 'climate window'. Climate envelope models indicate the direction of likely range changes but do not incorporate population dynamics, therefore observed responses may differ greatly from these projections. We use simulation modelling to explore the consequences of a period of environmental change for a species structured across an environmental gradient. Results indicate that a species' range may lag behind its climate envelope and demonstrate that the rate of movement of a range can accelerate during a period of climate change. We conclude that the inclusion of both population dynamics and spatial environmental variability is vital to develop models that can both predict, and be used to manage, the impact of changing climate on species' biogeography.

Every species experiences the landscape as a unique pattern of resource quality and heterogeneity. This subsequently affects aspects of life from the individual scale (fitness, home range size), to social group scale, up to landscape characteristics such as source–sink dynamics, connectivity and species diversity. Correctly characterising the quality and spatial pattern of resources is therefore key in modelling species’ persistence and spread. However, although many measures of heterogeneity are available for binary and ordinal landscape patterns, few are directly applicable to landscapes with a continuous description of landscape quality. Lacunarity is a measure of the structure of gaps in the landscape, first used to describe properties of fractal landscapes. We develop lacunarity analysis to allow the direct comparison of pattern in binary and continuous landscapes with differing mean quality. Using simulated landscapes with varying degrees of spatial autocorrelation and resource distribution broadly describing the spectrum of resource quality experienced by specialists and generalists, we show how the measurement of spatial pattern changes when different distributions are used to describe landscape quality. Our metric indicates the scale of measurement at which the pattern is most different from random, and thus informs the choice of scale for modelled processes in the model landscape, and the appropriate extent for landscape study. Our metric can be used to distinguish between any spatial pattern or resource description, from a simple parametric distribution for landscape quality to the variety of resources likely to be encountered in real landscapes.

1. Knowing how species are distributed across a landscape can considerably aid the management of populations and species richness. Insect parasitoids constitute a large fraction of terrestrial biodiversity and help regulate other insect populations, but their ecology is poorly known at a landscape scale. 2. Using Malaise traps distributed first extensively and then intensively across woodland patches in an agricultural landscape, we tested whether four ichneumonid subfamilies display (i) a positive relationship between abundance and occupancy, (ii) a positive relationship between abundance in the extensive sample and abundance in the intensive sample, and (iii) aggregation across traps. 3. A positive relationship between abundance and occupancy was found across species in both samples, and was relatively strong. Abundance in the extensive samples was positively correlated with abundance in the intensive samples. On average, species were aggregated in both samples, although aggregation was not necessary for a positive abundance–occupancy relationship. 4. These results suggest that ichneumonid species can largely be classified on a continuum from widespread and locally abundant to localised and locally scarce. The former species allow the potential for pervasive natural control of host populations. The latter species, which constitute a substantial majority of the species list, will be vulnerable to extinction through both stochastic forces and widespread adverse forces such as climate change and habitat modification. However, the assessment of species’ status is likely to be facilitated by the positive abundance–occupancy relationship. 5. Species inventories for ichneumonids will be taxing because of the need to sample both intensively and extensively to detect rare species, which constitute the majority of species. However, it is possible to generalise species abundances across spatial scales and years, facilitating monitoring.

1 Parasitoid wasps are species-rich and likely to be sensitive indicators of environmental change. Malaise traps are widely used for sampling certain taxa of parasitic Hymenoptera, but little is known about how they should best be used to monitor the community at an individual site. 2 To investigate the effects of sample duration, trap location and replication on the parasitoid assemblage, we sampled four ichneumonid subfamilies (Hymenoptera: Ichneumonidae) intensively using Malaise traps in two farm woods in the Vale of York, UK. 3 Species accumulation curves showed that even with 16 Malaise traps per wood, the community is incompletely sampled. Despite this, we caught up to 28% of all UK species in a single wood, implying that local parasitoid diversity may be very high. 4 Abundance and species richness of parasitoids differed significantly between sample periods (fortnights) and between traps, but did not differ overall between core and edge locations. 5 Parasitoid community composition differed between core and edge traps, but differences were much stronger in one wood than the other. One subfamily, the Poemeniinae, was found predominantly in edge locations. Catch differences became greater with increasing distance between traps. 6 The previous year, two traps in each of the same woods caught only half as many species, but species abundance was positively correlated between years. 7 Our results suggest that a small number of traps can contain useful information about the parasitoid community but is likely to seriously underestimate total species richness. To achieve extensive species coverage, sampling should continue over several weeks, with widely separated traps sampling both core and edge locations. Our focal taxa should prove excellent for monitoring the effects of environmental change on biodiversity.

1. Species would be expected to shift northwards in response to current climate warming, but many are failing to do so because of fragmentation of breeding habitats. Dispersal is important for colonisation and an individual-based spatially explicit model was developed to investigate impacts of habitat availability on the evolution of dispersal in expanding populations. Model output was compared with field data from the speckled wood butterfly Pararge aegeria, which currently is expanding its range in Britain. 2. During range expansion, models simulated positive linear relationships between dispersal and distance from the seed location. This pattern was observed regardless of quantity (100% to 10% habitat availability) or distribution (random vs. gradient distribution) of habitat, although higher dispersal evolved at expanding range margins in landscapes with greater quantity of habitat and in gradient landscapes. Increased dispersal was no longer evident in any landscape once populations had reached equilibrium; dispersal values returned to those of seed populations. However, in landscapes with the least quantity of habitat, reduced dispersal (below that of seed populations) was observed at equilibrium. 3. Evolutionary changes in adult flight morphology were examined in six populations of P. aegeria along a transect from the distribution core to an expanding range margin in England (spanning a latitudinal distance of >200 km). Empirical data were in agreement with model output and showed increased dispersal ability (larger and broader thoraxes, smaller abdomens, higher wing aspect ratios) with increasing distance from the distribution core. Increased dispersal ability was evident in populations from areas colonised >30 years previously, although dispersal changes were generally evident only in females. 4. Evolutionary increases in dispersal ability in expanding populations may help species track future climate changes and counteract impacts of habitat fragmentation by promoting colonisation. However, at the highest levels of habitat loss, increased dispersal was less evident during expansion and reduced dispersal was observed at equilibrium indicating that, for many species, continued habitat fragmentation is likely to outweigh any benefits from dispersal.

Coral reef fishes typically undergo a pelagic larval phase prior to recruitment to reef habitat. This is potentially risky, but likely to be important in connecting populations and avoiding local crowding. Predation pressures on larvae on and off the reef are likely to differ both in origin and intensity. In this study, we used individual-based models to explore in isolation the effect of elevated levels of larval mortality on the reef in 22 different landscapes. We allowed the movement of highly simplified larvae to evolve through selection and mutation events and tracked emerging strategies over 180 generations. The pressure of increased larval mortality on the reef affected overall popula- tion sizes and selected for higher levels of larval movement. However, the evolution of movement was constrained, and self-recruitment back to the reef of origin was prevalent, with levels rarely dropping below 50%. The evolved strategies were highly landscape specific, suggesting that movement in contiguous reefs is more readily evolved than at isolated reefs. Future development of this simulation approach will provide a valuable research tool for exploring important evolutionary, ecological, and management-based questions.

Movement underpins animal spatial ecology and is often modelled as habitat-dependent correlated random walks. Here, we develop such a model for the flightless tansy leaf beetle Chrysolina graminis moving within and between patches of its host plant tansy Tanacetum vulgare. To parameterize the model, beetle movement paths on timescales of minutes were observed in uniform plots of tansy and inter-patch matrix (meadow) vegetation. Movement lasted longer, covered greater distances and had narrower turning angles in the matrix. Simulations of the model emulated an independent two-season multi-patch mark-resight study at daily timescales and included variable boundary-mediated behaviour affecting the probability of leaving habitat patches. As boundaries in the model became stronger there were disproportionately large decreases in net displacements, inter-patch movements and the proportion of beetles in the matrix. The model produced realistic patterns of population-level displacement over periods up to 13 days with fully permeable boundaries for one dataset and strong boundaries for the other. This may be explained by the heights of the tansy patches in each study, as beetles will be unable to cross the boundary near the top of a patch that emerges from the matrix. The simulations demonstrate the important effects of boundary behaviour on displacement patterns and indicate temporal and spatial variability in permeability. Realistic models of movement must therefore include behaviour at habitat boundaries.

There is an increasing recognition that evolutionary processes play a key role in determining the dynamics of range expansion. Recent work demonstrates that neutral mutations arising near the edge of a range expansion sometimes surf on the expanding front leading them rather than that leads to reach much greater spatial distribution and frequency than expected in stationary populations. Here, we extend this work and examine the surfing behavior of nonneutral mutations. Using an individual-based coupled-map lattice model, we confirm that, regardless of its fitness effects, the probability of survival of a new mutation depends strongly upon where it arises in relation to the expanding wave front. We demonstrate that the surfing effect can lead to deleterious mutations reaching high densities at an expanding front, even when they have substantial negative effects on fitness. Additionally, we highlight that this surfing phenomenon can occur for mutations that impact reproductive rate (i.e., number of offspring produced) as well as mutations that modify juvenile competitive ability. We suggest that these effects are likely to have important consequences for rates of spread and the evolution of spatially expanding populations.