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Disease epidemics typically begin as an outbreak of a relatively small, spatially explicit population of infected individuals (focus), in which disease prevalence increases and rapidly spreads into the uninfected, at‐risk population. Studies of epidemic spread typically address factors influencing disease spread through the at‐risk population, but the initial outbreak may strongly influence spread of the subsequent epidemic. We initiated wheat stripe rust Puccinia striiformis f. sp. tritici epidemics to assess the influence of the focus on final disease prevalence when the degree of disease susceptibility differed between the at‐risk and focus populations. When the focus/at‐risk plantings consisted of partially genetic resistant and susceptible cultivars, final disease prevalence was statistically indistinguishable from epidemics produced by the focus cultivar in monoculture. In these experimental epidemics, disease prevalence was not influenced by the transition into an at‐risk population that differed in disease susceptibility. Instead, the focus appeared to exert a dominant influence on the subsequent epidemic. Final disease prevalence was not consistently attributable to either the focus or the at‐risk population when focus/at‐risk populations were planted in a factorial set‐up with a mixture (c. 28% susceptible and 72% resistant) and susceptible individuals. In these experimental epidemics, spatial heterogeneity in disease susceptibility within the at‐risk population appeared to counter the dominant influence of the focus. Cessation of spore production from the focus (through fungicide/glyphosate application) after 1·3 generations of stripe rust spread did not reduce final disease prevalence, indicating that the focus influence on disease spread is established early in the epidemic. Synthesis and applications. Our experiments indicated that outbreak conditions can be highly influential on epidemic spread, even when disease resistance in the at‐risk population is greater than that of the focus. Disease control treatments administered shortly after the initial outbreak within the focus may either prevent an epidemic from occurring or reduce its severity.

1. Debate continues regarding the ecological impacts of genetically modified (GM) crops and their coexistence with non-GM crops in Europe. In this debate, quantitative predictions of gene dispersal by pollen are necessary, and as a result numerous plot-to-plot gene flow experiments have been performed with various crops. However, plot-to-plot cross-pollination rates (CPR) depend on spatial configuration of plots, implying that (i) they are difficult to compare among experiments and (ii) functions directly fitted on CPR data are inappropriate for predictions in other spatial contexts. 2. Modelling pollen dispersal via an individual dispersal function (IDF) circumvents these problems by accounting for spatial designs. We detail for oilseed rape how this approach can be used to both estimate an IDF from field data and predict CPR between two neighbouring fields of various sizes and shapes. Predictions were used to investigate the sensitivity of CPR to the family of IDF, the uncertainty in parameter estimates and the effects of field dimensions and isolation distances. 3. We fitted a range of families of IDF, including several types of tails, on previously published data. The best IDF was a fat-tailed power-law function, meaning frequent long-distance dispersal. 4. The choice of IDF appeared crucial when predicting CPR between fields, occasionally being even more important than the distance between fields. Width of the source field and depth of the recipient field were next in importance. When approximated CPR were calculated without considering field dimensions, using distance between field centres gave better performance than field margins. 5. Synthesis and applications. This study demonstrates the value of IDF for quantitative predictions of pollen flow in variable spatial configurations. A spatially explicit model of agro-ecosystems used to define management rules for the commercial release of GM crops in Europe already employs IDF but underestimates long-distance dispersal for oilseed rape. These new parameter estimates will refine the performance of these models. Moreover, the detailed guidelines for estimating an IDF should encourage such statistical analysis of other dispersal data, enabling comparisons of dispersal data obtained for different environments and species and providing new IDF for management models.

Predicting the spread of populations across fragmented habitats is vital if we are to manage their persistence in the long term. We applied network theory with a model and an experiment to show that spread rate is jointly defined by the configuration of habitat networks (i.e., the arrangement and length of connections between habitat fragments) and the movement behavior of individuals. We found that population spread rate in the model was well predicted by algebraic connectivity of the habitat network. A multigeneration experiment with the microarthropod Folsomia candida validated this model prediction. The realized habitat connectivity and spread rate were determined by the interaction between dispersal behavior and habitat configuration, such that the network configurations that facilitated the fastest spread changed depending on the shape of the species’ dispersal kernel. Predicting the spread rate of populations in fragmented landscapes requires combining knowledge of species-specific dispersal kernels and the spatial configuration of habitat networks. This information can be used to design landscapes to manage the spread and persistence of species in fragmented habitats.

Because common ragweed (Ambrosia artemisiifolia L., henceforth Ambrosia) has negative effects on human health, it is a common focus for management, which would benefit from a better understanding of the underlying mechanisms by which the species spreads. Road systems are known to be invasion corridors, but the conduit function of vehicles for the rapid spread of Ambrosia along roads and for population extension along roadside verges has not yet been demonstrated convincingly. To quantify the effect of different traffic volumes on the dispersal and population extension of Ambrosia, we used two approaches: First, by combining field experiments along roads with records of the seed rain around single plants, we simulated a combined dispersal kernel that revealed the interactions between primary dispersal and traffic‐mediated secondary dispersal. Second, we recorded the seedling recruitment around isolated roadside populations over 2 years to determine how traffic‐related parameters affect population extension. The longest traffic‐mediated dispersal distances exceeded those of primary dispersal by about one order of magnitude. Traffic volume had a significant positive effect on dispersal distances and on the lateral deposition of seeds on the road verge. Seedling recruitment around isolated roadside populations was significantly higher in the driving direction than against, but only at the distance where the major seed rain of traffic‐mediated dispersal is to be expected according to the combined dispersal kernel (3–15 m). Synthesis and applications. This study isolates the effects of road traffic from confounding mechanisms (e.g. mowing machinery, propagule pressure from infested fields) on common ragweed (Ambrosia artemisiifolia L.) invasions. Results demonstrate the traffic‐mediated dispersal in Ambrosia invasions as a routine and predictable process that facilitates population extension in the direction of traffic along roadsides, depending on traffic volume. This highlights the importance of prioritizing mowing along high use roads and mowing of isolated populations to prevent seed abscission and further spread of common ragweed. Foreign Language Abstrakt Das Beifußblättrige Traubenkraut (Ambrosia artemsiifolia L., im folgenden Ambrosia) übt einen starken negativen Einfluss auf die menschliche Gesundheit aus und ist daher im Fokus von Bekämpfungsmaßnahmen, die von einem besseren Verständnis der zugrundeliegenden Ausbreitungsmechanismen profitieren können. Straßennetzwerke sind zwar als Invasionskorridore für Neophyten bekannt, doch für Straßenfahrzeuge konnte bisher noch nicht überzeugend gezeigt werden, ob der Transport von Diasporen durch Fahrzeuge auch für die beschleunigte Ausbreitung von Ambrosia entlang der Straßen sowie ihres Populationswachstums am Straßenrand eine Rolle spielt. Um den Effekt unterschiedlicher Verkehrsstärken auf die Diasporenausbreitung und das Populationswachstum zu untersuchen, nutzten wir zwei verschiedene methodische Ansätze: Zum einen verknüpften wir die Ergebnisse unserer Diasporenfreisetzungen in Straßenkorridoren mit der natürlichen Diasporenverteilung basierend auf isolierten Ambrosiapflanzen und verwendeten diese Daten zur Nachbildung eines kombinierten Ausbreitungsdistanzspektrums, der die Wechselwirkung zwischen Primär‐ und Sekundärausbreitung erkennbar macht. Zum anderen kartierten wir für einen Zeitraum von zwei Jahren die Sämlingsetablierung um isolierte Straßenrandpopulationen herum und analysierten, wie straßenfahrzeugbestimmte Parameter das Populationswachstum verändern. Die erfassten Distanzen der am weitesten durch den Straßenverkehr ausgebreiteten Diasporen überschritten die der Primärausbreitung um etwa das Zehnfache. Das Verkehrsaufkommen hatte hierbei einen signifikant positiven Effekt auf die Ausbreitungsdistanzen sowie auf die laterale Ablagerung von Diasporen am Straßenrand. Die Sämlingsetablierung um isolierte Straßenrandpopulationen herum war in Fahrtrichtung des Straßenverkehrs signifikant höher als entgegen der Fahrtrichtung, jedoch nur in dem Bereich, in dem sich die meisten von Fahrzeugen ausgebreiteten Diasporen gemäß unserem kombinierten Ausbreitungsdistanzspektrum angesammelt hatten (3–15 m). Synthese und Anwendung. Diese Studie isoliert für das Beifußblättrige Traubenkraut (Ambrosia artemsiifolia L., im folgenden Ambrosia) die Effekte des Straßenverkehrs von den begleitenden Ausbreitungsmechanismen (z.B. Mahdmaschinen, Diasporeneinschleppungen von befallenen Äckern) auf den Invasionsprozess dieses Neophyten im Straßenkorridor. Die Ergebnisse zeigen, dass die Ausbreitung von Ambrosia durch Fahrzeuge ein häufiger und vorhersagbarer Prozess ist, der das Populationswachstum am Straßenrand in Verkehrsrichtung abhängig vom Verkehrsaufkommen fördert. Dies unterstreicht, wie wichtig eine prioritäre Mahd zur Unterbindung der Samenfreisetzung insbesondere in Straßen mit hoher Verkehrslast ist, wobei es entscheidend ist, auch isolierte Straßenrandpopulationen von Ambrosia mit in die Maßnahmen einzubeziehen. Nur so kann eine weitere Verbreitung dieses Neophyten im Straßennetzwerk eingedämmt werden. This study isolates the effects of road traffic from confounding mechanisms (e.g. mowing machinery, propagule pressure from infested fields) on common ragweed (Ambrosia artemisiifolia L.) invasions. Results demonstrate the traffic‐mediated dispersal in Ambrosia invasions as a routine and predictable process that facilitates population extension in the direction of traffic along roadsides, depending on traffic volume. This highlights the importance of prioritizing mowing along high use roads and mowing of isolated populations to prevent seed abscission and further spread of common ragweed.

Large animals provide crucial seed dispersal services, yet face continued threats and are susceptible to changes in landscape composition and configuration. Thus, there is a growing imperative to improve understanding of animal‐generated seed dispersal using models that incorporate spatial complexity in a realistic, yet tractable, way. We developed a spatially explicit agent‐based seed dispersal model, with disperser movements informed by biotelemetry data, to evaluate how landscape composition and configuration affect seed dispersal patterns. We illustrated this approach for the world's second largest ratite, the emu (Dromaius novaehollandiae), a highly mobile generalist frugivore considered an important long‐distance disperser for many plant species across Australia. When animal movement is unrestricted, model parameters related to seed gut passage largely determine seed dispersal kernels. However, as habitat loss and fragmentation increase, the extent of long‐distance dispersal events is reduced and seed shadows became progressively more aggregated. This effect is due to the emu not being able to move between disconnected parts of the landscape, with small changes in habitat structure causing decreased long‐distance dispersal. We simulated seed dispersal patterns generated by three commonly used generic models of animal movement – unbiased and biased correlated random walks and Lévy walks – to evaluate how different representations of movement affect estimations of animal movements and emergent seed dispersal patterns. Simulated movements informed by the emu biotelemetry data resulted in longer median seed dispersal distances than do the three generic models. Synthesis. Changes in landscape composition and configuration can dramatically alter patterns of zoochorous seed dispersal as they influence animal movement. However, when models are used to simulate the patterns of seed dispersal, decisions about how animal movement is represented also affect estimates of seed dispersal. Changes in landscape composition and configuration can dramatically alter patterns of zoochorous seed dispersal as they influence animal movement. However, when models are used to simulate the patterns of seed dispersal, decisions about how animal movement is represented also affect estimates of seed dispersal.

Climate and land‐use changes will require species to move large distances following shifts in their suitable habitats, which will frequently involve traversing intensively human‐modified landscapes. Practitioners will therefore need to evaluate and act to enhance the degree to which habitat patches scattered throughout the landscape may function as stepping stones facilitating dispersal among otherwise isolated habitat areas. We formulate a new generalized network model of habitat connectivity that accounts for the number of dispersing individuals and for long‐distance dispersal processes across generations. By doing so, we bridge the gap between complex dynamic population models, which are generally too data demanding and hence difficult to apply in practical wide‐scale decision‐making, and simpler static connectivity models that only consider the amount of habitat that can be reached by a single average disperser during its life span. We find that the loss of intermediate and sufficiently large stepping‐stone habitat patches can cause a sharp decline in the distance that can be traversed by species (critical spatial thresholds) that cannot be effectively compensated by other factors previously regarded as crucial for long‐distance dispersal (fat‐tailed dispersal kernels, source population size). We corroborate our findings by showing that our model largely outperforms previous connectivity models in explaining the large‐scale range expansion of a forest bird species, the Black Woodpecker Dryocopus martius, over a 20‐year period. The capacity of species to exploit the opportunities created by networks of stepping‐stone patches largely depends on species‐specific life‐history traits, suggesting that species assemblages traversing fragmented landscapes may be exposed to a spatial filtering process driving long‐term changes in community composition. Synthesis and applications. Previous static connectivity models seriously underestimate the importance of stepping‐stone patches in sustaining rare but crucial dispersal events. We provide a conceptually broader model that shows that stepping stones (i) must be of sufficient size to be of conservation value, (ii) are particularly crucial for the spread of species (either native or invasive) or genotypes over long distances and (iii) can effectively reduce the isolation of the largest habitat blocks in reserves, therefore largely contributing to species persistence across wide spatial and temporal scales.

Frugivores play differing roles in shaping dispersal patterns yet seed dispersal distance is rarely quantified across entire communities. We model seed dispersal distance using gut passage times and bird movement for the majority (39 interactions) of known bird–tree interactions on the island of Saipan to highlight differences in seed dispersal distances provided by the five avian frugivores. One bird species was found to be a seed predator rather than a disperser. The remaining four avian species dispersed seeds but differences in seed dispersal distance were largely driven by interspecific variation in bird movement rather than intraspecific variation in gut passage times. The median dispersal distance was at least 56 m for all species-specific combinations, indicating all species play a role in reducing high seed mortality under the parent tree. However, one species—the Micronesian Starling—performed 94% of dispersal events greater than 500 m, suggesting this species could be a key driver of long-distance dispersal services (e.g. linking populations, colonizing new areas). Assessing variation in dispersal patterns across this network highlights key sources of variation in seed dispersal distances and suggests which empirical approaches are sufficient for modelling how seed dispersal mutualisms affect populations and communities.

Frugivores are highly variable in their contribution to fruit removal in plant populations. However, data are lacking on species-specific variation in two central aspects of seed dispersal, distance of dispersal and probability of dispersal among populations through long-distance transport. We used DNA-based genotyping techniques on Prunus mahaleb seeds dispersed by birds (small- and medium-sized passerines) and carnivorous mammals to infer each seed's source tree, dispersal distance, and the probability of having originated from outside the study population. Small passerines dispersed most seeds short distances (50% dispersed <51 m from source trees) and into covered microhabitats. Mammals and medium-sized birds dispersed seeds long distances (50% of mammals dispersed seeds >495 m, and 50% of medium-sized birds dispersed seeds to > 110 m) and mostly into open microhabitats. Thus, dispersal distance and microhabitat of seed deposition were linked through the contrasting behaviors of different frugivores. When the quantitative contribution to fruit removal was accounted for, mammals were responsible for introducing two-thirds of the immigrant seeds into the population, whereas birds accounted for one-third. Our results demonstrate that frugivores differ widely in their effects on seed-mediated gene flow. Despite highly diverse coteries of mutualistic frugivores dispersing seeds, critical long-distance dispersal events might rely on a small subset of large species. Population declines of these key frugivore species may seriously impair seed-mediated gene flow in fragmented landscapes by truncating the long-distance events and collapsing seed arrival to a restricted subset of available microsites.

Animal movement comes in a variety of ‘types’ including small foraging movements, larger one-way dispersive movements, seasonally-predictable round-trip migratory movements, and erratic nomadic movements. Although most individuals move at some point throughout their lives, movement patterns can vary widely across individuals within the same species: differing within an individual over time (intra-individual), among individuals in the same population (inter-individual), or among populations (inter-population). Yet, studies of movement (theoretical and empirical alike) more often focus on understanding ‘typical’ movement patterns than understanding variation in movement. Here, I synthesize current knowledge of movement variation (drawing parallels across species and movement types), describing the causes (what factors contribute to individual variation), patterns (what movement variation looks like), consequences (why variation matters), maintenance (why variation persists), implications (for management and conservation), and finally gaps (what pieces we are currently missing). By synthesizing across scales of variation, I span across work on plasticity, personality, and geographic variation. Individual movement can be driven by factors that act at the individual, population, community and ecosystem level and have ramifications at each of these levels. Generally the consequences of movement are less well understood than the causes, in part because the effects of movement variation are often nested, with variation manifesting at the population level, which in turn affects communities and ecosystems. Understanding both cause and consequence is particularly important for predicting when variation begets variation in a positive feedback loop, versus when a negative feedback causes variation to be dampened successively. Finally, maintaining standing variation in movement may be important for facilitating species’ ability to respond to future environmental change.