Synchrony In Population Dynamics Research Articles

Advances in understanding the drivers of population spatial synchrony

The causes of spatial synchrony in population dynamics are often elusive. We review how recent advances have enhanced understanding of the causes of the spatial synchrony of insect populations and revealed previously underappreciated complexities in patterns of synchrony. We highlight how regional-scale studies of population genetic structure have helped elucidate the role of dispersal in population synchronization and how novel data-analytic approaches have revealed variation in spatial synchrony across timescales and geographies and the underlying drivers. We also stress the limited current understanding of the impacts of climate change on the spatial synchrony of insect populations and the potential ramifications of these effects for pest management as well as species conservation.

Synchrony in population dynamics of juvenile Atlantic salmon: analyzing spatiotemporal variation and the influence of river flow and demography

Dispersal and shared environmental conditions can both synchronize the dynamics of local populations, but disentangling their relative influence on dynamics is challenging. We used a Bayesian approach to estimate the synchrony of a metapopulation of Atlantic salmon (Salmo salar) composed of 18 populations in Brittany, France, including a 24-year time series of the abundances of juveniles. We estimated the spatial synchrony at a regional and local spatial scale over the study period. We found a strong regional synchrony despite spatiotemporal variability of local synchrony in the abundance of juveniles. We then explored the drivers of synchrony, including environmental conditions (aspects of river flow) and abundance of adult breeders. This revealed that summer low-flow conditions seemed to synchronize the abundances of juveniles more than the synchrony in the abundance of adult breeders, suggesting a Moran effect. Given that drought conditions are expected to become more common with climate change, our work highlights the potentially strong synchronizing effect of summer low flow on the dynamics of local salmon populations and the benefits of considering synchrony at multiple scales.

Mapping shifts in spatial synchrony in grassland birds to inform conservation planning.

Spatial synchrony, defined as the correlated fluctuations in abundance of spatially separated populations, can be caused by regional fluctuations in natural and anthropogenic environmental population drivers. Investigations into the geography of synchrony can provide useful insight to inform conservation planning efforts by revealing regions of common population drivers and metapopulation extinction vulnerability. We examined the geography of spatial synchrony and decadal changes in these patterns for grassland birds in the United States and Canada, which are experiencing widespread and persistent population declines. We used Bayesian hierarchical models and over 50 years of abundance data from the North American Breeding Bird Survey to generate population indices within a 2° latitude by 2° longitude grid. We computed and mapped mean local spatial synchrony for each cell (mean detrended correlation of the index among neighboring cells), along with associated uncertainty, for 19 species in 2, 26-year periods, 1968-1993 and 1994-2019. Grassland birds were predicted to increase in spatial synchrony where agricultural intensification, climate change, or interactions between the 2 increased. We found no evidence of an overall increase in synchrony among grassland bird species. However, based on the geography of these changes, there was considerable spatial heterogeneity within species. Averaging across species, we identified clusters of increasing spatial synchrony in the Prairie Pothole and Shortgrass Prairie regions and a region of decreasing spatial synchrony in the eastern United States. Our approach has the potential to inform continental-scale conservation planning by adding an additional layer of relevant information to species status assessments and spatial prioritization of policy and management actions. Our work adds to a growing literature suggesting that global change may result in shifting patterns of spatial synchrony in population dynamics across taxa with broad implications for biodiversity conservation.

Outbreaking forest insect drives phase synchrony among sympatric folivores: Exploring potential mechanisms

AbstractWe explore a common feature of insect population dynamics, interspecific synchrony, which refers to synchrony in population dynamics among sympatric populations of different species. Such synchrony can arise via several possible mechanisms, including shared environmental effects and shared trophic interactions, but distinguishing the relative importance among different mechanisms can be challenging. We analyze interannual time series of population densities of the larch budmoth, Zeiraphera griseana (Lepidoptera: Tortricidae), along with six sympatric larch‐feeding folivores from a site in the European Alps 1952–1979. These species include five lepidopterans, Exapate duratella, Ptycholomoides aeriferana, Spilonota laricana, Epirrita autumnata and Teleiodes saltuum, and one hymenopteran sawfly Pristiphora laricis. We document that the highly regular oscillatory behavior (period 9–10 years) of Z. griseana populations is similarly evident in the dynamics of most of the sympatric folivores. We also find that all of the sympatric species are phase synchronized with Z. griseana populations with half of the sympatric species exhibiting nonlagged phase synchrony and three of the species exhibiting 2–5 year lags behind Z. griseana populations. We adapt a previously developed tritrophic model of Z. griseana dynamics to explore possible mechanisms responsible for observed phase synchronization. Results suggest that either shared stochastic influences (e.g., weather) or shared parasitoid impacts are likely causes of nonlagged phase synchronization. The model further indicates that observed patterns of lagged phase synchronization are most likely caused by either shared delayed induced host plant defenses or direct density‐dependent effects shared with Z. griseana.

Spatial Scales of Population Synchrony in Predator-Prey Systems

Many species show synchronous fluctuations in population size over large geographical areas, which are likely to increase their regional extinction risk. Here we examine how the degree of spatial synchrony in population dynamics is affected by trophic interactions using a two-species predator-prey model with spatially correlated environmental noise. We show that the predator has a larger spatial scale of population synchrony than the prey if the population fluctuations of both species are mainly determined by the direct effect of stochastic environmental variations in the prey. This result implies that in ecosystems regulated from the bottom up, the spatial scale of synchrony of the predator population increases beyond the scale of the spatial autocorrelation in the environmental noise and in the prey fluctuations. Harvesting the prey increases the spatial scale of population synchrony of the predator, while harvesting the predator reduces the spatial scale of the population fluctuations of its prey. Hence, the development of sustainable harvesting strategies should also consider the impact on unharvested species at other trophic levels as well as human perturbations of ecosystems, whether the result of exploitation or an effect on dispersal processes, as they can affect food web structures and trophic interactions over large geographical areas.

Nonlinear time series analysis unravels underlying mechanisms of interspecific synchrony among foliage‐feeding forest Lepidoptera species

AbstractInterspecific synchrony, that is, synchrony in population dynamics among sympatric populations of different species can arise via several possible mechanisms, including common environmental effects, direct interactions between species, and shared trophic interactions, so that distinguishing the relative importance of these causes can be challenging. In this study, to overcome this difficulty, we combine traditional correlation analysis with a novel framework of nonlinear time series analysis, empirical dynamic modeling (EDM). The EDM is an analytical framework to identify causal relationships and measure changing interaction strength from time series. We apply this approach to time series of sympatric foliage‐feeding forest Lepidoptera species in the Slovak Republic and yearly mean temperature, precipitation and North Atlantic Oscillation Index. These Lepidoptera species include both free‐feeding and leaf‐roller larval life histories: the former are hypothesized to be more strongly affected by similar exogenous environments, while the latter are isolated from such pressures. Correlation analysis showed that interspecific synchrony is generally strongest between species within same feeding guild. In addition, the convergent cross mapping analysis detected causal effects of meteorological factors on most of the free‐feeding species while such effects were not observed in the leaf‐rolling species. However, there were fewer causal relationships among species. The multivariate S‐map analysis showed that meteorological factors tend to affect similar free‐feeding species that are synchronous with each other. These results indicate that shared meteorological factors are key drivers of interspecific synchrony among members of the free‐feeding guild, but do not play the same role in synchronizing species within the leaf‐roller guild.

Temporal variation in spatial genetic structure during population outbreaks: Distinguishing among different potential drivers of spatial synchrony.

Spatial synchrony is a common characteristic of spatio‐temporal population dynamics across many taxa. While it is known that both dispersal and spatially autocorrelated environmental variation (i.e., the Moran effect) can synchronize populations, the relative contributions of each, and how they interact, are generally unknown. Distinguishing these mechanisms and their effects on synchrony can help us to better understand spatial population dynamics, design conservation and management strategies, and predict climate change impacts. Population genetic data can be used to tease apart these two processes as the spatio‐temporal genetic patterns they create are expected to be different. A challenge, however, is that genetic data are often collected at a single point in time, which may introduce context‐specific bias. Spatio‐temporal sampling strategies can be used to reduce bias and to improve our characterization of the drivers of spatial synchrony. Using spatio‐temporal analyses of genotypic data, our objective was to identify the relative support for these two mechanisms to the spatial synchrony in population dynamics of the irruptive forest insect pest, the spruce budworm (Choristoneura fumiferana), in Quebec (Canada). AMOVA, cluster analysis, isolation by distance, and sPCA were used to characterize spatio‐temporal genomic variation using 1,370 SBW larvae sampled over four years (2012–2015) and genotyped at 3,562 SNP loci. We found evidence of overall weak spatial genetic structure that decreased from 2012 to 2015 and a genetic diversity homogenization among the sites. We also found genetic evidence of a long‐distance dispersal event over >140 km. These results indicate that dispersal is the key mechanism involved in driving population synchrony of the outbreak. Early intervention management strategies that aim to control source populations have the potential to be effective through limiting dispersal. However, the timing of such interventions relative to outbreak progression is likely to influence their probability of success.

Spatial heterogeneity in climate change effects decouples the long-term dynamics of wild reindeer populations in the high Arctic.

The ‘Moran effect’ predicts that dynamics of populations of a species are synchronized over similar distances as their environmental drivers. Strong population synchrony reduces species viability, but spatial heterogeneity in density dependence, the environment, or its ecological responses may decouple dynamics in space, preventing extinctions. How such heterogeneity buffers impacts of global change on large‐scale population dynamics is not well studied. Here, we show that spatially autocorrelated fluctuations in annual winter weather synchronize wild reindeer dynamics across high‐Arctic Svalbard, while, paradoxically, spatial variation in winter climate trends contribute to diverging local population trajectories. Warmer summers have improved the carrying capacity and apparently led to increased total reindeer abundance. However, fluctuations in population size seem mainly driven by negative effects of stochastic winter rain‐on‐snow (ROS) events causing icing, with strongest effects at high densities. Count data for 10 reindeer populations 8–324 km apart suggested that density‐dependent ROS effects contributed to synchrony in population dynamics, mainly through spatially autocorrelated mortality. By comparing one coastal and one ‘continental’ reindeer population over four decades, we show that locally contrasting abundance trends can arise from spatial differences in climate change and responses to weather. The coastal population experienced a larger increase in ROS, and a stronger density‐dependent ROS effect on population growth rates, than the continental population. In contrast, the latter experienced stronger summer warming and showed the strongest positive response to summer temperatures. Accordingly, contrasting net effects of a recent climate regime shift—with increased ROS and harsher winters, yet higher summer temperatures and improved carrying capacity—led to negative and positive abundance trends in the coastal and continental population respectively. Thus, synchronized population fluctuations by climatic drivers can be buffered by spatial heterogeneity in the same drivers, as well as in the ecological responses, averaging out climate change effects at larger spatial scales.

Does harvesting amplify environmentally induced population fluctuations over time in marine and terrestrial species?

Abstract In marine and terrestrial ecosystems, organisms are affected by environmental variations that cause fluctuations in population size. The harvest–interaction hypothesis predicts that environmentally induced fluctuations in population size are magnified by harvesting. Empirical evidence is urgently needed in the context of global change because greater fluctuations will increase extinction risk. Here, we review theoretical and empirical work that has addressed the harvest–interaction hypothesis in fish, birds and mammals. We identify the mechanisms by which harvesting might make population size more variable over time and thereby increase the risk of extinction. Theoretical models show that harvest can modify population structure in time and space, and that changes in the amplitude and synchrony of population dynamics both increase extinction risk. Empirical evidence indicates that fishing amplifies the effects of environmental changes on the population variability, but no empirical study of terrestrial species has tested for amplified environmentally induced fluctuations due to hunting. Synthesis and applications. In terrestrial species, theoretical studies have evaluated how environmentally induced fluctuations in population size are magnified by different harvest strategies, but there is now an urgent need for an empirical evaluation of this hypothesis. Future research is needed to explore how hunting and climate interact and to test whether hunting enhances environmentally induced fluctuations in population numbers of terrestrial species.

Spatial synchrony in sub-arctic geometrid moth outbreaks reflects dispersal in larval and adult life cycle stages.

Spatial synchrony in population dynamics can be caused by dispersal or spatially correlated variation in environmental factors like weather (Moran effect). Distinguishing between these mechanisms is challenging for natural populations, and the study of dispersal-induced synchrony in particular has been dominated by theoretical modelling and laboratory experiments. The goal of the present study was to evaluate the evidence for dispersal as a cause of meso-scale (distances of tens of kilometres) spatial synchrony in natural populations of the two cyclic geometrid moths Epirrita autumnata and Operophtera brumata in sub-arctic mountain birch forest in northern Norway. To infer the role of dispersal in geometrid synchrony, we applied three complementary approaches, namely estimating the effect of design-based dispersal barriers (open sea) on synchrony, comparing the strength of synchrony between E.autumnata (winged adults) and the less dispersive O.brumata (wingless adult females), and relating the directionality (anisotropy) of synchrony to the predominant wind directions during spring, when geometrid larvae engage in windborne dispersal (ballooning). The estimated effect of dispersal barriers on synchrony was almost three times stronger for the less dispersive O.brumata than E.autumnata. Inter-site synchrony was also weakest for O.brumata at all spatial lags. Both observations argue for adult dispersal as an important synchronizing mechanism at the spatial scales considered. Further, synchrony in both moth species showed distinct anisotropy and was most spatially extensive parallel to the east-west axis, coinciding closely to the overall dominant wind direction. This argues for a synchronizing effect of windborne larval dispersal. Congruent with most extensive dispersal along the east-west axis, E.autumnata also showed evidence for a travelling wave moving southwards at a speed of 50-80km/year. Our results suggest that dispersal processes can leave clear signatures in both the strength and directionality of synchrony in field populations, and highlight wind-driven dispersal as promising avenue for further research on spatial synchrony in natural insect populations.

Spatial synchrony in Drosophila suzukii population dynamics along elevational gradients

1. Spotted wing drosophila (SWD; Drosophila suzukii Matsumura, 1931) is a polyphagous invasive crop pest native of Southeast Asia able to attack a wide array of host plant species in both cultivated and natural habitats. SWD is now widespread in several mountain regions, but it is still unclear how the species moves to different elevations across the seasons, and how this depends on environmental conditions and food resources.2. The temporal dynamics of several SWD populations were studied along elevational gradients in the Alps using a synchrony analysis. Twelve transects were selected, covering an overall elevational gradient of 2100 m. SWD abundance was monitored every 2 weeks during the growing season (from June to November 2015) when cultivated and wild hosts are potentially susceptible (i.e. fruits are ripe).3. Spotted wing drosophila were widely distributed along all the tested elevations, revealing synchrony in population dynamics across ranges in elevation and geographic distance. Synchronised populations were observed at distances of up to 100 km at sites with similar temperatures. The high dispersal potential of the pest together with the seasonal variation in temperature are likely to be the dominant mechanisms causing the observed spatial synchrony. A factor that seemed to reduce synchrony is the large concentration of host plants (i.e. crop) in lowland agricultural landscapes.4. The spatial synchrony in pest abundance at large spatial scale indicates that the risk of SWD outbreaks is highly dependent on drivers beyond the control of traditional field‐scale management. These findings could help in developing monitoring and predictive models of SWD population dynamics.

Geographic variation in forest composition and precipitation predict the synchrony of forest insect outbreaks

Evaluating the causes of spatial synchrony in population dynamics in nature is notoriously difficult due to a lack of data and appropriate statistical methods. Here, we use a recently developed method, a multivariate extension of the local indicators of spatial autocorrelation statistic, to map geographic variation in the synchrony of gypsy moth outbreaks. Regression analyses indicated that local synchrony of gypsy moth defoliation increased with the local synchrony of precipitation and the proportion of host tree density composed of oaks, especially those in the Lobatae (red oak) section. This may be the first study that demonstrates a relationship between defoliator population synchrony and host tree composition. More broadly, this study contributes to a small body of recent work that illustrates how mapping hotspots of unusually high or low synchrony facilitates an improved understanding of factors influencing spatially synchronous population dynamics generally, and triggers of pest insect outbreaks, more specifically.

Using geography to infer the importance of dispersal for the synchrony of freshwater plankton

Spatial synchrony in population dynamics is a ubiquitous ecological phenomenon that can result from predator–prey interactions, synchronized environmental variation (Moran effects), or dispersal. Of these, dispersal historically has been the least well studied in natural systems, partly because of the difficulty in quantifying dispersal in situ. We hypothesized that dispersal routes of plankton were based on the major and consistent water current movements in Kentucky Lake, a large reservoir in western Kentucky, USA. Then, using 26‐year time series collected at 16 locations, we used matrix regression techniques to test whether spatial heterogeneity in strengths of hypothesized dispersal predicted spatial patterns of synchrony of phytoplankton and zooplankton, thereby testing for evidence of dispersal as a possible mechanism of synchrony in this system. Nearly all taxa showed significant spatial synchrony that did not decline with increasing linear distance between locations. All taxa also showed substantial geographic structure in synchrony that was not explained by linear distance. Matrix regression revealed that our hypothesized matrix of dispersal pathways, which differed substantially from linear distance, was a significant predictor of spatial variability in synchrony in phytoplankton biomass, and Bosmina longirostris and Daphnia lumholtzi densities. Thus dispersal was a likely mechanism of synchrony for these taxa. Our hypothesized dispersal matrix was a significant predictor of spatial patterns of synchrony for these taxa even after accounting for numerous alternative possible mechanisms, including possible Moran effects through any of ten physical/abiotic constraints. Our findings indicate that statistically comparing hypothesized or measured dispersal pathway information to synchrony data via matrix regressions can provide valuable evidence for the importance of dispersal as a mechanism of spatial synchrony.

The Pursuit of Population Collapses: Long-Term Dynamics of Semi-Domestic Reindeer in Sweden

Spatiotemporal reindeer population fluctuations are a result of multiple factors that working in concert affecting the structure and functioning of many Arctic and Sub-Arctic ecosystems. We investigated the population dynamics of Swedish semi-domestic reindeer from 1945 to 2012 at the reindeer herding district-level (Sameby) to identify possible population collapses or declines. We also explored spatial trends and synchrony in population dynamics across latitudinal-longitude gradients for two distinct periods: 1945–1965 and 1995–2012 but found no evidence of large-scale reindeer population declines and no visible synchrony across adjacent populations. Our findings were unexpected as both reindeer populations and the pastoral lifestyle face increased habitat loss, predation, fragmentation and climate change.

Spatial synchrony in population dynamics: The effects of demographic stochasticity and density regulation with a spatial scale

We generalize a previous simple result by Lande et al. (1999) on how spatial autocorrelated noise, dispersal rate and distance as well as strength of density regulation determine the spatial scale of synchrony in population density. It is shown how demographic noise can be incorporated, what effect it has on variance and spatial scale of synchrony, and how it interacts with the point process for locations of individuals under random sampling. Although the effect of demographic noise is a rather complex interaction with environmental noise, migration and density regulation, its effect on population fluctuations and scale of synchrony can be presented in a transparent way. This is achieved by defining a characteristic area dependent on demographic and environmental variances as well as population density, and subsequently using this area to define a spatial demographic coefficient. The demographic noise acts through this coefficient on the spatial synchrony, which may increase or decrease with increasing demographic noise depending on other parameters. A second generalization yields the modeling of density regulation taking into account that regulation at a given location does not only depend on the density at that site but also on densities in the whole territory or home range of individuals. It is shown that such density regulation with a spatial scale reduces the scale of synchrony in population fluctuations relative to the simpler model with density regulation at each location determined only by the local point density, and may even generate negative spatial autocorrelations.

Increasing frequency of low summer precipitation synchronizes dynamics and compromises metapopulation stability in the Glanville fritillary butterfly.

Climate change is known to shift species' geographical ranges, phenologies and abundances, but less is known about other population dynamic consequences. Here, we analyse spatio-temporal dynamics of the Glanville fritillary butterfly (Melitaea cinxia) in a network of 4000 dry meadows during 21 years. The results demonstrate two strong, related patterns: the amplitude of year-to-year fluctuations in the size of the metapopulation as a whole has increased, though there is no long-term trend in average abundance; and there is a highly significant increase in the level of spatial synchrony in population dynamics. The increased synchrony cannot be explained by increasing within-year spatial correlation in precipitation, the key environmental driver of population change, or in per capita growth rate. On the other hand, the frequency of drought during a critical life-history stage (early larval instars) has increased over the years, which is sufficient to explain the increasing amplitude and the expanding spatial synchrony in metapopulation dynamics. Increased spatial synchrony has the general effect of reducing long-term metapopulation viability even if there is no change in average metapopulation size. This study demonstrates how temporal changes in weather conditions can lead to striking changes in spatio-temporal population dynamics.

Genetic similarity of island populations of tent caterpillars during successive outbreaks.

Cyclic or fluctuating populations experience regular periods of low population density. Genetic bottlenecks during these periods could give rise to temporal or spatial genetic differentiation of populations. High levels of movement among increasing populations, however, could ameliorate any differences and could also synchronize the dynamics of geographically separated populations. We use microsatellite markers to investigate the genetic differentiation of four island and one mainland population of western tent caterpillars, Malacosoma californicum pluviale, in two periods of peak or pre-peak density separated by 8 years. Populations showed high levels of genetic variation and little genetic differentiation either temporally between peaks or spatially among sites. Mitochondrial haplotypes were also shared between one island population and one mainland population in the two years studied. An isolation-by-distance analysis showed the FST values of the two geographically closest populations to have the highest level of differentiation in both years. We conclude that high levels of dispersal among populations maintain both synchrony of population dynamics and override potential genetic differentiation that might occur during population troughs. As far we are aware, this is the first time that genetic similarity between temporally separated population outbreaks in insects has been investigated. A review of genetic data for both vertebrate and invertebrate species of cyclic animals shows that a lack of spatial genetic differentiation is typical, and may result from high levels of dispersal associated with fluctuating dynamics.

Spatial synchrony in stream fish populations: influence of species traits

Spatial synchrony in population dynamics has been identified in most taxonomic groups. Numerous studies have reported varying levels of spatial synchrony among closely‐related species, suggesting that species' characteristics may play a role in determining the level of synchrony. However, few studies have attempted to relate this synchrony to the ecological characteristics and/or life‐history traits of species. Yet, as to some extent the extinction risk may be related to synchrony patterns, identifying a link between species' characteristics and spatial synchrony is crucial, and would help us to define effective conservation planning. Here, we investigated whether species attributes and temperature synchrony (i.e. a proxy of the Moran effect) account for the differences in spatial population synchrony observed in 27 stream fish species in France. After measuring and testing the level of synchrony for each species, we performed a comparative analysis to detect the phylogenetic signal of these levels, and to construct various multi‐predictor models with species traits and temperature synchrony as covariates, while taking phylogenetic relatedness into account. We then performed model averaging on selected models to take model uncertainty into account in our parameter estimates. Fifteen of the 27 species displayed a significant level of synchrony. Synchrony was weak, but highly variable between species, and was not conserved across the phylogeny. We found that some species' characteristics significantly influenced synchrony levels. Indeed, the average model indicated that species associated with greater dispersal abilities, lower thermal tolerance, and opportunistic strategy displayed a higher degree of synchrony. These findings indicate that phylogeny and spatial temperature synchrony do not provide information pertinent for explaining the variations in species' synchrony levels, whereas the dispersal abilities, the life‐history strategies and the upper thermal tolerance limits of species do appear to be quite reliable predictors of synchrony levels.

Synchrony in dynamics of giant kelp forests is driven by both local recruitment and regional environmental controls.

Populations of many species display spatially synchronous fluctuations in abundance. Synchrony is most commonly attributed to three processes: factors that influence recruitment (e.g., dispersal, early survival), large-scale environmental variability, and spatially autocorrelated trophic interactions. However it is often difficult to link population synchrony to a specific dominant process, particularly when multiple synchronizing forces are operating. We utilized a new satellite-based data set of giant kelp (Macrocystis pyrifera) canopy biomass to examine population synchrony in southern California kelp forests on spatial scales ranging from 50 m to 300 km and temporal scales ranging from 1 to 11 years. We examined the relationship between synchrony and distance for adult kelp populations, kelp recruits, sea urchin abundance (a major grazer of kelp), and environmental variables known to influence kelp population dynamics. Population synchrony in giant kelp decreased with distance between populations: an initial rapid exponential decrease between 50 m and 1.3 km was followed by a second, large-scale decrease between distances of 1.3 km and 172 km. The 50-m to 1.3-km spatial scale corresponded to the scales of synchrony in the abundance of sea urchins and young kelp recruits, suggesting that local drivers of predation and recruitment influence small-scale synchrony in kelp populations. The spatial correlation patterns of environmental variables, particularly wave height, were similar to the synchrony-distance relationship of kelp populations from 1.3 km to 172 km, suggesting that regional environmental variability, i.e., the Moran effect, was the dominant process affecting synchrony at larger spatial scales. This two-step pattern in the relationship between kelp biomass synchrony and distance was apparent in each of the 11 years of our study. Our results highlight the potential for synthesizing approaches from both landscape and population ecology in order to identify the multiple processes that generate synchrony in population dynamics.

Delimiting synchronous populations from monitoring data

We propose to investigate spatial synchrony in population dynamics from monitoring data. We develop a statistical procedure to delineate populations of sites with synchronous dynamics from short time series. The procedure relies on a new norm, the synchronous total variation norm, which promotes synchrony in the estimation of the sites dynamics. The method is tested on some synthetic data sets and is applied on data from the French breeding bird monitoring program.