Spatial Synchrony Research Articles

Inferring spatial structure from population genetics and spatial synchrony in demography of Baltic Sea fishes: implications for management

AbstractThe spatial structure of species is important for their dynamics and evolution, but also for management and conservation. There are numerous ways of inferring spatial structures, and information from multiple methods is becoming more common to examine how different processes shape the spatial structures of species to improve fish management. Here, we investigate the spatial structure of a suite of Baltic Sea fish species based on the following: (i) spatial (presumably neutral) genetic differentiation, reviewed from the literature, and (ii) spatial synchrony in abundance changes from time series of fishery‐independent surveys, which we currently find to be underused given the amount of data available. For each of these two methods, species were classified as having a distinct, continuous or no/weak spatial structure. In addition, based on each source of information, we estimated the spatial scale of management units for species. The results show that only among species confined to the coastal zone the two sources of information yielded a congruence of the spatial structure (displaying a continuous spatial structure). In contrast, offshore species show weak spatial genetic structure but stronger spatial structure of synchrony in abundance. Based on this, we suggest that population genetic structure and synchrony in abundance should be used as complementary information as they reflect different spatial processes and suggest that management actions should differ with respect to scale depending on the management targets applied. We propose similar analysis should be applied to areas outside the Baltic Sea, and other stock identification methods, to improve management of fish resources.

Chimera patterns induced by distance-dependent power-law coupling in ecological networks.

This paper reports the occurrence of several chimera patterns and the associated transitions among them in a network of coupled oscillators, which are connected by a long-range interaction that obeys a distance-dependent power law. This type of interaction is common in physics and biology and constitutes a general form of coupling scheme, where by tuning the power-law exponent of the long-range interaction the coupling topology can be varied from local via nonlocal to global coupling. To explore the effect of the power-law coupling on collective dynamics, we consider a network consisting of a realistic ecological model of oscillating populations, namely the Rosenzweig-MacArthur model, and show that the variation of the power-law exponent mediates transitions between spatial synchrony and various chimera patterns. We map the possible spatiotemporal states and their scenarios that arise due to the interplay between the coupling strength and the power-law exponent.

Phase-Dependent Modulation of Oscillatory Phase and Synchrony by Long-Lasting Depolarizing Inputs in Central Neurons.

Oscillatory neural activities have been implicated in various types of information processing in the CNS. The procerebral (PC) lobe of the land mollusk Limax valentianus shows an ongoing oscillatory local field potential (LFP). Olfactory input increases both the frequency and spatial synchrony of the LFP oscillation by a nitric oxide (NO)-mediated mechanism, but how NO modulates the activity in a specific manner has been unclear. In the present study, we used electrical stimulation and NO uncaging to systematically analyze the response of the LFP oscillation and found phase-dependent effects on phase shifting and synchrony. The neurons that presumably release NO in the PC lobe preferentially fired at phases in which NO has a synchronizing effect, suggesting that the timing of NO release is regulated to induce a stereotyped response to natural sensory stimuli. The phase-response curve (PRC) describes the timing dependence of responses of an oscillatory system to external input. PRCs are usually constructed by recording the temporal shifts of the neural activity in response to brief electrical pulses. However, NO evokes a long-lasting depolarization persisting for several cycles of oscillation. The phase-response relationship obtained by NO stimulation was approximately the integral of the PRC. A similar relationship was also shown for regular firing of mouse cerebellar Purkinje cells receiving step depolarization, suggesting the generality of the results to oscillatory neural systems with highly distinct properties. These results indicate novel dynamic effects of long-lasting inputs on network oscillation and synchrony, which are based on simple and ubiquitous mechanisms.

Cross-modal integration of multimodal courtship signals in a wolf spider.

Cross-modal integration, i.e., cognitive binding of information transmitted in more than one signal mode, is important in animal communication, especially in complex, noisy environments in which signals of many individuals may overlap. Males of the brush-legged wolf spider Schizocosa ocreata (Hentz) use multimodal communication (visual and vibratory signals) in courtship. Because females may be courted by multiple males at the same time, they must evaluate co-occurring male signals originating from separate locations. Moreover, due to environmental complexity, individual components of male signals may be occluded, altering detection of sensory modes by females. We used digital multimodal playback to investigate the effect of spatial and temporal disparity of visual and vibratory components of male courtship signals on female mate choice. Females were presented with male courtship signals with components that varied in spatial location or temporal synchrony. Females responded to spatially disparate signal components separated by ≥90° as though they were separate sources, but responded to disparate signals separated by ≤45° as though they originated from a single source. Responses were seen as evidence for cross-modal integration. Temporal disparity (asynchrony) in signal modes also affected female receptivity. Females responded more to male signals when visual and vibratory modes were in synchrony than either out-of-synch or interleaved/alternated. These findings are consistent with those seen in both humans and other vertebrates and provide insight into how animals overcome communication challenges inherent in a complex environment.

Spatial and stage-structured model testing effects of spatial synchrony on the persistence of mosquito populations

Spatial and stage-structured model testing effects of spatial synchrony on the persistence of mosquito populations

Temporal development and spatial scale of coastal fish indicators in reference ecosystems: hydroclimate and anthropogenic drivers

Summary Indicators of ecosystem status are of increasing importance for management. Many studies infer associations between the environment and fish communities, but little is known about how fish community indicators are related to temporal variation in anthropogenic and hydroclimate drivers, and on what geographical scale, these indicators are representative. Here, we investigate the spatial synchrony of seven indicators of coastal fish community status among eleven reference sites 2002–2014 in the Baltic Sea. At three of these sites, we study the temporal covariation between indicators and anthropogenic and hydroclimate drivers over 25 years. The indicators (abundance of) – Perch, Large Piscivores and Non‐perch Piscivores – showed spatial synchrony over the study scale (100–1000 km), whereas temporal dynamics of other indicators reflected changes at scales <100 km. At the studied reference sites, temporal changes of indicators were mainly associated with climate‐related hydrological variables, but nutrient‐related variables were important in the northern Baltic Sea. Landings showed no associations with any indicator. Four of the indicators showed evident temporal autocorrelation reflecting an influence of internal population/community processes. Synthesis and applications. Environmental status of coastal fish communities in the Baltic Sea should be assessed and managed at a local scale. The main drivers of fish community indicators of ecosystem status tend to differ between coastal areas, but among the reference sites assessed in this study, hydroclimatic variation and internal processes seem to be of greater importance for the temporal development of indicators than anthropogenic pressures. Therefore, when assessing the status of coastal fish communities and evaluating management measures in areas impacted by anthropogenic activities, it is important to account for variation in salinity, temperature and time lags.

Spatial and temporal synchrony in reptile population dynamics in variable environments.

Resources are seldom distributed equally across space, but many species exhibit spatially synchronous population dynamics. Such synchrony suggests the operation of large-scale external drivers, such as rainfall or wildfire, or the influence of oasis sites that provide water, shelter, or other resources. However, testing the generality of these factors is not easy, especially in variable environments. Using a long-term dataset (13-22years) from a large (8000km(2)) study region in arid Central Australia, we tested firstly for regional synchrony in annual rainfall and the dynamics of six reptile species across nine widely separated sites. For species that showed synchronous spatial dynamics, we then used multivariate follow a multivariate auto-regressive state-space (MARSS) models to predict that regional rainfall would be positively associated with their populations. For asynchronous species, we used MARSS models to explore four other possible population structures: (1) populations were asynchronous, (2) differed between oasis and non-oasis sites, (3) differed between burnt and unburnt sites, or (4) differed between three sub-regions with different rainfall gradients. Only one species showed evidence of spatial population synchrony and our results provide little evidence that rainfall synchronizes reptile populations. The oasis or the wildfire hypotheses were the best-fitting models for the other five species. Thus, our six study species appear generally to be structured in space into one or two populations across the study region. Our findings suggest that for arid-dwelling reptile populations, spatial and temporal dynamics are structured by abiotic events, but individual responses to covariates at smaller spatial scales are complex and poorly understood.

Timing of population peaks of Norway lemming in relation to atmospheric pressure: A hypothesis to explain the spatial synchrony.

Herbivore cycles are often synchronized over larger areas than what could be explained by dispersal. In Norway, the 3–4 year lemming cycle usually show no more than a one-year time lag between different regions, despite distances of up to 1000 km. If important food plants are forced to reallocate defensive proteins in years with high seed production, spatially synchronized herbivore outbreaks may be due to climate-synchronized peaks in flowering. Because lemming peaks are expected to occur one year after a flowering peak, and the formation of flower buds is induced in the year before flowering, a two-year time lag between flower-inducing climate events and lemming peaks is predicted. At Hardangervidda, South Norway, the probability that a year was a population peak year of lemming during 1920–2014 increased with increasing midsummer atmospheric pressure two years earlier, even when the number of years since the previous peak was accounted for.

Evaluating confidence in climate‐based predictions of population change in a migratory species

AbstractAimForecasting ecological responses to climate change is a common objective, but there are few methods for evaluating confidence in such predictions. For migratory species, in particular, it is also essential to consider the extent of spatial synchrony among separate breeding populations in range‐wide predictions. We develop a quantitative method to evaluate the accuracy of climate‐based ecological predictions and use this approach to assess the extent of spatio‐temporal synchrony among distinct regions within the breeding range of a single migratory population.LocationWe model weekly site‐specific summer abundances (1996–2011) of monarch butterflies (Danaus plexippus) in the Midwestern USA as a function of climate conditions experienced during a shared spring migration/breeding phase in Texas and separate summer recruitment periods in Ohio and Illinois.MethodsUsing negative binomial regression models, we evaluate spatio‐temporal synchrony between monarchs in the two states and develop a novel quantitative assessment approach to determine the temporal predictive strength of our model with BayesianP‐values.ResultsMonarchs breeding in the Midwest exhibit spatio‐temporal synchrony in Ohio and Illinois; cooler spring temperatures, average to above average precipitation in Texas and cooler than average summer temperatures are associated with higher population abundances in both states. At least 10 years of data are needed for adequate model predictability of average future counts. Because annual spring weather conditions in Texas primarily drive yearly abundances, as opposed to localized summer effects, year‐specific counts are often difficult to predict reliably, specifically when predictive spring conditions are outside the range of typical regional conditions.Main conclusionsOur assessment method can be used in similar analyses to more confidently interpret ecological responses to climate change. Our results demonstrate the relative importance of climatic drivers in predicting abundances of a migratory species and the difficulties in producing reliable predictions of animal populations in the face of climate change.

Seasonal variability of cephalopod populations: a spatio‐temporal approach in the Western Mediterranean Sea

AbstractCephalopod populations show wide temporal fluctuations in abundance, which have usually been investigated at inter‐annual scales related to environmental variability. However, cephalopods are also strongly linked to seasonal environmental fluctuations owing to their short life cycles and single seasonal breeding. Therefore, population abundance critically depends on the success of breeding and recruitment from the previous year and the optimization of resources in a narrow period of favorable conditions. This adaptation of population dynamics is paramount in marked oligotrophic systems, such as the western Mediterranean Sea. We used monthly landings per unit effort (LPUE) to explore the spatio‐temporal variability in seasonal patterns of three cephalopod species (Illex coindetii, Eledone cirrhosa and Octopus vulgaris). Common trends across the study area were characterized for each species. In all cases, seasonal patterns were geographically aggregated in relation to differences in local environment (i.e., primary production and surface hydro‐climatology). Variability in the mean seasonal pattern over time was also investigated under contrasting environmental or population regimes. The mean seasonal trend was more pronounced in regimes of high‐population densities, suggesting a density‐dependent control that can modify the strength of the environmental forcing in the seasonal patterns. Our study also evidences a spatial synchrony in the seasonal fluctuations of LPUEs. Scales of synchrony ranged from 70 to 200 km, indicating a patchy‐aggregated spatial pattern as a part of complex population structures in the western Mediterranean. Improving our understanding of seasonal dynamics of cephalopods across temporal and spatial scales may lead to improved forecasts and management strategies.

Resource subsidies between stream and terrestrial ecosystems under global change.

Streams and adjacent terrestrial ecosystems are characterized by permeable boundaries that are crossed by resource subsidies. Although the importance of these subsidies for riverine ecosystems is increasingly recognized, little is known about how they may be influenced by global environmental change. Drawing from available evidence, in this review we propose a conceptual framework to evaluate the effects of global change on the quality and spatiotemporal dynamics of stream-terrestrial subsidies. We illustrate how changes to hydrological and temperature regimes, atmospheric CO2 concentration, land use and the distribution of nonindigenous species can influence subsidy fluxes by affecting the biology and ecology of donor and recipient systems and the physical characteristics of stream-riparian boundaries. Climate-driven changes in the physiology and phenology of organisms with complex life cycles will influence their development time, body size and emergence patterns, with consequences for adjacent terrestrial consumers. Also, novel species interactions can modify subsidy dynamics via complex bottom-up and top-down effects. Given the seasonality and pulsed nature of subsidies, alterations of the temporal and spatial synchrony of resource availability to consumers across ecosystems are likely to result in ecological mismatches that can scale up from individual responses, to communities, to ecosystems. Similarly, altered hydrology, temperature, CO2 concentration and land use will modify the recruitment and quality of riparian vegetation, the timing of leaf abscission and the establishment of invasive riparian species. Along with morphological changes to stream-terrestrial boundaries, these will alter the use and fluxes of allochthonous subsidies associated with stream ecosystems. Future research should aim to understand how subsidy dynamics will be affected by key drivers of global change, including agricultural intensification, increasing water use and biotic homogenization. Our conceptual framework based on the match-mismatch between donor and recipient organisms may facilitate understanding of the multiple effects of global change and aid in the development of future research questions.

Integrating spatial synchrony/asynchrony of population distribution into stock assessment models: a spatial hierarchical Bayesian statistical catch-at-age approach

Abstract In many marine fisheries assessments, population abundance indices from surveys collected by different states and agencies do not always agree with each other. This phenomenon is often due to the spatial synchrony/asynchrony. Those indices that are asynchronous may result in discrepancies in the assessment of temporal trends. In addition, commonly employed stock assessment models, such as the statistical catch-at-age (SCA) models, do not account for spatial synchrony/asynchrony associated with spatial autocorrelation, dispersal, and environmental noise. This limits the value of statistical inference on key parameters associated with population dynamics and management reference points. To address this problem, a set of geospatial analyses of relative abundance indices is proposed to model the indices from different surveys using spatial hierarchical Bayesian models. This approach allows better integration of different surveys with spatial synchrony and asynchrony. We used Atlantic weakfish (Cynoscion regalis) as an example for which there are state-wide surveys and expansive coastal surveys. We further compared the performance of the proposed spatially structured hierarchical Bayesian SCA models with a commonly used Bayesian SCA model that assumes relative abundance indices are spatially independent. Three spatial models developed to mimic different potential spatial patterns were compared. The random effect spatially structured hierarchical Bayesian model was found to be better than the commonly used SCA model and the other two spatial models. A simulation study was conducted to evaluate the uncertainty resulting from model selection and the robustness of the recommended model. The spatially structured hierarchical Bayesian model was shown to be able to integrate different survey indices with/without spatial synchrony. It is suggested as a useful tool when there are surveys with different spatial characteristics that need to be combined in a fisheries stock assessment.

Fine-scale spruce mortality dynamics driven by bark beetle disturbance in Babia Góra National Park, Poland

Bark beetle outbreaks have had major impacts on Norway spruce forests in Europe. The large majority of these forests are located in areas under forest management; thus, few studies have investigated outbreak-driven spruce mortality patterns unaffected by humans. Our study examined spruce mortality resultant from a beetle outbreak in a high-elevation, unmanaged forest over a 17-year span. We analyzed three tree-level survivorship and DBH datasets collected during pre-, mid-, and post-outbreak conditions to evaluate long-term mortality dynamics. We measured changes in mortality severity, topographic and stand structure characteristics, and stand complexity using ANOVAs, and we assessed five topographic and stand structure mortality predictors by employing boosted regression trees. Our results showed that though spruce mortality increased significantly over time, such increases were disproportionate with spatial synchrony. Moreover, the outbreak did not significantly alter the living stand structure and had little effect on stand complexity, exhibiting the effects of an outbreak that spread throughout the forest without causing major stand-level damage. Larger trees at higher elevations on south-facing slopes were targeted most frequently, particularly during the later stages of the outbreak. Aspect, elevation, and slope were the best predictors of mortality, demonstrating moderate forecasting ability. We showed that bark beetle outbreaks can operate on patch-scale gradients, affecting microhabitat conditions, without resulting in sweeping, stand-altering mortality. Small-scale outbreaks may increase forest resilience against more severe outbreaks in the future by creating canopy gaps that facilitate regeneration, which leads to more complex age and size structures within the stand.

Observations on the life-history traits of the North American parasitoidPhasgonophora sulcataWestwood (Hymenoptera: Chalcididae) attackingAgrilus planipennis(Coleoptera: Buprestidae) in Ontario, Canada

AbstractUnder laboratory and field conditions in Ontario, Canada, we explored the natural history ofPhasgonophora sulcataWestwood (Hymenoptera: Chalcididae), an indigenous solitary endoparasitoid ofAgrilus planipennisFairmaire (Coleoptera: Buprestidae) in North America. AdultP. sulcataemergence was ~20.2–23.9 days after host emergence at 21°C, withP. sulcatafemales emerging an ~5.4–5.8 days before males. Females also represented 61.8 and 67.0% of emerging adults in the two years sampled. Mean adult longevities for males and females ofP. sulcatawere 23.8±1.10 and 28.9±1.11 days at 21°C, respectively. Mean potential fecundity ofP. sulcataat emergence was 55.7±2.9 eggs per female. Based on adult emergence, parasitism at two sites varied from 11.7% to 34.4%. Adult parasitoids were first observed in the field in early June, with peak capture occurring in late June. Parasitism rates inA. planipennis-infested ash trees was not affected by tree height below 360 cm, whereas parasitism was not observed at heights>360 cm. Our results suggest that although mass rearing will be challenging, observed parasitism rates in conjunction with temporal and spatial synchrony indicate that indigenousP. sulcatamay be an important source of mortality forA. planipennispopulations.

Climate change-related regime shifts have altered spatial synchrony of plankton dynamics in the North Sea.

During the 1980s, the North Sea plankton community underwent a well-documented ecosystem regime shift, including both spatial changes (northward species range shifts) and temporal changes (increases in the total abundances of warmer water species). This regime shift has been attributed to climate change. Plankton provide a link between climate and higher trophic-level organisms, which can forage on large spatial and temporal scales. It is therefore important to understand not only whether climate change affects purely spatial or temporal aspects of plankton dynamics, but also whether it affects spatiotemporal aspects such as metapopulation synchrony. If plankton synchrony is altered, higher trophic-level feeding patterns may be modified. A second motivation for investigating changes in synchrony is that the possibility of such alterations has been examined for few organisms, in spite of the fact that synchrony is ubiquitous and of major importance in ecology. This study uses correlation coefficients and spectral analysis to investigate whether synchrony changed between the periods 1959-1980 and 1989-2010. Twenty-three plankton taxa, sea surface temperature (SST), and wind speed were examined. Results revealed that synchrony in SST and plankton was altered. Changes were idiosyncratic, and were not explained by changes in abundance. Changes in the synchrony of Calanus helgolandicus and Para-pseudocalanus spp appeared to be driven by changes in SST synchrony. This study is one of few to document alterations of synchrony and climate-change impacts on synchrony. We discuss why climate-change impacts on synchrony may well be more common and consequential than previously recognized.

Temporally increasing spatial synchrony of North American temperature and bird populations

The degree of spatial synchrony of many North American wintering bird species has increased over the past 50 years. This may affect ecological resilience by decreasing the potential for demographic rescue from interacting subpopulations.

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.

Population studies of tree-defoliating insects in Canada: a century in review

AbstractOur review highlights research during the past century focussed on the population ecology of outbreak-prone insect defoliators in Canadian forests. Based on reports from national and provincial surveys that began in the 1930s, there have been at least 106 insect defoliators reported to outbreak, most of which are native Lepidoptera, Hymenoptera (sawflies), or Coleoptera (in order of frequency from most to least). Studies comparing life-history traits of outbreak versus non-outbreak species to better understand why certain species are more outbreak-prone indicate several traits especially common among outbreak species, including egg clustering and aggregative larval feeding. There have been at least 50 time-series studies examining the spatiotemporal population behaviour of 12 major defoliator species. These studies provide evidence for both regular periodicity and spatial synchrony of outbreaks for most major species. Life-table studies seeking to understand the agents causing populations to fluctuate have been carried out for at least seven outbreak species, with the majority identifying natural enemies (usually parasitoids) as the major driver of outbreak collapse. Our review concludes with several case studies highlighting the impact and historical underpinnings of population studies for major defoliator species and a discussion of potential avenues for future research.

Spatial synchrony of amphipods in giant kelp forests

Amphipods are abundant in marine ecosystems worldwide and are important as prey and as consumers of macrophytes and detritus in food webs. Due to the spatially complex and dynamic nature of giant kelp (Macrocystis pyrifera) forests, assessment of the abundances of giant kelp and amphipods through time and space should provide insight into their potential interactions within the system. In an extensive field study within the surface canopy of giant kelp, the abundance of amphipods was quantified on artificial substrates at an array of 18 sites within kelp forests along Point Loma, California, USA, from July to October 2009 and 2010. Biomass of giant kelp canopy was estimated using remotely sensed imagery, and the spatial synchrony (autocorrelation through time) of kelp canopy was compared with synchrony of caprellid and non-caprellid amphipods. Caprellids exhibited high spatial synchrony that did not decrease with distance, while non-caprellids were synchronous on local scales, indicating high spatial heterogeneity in abundance through time. Gammarids showed a rapid exponential decrease in synchrony within the first 550 m that was consistent with synchrony of giant kelp. This suggests a local-scale biotic link between non-caprellids and giant kelp canopy, whereas caprellid synchrony is more likely to be influenced by regional-scale environmental variables. Caprellids and other amphipods are important prey resources for common kelp forest fishes, so these differences may in turn affect the spatial distributions of these predators. Moreover, excretion by amphipods may be an important source of nitrogen to giant kelp during periods of nitrogen limitation.

Timing and location of reproduction in African waterfowl: an overview of >100years of nest records.

The timing and location of reproduction are fundamental elements of reproductive success for all organisms. Understanding why animals choose to reproduce at particular times and in particular places is also important for our understanding of other aspects of organismal ecology, such as their habitat requirements, movement strategies, and biogeography. Although breeding patterns in waterfowl are relatively well documented, most studies are from northern temperate regions and the influences of location and time of year on breeding in Afrotropical ducks (Anatidae) are poorly understood. We outline six alternative (but not mutually exclusive) hypotheses that might explain where and when Afrotropical ducks choose to breed. To explore these hypotheses, we assembled and analyzed a new database of c.22,000 breeding records for 16 Afrotropical ducks and one introduced Palearctic species (the Mallard Anas platyrhynchos). The full database is available on line as an appendix to this article. We identified five distinct breeding strategies as well as two outliers. Peak breeding for 9 of 16 indigenous duck species occurs during the dry season. We found no evidence for spatial synchrony or spatial autocorrelation in breeding, suggesting a high level of flexibility in waterfowl responses to prevailing conditions in any given year. More intensive analyses of alternative hypotheses are needed, but our initial analysis suggests that the timing of breeding for the majority of Afrotropical ducks is driven by a combination of resource availability and predation risk.