Synchrony In Fluctuations Research Articles

Political context is associated with extent of everyday physiological synchrony in older couples

Social units such as couples exist within a broader societal and cultural context. Characteristics of this macro-level context may indirectly shape couple dynamics by influencing opportunities and motivation for interdependence, e.g. through legislation and prevalent norms/values. The current study investigates the association between political context (left-right political spectrum) and physiological linkage (cortisol synchrony) in older couples’ daily lives. Older adult couples (N = 162) aged 56 to 89 years (M age = 72.3 years) and residing in Germany provided salivary cortisol samples 7 times daily for a 7-day period. Political context in which dyads lived was quantified with respect to where the federal state of residence was located on the left-right political spectrum using voting data from the 2017 federal election. Links between macro-context and extent of cortisol synchrony were examined using multilevel models, controlling for differences in diurnal rhythm, sex, age, body mass index, and individual-level political orientation. On average, there was evidence of synchrony in fluctuations in partners’ cortisol (b = 0.08, SE = 0.02, p < .001). The extent of cortisol synchrony was moderated by macro-context, such that couples living in a federal state placed further right on the left-right political spectrum exhibited greater cortisol synchrony (b = 0.03, SE = 0.01, p = .010). This new evidence provides a foundation for theorizing about and investigating how specific mechanisms contributing to political context, including family values, gender role attitudes, and laws supporting gender equality contribute to interpersonal linkages of physiological stress responses in daily life.

Complex interactions can create persistent fluctuations in high-diversity ecosystems.

When can ecological interactions drive an entire ecosystem into a persistent non-equilibrium state, where many species populations fluctuate without going to extinction? We show that high-diversity spatially heterogeneous systems can exhibit chaotic dynamics which persist for extremely long times. We develop a theoretical framework, based on dynamical mean-field theory, to quantify the conditions under which these fluctuating states exist, and predict their properties. We uncover parallels with the persistence of externally-perturbed ecosystems, such as the role of perturbation strength, synchrony and correlation time. But uniquely to endogenous fluctuations, these properties arise from the species dynamics themselves, creating feedback loops between perturbation and response. A key result is that fluctuation amplitude and species diversity are tightly linked: in particular, fluctuations enable dramatically more species to coexist than at equilibrium in the very same system. Our findings highlight crucial differences between well-mixed and spatially-extended systems, with implications for experiments and their ability to reproduce natural dynamics. They shed light on the maintenance of biodiversity, and the strength and synchrony of fluctuations observed in natural systems.

Trends and synchrony in fluctuations of the numbers of Whinchat (Saxicola rubetra) and European Stonechat (S. rubicola) in chalk steppe of North-eastern Ukraine

The problem of coexistence of related species within the same communities poses a question of how similar are the fluctuations of their numbers. Whinchat (Saxicola rubetra) and European Stonechat (S. rubicola) is an example of such a pair of phylogenetically related bird species, which are members of a foraging guild of sit-and-wait insectivores in open habitats. In Ukraine both species are quite common in meadows, steppes, fallow lands and other grassland habitats including undisturbed areas in nature reserves. In North-eastern Ukraine Whinchat and European Stonechat are characteristic of the bird communities of hills with chalk outcrops where they represent a group of species linked to chalk steppe. The trends in numbers and synchrony in fluctuations in the numbers of both species in this habitat were studied in national nature park ‘Dvorichanskyi’, Kharkiv region, North-eastern Ukraine for 9 years’ period (2010–2018). The data were retrieved from the results of yearly monitoring bird counts in chalk grassland habitats. The total-area census method was used on 3 plots of unequal size (17.8, 33.2, and 41.0 ha). The trends were analysed in programme TRIM (TRends &amp; Indices for Monitoring data) vers. 3.53. The extent of synchrony was estimated by means of zero-lag cross-correlation between the time series of log-transformed growth rates. Additionally, the coincidence of the direction of changes and the coincidence of peaks in series were checked. The trend in Whinchat abundance is characterised as significant steep decline (multiplicative slope 0.840, standard error 0.03; p&lt;0.01). The trend in European Stonechat abundance is classified as non-significant uncertain (multiplicative slope 0.909, standard error 0.06). The trends in both species correspond to general trends in Europe evidenced in PanEuropean Common Bird Monitoring Scheme for 1980–2016 and 1989–2016 for Whinchat and European Stonechat accordingly. The synchrony in fluctuations of the numbers of Whinchat and European Stonechat in chalk steppe habitats proved to be weak. Time series of both species abundances run in different directions almost in all cases where the comparison was possible that indicates probable differences in the causes of the dynamics of their populations. The study prompts to launch new or extend existing monitoring schemes in nature reserves and national parks in Ukraine to get reliable estimates for the trends in numbers of both rare and common bird species.

Spatial scales of population synchrony of two competing species: effects of harvesting and strength of competition

Theoretical analyses of single‐species models have revealed that the degree of synchrony in fluctuations of geographically separated populations increases with increasing spatial covariation in environmental fluctuations and increased interchange of individuals, but decreases with local strength of density dependence. Here we extend these results to include interspecific competition between two species as well as harvesting. We show that the effects of interspecific competition on the geographical scale of population synchrony are dependent on the pattern of spatial covariation of environmental variables. If the environmental noise is uncorrelated between the competing species, competition generally increases the spatial scale of population synchrony of both species. Otherwise, if the environmental noises are strongly correlated between species, competition generally increases the spatial scale of population synchrony of at least one, but also often of both species. The magnitude of these spatial scaling effects is, however, strongly influenced by the dispersal capacity of the two competing species. If the species are subject to proportional harvesting, this may synchronise population dynamics over large geographical areas, affecting the vulnerability of harvested species to environmental changes. However, the strength of interspecific competition may strongly modify this effect of harvesting on the spatial scale of population synchrony. For example, harvesting of one species may affect the spatial distribution of competing species that are not subject to harvesting. These analytical results provide an important illustration of the importance of applying an ecosystem rather than a single‐species perspective when developing harvest strategies for a sustainable management of exploited species.

Synchronous patterns of fluctuations in two stocks of anchovy Engraulis ringens Jenyns, 1842 in the Humboldt Current System

Summary Most of the studies investigating synchrony in fluctuations of abundance of small pelagic fish have been based on catch data only, which do not describe the dynamics of populations as a relative abundance index. In this paper, catch, biomass, recruitment and recruitment rate, were used to compare synchronous changes for two stocks of anchovy (Engraulis ringens) from 1982 to 2004. One is the North Central Peru stock (NCP) and the other is the shared South Peru-Northern Chile stock (SPNC). Correlation analysis demonstrated a significant association between population time series, particularly during the growing phase of the stocks. Thus, the synchronous fluctuation pattern of the two stocks is due to the recovery phase and probably driven by density-independent effects of simultaneous favorable environmental conditions occurring in the two regions. The conclusions were: (i) both NCP and SPNC anchovy stocks are in an overall positive phase of synchrony, (ii) higher correlations in the synchronous pattern of fluctuations occurred during simultaneous increase of biomass, and (iii) short-term fluctuations were negative when the abundance of the stock was lower and/or impacted by El Nino events.

Spatial–temporal scales of synchrony in marine zooplankton biomass and abundance patterns: A world-wide comparison

Large scale synchrony in the fluctuations of abundance or biomass of marine fish populations in regions on opposite sides of an ocean basin or in different oceans have been viewed as externally forced by correlated environmental stochasticity (e.g., common external forcing), most often as atmospheric teleconnections of basin-to-global scale atmospheric forcing, such as the Arctic Oscillation, North Atlantic Oscillation or the Pacific Decadal Oscillation. Specific causal mechanisms have been difficult to unequivocally discover, but possible mechanisms include influences on habitat temperatures, productivity operating through bottom-up (trophodynamic) mechanisms or direct climate influence on the fish populations (top-down mechanisms). For small pelagic fishes (sardines and anchovies) in widely separated large marine ecosystems that lack obvious ocean interconnectivity, it has been argued that the teleconnections may be atmospheric, acting on the fishes directly and propagating to the ecosystem from the middle out (wasp-waist species). Zooplankton biomass or abundance time series data from >100 sites world-wide are used to examine the spatial scales of coherent temporal synchrony. If spatially correlated environmental factors (like climate) are important for creating synchrony in fish populations via bottom-up effects (trophic interactions involving fish prey, e.g., zooplankton), then we would expect to observe synchrony in fluctuations of zooplankton biomass/numbers at spatial scales similar to those found for fish species. Zooplankton biomass/abundance have 50% spatial decorrelation scales of ca. 700–1400km and scales of significant coherence that extend to separation distances of ca. 3000km. These are also the spatial scales of environmental (sea surface temperature) synchrony from our global analysis. These scales are slightly greater than the 50% decorrelation scales of ca. 150–700km for recruitment synchrony in Atlantic marine fish and survival and recruitment synchrony of Northeast Pacific salmonids (150–1000km depending on species). However, the spatial scales of synchrony of annual zooplankton biomass anomalies in the Humboldt Current, California Current and Kuroshio ecosystems of the Pacific are much too small (ca. 2000km) to be directly causal of the basin-scale (7000–15,000km) synchrony exhibited by sardine and/or anchovy populations in those ecosystems.

Dispersal and natural enemies interact to drive spatial synchrony and decrease stability in patchy populations

Spatial synchrony is widespread in natural populations but the mechanisms that underpin it are not yet fully understood. Two key biotic drivers of spatial synchrony have been identified: dispersal and trophic interactions (e.g. natural enemies). We used spatially structured, patchy bacterial populations to show that although increased dispersal always enhanced spatial synchrony of fluctuations in bacterial abundance, this effect was far stronger in the presence of a bacteriophage parasite. Bacteriophages drove strong within patch fluctuations in bacterial abundance that became phase locked through dispersal. Furthermore, the way in which stability, measured as constancy, responded to increasing dispersal was qualitatively different depending on whether parasites were present or not. Patch-level constancy decreased with dispersal in the presence of parasites, whereas dispersal increased patch-level constancy in the absence of parasites. Population-level constancy also decreased with dispersal in the presence of parasites, but was unaffected by dispersal in the absence of parasites. These contrasting patterns were likely due to the different role played by dispersal in the presence and absence of parasites, synchronizing dynamics in the former case and averaging stochastic fluctuations in the latter. Taken together, our findings suggest that dispersal and natural enemies can interact to drive spatially synchronous population fluctuations that decrease stability at both the patch and population level.

Spatial dynamics of Microtus vole populations in continuous and fragmented agricultural landscapes

Small mammal populations often exhibit large-scale spatial synchrony, which is purportedly caused by stochastic weather-related environmental perturbations, predation or dispersal. To elucidate the relative synchronizing effects of environmental perturbations from those of dispersal movements of small mammalian prey or their predators, we investigated the spatial dynamics of Microtus vole populations in two differently structured landscapes which experience similar patterns of weather and climatic conditions. Vole and predator abundances were monitored for three years on 28 agricultural field sites arranged into two 120-km-long transect lines in western Finland. Sites on one transect were interconnected by continuous agricultural farmland (continuous landscape), while sites on the other were isolated from one another to a varying degree by mainly forests (fragmented landscape). Vole populations exhibited large-scale (>120 km) spatial synchrony in fluctuations, which did not differ in degree between the landscapes or decline with increasing distance between trapping sites. However, spatial variation in vole population growth rates was higher in the fragmented than in the continuous landscape. Although vole-eating predators were more numerous in the continuous agricultural landscape than in the fragmented, our results suggest that predators do not exert a great influence on the degree of spatial synchrony of vole population fluctuations, but they may contribute to bringing out-of-phase prey patches towards a regional density level. The spatial dynamics of vole populations were similar in both fragmented and continuous landscapes despite inter-landscape differences in both predator abundance and possibilities of vole dispersal. This implies that the primary source of synchronization lies in a common weather-related environment.

SPATIAL SYNCHRONY IN CORAL REEF FISH POPULATIONS AND THE INFLUENCE OF CLIMATE

We investigated spatial patterns of synchrony among coral reef fish populations and environmental variables over an eight-year period on the Great Barrier Reef, Australia. Our aims were to determine the spatial scale of intra- and interspecific synchrony of fluctuations in abundance of nine damselfish species (genus Pomacentrus) and assess whether environmental factors could have influenced population synchrony. All species showed intraspecific synchrony among populations on reefs separated by < or =100 km, and interspecific synchrony was also common at this scale. At greater spatial scales, only four species showed intraspecific synchrony, over distances ranging from 100-300 km to 500-800 km, and no cases of interspecific synchrony were recorded. The two mechanisms most likely to cause population synchrony are dispersal and environmental forcing through regionally correlated climate (the Moran effect). Dispersal may have influenced population synchrony over distances up to 100 km as this is the expected spatial range for ecologically significant reef fish dispersal. Environmental factors are also likely to have synchronized population fluctuations via the Moran effect for three reasons: (1) dispersal could not have caused interspecific synchrony that was common over distances < or =100 km because dispersal cannot link populations of different species, (2) variations in both sea surface temperature and wind speed were synchronized over greater spatial scales (>800 km) than fluctuations in damselfish abundance (< or =800 km) and were correlated with an index of global climate variability, the El Niño-Southern Oscillation (ENSO), and (3) synchronous population fluctuations of most damselfish species were correlated with ENSO; large population increases often followed ENSO events. We recorded regional variations in the strength of population synchrony that we suspect are due to spatial differences in geophysical, oceanographic, and population characteristics, which act to dilute or enhance the effects of synchronizing mechanisms. We conclude that synchrony is common among Pomacentrus populations separated by tens of kilometers but less prevalent at greater spatial scales, and that environmental variation linked to global climate is likely to be a driving force behind damselfish population synchrony at all spatial scales on the Great Barrier Reef.

Estimating the pattern of synchrony in fluctuating populations

Summary A central question in population ecology is how to estimate the effects of common environmental noise, e.g. due to large‐scale climate patterns, on the synchrony in population fluctuations over large distances. We show how the environmental variance can be split into components generated by several environmental variables and how these can be estimated from time‐series observations. With a set of time‐series observations from different locations not necessarily covering the same time span, it is shown how the spatial autocorrelation of the residual variance component, not explained by the covariates and corrected for demographic stochasticity, can be estimated using classical multinormal theory. Some previous results on spatial scaling in continuous linearized models on log scale are extended to also provide the scaling for the residuals. This is shown to be close to the spatial scaling of the autocorrelation in the environmental noise and only weakly affected by migration. The logistic model of local population dynamics with the NAO index as the only covariate is fitted to 22 populations of the Continental great cormorant Phalacrorax carbo sinensis. The spatial scale of the environmental noise is estimated to be about 155 km. The NAO index alone accounts for about 10% of the total environmental variance and nearly all of the regional environmental variance (long‐distance environmental autocorrelation).

Spatial synchrony in vole population fluctuations – a field experiment

Three mechanisms have been proposed to induce spatial synchrony in fluctuations of small mammal populations: climate‐related environmental effects, predation and dispersal. We conducted a field experiment in western Finland to evaluate the relative roles of these mechanisms in inducing spatial synchrony among cyclic populations of field voles Microtus agrestis. The study was conducted during the increase and peak phases of a vole population cycle on four agricultural field sites situated 1.5–7.0 km apart. Each field contained two 0.5‐ha fenced enclosures and one 1‐ha unfenced control area. One enclosure per field allowed access by small mustelid predators and the other by avian predators; all enclosures prevented the dispersal of voles. The unfenced control areas allowed access by all predators as well as dispersal by voles. Enclosed vole populations were in a treatment‐wise asynchronous phase before the predator access treatments were applied. The growth rates of all enclosed populations were tightly synchronized during the course of the experiment. Conversely, synchrony both among the unfenced populations and between the fenced and unfenced populations was practically non‐existent. During winter, in the increase phase of the cycle, vole populations in all treatments declined to low densities due to a seasonal effect of winter food depletion. During summer, in the peak year of the vole cycle, all populations fluctuated in synchrony. At this time, both small mustelids and birds of prey appeared to be abundant enough to induce synchrony. Dispersal was identified as a potential contributor to synchronization, but the magnitude of its effects could not be reliably discerned. Our results indicate that no single mechanism can account for the observed patterns of spatial synchrony among cyclic northern vole populations. Rather, spatial synchronization is induced by different mechanisms, namely seasonality and predation, acting successively during different seasons and phases of the vole cycle.

Global patterns of environmental synchrony and the Moran effect

There is considerable debate over the relative importance of dispersal and environmental disturbances (the Moran effect) as causes of spatial synchrony in fluctuations of animal populations. If environmental factors generally exhibit high levels of spatial autocorrelation, they may be playing a more important role in synchronizing animal populations than sometimes recognized. Here I examine this issue by analyzing spatial autocorrelation in annual rainfall and mean annual temperatures from sites throughout the world using the database maintained by the Global Historical Climatology Network. Both annual precipitation and mean annual temperatures exhibit high synchrony declining with distance and are statistically significant over large distance, often on a continental scale. In general, synchrony was slightly higher in annual precipitation at short distances, but greater in mean annual temperatures at long distances. No latitudinal gradient in synchrony of either variable was detected. The high overall synchrony observed in these environmental variables combined with a pattern of decline with distance similar to that observed in many animal populations suggest that the Moran effect can potentially play an important role in driving synchrony in a wide variety of ecological phenomena regardless of scale.

Cycles and synchrony in the Collared Lemming (Dicrostonyx groenlandicus) in Arctic North America.

Lemming populations are generally characterised by their cyclic nature, yet empirical data to support this are lacking for most species, largely because of the time and expense necessary to collect long-term population data. In this study we use the relative frequency of yearly willow scarring by lemmings as an index of lemming abundance, allowing us to plot population changes over a 34-year period. Scars were collected from 18 sites in Arctic North America separated by 2-1,647km to investigate local synchrony among separate populations. Over the period studied, populations at all 18 sites showed large fluctuations but there was no regular periodicity to the patterns of population change. Over all possible combinations of pairs of sites, only sites that were geographically connected and close (<6km) showed significant synchrony in fluctuations. The populations studied may not even be cyclic, at least for the time period 1960 to 1994, and although fluctuating, randomisation tests could not reject the null hypothesis of random fluctuations. These data have implications for the testing of hypotheses regarding lemming cycles and highlight the need for long-term trapping data to characterise the lemming cycle.

Population Cycles of Western Tent Caterpillars: Experimental Introductions and Synchrony of Fluctuations

To test several of the hypotheses to explain population cycles of forest Lepidoptera, it must be known if the decline phase is related to the local history of the insect population, and if population declines are synchronous among populations in a geographic region. To determine if out—of—phase population cycles could be initiated experimentally, egg masses of western tent caterpillars, Malacosoma californicum pluviale, were introduced to seven sites of low caterpillar density during the increase and peak phases of population fluctuation. The beginning of the decline phase occurred in 1986 in most introduced and source populations, but was delayed until 1987 in three populations initiated from egg—mass introductions in 1984 or 1985. Regardless of the history of the population, or the size and species of food—plant trees, all populations were very low by 1988. In 1986, the year of peak density at most sites, early larva