Synchrony In Abundance Research Articles

Synchrony in adult survival is remarkably strong among common temperate songbirds across France.

Synchronous variation in demographic parameters across species increases the risk of simultaneous local extinction, which lowers the probability of subsequent recolonization. Synchrony therefore tends to destabilize meta-populations and meta-communities. Quantifying interspecific synchrony in demographic parameters, like abundance, survival, or reproduction, is thus a way to indirectly assess the stability of meta-populations and meta-communities. Moreover, it is particularly informative to identify environmental drivers of interspecific synchrony because those drivers are important across species. Using a Bayesian hierarchical multisite multispecies mark-recapture model, we investigated temporal interspecific synchrony in annual adult apparent survival for 16 common songbird species across France for the period 2001-2016. Annual adult survival was largely synchronous among species (73%, 95% credible interval [47%-94%] of the variation among years was common to all species), despite species differing in ecological niche and life history. This result was robust to different model formulations, uneven species sample sizes, and removing the long-term trend in survival. Synchrony was also shared across migratory strategies, which suggests that environmental forcing during the 4-month temperate breeding season has a large-scale, interspecific impact on songbird survival. However, the strong interspecific synchrony was not easily explained by a set of candidate weather variables we defined a priori. Spring weather variables explained only 1.4% [0.01%-5.5%] of synchrony, while the contribution of large-scale winter weather indices may have been stronger but uncertain, accounting for 12% [0.3%-37%] of synchrony. Future research could jointly model interspecific variation and covariation in breeding success, age-dependent survival, and age-dependent dispersal to understand when interspecific synchrony in abundance emerges and destabilizes meta-communities.

Atlantic salmon survival at sea: temporal changes that lack regional synchrony

Spatial and temporal synchrony in abundance or survival trends can be indicative of whether populations are affected by common environmental drivers. In Atlantic salmon ( Salmo salar), return rates to natal rivers have generally been assumed to be affected primarily by shared oceanic conditions, leading to spatially synchronous trends in mortality. Here, we investigated the existence of parallel trends in salmon sea survival, using data on migrating smolts and returning adults from seven Canadian populations presumed to share feeding grounds. We analysed sea survival, using a Bayesian change-point model capable of detecting nonstationarity in time series data. Our results indicate that while salmon have experienced broadly comparable patterns in survival, finer-scale temporal shifts are not synchronous among populations. Our findings are not consistent with the hypothesis that salmon populations consistently share the same mortality-related stressors in the marine environment. Although populations may have shared greater synchrony in survival patterns in the past, this synchrony may be breaking down. It may be prudent to direct greater attention to smaller-scale regional and population-level correlates of survival.

Effects of nonnative species on the stability of riverine fish communities

Despite the increasing ubiquity of biological invasions worldwide, little is known about the scale‐dependent effects of nonnative species on real‐world ecological dynamics. Here, using an extensive time series dataset of riverine fish communities across different biogeographic regions of the world, we assessed the effects of nonnative species on the temporal variability and synchrony in abundance at different organizational levels (population, metapopulation, community and metacommunity) and spatial scales (stream reach and river basin). At the reach scale, we found that populations of nonnative species were more variable over time than native species, and that this effect scaled up to the community level – significantly destabilizing the dynamics of riverine fish communities. Nonnative species not only contributed to reduced community stability, but also increased variability of native populations. By contrast, we found no effect of nonnative species dominance on local interspecific synchrony among native species. At the basin scale, nonnative metapopulations were again more variable than the native ones. However, neither native metapopulations nor metacommunities showed differences in temporal variability or synchrony as nonnative species dominance increased basin‐wide. This suggests a ‘dilution effect’ where the contribution to regional stability of local native populations from sites displaying low levels of invasion reduced the destabilizing effects of nonnative species. Overall, our results indicate that accounting for the destabilizing effect of nonnative species is critical to understanding native species persistence and community stability.

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.

Experimental evaluation shows limited influence of pine plantations on the connectivity of highly fragmented bird populations

Summary Conversion of natural and agricultural areas to conifer plantations is an important element of global change. Despite their widespread distribution and global importance, it is still unclear whether conifer plantations hinder or enhance movement by biota. Population connectivity is difficult to quantify without detailed studies such as those using capture–mark–recapture methods. A novel solution is to quantify the synchrony in abundance between populations over time. Using this approach, more connected populations are expected to display synchrony, whereas disconnected populations are expected to fluctuate asynchronously. Here, we compared the relative effects of spatial proximity and matrix type on the population synchrony of a suite of forest‐dependent birds in a long‐term, fully controlled, and replicated landscape‐scale experiment in south‐eastern Australia. Our experiment consisted of comparing bird populations inhabiting remnant eucalypt patches surrounded by Radiata pine Pinus radiata plantations (50 patches) with bird populations inhabiting remnant eucalypt patches where the surrounding landscapes are grazing fields (55 patches). Our data set encompassed 10 years and included 52 bird species characterized by different life history traits. After controlling for the effects of rainfall and patch characteristics on population dynamics, we found that spatial proximity, not matrix type, was the main driver of population synchrony for 16 species. The effect of the pine plantation matrix was negative (it reduced synchrony). However, the magnitude of its effect was particularly low (being significant only in four species). Synthesis and applications. Our results show that pine plantations do not increase connectivity. In fact, they have little effect, with the exception of a few species, for which they may constitute a barrier. The implications of our findings for landscape management are that the conversion of agricultural areas to plantation forestry does not promote substantial movement of individuals (to the extent that would synchronize populations). Therefore, plantation expansion should not be promoted on the belief that it increases connectivity relative to an agricultural matrix.

SPATIAL SCALING OF AVIAN POPULATION DYNAMICS: POPULATION ABUNDANCE, GROWTH RATE, AND VARIABILITY

Synchrony in population fluctuations has been identified as an important component of population dynamics. In a previous study, we determined that local-scale (<15-km) spatial synchrony of bird populations in New England was correlated with synchronous fluctuations in lepidopteran larvae abundance and with the North Atlantic Oscillation. Here we address five questions that extend the scope of our earlier study using North American Breeding Bird Survey data. First, do bird populations in eastern North America exhibit spatial synchrony in abundances at scales beyond those we have documented previously? Second, does spatial synchrony depend on what population metric is analyzed (e.g., abundance, growth rate, or variability)? Third, is there geographic concordance in where species exhibit synchrony? Fourth, for those species that exhibit significant geographic concordance, are there landscape and habitat variables that contribute to the observed patterns? Fifth, is spatial synchrony affected by a species' life history traits? Significant spatial synchrony was common and its magnitude was dependent on the population metric analyzed. Twenty-four of 29 species examined exhibited significant synchrony in population abundance: mean local autocorrelation (rho)= 0.15; mean spatial extent (mean distance where rho=0) = 420.7 km. Five of the 29 species exhibited significant synchrony in annual population growth rate (mean local autocorrelation = 0.06, mean distance = 457.8 km). Ten of the 29 species exhibited significant synchrony in population abundance variability (mean local autocorrelation = 0.49, mean distance = 413.8 km). Analyses of landscape structure indicated that habitat variables were infrequent contributors to spatial synchrony. Likewise, we detected no effects of life history traits on synchrony in population abundance or growth rate. However, short-distance migrants exhibited more spatially extensive synchrony in population variability than either year-round residents or long-distance migrants. The dissimilarity of the spatial extent of synchrony across species suggests that most populations are not regulated at similar spatial scales. The spatial scale of the population synchrony patterns we describe is likely larger than the actual scale of population regulation, and in turn, the scale of population regulation is undoubtedly larger than the scale of individual ecological requirements.

MEASURING AND TESTING FOR SPATIAL SYNCHRONY

Spatial synchrony in abundance among populations at different locations has been studied for many species. Different statistics have been used as measures of synchrony, and various techniques have been employed to test the hypothesis that there is no synchrony. In this paper we first describe and contrast various measures of synchrony and then discuss testing for no synchrony. Tests that ignore the serial correlation are commonly employed but are incorrect if there is serial correlation present, as is often the case with populations followed over time. Alternative approaches and their limitations are presented including tests based on residuals, adjusted degrees of freedom tests, and bootstrap procedures. We recommend tests based on residuals in a model-based setting. We also discuss some of the difficulties of finding model-free approaches and suggest some methods based on confidence intervals for future study.

Measuring and Testing for Spatial Synchrony

Spatial synchrony in abundance among populations at different locations has been studied for many species. Different statistics have been used as measures of synchrony, and various techniques have been employed to test the hypothesis that there is no synchrony. In this paper we first describe and contrast various measures of synchrony and then discuss testing for no synchrony. Tests that ignore the serial correlation are commonly employed but are incorrect if there is serial correlation present, as is often the case with populations followed over time. Alternative approaches and their limitations are presented including tests based on residuals, adjusted degrees of freedom tests, and bootstrap procedures. We recommend tests based on residuals in a model-based setting. We also discuss some of the difficulties of finding model-free approaches and suggest some methods based on confidence intervals for future study.

Canonical functions for dispersal-induced synchrony.

Two processes are universally recognized for inducing spatial synchrony in abundance: dispersal and correlated environmental stochasticity. In the present study we seek the expected relationship between synchrony and distance in populations that are synchronized by density-independent dispersal. In the absence of dispersal, synchrony among populations with simple dynamics has been shown to echo the correlation in the environment. We ask what functional form we may expect between synchrony and distance when dispersal is the synchronizing agent. We formulate a continuous-space, continuous-time model that explicitly represents the time evolution of the spatial covariance as a function of spatial distance. Solving this model gives us two simple canonical functions for dispersal-induced covariance in spatially extended populations. If dispersal is rare relative to birth and death, then covariances between nearby points will follow the dispersal distance distribution. At long distances, however, the covariance tails off according to exponential or Bessel functions (depending on whether the population moves in one or two dimensions). If dispersal is common, then the covariances will follow the mixture distribution that is approximately Gaussian around the origin and with an exponential or Bessel tail. The latter mixture results regardless of the original dispersal distance distribution. There are hence two canonical functions for dispersal-induced synchrony