The role of indirect interspecific effects in the stochastic dynamics of a simple trophic system.

Indirect interspecific effects (IIEs) occur when one species affects another through a third intermediary species. Understanding the role of IIEs in population dynamics is key for predicting community-level impacts of environmental change. Yet, empirically teasing apart IIEs from other interactions and population drivers has proven challenging and data-demanding, particularly in species-rich communities.

Effects of local density dependence and temperature on the spatial synchrony of marine fish populations.

Disentangling empirically the many processes affecting spatial population synchrony is a challenge in population ecology. Two processes that could have major effects on the spatial synchrony of wild population dynamics are density dependence and variation in environmental conditions like temperature. Understanding these effects is crucial for predicting the effects of climate change on local and regional population dynamics.

The role of seasonal migration in spatial population synchrony.

Spatially synchronized population dynamics are common in nature, and understanding their causes is key for predicting species persistence. A main driver of synchrony between populations of the same species is shared environmental conditions, which cause populations closer together in space to be more synchronized than populations further from one another. Most theoretical and empirical understanding of this driver considers resident species.

Generation time and seasonal migration explain variation in spatial population synchrony across European bird species.

Spatial population synchrony is common among populations of the same species and is an important predictor of extinction risk. Despite the potential consequences for metapopulation persistence, we still largely lack understanding of what makes one species more likely to be synchronized than another given the same environmental conditions. Generally, environmental conditions in a shared environment or a species' sensitivity to the environment can explain the extent of synchrony.

Harvesting can stabilise population fluctuations and buffer the impacts of extreme climatic events.

Harvesting can magnify the destabilising effects of environmental perturbations on population dynamics and, thereby, increase extinction risk. However, population-dynamic theory predicts that impacts of harvesting depend on the type and strength of density-dependent regulation. Here, we used logistic population growth models and an empirical reindeer case study to show that low to moderate harvesting can actually buffer populations against environmental perturbations.

Age-dependent patterns of spatial autocorrelation in fish populations.

The degree of spatial autocorrelation in population fluctuations increases with dispersal and geographical covariation in the environment, and decreases with strength of density dependence. Because the effects of these processes can vary throughout an individual's lifespan, we studied how spatial autocorrelation in abundance changed with age in three marine fish species in the Barents Sea. We found large interspecific differences in age-dependent patterns of spatial autocorrelation in density.

The neglected season: Warmer autumns counteract harsher winters and promote population growth in Arctic reindeer.

Arctic ungulates are experiencing the most rapid climate warming on Earth. While concerns have been raised that more frequent icing events may cause die-offs, and earlier springs may generate a trophic mismatch in phenology, the effects of warming autumns have been largely neglected. We used 25 years of individual-based data from a growing population of wild Svalbard reindeer, to test how warmer autumns enhance population growth.

High-Arctic family planning: earlier spring onset advances age at first reproduction in barnacle geese.

Quantifying how key life-history traits respond to climatic change is fundamental in understanding and predicting long-term population prospects Age at first reproduction (AFR), which affects fitness and population dynamics, may be influenced by environmental stochasticity but has rarely been directly linked to climate change Here, we use a case study from the highly seasonal and stochastic environment in High-Arctic Svalbard, with strong temporal trends in breeding conditions, to test whether rapid climate warming may induce changes in AFR in barnacle geese, . Using long-term mark-recapture and reproductive data (1991-2017) we developed a multi-event model to estimate individual AFR (i.e.

Decomposing demographic contributions to the effective population size with moose as a case study.

Levels of random genetic drift are influenced by demographic factors, such as mating system, sex ratio and age structure. The effective population size (N ) is a useful measure for quantifying genetic drift. Evaluating relative contributions of different demographic factors to N is therefore important to identify what makes a population vulnerable to loss of genetic variation.

Spatial covariation of competing species in a fluctuating environment.

Understanding how stochastic fluctuations in the environment influence population dynamics is crucial for sustainable management of biological diversity. However, because species do not live in isolation, this requires knowledge of how species interactions influence population dynamics. In addition, spatial processes play an important role in shaping population dynamics.

Spatial scaling of population synchrony in marine fish depends on their life history.

The synchrony of population dynamics in space has important implications for ecological processes, for example affecting the spread of diseases, spatial distributions and risk of extinction. Here, we studied the relationship between spatial scaling in population dynamics and species position along the slow-fast continuum of life history variation. Specifically, we explored how generation time, growth rate and mortality rate predicted the spatial scaling of abundance and yearly changes in abundance of eight marine fish species.

More frequent extreme climate events stabilize reindeer population dynamics.

Extreme climate events often cause population crashes but are difficult to account for in population-dynamic studies. Especially in long-lived animals, density dependence and demography may induce lagged impacts of perturbations on population growth. In Arctic ungulates, extreme rain-on-snow and ice-locked pastures have led to severe population crashes, indicating that increasingly frequent rain-on-snow events could destabilize populations.

Spatial distribution and optimal harvesting of an age-structured population in a fluctuating environment.

We analyze a spatial age-structured model with density regulation, age specific dispersal, stochasticity in vital rates and proportional harvesting. We include two age classes, juveniles and adults, where juveniles are subject to logistic density dependence. There are environmental stochastic effects with arbitrary spatial scales on all birth and death rates, and individuals of both age classes are subject to density independent dispersal with given rates and specified distributions of dispersal distances.

Modelling time to population extinction when individual reproduction is autocorrelated.

In nature, individual reproductive success is seldom independent from year to year, due to factors such as reproductive costs and individual heterogeneity. However, population projection models that incorporate temporal autocorrelations in individual reproduction can be difficult to parameterise, particularly when data are sparse. We therefore examine whether such models are necessary to avoid biased estimates of stochastic population growth and extinction risk, by comparing output from a matrix population model that incorporates reproductive autocorrelations to output from a standard age-structured matrix model that does not.

Inbreeding parents should invest more resources in fewer offspring.

Inbreeding increases parent-offspring relatedness and commonly reduces offspring viability, shaping selection on reproductive interactions involving relatives and associated parental investment (PI). Nevertheless, theories predicting selection for inbreeding versus inbreeding avoidance and selection for optimal PI have only been considered separately, precluding prediction of optimal PI and associated reproductive strategy given inbreeding. We unify inbreeding and PI theory, demonstrating that optimal PI increases when a female's inbreeding decreases the viability of her offspring.

Modelling effects of nonbreeders on population growth estimates.

Adult individuals that do not breed in a given year occur in a wide range of natural populations. However, such nonbreeders are often ignored in theoretical and empirical population studies, limiting our knowledge of how nonbreeders affect realized and estimated population dynamics and potentially impeding projection of deterministic and stochastic population growth rates. We present and analyse a general modelling framework for systems where breeders and nonbreeders differ in key demographic rates, incorporating different forms of nonbreeding, different life histories and frequency-dependent effects of nonbreeders on demographic rates of breeders.

Contrasting effects of summer and winter warming on body mass explain population dynamics in a food-limited Arctic herbivore.

The cumulative effects of climate warming on herbivore vital rates and population dynamics are hard to predict, given that the expected effects differ between seasons. In the Arctic, warmer summers enhance plant growth which should lead to heavier and more fertile individuals in the autumn. Conversely, warm spells in winter with rainfall (rain-on-snow) can cause 'icing', restricting access to forage, resulting in starvation, lower survival and fecundity.

Demographic buffering of life histories? Implications of the choice of measurement scale.

Life-history theory predicts that the vital rates that influence population growth the most should be buffered against environmental fluctuations due to selection for reduced variation. However, it remains unclear whether populations actually are influenced by such "demographic buffering," because variation in vital rates can be compared on different measurement scales, and there has been little attempt to investigate whether the choice of scale influences the chance of detecting demographic buffering. We compared two statistical approaches to examine whether demographic buffering has influenced vital rates in wild Svalbard reindeer (Rangifer tarandus platyrhynchus).

Evidence of inbreeding depression but not inbreeding avoidance in a natural house sparrow population.

Inbreeding is common in small and threatened populations and often has a negative effect on individual fitness and genetic diversity. Thus, inbreeding can be an important factor affecting the persistence of small populations. In this study, we investigated the effects of inbreeding on fitness in a small, wild population of house sparrows (Passer domesticus) on the island of Aldra, Norway.

Demographic stochasticity, allee effects, and extinction: the influence of mating system and sex ratio.

Demographic stochasticity has a substantial influence on the growth of small populations and consequently on their extinction risk. Mating system is one of several population characteristics that may affect this. We use a stochastic pair-formation model to investigate the combined effects of mating system, sex ratio, and population size on demographic stochasticity and thus on extinction risk.

The influence of persistent individual differences and age at maturity on effective population size.

Ratios of effective populations size, N(e), to census population size, N, are used as a measure of genetic drift in populations. Several life-history parameters have been shown to affect these ratios, including mating system and age at sexual maturation. Using a stochastic matrix model, we examine how different levels of persistent individual differences in mating success among males may affect N(e)/N, and how this relates to generation time.

In vitro assessment of eye irritancy using the Reconstructed Human Corneal Epithelial SkinEthic HCE model: application to 435 substances from consumer products industry.

The 7th amendment of the EU Cosmetics Directive led to the ban of eye irritation testing for cosmetic ingredients in animals, effective from March 11th 2009. Over the last 20years, many efforts have been made to find reliable and relevant alternative methods. The SkinEthic HCE model was used to evaluate the in vitro eye irritancy potential of substances from a cosmetic industry portfolio.

Fixation of slightly beneficial mutations: effects of life history.

Recent studies of rates of evolution have revealed large systematic differences among organisms with different life histories, both within and among taxa. Here, we consider how life history may affect the rate of evolution via its influence on the fixation probability of slightly beneficial mutations. Our approach is based on diffusion modeling for a finite, stage-structured population with stochastic population dynamics.

Understanding mating systems: a mathematical model of the pair formation process.

Mechanisms generating inequalities among males in reproductive success are key to understanding the evolutionary significance of sexual selection. This paper develops a stochastic model to quantitatively describe and analyze mating systems on a continuous scale from strict monogamy to extreme polygyny. The variance in male mating success is shown to increase with increased differences among males, with decreased interdependence of mating events, with increased population size, and with an increased number of females per male.