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Theoretical and applied cancer studies that use individual-based models (IBMs) have been limited by the lack of a mathematical formulation that enables rigorous analysis of these models. However, spatial cumulant models (SCMs), which have arisen from theoretical ecology, describe population dynamics generated by a specific family of IBMs, namely spatio-temporal point processes (STPPs). SCMs are spatially resolved population models formulated by a system of differential equations that approximate the dynamics of two STPP-generated summary statistics: first-order spatial cumulants (densities), and second-order spatial cumulants (spatial covariances).We exemplify how SCMs can be used in mathematical oncology by modelling theoretical cancer cell populations comprising interacting growth factor-producing and non-producing cells. To formulate model equations, we use computational tools that enable the generation of STPPs, SCMs and mean-field population models (MFPMs) from user-defined model descriptions (Cornell et al., 2019). To calculate and compare STPP, SCM and MFPM-generated summary statistics, we develop an application-agnostic computational pipeline. Our results demonstrate that SCMs can capture STPP-generated population density dynamics, even when MFPMs fail to do so. From both MFPM and SCM equations, we derive treatment-induced death rates required to achieve non-growing cell populations. When testing these treatment strategies in STPP-generated cell populations, our results demonstrate that SCM-informed strategies outperform MFPM-informed strategies in terms of inhibiting population growths. We thus demonstrate that SCMs provide a new framework in which to study cell-cell interactions, and can be used to describe and perturb STPP-generated cell population dynamics. We, therefore, argue that SCMs can be used to increase IBMs’ applicability in cancer research.Statements and DeclarationsThe authors have no competing interests to declare that are relevant to the content of this article.

Identifying factors that drive infection dynamics in reservoir host populations is essential in understanding human risk from wildlife-originated zoonoses. We studied zoonotic Puumala orthohantavirus (PUUV) in the host, the bank vole ( Myodes glareolus ), populations in relation to the host population, rodent and predator community and environment-related factors and whether these processes are translated into human infection incidence. We used 5-year rodent trapping and bank vole PUUV serology data collected from 30 sites located in 24 municipalities in Finland. We found that PUUV seroprevalence in the host was negatively associated with the abundance of red foxes, but this process did not translate into human disease incidence, which showed no association with PUUV seroprevalence. The abundance of weasels, the proportion of juvenile bank voles in the host populations and rodent species diversity were negatively associated with the abundance index of PUUV positive bank voles, which, in turn, showed a positive association with human disease incidence. Our results suggest certain predators, a high proportion of young bank vole individuals, and a diverse rodent community, may reduce PUUV risk for humans through their negative impacts on the abundance of infected bank voles.

Temperature and intraspecific competition are important factors influencing the growth of all organisms, including parasites. The temperature increase is suggested to stimulate the development of parasites within poikilothermic hosts. However, at high parasite densities, this effect could be diminished, due to stronger intraspecific competition. Our study, for the first time, addressed the joint effects of warming and parasite abundances on parasite growth in poikilothermic hosts. The growth of the common fish parasite larvae (trematode Diplostomum pseudospathaceum) within the rainbow trout at different infection intensities and temperatures (15°C and 18°C) was experimentally investigated. The results showed that temperature was positively correlated with both parasite infection success and growth rates. The growth rates increased much more compared to those in many free-living poikilothermic animals. Atypically for a majority of parasites, D. pseudospathaceum larvae grow faster when abundant (Allee effect). The possible causes for this phenomenon (manipulation cost sharing, etc.) are discussed in this study. Importantly, limited evidence of the interaction between temperature and population density was found. It is likely that temperature did not change the magnitude of the Allee effect but affected its timing. The impact of these effects is supposed to become more pronounced in freshwater ecosystems under current climate changes.

Most small rodent populations in the world have fascinating population dynamics. In the northern hemisphere, voles and lemmings tend to show population cycles with regular fluctuations in numbers. In the southern hemisphere, small rodents tend to have large amplitude outbreaks with less regular intervals. In the light of vast research and debate over almost a century, we here discuss the driving forces of these different rodent population dynamics. We highlight ten questions directly related to the various characteristics of relevant populations and ecosystems that still need to be answered. This overview is not intended as a complete list of questions but rather focuses on the most important issues that are essential for understanding the generality of small rodent population dynamics.

Climatic anomalies are increasing in intensity and frequency due to rapid rates of global change, leading to increased extinction risk for many species. The impacts of anomalies are likely to vary between species due to different degrees of sensitivity and extents of local adaptation. Here, we used long-term butterfly monitoring data of 143 species across six European bioclimatic regions to show how species’ population dynamics have responded to local or globally-calculated climatic anomalies, and how species attributes mediate these responses. Contrary to expectations, degree of apparent local adaptation, estimated from the relative population sensitivity to local versus global anomalies, showed no associations with species mobility or reproductive rate but did contain a strong phylogenetic signal. The existence of phylogenetically-patterned local adaptation to climate has important implications for forecasting species responses to current and future climatic conditions and for developing appropriate conservation practices.

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 L.), 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 non-stationarity 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. peerReviewed

Our knowledge of the factors affecting species abundances is mainly based on time-series analyses of a few well-studied species at single or few localities, but we know little about whether results from such analyses can be extrapolated to the community level. We apply a joint species distribution model to long-term time-series data on British bird communities to examine the relative contribution of intra- and interspecific density dependence at different spatial scales, as well as the influence of environmental stochasticity, to spatiotemporal interspecific variation in abundance. Intraspecific density dependence has the major structuring effect on these bird communities. In addition, environmental fluctuations affect spatiotemporal differences in abundance. In contrast, species interactions had a minor impact on variation in abundance. Thus, important drivers of single-species dynamics are also strongly affecting dynamics of communities in time and space.

International audience; Globalization has led to the introduction of thousands of alien species worldwide. With growing impacts by invasive species, understanding the invasion process remains critical for predicting adverse effects and informing efficient management. Theoretically, invasion dynamics have been assumed to follow an "invasion curve" (S-shaped curve of available area invaded over time), but this dynamic has lacked empirical testing using large-scale data and neglects to consider invader abundances. We propose an "impact curve" describing the impacts generated by invasive species over time based on cumulative abundances. To test this curve's large-scale applicability, we used the data-rich New Zealand mud snail Potamopyrgus antipodarum, one of the most damaging freshwater invaders that has invaded almost all of Europe. Using long-term (1979-2020) abundance and environmental data collected across 306 European sites, we observed that P. antipodarum abundance generally increased through time, with slower population growth at higher latitudes and with lower runoff depth. Fifty-nine percent of these populations followed the impact curve, characterized by first occurrence, exponential growth, then long-term saturation. This behaviour is consistent with boom-bust dynamics, as saturation occurs due to a rapid decline in abundance over time. Across sites, we estimated that impact peaked approximately two decades after first detection, but the rate of progression along the invasion process was influenced by local abiotic conditions. The S-shaped impact curve may be common among many invasive species that undergo complex invasion dynamics. This provides a potentially unifying approach to advance understanding of large-scale invasion dynamics and could inform timely management actions to mitigate impacts on ecosystems and economies.

According to the theory of compensatory dynamics, depleted populations should recover when the threat responsible for their decline is removed because per capita population growth is assumed to be highest when populations are at their smallest viable sizes. Yet, many seriously depleted fish populations have failed to recover despite threat mitigation. Atlantic cod (Gadus morhua) stocks off Newfoundland, despite 30 years of dramatically reduced fishing mortality and numerous fishery closures, have not recovered, suggesting that drivers other than fishing can regulate the growth of collapsed fish populations, inhibiting or preventing their recovery. Here, using Bayesian inference, we show strong evidence of Allee effects in a south Newfoundland cod population, based on data on recruitment and spawning stock biomass. We infer the Allee-effect threshold, below which recovery is impaired. We demonstrate the necessity of data at low population sizes to make inferences about the nature of low-abundance dynamics. Our work indicates that Allee effects are not negligible in commercially exploited fish populations, as commonly projected, and that they represent an inhibitory force that can effectively prevent recovery from overfishing. Our findings contrast with prevailing fisheries management practices that assume compensatory dynamics at low abundances with potential to seriously overestimate the recovery potential of collapsed populations. peerReviewed

The ICES Workshop on ICES reference points (WKREF2) was tasked review the WKREF1 report and based on the outcome develop updated guidelines for the ICES reference points system and recommendations for ACOM consideration. The WKREF1 report has suggested 5 key recommendations to simplify and harmonise the ICES reference points framework representing a major change to the current guidelines. At WKREF2, we detailed discussions and four key concerns were raised about the proposed approach. The first related to the simplification of rules to define Blim. Around two thirds of category 1 stocks would end up as WKREF1 “Blim Type 2” where Blim would be set as a fraction of B0. The Allee effect or “depensation” maybe more important than previously thought and should be furthered explored for ICES stocks since it has important consequences for Blim. A number of challenges and issues around defining Blim using the current guidelines were documented. Some suggestions on improvement criteria were discussed including using classifiers to define spasmodic stocks and using change point algorithms to address non-stationary productivity regimes. However, further work is need to make these approaches operational and there was no consensus that the WKREF1 Blim types should replace the current guidelines. WKREF1 recommended that the FMSY proxy should be based on a biological proxies and should be less than the deterministic FMSY. It was pointed out that the stochastic FMSY estimated in EqSim for example, is lower than the deterministic FMSY and that the current guidelines ensure that the FMSY should not pose a more than 5% risk to Blim. A large amount of work described in WD 1 was carried out to develop an MSE framework to consistency and robustness test a candidate reference point system for North East Atlantic stocks. However, WKREF2 recommended that further work needs to be carried out to condition and test the simulation framework before the conclusions could be adopted by ICES and incorporated into the guidelines. A number of considerations for defining MSY related reference points were discussed including using model validation and prediction skill to ensure that ICES provide robust and credible advice. There is evidence that density dependence (DD) is important in the majority of ICES stocks (68% in recruitment and 54% in growth). The correct prediction of the shape and strength of density-dependence in productivity is key to predicting future stock development and providing the best possible long-term fisheries management advice. A suggested approach to use surplus production models (SPMs) to account for DD in FMSY was suggested and discussed but there was no consensus on whether that approach was appropriate. There was consensus that the FECO approach as a means of adapting target fishing mortality to medium-term changes in productivity should be included in the guidelines subject to a benchmark and ACOM approval. While WKREF1 and 2 focused mainly on Category 1 stocks ToR c) called for a “simplified and harmonised set of guidelines for estimating MSY and precautionary reference points applicable in the advice framework across various ICES stock categories.” Ideally the ICES assessment categories should provide equivalent risk across all stocks. This issue was discussed but no recommendations emerged. There was no consensus a revised reference point framework was proposed at WKREF2. However, it was agreed that it should be presented here for further discussion at ACOM and other fora. The key feature of the suggested approach is that the stock status evaluation is treated independent of the Advice Rule (AR). The main feature of the system is that the biomass trigger is not linked to a stock status evaluation, it is linked to the expected biomass when fishing at the target fishing mortality, in contrast to the current ICES approach. It also entailed that FMSY would also become an upper limit of fishing mortality and that the advised fishing mortality would be set at or lower than that level. WKREF2 did not discuss what to do in situations where SSB< Blim or alternative forms of HCR for the advice rule. Building community understanding and consensus around simplified and harmonised guidelines has yet to be achieved. A further workshop WKREF3 will be required to achieve that aim. The report includes 6 recommendations for ACOM consideration. nonPeerReviewed

Zoonotic diseases, caused by pathogens transmitted between other vertebrate animals and humans, pose a major risk to human health. Rodents are important reservoir hosts for many zoonotic pathogens, and rodent population dynamics affect the infection dynamics of rodent-borne diseases, such as diseases caused by hantaviruses. However, the role of rodent population dynamics in determining the infection dynamics of rodent-associated tick-borne diseases, such as Lyme borreliosis (LB), caused by Borrelia burgdorferi sensu lato bacteria, have gained limited attention in Northern Europe, despite the multiannual abundance fluctuations, the so-called vole cycles, that characterise rodent population dynamics in the region. Here, we quantify the associations between rodent abundance and LB human cases and Puumala Orthohantavirus (PUUV) infections by using two time series (25-year and 9-year) in Finland. Both bank vole (Myodes glareolus) abundance as well as LB and PUUV infection incidence in humans showed approximately 3-year cycles. Without vector transmitted PUUV infections followed the bank vole host abundance fluctuations with two-month time lag, whereas tick-transmitted LB was associated with bank vole abundance ca. 12 and 24 months earlier. However, the strength of association between LB incidence and bank vole abundance ca. 12 months before varied over the study years. This study highlights that the human risk to acquire rodent-borne pathogens, as well as rodent-associated tick-borne pathogens is associated with the vole cycles in Northern Fennoscandia, yet with complex time lags. peerReviewed

Community ecology has had a strong focus on single snapshots of species compositional variation in time. However, environmental change often occurs slowly at relatively broad spatio-temporal scales, which requires historically explicit assessments of long-term metacommunity dynamics, such as the order of species arrival during community assembly (i.e., priority effects), a theme that merits further empirical quantification. In this study, we applied the Bayesian inference scheme of Hierarchical Modeling of Species Communities together with information on functional traits and evolutionary dependencies to efficiently explore the question of how ecological communities are organized in space and time. To do this, we used a comprehensive time-series dataset from boreal lake plants and adopted the perspective that more sound conclusions on metacommunity dynamics can be gained from studies that consider a historically integrative approach over long timeframes. Our findings revealed that historical contingency via priority effects can profoundly shape community assembly under the influence of environmental change across decades (here, from the 1940s to the 2010s). Similarly, our results supported the existence of both positive and negative species-to-species associations in lake plants, suggesting that functional divergence can switch the inhibition–facilitation balance at the metacommunity level. Perhaps more importantly, this proof-of-concept study supports the notion that community ecology should include a historical perspective and suggests that ignoring priority effects may risk our ability to identify the true magnitude of change in present-day biotic communities.

Motivation Certain early-succession habitats may emerge only at restricted locations following disturbance. Therefore, whether disturbances tend to occur at certain sites or not can significantly affect habitat availability and metapopulation persistence of early-successional habitat specialists. Available models that combine metapopulation and landscape processes do not address how to model mobile, spatially shifting disturbance intensities independent of factors of site suitability. We present a model that allows the study on how a mobile disturbance pattern, of either natural or anthropogenic origin, affects patch network and metapopulation dynamics in realistic, heterogeneous landscapes. Methods We simulate metapopulation dynamics using a realistic landscape and varying patch destruction (and turnover) rates. We model the local patch emergence rate as the function of site suitability to patch emergence –a permanent factor–and local disturbance intensity, which we first estimate from empirical data and then simulate using annually updating spatial random fields. Using this model, we test whether and how a mobile disturbance pattern affects metapopulation persistence of the false heath fritillary butterfly (Melitaea diamina). Results In our case study, a mobile disturbance pattern caused new patches to emerge further away from occupied patches over time. This decreased the probability of new patches becoming colonized and thus impaired metapopulation persistence even when the median distance between patches appeared unchanging. However, if disturbances moved to areas that were highly suitable to patch emergence, increased habitat availability could compensate the otherwise detrimental effects of a mobile disturbance pattern. Disturbances that had a moderate degree of mobility had the most uncertain effects to metapopulation persistence. Conclusions Our modelling approach distinguishes between two processes behind the spatio-temporal pattern and rates of patch emergence–disturbance dynamics and varying site suitability. It enables the use of social and environmental data for forecasting habitat availability for early-succession habitat specialists under alternative future scenarios. It can be applied and developed further to suit multiple study systems. Our case study suggests that for species conservation, it is either beneficial to organize recurring management activities to take place at constant locations, or to gradually shift them towards areas that are highly suitable to patch emergence.

Benthic species and communities are linked to pelagic zooplankton through life‐stages encompassing both benthic and pelagic habitats and through a mutual dependency on primary producers as a food source. Many zooplankton taxa contribute to the sedimentary system as benthic eggs. Our main aim was to investigate the nature of the population level biotic interactions between and within these two seemingly independent communities, both dependent on the pelagic primary production, while simultaneously accounting for environmental drivers (salinity, temperature, and oxygen conditions). To this end, we applied multivariate autoregressive state‐space models to long (1966–2007) time series of annual abundance data, comparing models with and without interspecific interactions, and models with and without environmental variables included. We were not able to detect any direct coupling between sediment‐dwelling benthic taxa and pelagic copepods and cladocerans on the annual scale, but the most parsimonious model indicated that interactions within the benthic community are important. There were also positive residual correlations between the copepods and cladocerans potentially reflecting the availability of a shared resource or similar seasonal dependence, whereas both groups tended to correlate negatively with the zoobenthic taxa. The most notable single interaction within the benthic community was a tendency for a negative effect of Limecola balthica on the amphipods Monoporeia affinis and Pontoporeia femorata which can help explain the observed decrease in amphipods due to increased competitive interference., We investigated the abiotic drivers and biotic interactions of pelagic cladocerans and copepods and multiple macrozoobenthic species. Previous laboratory studies have shown that benthic species can reduce zooplankton emergence from resting eggs in the sediment. Our most supported model included no interactions between zooplankton and benthos on interannual scale, but did contain interactions between benthic species.

Senescence is often described as an age-dependent increase in natural mortality (known as actuarial senescence) and an age-dependent decrease in fecundity (known as reproductive senescence), and its role in nature is still poorly understood. Based on empirical estimates of reproductive and actuarial senescence, we used mathematical simulations to explore how senescence affects the population dynamics of Coregonus albula, a small, schooling salmonid fish. Using an empirically based eco-evolutionary model, we investigated how the presence or absence of senescence affects the eco-evolutionary dynamics of a fish population during pristine, intensive harvest, and recovery phases. Our simulation results showed that the presence or absence of senescence affected how the population responded to the selection regime. At an individual level, gillnetting caused a larger decline in asymptotic length when senescence was present, compared to the nonsenescent population, and the opposite occurred when fishing was done by trawling. This change was accompanied by evolution toward younger age at maturity. At the population level, the change in biomass and number of fish in response to different fishery size-selection patterns depended on the presence or absence of senescence. Since most life-history and fisheries models ignore senescence, they may be over-estimating reproductive capacity and under-estimating natural mortality. Our results highlight the need to understand the combined effects of life-history characters such as senescence and fisheries selection regime to ensure the successful management of our natural resources. peerReviewed

We analyzed the variability in vendace population parameters in the context of a life table. Parameters related to growth, fecundity and survival were estimated for post-recruitment (age > 1 growing season) life stages of Lake Southern Konnevesi vendace in both very high and low population abundance regimes. Pre-recruitment survival producing population stability was then determined. We found a very strong compensatory density dependence in growth, fecundity and survival: during low abundance, a lifetime reproductive output of a female was almost 20 times that of the abundant regime. To maintain the low abundance regime, pre-recruitment survival must counterbalance it by decreasing to a very low level. Potential drivers of high variability in pre-recruit survival and potential for depensation, Allee effect, are discussed, as well as the implications of the results on fisheries management and risk of extinction due to anthropogenic stressors such as global warming or extensive predator stocking. peerReviewed

Food quality is one of the key factors influencing zooplankton population dynamics. Eutrophication drives phytoplankton communities toward the dominance of cyanobacteria, which means a decrease in the availability of sterols and long-chain polyunsaturated fatty acids (EPA and DHA). The effects of different restoration measures on the nutritional quality of the phytoplankton community and subsequent impacts on zooplankton biomass have rarely been considered. We analyzed the nutritional quality of phytoplankton in the eutrophic Lake Vesijärvi in southern Finland over a 37-year period, and studied the impacts of two restoration measures, biomanipulation and hypolimnetic aeration, on the abundance of high-quality phytoplankton. We found that biomanipulation had a positive impact on the abundance of taxa synthesizing sterols, EPA, and DHA and, concurrently, on the biomass of the keystone species Daphnia. In contrast, hypolimnetic aeration did not result in such a beneficial outcome, manifested as a decrease in the abundance of Daphnia and frequent phytoplankton blooms dominated by cyanobacteria suggesting reduction in the nutritional quality of food for Daphnia. Our analysis shows that the determination of the nutritional value of algae and the contribution of essential fatty acids and sterols is an effective method to evaluate the success of various restoration measures.

This book chapter describes various aspects of diplostomiasis caused by Diplostomum spathaceum: diagnosis, epidemiology, life cycle, transmission, developmental stages, population dynamics, effects of climate change on parasite distribution, and disease control and prevention. peerReviewed

Although it is well known that insects are sensitive to temperature, how they will be affected by ongoing global warming remains uncertain because these responses are multifaceted and ecologically complex. We reviewed the effects of climate warming on 31 globally important phytophagous (plant‐eating) insect pests to determine whether general trends in their responses to warming were detectable. We included four response categories (range expansion, life history, population dynamics, and trophic interactions) in this assessment. For the majority of these species, we identified at least one response to warming that affects the severity of the threat they pose as pests. Among these insect species, 41% showed responses expected to lead to increased pest damage, whereas only 4% exhibited responses consistent with reduced effects; notably, most of these species (55%) demonstrated mixed responses. This means that the severity of a given insect pest may both increase and decrease with ongoing climate warming. Overall, our analysis indicated that anticipating the effects of climate warming on phytophagous insect pests is far from straightforward. Rather, efforts to mitigate the undesirable effects of warming on insect pests must include a better understanding of how individual species will respond, and the complex ecological mechanisms underlying their responses. peerReviewed

In recent decades, Norway spruce (Picea abies L. Karst.) forests of the High Tatra Mountains have suffered unprecedented tree mortality caused by European spruce bark beetle (Ips typographus L.). Analysis of the spatiotemporal pattern of bark beetle outbreaks across the landscape in consecutive years can provide new insights into the population dynamics of tree-killing insects. A bark beetle outbreak occurred in the High Tatra Mountains after a storm damaged more than 10,000 ha of forests in 2004. We combined yearly Landsat-derived bark beetle infestation spots from 2006 to 2014 and meteorological data to identify the susceptibility of forest stands to beetle infestation. We found that digital elevation model (DEM)-derived potential radiation loads predicted beetle infestation, especially in the peak phase of beetle epidemic. Moreover, spots attacked at the beginning of our study period had higher values of received solar radiation than spots at the end of the study period, indicating that bark beetles prefer sites with higher insolation during outbreak. We conclude that solar radiation, easily determined from the DEM, better identified beetle infestations than commonly used meteorological variables. We recommend including potential solar radiation in beetle infestation prediction models.

Predicting population colonisations requires understanding how spatio‐temporal changes in density affect dispersal. Density can inform on fitness prospects, acting as a cue for either habitat quality, or competition over resources. However, when escaping competition, high local density should only increase emigration if lower‐density patches are available elsewhere. Few empirical studies on dispersal have considered the effects of density at the local and landscape scale simultaneously. To explore this, we analyze 5 years of individual‐based data from an experimental introduction of wild guppies Poecilia reticulata. Natal dispersal showed a decrease in local density dependence as density at the landscape level increased. Landscape density did not affect dispersal among adults, but local density‐dependent dispersal switched from negative (conspecific attraction) to positive (conspecific avoidance), as the colonisation progressed. This study demonstrates that densities at various scales interact to determine dispersal, and suggests that dispersal trade‐offs differ across life stages. peerReviewed

Dickeya and Pectobacterium are responsible for causing blackleg of plants and soft rot of tubers in storage and in the field, giving rise to losses in seed potato production. In an attempt to improve potato health, biocontrol activity of known and putative antagonists was screened using in vitro and in planta assays, followed by analysis of their persistence at various storage temperatures. Most antagonists had low survival on potato tuber surfaces at 4 °C. The population dynamics of the best low‐temperature tolerant strain and also the most efficient antagonist, Serratia plymuthica A30, along with Dickeya solani as target pathogen, was studied with TaqMan real‐time PCR throughout the storage period. Tubers of three potato cultivars were treated in the autumn with the antagonist and then inoculated with D. solani. Although the cell densities of both strains decreased during the storage period in inoculated tubers, the pathogen population was always lower in the presence of the antagonist. The treated tubers were planted in the field the following growing season to evaluate the efficiency of the bacterial antagonist for controlling disease incidence. The potato endophyte S. plymuthica A30 protected potato plants by reducing blackleg development on average by 58.5% and transmission to tuber progeny as latent infection by 47–75%. These results suggest that treatment of potato tubers with biocontrol agents after harvest can reduce the severity of soft rot disease during storage and affect the transmission of soft rot bacteria from mother tubers to progeny tubers during field cultivation. peerReviewed

Climate change, habitat loss and fragmentation are major threats for populations and a challenge for individual behavior, interactions and survival. Predator–prey interactions are modified by climate processes. In the northern latitudes, strong seasonality is changing and the main predicted feature is shortening and instability of winter. Vole populations in the boreal Fennoscandia exhibit multiannual cycles. High amplitude peak numbers of voles and dramatic population lows alternate in 3–5‐year cycles shortening from North to South. One key factor, or driver, promoting the population crash and causing extreme extended lows, is suggested to be predation by the least weasel. We review the arms race between prey voles and weasels through the multiannual density fluctuation, affected by climate change, and especially the changes in the duration and stability of snow cover. For ground‐dwelling small mammals, snow provides thermoregulation and shelter for nest sites, and helps them hide from predators. Predicted increases in the instability of winter forms a major challenge for species with coat color change between brown summer camouflage and white winter coat. One of these is the least weasel, Mustela nivalis nivalis. Increased vulnerability of wrong‐colored weasels to predation affects vole populations and may have dramatic effects on vole dynamics. It may have cascading effects on other small rodent–predator interactions and even on plant–animal interactions and forest dynamics. peerReviewed

The early life environment can have profound, long‐lasting effects on an individual's fitness. For example, early life quality might (a) positively associate with fitness (a silver spoon effect), (b) stimulate a predictive adaptive response (by adjusting the phenotype to the quality of the environment to maximize fitness) or (c) be obscured by subsequent plasticity. Potentially, the effects of the early life environment can persist beyond one generation, though the intergenerational plasticity on fitness traits of a subsequent generation is unclear. To study both intra‐ and intergenerational effects of the early life environment, we exposed a first generation of bank voles to two early life stimuli (variation in food and social environment) in a controlled environment. To assess possible intra‐generational effects, the reproductive success of female individuals was investigated by placing them in large outdoor enclosures in two different, ecologically relevant environments (population densities). Resulting offspring were raised in the same population densities where they were conceived and their growth was recorded. When adult, half of the offspring were transferred to opposite population densities to evaluate their winter survival, a crucial fitness trait for bank voles. Our setup allowed us to assess: (a) do early life population density cues elicit an intra‐generational adaptive response, that is a higher reproductive success when the density matches the early life cues and (b) can early life stimuli of one generation elicit an intergenerational adaptive response in their offspring, that is a higher growth and winter survival when the density matches the early life cues of their mother. Our results show that the early life environment directly affects the phenotype and reproductive success of the focal generation, but adaptive responses are only evident in the offspring. Growth of the offspring is maintained only when the environment matches their mother's early life environment. Furthermore, winter survival of offspring also tended to be higher in high population densities if their mothers experienced an competitive early life. These results show that the early life environment can contribute to maintain high fitness in challenging environments, but not necessarily in the generation experiencing the early life cues. peerReviewed

The timing of sex in facultatively sexual organisms is critical to fitness, due to the differing demographic consequences of sexual versus asexual reproduction. In addition to the costs of sex itself, an association of sex with the production of dormant life stages also influences the optimal use of sex, especially in environments where resting eggs are essential to survive unfavourable conditions. Here we document population dynamics and the occurrence of sexual reproduction in natural populations of Daphnia magna across their growing season. The frequency of sexually reproducing females and males increased with population density and with decreasing asexual clutch sizes. The frequency of sexually reproducing females additionally increased as population growth rates decreased. Consistent with population dynamic models showing that the opportunity cost of sexual reproduction (foregoing contribution to current population growth) diminishes as populations approach carrying capacity, we found that investment in sexual reproduction was highest when asexual population growth was low or negative. Our results support the idea that the timing of sex is linked with periods when the relative cost of sex is reduced due to low potential asexual growth at high population densities. Thus, a combination of ecological and demographic factors affect the optimal timing of sexual reproduction, allowing D. magna to balance the necessity of sex against its costs.

Background: Periodical cicadas (Magicicada spp.) have a life cycle that ends with the entire underground nymph population exhibiting a synchronized mass emergence to mate above ground. Previous studies have hypothesized that the periodical cicadas evolved from non-periodical cicadas by switching from a life-cycle length determined by body size to one determined by age. Questions: When can a mutation coding for fixed life-cycle length invade a resident population in which life-cycle length is variable? What determines the length of the fixed cycle? Methods: Numerical analysis of a mathematical model and simulations of an individual-based model. Results: If there is a sufficiently strong predation intensity affecting the pool of individuals emerging to reproduce, a non-periodical population may become proto-periodical such that reproductive success varies yearly. Then, an emergence strategy with a fixed life-cycle length targeting years of high emergence density can invade. © 2018 Jaakko Toivonen peerReviewed

SUMMARYParasites manipulate their hosts’ phenotype to increase their own fitness. Like any evolutionary adaptation, parasitic manipulations should be costly. Though it is difficult to measure costs of the manipulation directly, they can be evaluated using an indirect approach. For instance, theory suggests that as the parasite infrapopulation grows, the investment of individual parasites in host manipulation decreases, because of cost sharing. Another assumption is that in environments where manipulation does not pay off for the parasite, it can decrease its investment in the manipulation to save resources. We experimentally infected rainbow trout Oncorhynchus mykiss with the immature larvae of the trematode Diplostomum pseudospathaceum, to test these assumptions. Immature D. pseudospathaceum metacercariae are known for their ability to manipulate the behaviour of their host enhancing its anti-predator defenses to avoid concomitant predation. We found that the growth rate of individual parasites in rainbow trout increased with the infrapopulation size (positive density-dependence) suggesting cost sharing. Moreover, parasites adjusted their growth to the intensity of infection within the eye lens where they were localized suggesting population density sensing. Results of this study support the hypothesis that macroparasites can adjust their growth rate and manipulation investment according to cost sharing level and infrapopulation size.

Background Tick-borne pathogens pose an increasing threat to human and veterinary health across the northern hemisphere. While the seasonal activity of ticks is largely determined by climatic conditions, host-population dynamics are also likely to affect tick abundance. Consequently, abundance fluctuations of rodents in northern Europe are expected to be translated into tick dynamics, and can hence potentially affect the circulation of tick-borne pathogens. We quantified and explained the temporal dynamics of the tick Ixodes ricinus in the northernmost part of its European geographical range, by estimating (i) abundance in vegetation and (ii) infestation load in the most common rodent species in the study area, the bank vole Myodes glareolus. Results Ixodes ricinus nymphs and adult females, the life stages responsible for the most of tick bites in humans, peaked in May-June and August-September. Larvae and nymphs were simultaneously active in June and abundance of questing larvae and nymphs in the vegetation showed a positive association with bank vole abundance. Moreover, infesting larvae and nymphs were aggregated on bank voles, and the infestation of bank voles with I. ricinus larvae and nymphs was positively associated with bank vole abundance. Conclusion Our results indicate early summer and early autumn as periods of increased risk for humans to encounter I. ricinus ticks in boreal urban forests and suggest a 2 years life-cycle for I. ricinus with two cohorts of ticks during the same year. Moreover, we identified a simultaneous activity of larvae and nymphs which allows co-feeding on the rodent host, which in turn supports the transmission of several important zoonotic tick-borne pathogens. Finally, we showed that a high density of the rodent host may enhance the risk that ticks and, potentially, tick-borne pathogens pose to human health. Electronic supplementary material The online version of this article (doi:10.1186/s13071-017-2112-x) contains supplementary material, which is available to authorized users.

Marie Vaugoyeau [et al.], The increase in size of human populations in urban and agricultural areas has resulted in considerable habitat conversion globally. Such anthropogenic areas have specific environmental characteristics, which influence the physiology, life history, and population dynamics of plants and animals. For example, the date of bud burst is advanced in urban compared to nearby natural areas. In some birds, breeding success is determined by synchrony between timing of breeding and peak food abundance. Pertinently, caterpillars are an important food source for the nestlings of many bird species, and their abundance is influenced by environmental factors such as temperature and date of bud burst. Higher temperatures and advanced date of bud burst in urban areas could advance peak caterpillar abundance and thus affect breeding phenology of birds. In order to test whether laying date advance and clutch sizes decrease with the intensity of urbanization, we analyzed the timing of breeding and clutch size in relation to intensity of urbanization as a measure of human impact in 199 nest box plots across Europe, North Africa, and the Middle East (i.e., the Western Palearctic) for four species of hole-nesters: blue tits (Cyanistes caeruleus), great tits (Parus major), collared flycatchers (Ficedula albicollis), and pied flycatchers (Ficedula hypoleuca). Meanwhile, we estimated the intensity of urbanization as the density of buildings surrounding study plots measured on orthophotographs. For the four study species, the intensity of urbanization was not correlated with laying date. Clutch size in blue and great tits does not seem affected by the intensity of urbanization, while in collared and pied flycatchers it decreased with increasing intensity of urbanization. This is the first large-scale study showing a species-specific major correlation between intensity of urbanization and the ecology of breeding. The underlying mechanisms for the relationships between life history and urbanization remain to be determined. We propose that effects of food abundance or quality, temperature, noise, pollution, or disturbance by humans may on their own or in combination affect laying date and/or clutch size., E. Barba acknowledges funding of project CGL2013-48001-C2-1-P (Spanish Ministry of Science and Innovation).

Parasites are an inseparable part of the life of wild birds. They may cause morbidity, mortality or reduction in fecundity. Parasite distribution in hosts is typically not uniform and many host factors (e.g. age) may affect the pattern of distribution. Under certain conditions, parasites even have the potential to regulate the host population. The grouse species of Finnish forests — the capercaillie Tetrao urogallus , the black grouse Lyrurus tetrix and the hazel grouse Tetrastes bonasia — harbour several species of intestinal helminth parasites. The populations have fluctuated in cyclic manner but the mechanisms behind the cycles are largely unknown. I studied the interactions of forest grouse and their intestinal helminth parasites by using intestinal samples collected by hunters in five game management districts during eight years (1995–2002). The most common parasite species in the samples was the nematode Ascaridia compar. Also, three species of cestodes (Skrjabinia cesticillus, Paroniella urogalli and Hymenolepis sp.) were found. Large size, male gender and age over 1 year were connected with an increased probability and intensity of A. compar infection. Juvenile grouse were commonly infected with cestodes while in adults infections were quite rare. The influence of inbreeding on the susceptibility to parasite infections was studied in the capercaillie by analysing microsatellite heterozygosity. The less heterozygous birds were more likely to be infected with A. compar and were more intensely infected suggesting negative influence of inbreeding on parasite resistance. An indirect negative effect of parasites was found by comparing bags hunted with a trained dog or without a dog. Grouse infected by cestodes were significantly more common in the dog-assisted bag. Thus, cestode infection seemed to make grouse more vulnerable to canine predation. The interaction between grouse population dynamics and parasites was studied by analyzing the grouse densities obtained from annual wildlife counts and parasite indices. A. compar was most common and most abundant in the years of grouse population decline. The grouse population growth rate was negatively correlated with the annual mean abundance of A. compar. Relative survival but not breeding success decreased as the abundance of A. compar increased. The findings suggest that A. compar influences the dynamics of Finnish grouse even though regular cyclic dynamics are no longer evident. Tiivistelmä Loiset kuuluvat erottamattomana osana luonnonvaraisten lintujen elämään. Ne voivat aiheuttaa sairautta, kuolleisuutta tai hedelmällisyyden alentumista. Tyypillisesti loiset ovat levinneet isäntäpopulaatioon epätasaisesti ja monet isännän ominaisuudet (esim. ikä) vaikuttavat levinneisyyteen. Tietyissä oloissa loiset voivat jopa säädellä isäntäpopulaatiotaan. Suomalaiset metsäkanalinnut — metso Tetrao urogallus, teeri Lyrurus tetrix ja pyy Tetrastes bonasia — ovat useiden suolistoloismatolajien isäntiä. Metsäkanapopulaatiot ovat vaihdelleet syklisesti, mutta syklejä aiheuttavat mekanismit ovat yhä tuntemattomia. Tutkin metsäkanalintujen ja niiden suolistoloisten välisiä vuorovaikutuksia käyttäen metsästäjien vuosina 1995–2002 viidestä eri riistanhoitopiiristä keräämiä suolistonäytteitä. Yleisin loislaji näytteissä oli kanalintusuolinkainen, Ascaridia compar. Myös kolme heisimatolajia (Skrjabinia cesticillus, Paroniella urogalli ja Hymenolepis sp.) todettiin. Suuri koko, koirassukupuoli ja yli yhden vuoden ikä olivat yhteydessä suurempaan kanalintusuolinkaistartunnan todennäköisyyteen ja voimakkuuteen. Nuorilla (alle 1 v.) linnuilla heisimadot olivat yleisiä, kun taas aikuisilla tartunnat olivat varsin harvinaisia. Sisäsiittoisuuden vaikutusta loistartuntaherkkyyteen tutkittiin metsolla mikrosatelliittiheterotsygotian perusteella. Vähemmän heterotsygoottiset metsot olivat todennäköisemmin ja voimakkaammin suolinkaisten infektoimia, mikä viittaa sisäsiittoisuuden negatiiviseen vaikutukseen loisten vastustuskykyyn. Loisten epäsuora haitallinen vaikutus havaittiin, kun verrattiin koiran kanssa ja ilman koiraa metsästettyä lintusaalista. Heisimadot olivat selvästi yleisempiä linnuilla, jotka oli metsästetty koiran kanssa kuin ilman koiraa metsästetyillä. Heisimatotartunta näytti siis altistavan metsäkanoja koiraeläinten saalistukselle. Metsäkanalintu- ja loispopulaatioiden välistä vuorovaikutusta tutkittiin analysoimalla vuosittaisia metsäkanatiheyksiä ja loisten runsautta. Kanalintusuolinkainen oli yleisimmillään ja runsaimmillaan metsäkanatiheyden laskuvuosina. Metsäkanapopulaation vuosittainen kasvuvauhti korreloi negatiivisesti kanalintusuolinkaisen vuosittaisen runsauden kanssa. Suhteellinen elossasäilyvyys laski kanalintusuolinkaisen runsauden lisääntyessä, mutta lisääntymistuloksen suhteen ei ollut samaa ilmiötä. Löydökset viittaavat siihen, että kanalintusuolinkaisella on vaikutusta suomalaisten metsäkanalintukantojen vaihteluihin, vaikka syklisiä kannanvaihteluja ei enää havaitakaan.

The cyclic population dynamics of vole and predator communities is a key phenomenon in northern ecosystems, and it appears to be influenced by climate change. Reports of collapsing rodent cycles have attributed the changes to warmer winters, which weaken the interaction between voles and their specialist subnivean predators. Using population data collected throughout Finland during 1986–2011, we analyse the spatio-temporal variation in the interactions between populations of voles and specialist, generalist and avian predators, and investigate by simulations the roles of the different predators in the vole cycle. We test the hypothesis that vole population cyclicity is dependent on predator–prey interactions during winter. Our results support the importance of the small mustelids for the vole cycle. However, weakening specialist predation during winters, or an increase in generalist predation, was not associated with the loss of cyclicity. Strengthening of delayed density dependence coincided with strengthening small mustelid influence on the summer population growth rates of voles. In conclusion, a strong impact of small mustelids during summers appears highly influential to vole population dynamics, and deteriorating winter conditions are not a viable explanation for collapsing small mammal population cycles.

Onko atomistisen selittämisen pätevyysalue ylitetty soveltamalla atomistista ajattelutapaa sellaiseen mihin se ei sovellu? Onko atomismia sovellettu niin ponnekkaasti, että on perusteltua puhua harharetkestä?