Characterizing the temporal changes of biotic communities and disentangling the importance of their driving mechanisms are central themes in ecology and environmental management. Non-native species have multiple adverse impact on native communities and species. However, there is a dearth of information on how non-natives influence the long-term dynamics of native communities. In this study, we compared the role of non-native species alongside various local and regional factors in the long-term dynamics of stream fish assemblages in the catchment area of Lake Balaton, Hungary, the largest lake in Central-Europe. Although, we found no consistent trend in species re-ordering between native and non-native species, native fish assemblages indicated significantly lower temporal stability with increasing relative abundance of co-occurring non-natives. Structural equation modelling revealed that assemblage dynamic patterns were also determined by a habitat degradation gradient. Moreover, habitat degradation and the presence of fishponds increased the relative abundance of non-native species, further affecting native assemblages through indirect interactions. Fish assemblage dynamics showed also some degree of finer-scale spatial structure. Non-metric multidimensional scaling further reinforced the destabilizing effect of non-native species but highlighted that native fish assemblages could generally be described by non-directional gradual or saltatory changes over time, regardless of the relative abundance of non-natives. Our results thus revealed that the studied native fish assemblages may possess some degree of resilience against biological invasions. However, increasing temporal variability induced by non-natives makes native assemblages more vulnerable to environmental stochasticity threatening their long-term persistence. This is especially worrying, since the frequency and intensity of environmental disturbances are expected to rise in the future due to climate change and increasing anthropogenic pressure on aquatic ecosystems.

As biodiversity is declining, the dynamics of species interactions is a growing conservation concern. However, estimating and monitoring species interactions across large spatial and temporal scales remain challenging, and thus changes in species interactions and the subsequent networks of interactions remain relatively unexplored. Here, we assess changes in the network structure of common bird communities from France. We estimate associated species pairs using spatial and temporal information for 109 species monitored across 1,969 sites during 17 years. We validate the ecological significance of associated species pairs by testing the relationship between the propensity to be associated and species functional proximity or shared habitat preference. We reconstruct association networks for these intra-guild bird communities and track temporal changes in network layout in terms of size, density of links, modularity and degree distribution. We show that, beyond species change, birds' local association networks become smaller with a similar relative number of associations that becomes unevenly distributed. These structural changes vary among types of bird communities and may impact community functioning and how communities can cope with global change.

Parasite occurrence and infection estimates vary through time and space, making understanding the underlying drivers highly complex. Comparative studies based on empirical data must consider the factors of variation involved in estimating infection metrics in natural populations to make appropriate and reliable comparisons. Using a multi-scale approach, we explored the sources of variation in the estimation of infection prevalence, focusing on black spot disease in littoral freshwater fish communities sampled across 15 lakes in Québec, Canada. Our results show that infection prevalence is spatially heterogeneous across the landscape with evidence of infection hotspots and coldspots. Method-related sampling biases led to significant variations in prevalence estimates and spatial patterns of disease occurrence. Our results also indicated that low sampling efforts tend to overestimate the prevalence of infection in the landscape, and that the sampling effort required to estimate an accurate infection prevalence depends on the sampling method employed. Physico-chemical characteristics of the sites and local fish community structure were found to be the best drivers of infection at smaller spatial scales. Furthermore, our results suggest dilution effects due to obstruction and compatibility barriers limit the survival of the free-living cercaria parasite lifestage. Several relationships between infection prevalence and environmental drivers revealed non-linearity, suggesting complex interactions. Examining infection prevalence data at various spatial scales revealed method-induced biases, sampling effort effect and environment driven relationships underscoring the importance of context-dependencies and scale-dependencies in studies on host-parasite interactions.

The degree of spatial overlap between size groups within a population (hereafter, spatial overlap) influences key biological processes, such as connectivity and competition within a population. However, how changes in spatial overlap with abundance vary across populations, particularly in relation to life history traits, is largely unknown. In this study, we analyzed spatial time series data from 1982 to 2019 to investigate how spatial overlap responded to changing abundance in 56 marine fish populations across four regions. Our results show that 33 populations exhibited positive relationships between spatial overlap and abundance in over 50% of size group pairs. In the North Sea and on the Scottish West Coast, certain size group pairs showed a stronger spatial overlap-abundance relationship in populations characterized by slower growth (higher growth coefficient, longer lifespan, later maturity) and larger body sizes (greater maximum and asymptotic size), compared to populations with faster growth and smaller body sizes. This suggests that size groups within slower-growing and larger-bodied populations tend to spatially segregate more rapidly when abundance declines, making them vulnerable to local disturbances such as in hotspots of fishing pressure and habitat destruction. Our analytical approach suggests that the spatial overlap-abundance relationship could serve as a useful vulnerability index for conservation and management efforts.

Nutrient composition varies greatly across landscapes, influencing the spatiotemporal variation and dynamics of populations, yet few studies have investigated this pattern across multiple scales. We tested how nutrient limitation affects herbivore populations, from individual behavior to landscape-level population dynamics, using the Australian plague locust, Chortoicetes terminifera (Walker), with field populations and long-term survey data from across their range. At the individual level, juvenile locusts selected for a carbohydrate-biased intake target of 1 protein (p) to 2 carbohydrate (c), and exhibited the highest growth and shortest development time when fed artificial diets with that same 1p:2c ratio during the final juvenile instar. At the field level, locusts kept in cages with protein-biased plants redressed their nutritional imbalance by selecting carbohydrate-biased diets (up to a 1p:20c ratio) for over a week after being removed from the protein-biased environment, returning to the 1p:2c intake target once the deficiency was met. At the landscape level, locust outbreaks were negatively correlated with soil nitrogen and showed a non-linear relationship with soil phosphorus, peaking at approximately 4% soil phosphorus. We disentangled the interaction between mean annual precipitation and soil nitrogen using comprehensive locust surveys and remotely sensed soil and weather data spanning decades. This study is the first to integrate lab, field, and remote sensing approaches, demonstrating the importance of nutrient balancing and acquisition across scales for herbivores. Specifically for locusts, we show that low-nitrogen environments promote outbreaks, likely by reducing plant protein-to-carbohydrate ratios. Incorporating soil quality data into locust plague forecasting models could help improve prediction accuracy.

Changes in biodiversity reflect processes acting at multiple spatial scales, including globally, among habitats and within communities. This complexity makes it difficult to analyse the mechanisms that change biodiversity over time. To resolve this, we propose a novel approach to partition temporal changes in biodiversity into contributions from selection at multiple scales. We apply this approach to study changes in the biodiversity of invertebrate herbivores from a large-scale, plant community experiment. Though the experiment was designed to foster distinct insect communities due to differences in host plants, our approach shows that selection among these treatments was a negligible facet of diversity change. Instead, the dominant source of community dynamics was rapid changes in the relative abundances of individual species. These shifts produced surprisingly small changes in biodiversity. More broadly our work highlights how total change in biodiversity across a biogeographic region can be partitioned into logically distinct mechanisms.

Resources, such as nitrogen, are widely hypothesized to underlie the expression and evolution of plant defenses to herbivory. However, resource availability can affect selection on plant defense traits in contrasting ways: resource availability can 1) weaken selection on defense traits by reducing the costs of herbivory, or 2) strengthen selection on defense traits by increasing herbivore pressure. Previous studies have compared herbivore resistance in populations across natural resource gradients to infer how resource availability affects the microevolution of plant defenses. However, because these studies do not manipulate resource availability, they are unable to directly test the effects of resources of plant defense trait evolution. We used a three-decade-long nitrogen fertilization field experiment to test how nitrogen availability affects the evolution of an architectural plant defense trait: stem nodding in Solidago altissima. Stem nodding is a genetic dimorphism that helps plants to evade apex-galling herbivores. By comparing the frequency of defensive nodding versus erect morphs in experimentally fertilized or unfertilized plots, we assessed how nitrogen addition affects the evolution of this defense trait. We found that the defensive nodding morph was 3-4 times more common in plots that evolved under nitrogen fertilization compared to those that evolved in unfertilized control plots. This study provides empirical evidence for resource availability driving plant defense evolution and demonstrates that this evolution can occur on time-scales conducive to study at many long-term nutrient fertilization experiments.

Understanding how metacommunities respond to natural and anthropogenic disturbances is a key objective in ecology. In this study, we introduce a robust analytical framework to identify communities whose extirpation triggers stronger (hereafter keystone communities) or weaker (hereafter idle communities) cascading effects on extinction and colonization events that ultimately drive temporal changes in compositional patterns of the remaining communities. These cascading dynamics reflect the impact of extirpated communities on connectivity and subsequent dispersal dynamics. Since the framework uses spatial information on compositional similarities to infer changes that would unfold over time due to the extirpation of one or more communities, we describe it as a space-for-time approach. Through mechanistic simulation models that replicate removal experiments, we demonstrate that our framework accurately estimates ”keystoneness”, ranking local communities by their role in maintaining the metacommunity’s compositional patterns. As such, our models demonstrate that the relationship between patch characteristics and our keystoneness metric is closely linked to the structure and dynamics of their metacommunities. A key feature of our framework is its ability to generate community keystoneness estimates that are statistically independent of local diversity, providing a valuable tool for assessing the relevance and conservation value of local communities. This is particularly important in cases where high local diversity reflects an influx of individuals into demographic sinks, a common consequence of human activities near natural areas. To showcase the unique insights of this framework, we examined and contrasted the effects of artificial light at night on the diversity and keystoneness of a moth metacommunity sampled over two decades. We conclude with a discussion of the framework’s potential applications and underlying assumptions, emphasizing its relevance for addressing both conceptual and applied ecological questions, particularly its potential to assess the conservation value of local communities under ecological stress.

In freshwater communities, organisms interact in a variety of ways, including predation, competition and parasitism. Parasites are ubiquitous, playing an important role in shaping freshwater communities. Endoparasites live within internal organs of their host, while ectoparasites, also known as epibionts, are confined to the external part of the host’s body. We conducted a series of experiments to examine the relationship between endoparasites and epibionts using the crustacean Daphnia magna as host, the rotifer Brachionus rubens as epibiont and three species of endoparasites. First, we tested host preference of the epibiont between Daphnia infected by endoparasites and uninfected Daphnia. Epibiont were found to attach more to uninfected Daphnia than to Daphnia infected by the yeast Metschnikowia bicuspidata. On the other hand, epibionts attached more to Daphnia infected by the microsporidium Hamiltosporidium tvaerminnensis than to uninfected Daphnia. Second, we examined the effect of epibionts on the infection of Daphnia by endoparasites. Infection prevalence tended to be higher, though not significantly, in the presence of epibionts. For two of the endoparasites, M. bicuspidata and H. tvaerminnensis, infection intensity (i.e., parasite spore production) was higher in the presence of epibionts. The infection intensity of M. bicuspidata and the bacterium Pasteuria ramosa was affected by the time of death of the Daphnia (i.e., virulence). Finally, we examined the effects of endoparasites and epibionts on the survival and offspring production of the Daphnia. Both host survival and offspring production were negatively affected by the endoparasites, while epibionts did not seem to affect the fitness of their host.

The study of functional diversity has been gaining increasing prominence in Ecology, as a way of evaluating how the species traits affect ecosystem processes. Several empirical studies indicate a strong relationship between trait diversity and ecosystem attributes, and high values of functional diversity are an indication of the robustness of a given ecosystem. However, there are important theoretical differences between the studies that evaluated these relationships, which lead to relevant methodological differences. Here we will discuss the need to choose response and effect traits in a theoretically-sound manner, arguing for their choice based on their functional contribution to ecosystem process as conceived by the organizational theory of ecological functions. From this perspective, the contribution of effect traits to the organizational closure of an ecological system can provide a fundamental criterion for their choice in empirical studies. Similarly, we point out criteria for choosing response traits. Furthermore, we will argue that the new mechanistic philosophy of science can be used in studies of functional diversity as a way to robustly establish cause and effect relationships in empirical studies. Finally, we will model an example of the application of the approach proposed in the paper in pollination ecology, indicating its heuristic potential for empirical studies.

Climate change and anthropogenic alteration of landscapes negatively impact the abundance and diversity of plant and animal communities worldwide. Much less is known about the effects on phylogenetic diversity and community functioning. Here we use long-term observation data (1980 – 2022) from the Austrian Alps to assess how butterfly communities adjust community structures and functionality to increasing temperatures along the elevation gradient and how these changes are linked to trait expression and community functioning? Diversity significantly decreased at low and intermediate, and increased at high altitudes. Functional attribute diversity was significantly lower than expected by a random model at intermediate and high altitudes and increased with time at high, but not at intermediate and low altitudes. Multifunctionality significantly decreased at intermediate and high altitudes Phylogenetic diversity did not show significant temporal trends at low altitude, but significantly increased with time at intermediate and high altitudes. Multifunctionality was not significantly correlated with FAD, but decreased with increasing phylogenetic diversity. We conclude that the ongoing homogenisation of Alpine butterfly communities strongly affect species, functional and phylogenetic diversity. The directions of these changes heavily depend on altitude and therefore on specific climatic conditions. Higher altitudes face decreasing butterfly multifunctionality despite of increasing species richness due to climate induced altitudinal up-hill shifts of many species. The assessment of species richness and diversity alone, as provided by common species surveys, might give a false impression about the state and functioning of Alpine insect communities in the course of climate change.

Zoonotic diseases account for 75% of emerging infectious diseases, posing significant global health challenges. Understanding the complex host-pathogen interactions is crucial for effective disease management. This study constructs and analyses a global bipartite network of zoonotic bacteria and their domestic mammal hosts, aiming to explore how domestication time and phylogenetic relationships influence network structure. The network, consisting of 24 domestic mammal species and 51 zoonotic bacterial species, reveals a non-random structure with high nestedness and low modularity. Results indicate that the richness of zoonotic bacteria per host is positively correlated with domestication time but not with phylogenetic distance from humans. These findings suggest that early-domesticated species act as ”sinks” for newly exposed zoonotic bacteria, driven by preferential attachment dynamics. This network-level insight provides a valuable framework for predicting and managing zoonotic disease transmission, emphasising the importance of targeted interventions for highly connected host species.

not-yet-known not-yet-known not-yet-known unknown Roads in cold climate mountains are known to be important vectors in the introduction and spread of non-native plant species. In the same context, mycorrhizal fungi communities are also altered by roads with a known positive effect on arbuscular mycorrhizal (AM) fungi diversity and abundance in disturbed roadsides. However, to what degree these two effects of roads are intertwined and how they are evolving over time is not well understood. In this study we conducted repeated surveys of non-native plants and AM fungi between 2012 and 2022, in the northern Scandes mountains to investigate temporal changes and interactions between roads, mycorrhizal fungi, and non-native plants. We found that the upward spread of non-native plants and lateral spread away from the roadside into the natural vegetation were so far extremely limited, with only two out of 23 non-native species showing an increase in their upper elevational limit. However, non-native plant species cover did increase over the ten year period, especially at lower elevations, and non-native richness increased from 17 to 23 species. Likewise, we saw an increase in AM fungal abundance over the last four years along the roadsides at lower elevations. Furthermore, our results suggest that increases in non-native species are unlikely to be the driving cause of the observed increase in AM fungal abundance, as AM fungi colonization varied independently of non-native species cover dynamics.

1. Leaching – the release of elements from organic matter through dissolution in water – plays an important role in biogeochemical cycling and ecosystem processes. However, understanding the patterns in and underlying drivers of element solubility in leaves lags far behind that of other related plant traits. 2. In this study, we quantify the solubility of carbon (C), nitrogen (N), and phosphorus (P) from leaves of Betula pubescens - a widespread boreal tree species - across a 5182 year postfire retrogressive chronosequence. 3. We find that P is much more soluble than C and N, and is released in solution mainly in readily accessible mineral form. Solubility patterns are strongly related to foliar chemical and structural traits, particularly for green leaves, whereas metrics related to stand structure exert a stronger influence over solubility from senesced leaf litter. 4. Overall, our results indicate that leaching could constitute an important flux of nutrients to the soil, particularly of P, and that the rate and spatio-temporal pattern of this flux appear readily predictable from foliar and ecosystem properties. Further application of the method across more species and environmental contexts should allow for rapid integration of leaching-related foliar traits into broader plant trait frameworks.

The loss and fragmentation of habitats caused by anthropogenic activities in the last decades has affected foraging habitat quality and, therefore, foraging success (food quantity, quality and foraging range) of many animals, including many pollinators. Honeybees (Apis mellifera) are important pollinators of many plant species, and habitat change has also affected their ability to collect the resources they need to maintain the colony. Two important biological traits that might be affected by land use are body size and fat stores, which have the potential to affect body condition, and therefore success, and colony health. However, few studies have investigated these traits in different landscapes and different times of year. We surveyed 47 sites in three different landscape types (agriculture, urban and mixed habitats) in south-western Germany. We measured honeybee body size, wing wear and analysed body fat quantity and composition using GC-MS in the spring, summer and autumn. We found that summer honeybees were smaller in urban and mixed habitats, they showed the greatest wing wear, but they had 18.4-21.3% larger fat stores compared to agricultural sites. Bees in agricultural habitats experienced a drop in fat stores in summer, while body size remained unaffected. In autumn, just before honeybees enter the inactive winter period, bees in urban and mixed areas experienced a drop in fat stores. Wing length decreased from spring to autumn irrespective of habitat type. Our findings indicate that bees in agricultural settings experience physiological challenges in a central European region in summer, possibly because urban and mixed habitats provide better nutritional conditions during summer. Our findings, thus, confirm that honeybees undergo morphological and physiological changes in response to land use and season, which could impact their physiological condition and winter survival.

Body size determines mobility and fitness of insects in various ways. Yet, especially in parasitoid species, drivers of body size are poorly understood, as they can be influenced by complex interactions between parasitoid behaviour, the environment, and their hosts. We measured the body size of 393 individuals of four parasitoid species sampled with trap nests for cavity-nesting bees and wasps in the Southern Black Forest, Germany. We related the body size of the parasitoids to the size of 15 host species and the diameters of their nests along four environmental gradients (canopy cover, structural complexity, herb cover and deadwood diameter). Host identity, nest diameter, and to a lesser extent, size differences within host species, were primary drivers of parasitoid body size, albeit parasitoid species differed in their responses. For instance, when the host Trypoxylon figulus doubled in size, Nematopodius debilis (parasitizing the host directly) increased by 37% in size, while Trichrysis cyanea (parasitizing food resources) increased by only 8%. Across host-parasitoid species combinations, there was only a weak positive relationship between the size of parasitoids and their hosts. In addition, we did not observe size variations in hosts and parasitoids across environmental gradients. Our findings highlight the primary factors influencing parasitoid size, with host identity and nest diameter emerging as influential factors within and between species, though not uniformly across all species. In contrast, the relationship between parasitoid and host size and environmental gradients were less influential. Considering the environmental variables that directly affect body size, such as microhabitat conditions and biotic interactions, may further clarify the dynamics shaping variation in parasitoid size.

Participatory science (or ”citizen science”) records are becoming increasingly useful for wildlife monitoring due to their volume and spatiotemporal coverage. However, statistical analysis using these data can be challenging due to the many sources of bias that need to be corrected. Many previous studies characterize sampling biases across entire participatory science datasets, such as spatial heterogeneity in sampling effort or species preferences. User-level heterogeneity in sampling behavior is less well studied, but it may be just as important as dataset-level bias in contributing to error in downstream analyses. Here, we investigate user-level novelty and specialization bias. Novelty bias occurs when an individual observer preferentially reports species that have not seen before, while specialization bias occurs when an observer preferentially reports species they have previously observed (i.e., they specialize in particular species). We provide the first test of this kind of user-level sampling bias in participatory science data by analyzing the sampling histories of more than 540 observers on the popular participatory science platform iNaturalist in Pennsylvania, USA. We find evidence of specialization or novelty bias in the overall sampling behavior of 66% of the observers considered. Specialization bias was more than 5 times more common than novelty bias, indicating that observers reported species they had reported previously at a higher rate than expected. Looking within taxonomic groups, 41% of observers deviated from unbiased sampling. Novelty bias and specialization bias were both common within taxa. These findings suggest that iNaturalist observers often specialize in favorite taxa or species, while within taxa some users simultaneously seek out previously unobserved species.

Comparing cases of parasitism and predation that lead to victim death, parasites need more time to complete victim exploitation. This longer “interaction durability” delays energy transfer from host to parasite. During exploitation, parasite virulence differentiates the infected from the susceptible host dynamics. However, how this parasite characteristic influences the dynamics of their host and nonhost (insusceptible) species in the same community is largely unknown. Here, we use mathematical modelling to investigate the influence, exemplifying an experimental plankton community. In this community, nonhost zooplankton feeds on edible nonhost phytoplankton (resource competitor of the host) and parasite propagules released from infected inedible phytoplankton (“mycoloop” pathway). To assess the effects of parasite-host durability, we contrast parasite-host implementations as Lotka-Volterra predator-prey interaction (immediate energy transfer) with susceptible-infected (SI) host-parasite interactions. For the latter, parasite energy intake depends on infected host density but not susceptible hosts directly (delayed transfer). We further consider the difference between susceptible and infected host dynamics modulated by parasite virulence via its effect on host nutrient uptake. To assess the within-community effects, subcommunities are also investigated, excluding/including the parasite without/with the mycoloop. Our results show that, besides host elimination, longer interaction durability of the host-parasite interaction delays parasite attacks on susceptible hosts, allowing them to increase further (a hydra effect), independent of parasite virulence level. This effect observed in the isolated host-parasite systems is preserved in larger communities with negative consequences for the nonhost species, independent of the mycoloop. These theoretical results are supported by empirical observations within and beyond plankton realms. Our study reveals distinctive influences of parasites on community shot-term dynamics, which stem from the longer interaction durability.