Spatial synchrony, the tendency for temporal fluctuations in an ecological variable to be positively associated in different locations, is a widespread and important phenomenon in ecology. Understanding of the nature and mechanisms of synchrony, and how synchrony is changing, has developed rapidly over the past two decades. Many recent developments have taken place through the study of long-term datasets. Here, we review and synthesize some important recent advances in spatial synchrony, with a focus on how long-term data have facilitated new understanding. Longer time series do not just facilitate better testing of existing ideas or more precise statistical results; more importantly, they also frequently make possible the expansion of conceptual paradigms. We discuss several such advances in our understanding of synchrony, how long-term data led to these advances, and how future studies can continue to improve the state of knowledge.

While multiple reasons make long-term demographic studies disproportionally valuable, much of their importance comes from the ability to detect and quantify rare events. We argue here that rare events can be critical for understanding important ecological and evolutionary processes. We highlight the additive or interactive nature of anthropogenic rare events with environmental rare events that may cause outsized changes in vital rates and therefore in population dynamics. Rare events may also generate complex responses in populations due to interactions between demographic processes and evolutionary responses. Complex, non-linear dynamics of populations may include threshold, extreme responses such as long transients, tipping points, regime shifts and collapse. When occurring locally, rare events may also exacerbate spatial heterogeneity with consequences for demographic processes. In sum, these effects represent substantial challenges for prediction, especially when considering the increase in the frequency of rare extreme events, and emphasise the need for long-term studies. Our perspective attempts to integrate the occurrence of rare events in variable environments and the consequences for the overall fitness, growth rates, and the spatial-temporal dynamics of populations.

Climate change is implicated as a leading cause of insect declines. One way that insects respond to the warming climate is by advancing phenology and increasing voltinism (adding generations). However, if earlier phenology changes cue-response relationships, then late season generations might lack time or resources to complete development before winter and insects attempt doomed “lost generations”. Using 27 years of monitoring of 30 butterfly species, we find the opposite, as added generations increase population growth rates of multivoltine butterflies. We find lost generations are rare and occur at cooler sites in years with cold winters or early frosts. Overall, long-term population trends are positively correlated with increasing voltinism over time, suggesting additional generations as one mechanism by which species adapt to the changing climate. Long-term monitoring programs can test mechanistic hypotheses about biotic responses to warming while simultaneously tracking if population consequences match the predicted outcomes.

A document by Ismaël Lajaaiti. Click on the document to view its contents.

Trophic change has induced substantial changes in biomass and composition of aquatic communities. Based on phytoplankton data from Lake Constance we demonstrate that community function is closely connected to community composition and responds strongly to trophic change. Community mean traits phosphate affinity and light affinity are tightly linked to trophic state during eutrophication and re-oligotrophication, suggesting reversibility of community function. Phosphate and light affinity are anti-correlated. This anti-correlation is weak in the species pool distinguished in the dataset, but strong when weighting the traits by the species biovolumes or when comparing community mean traits from different trophic states. The emergence of this tradeoff between phosphate and light affinity indicates competitive advantage of species with traits near the tradeoff line. The correlation between community mean maximum growth rate and trophic state turned out to be spurious and resulted from the development of Dinophyceae spp. which have an alternative mode of nutrition.

Plant-soil feedback (PSF), the reciprocal interaction between plants and their soil environment, is a fundamental ecological process that influences coexistence and functional structure in plant communities. Current theory establishes that PSF may enhance diversity or lead to exclusion depending on whether soil conditioning disproportionately benefits heterospecific or conspecific individuals. However, a more complete picture of the impact of PSF requires understanding how PSF synergizes with competition. To that end, here we propose an integrated mathematical model combining trait-based competition and soil-explicit PSF. Contrary to the current paradigm, we find that soil conditioning that disproportionately favors conspecific individuals can promote coexistence. Additionally, we show that priority effects are common when soil-conditioning species differ in their edaphic preferences. These effects can allow species with large differences in competitive ability to coexist under certain soil conditions. Our results provide testable predictions tying community-level functional patterns in plant communities to PSF and competition.

Understanding how species adjust to seasonality is fundamental in ecology, especially with rapidly increasing global air temperatures. Bioacoustic monitoring offers promise for tracking shifts in seasonal timing of vocal species, as recent automated sound recorders enable large-scale and long-term data collection. Yet, analyzing vast datasets necessitates automation and innovative detection methods. Here, we introduce BioSoundNet, a deep learning model designed for bird vocalization detection. Trained on field data and open-access databases, BioSoundNet achieved AUC scores of 0.88-0.93 and average precisions of 0.87-0.97 across five datasets spanning various ecosystems, and effectively captured the temporal patterns of avian acoustic activity at different time scales. Our findings underline the importance of evaluating models in ecological contexts and to address the potential consequences of missing detections. Operating efficiently on standard computers, BioSoundNet is a robust tool for automated bird vocalization detection, providing a valuable resource for ecological phenology studies and acoustic dataset analysis.

Aquatic ectotherms often attain smaller body sizes at higher temperatures. By analysing ~15,000 coastal-reef fish surveys across a 15oC spatial sea surface temperature (SST) gradient, we found that the mean length of fish length in communities decreases by ~5% for each 1oC temperature increase across space. This equated to a 50% decrease in mean length from 14 to 29oC mean annual SST. We found that trophic guild composition shifts from domination by herbivores and planktivores in the tropics, to invertivores and piscivores in cooler waters. By investigating the contribution of trophic composition to community-level mean length, we show ~25% of temperature-related changes could be attributed to trophic composition at the warmest sites, but <1% at colder temperatures. Our findings suggest that small changes in temperature will lead to large changes in fish community body sizes, driven both by community trophic composition in warm waters and mean sizes within trophic guilds.

Human activities have altered the species composition of assemblages through introductions and extinctions, but it remains unclear how those changes can affect the different facets of biodiversity. Here we assessed the impact of changes in species composition on taxonomic, functional, and phylogenetic diversity across 281 bird assemblages worldwide. To provide a more nuanced understanding of functional diversity, we distinguished morphological from life-history traits. We showed that shifts in species composition could trigger a global decline in avian biodiversity due to the high number of potential extinctions. Moreover, these extinctions were not random but unique in terms of function and phylogeny at the regional level. Our findings demonstrated that non-native species cannot compensate for these losses, as they are both morphologically and phylogenetically close to the native fauna. In the context of the ongoing biodiversity crisis, such alterations in the functional and phylogenetic structure of bird assemblages could heighten ecosystem vulnerability.

Biodiversity-function relationships in ecosystems are known to be driven by environmental conditions, including climate change. Plant functional groups (PFGs), specifically their evolutionary history, nitrogen-fixation capacity or photosynthetic-pathway likely play a critical role in shaping microbial communities and their impact on ecosystem functions, but experimental evidence is limited. Here, we simultaneously manipulated plant and microbial diversity in a microcosm study to investigate their interactions and impact on soil functions during drought. Our results highlight the dominant role of PFGs in explaining the effects of biodiversity loss on soil functions. Microbial diversity loss significantly influenced microbially-driven soil N and P pools and processes, with PFGs moderating these effects, especially under drought. Our findings offer crucial mechanistic insights for ecosystem management in the face of climate change, emphasizing the significance of PFGs in shaping soil functions and their resilience. This study underscores the importance of considering above- and belowground biodiversity, for preserving belowground functions in changing environments.

Generalists are thought to adapt to a broader breadth of ecological conditions compared to less flexible specialists. However, few studies have systematically tested what ecological or life-history traits are associated with organisms' ecological flexibility. Here, we used stony corals to test the relative effects of host traits and ecological factors on corals' flexibility to form photosymbioses with algae. We analyzed data from 211 stony coral species to test if coral's geographic distribution, depth range, symbiont transmission mode, or colony morphology predict coral-algal flexibility. We report a novel positive correlation between coral-algal flexibility and coral species' geographic range. Symbiont transmission mode is also a predictor of flexibility, albeit the result is less robust against sampling bias. Coral depth range and morphology did not show significant effects. We discuss how host-symbiont dispersal abilities, interactions, and evolutionary history could contribute to the observed patterns and how this finding could inform conservation efforts.

Biodiversity drives stability in communities, allowing it to withstand environmental fluctuations without changes in aggregate properties like total abundance or biomass. We investigated biodiversity’s influence on two crucial population-level mechanisms governing abundance stability in mesopredatory coral reef fishes: ‘community asynchrony,’ where species populations fluctuate inversely over time, and ‘dominant stability,’ where highly abundant species with significant community contributions display minimal population fluctuations. Analyzing data from 83 reef fish communities across the Indian and Pacific Oceans over a decade, we found that community asynchrony, rather than dominant stability, primarily predicts community stability. Functional diversity, not taxonomic diversity, regulates this stability, emphasizing the role of niche differences in stabilizing communities. We highlight that community attributes that promote asynchronous population fluctuations, enhancing response diversity and tempering strong trophic interactions are vital for stabilizing mesopredatory reef fish communities in the face of global change.

The Janzen-Connell hypothesis is one of the most important hypotheses in ecology, but is mostly tested indirectly without accounting for the underlying plant-associated organisms, or only for highly host-specific organisms. Advances in massive sequencing allow to sample, for example, the fungi communities associated with different plant species, and spatial analysis can reveal spatial patterns in the number of organisms (species) shared by plant species and their neighbours. We show how combining these tools provides new perspectives for testing the Janzen Connell hypothesis. We illustrate our approach using a natural experiment in two fully-mapped Mediterranean forest plots, where the dominant dry- and fleshy-fruited species have distinctly different seed deposition patterns, leading to contrasting expectation about the emerging spatial structures. Our analysis confirmed these expectations and provided deep insights into how the neighbourhood load of plant-associated fungi and herbivorous insects changes during plant ontogeny and how seed dispersal mechanisms modulates Janzen-Connell effects.

Genetic diversity is a fundamental component of biodiversity. Examination of global patterns of genetic diversity can help highlight mechanisms underlying species diversity, though patterns may differ across the genome. Here, we compiled 6862 observations of genetic diversity from 492 species of marine fish, assessed their associations with macroecological drivers, and tested among hypotheses for diversity gradients: the founder effect hypothesis, the kinetic energy hypothesis, and the productivity-diversity hypothesis. We found that mitochondrial genetic diversity followed geographic gradients similar to those of species diversity, being highest near the equator, particularly in the Coral Triangle, while nuclear genetic diversity did not follow clear global patterns. Despite these differences, all genetic diversity metrics were strongly correlated with chlorophyll-a concentration, while mitochondrial diversity was also positively associated with sea surface temperature. Our results provide support for the kinetic energy hypothesis, which predicts that elevated mutation rates at higher temperatures increase mitochondrial diversity, and the productivity-diversity hypothesis, which posits that resource-rich regions support larger populations with greater genetic diversity. Overall, these findings reveal how environmental variables can influence mutation rates and drift in the ocean, caution against using mitochondrial macrogenetic patterns as proxies for nuclear DNA, and aid in defining global gradients of genetic diversity.

Lakes face threats from human activities like unsustainable development, population growth, and industrial technologies. These challenges impact the ecosystem services of lakes. Research has assessed the value of services from freshwater biomes annually. This article reviews these values, estimating lakes’ global ecosystem services to be within the region of USD 1.5 to 5.5 trillion annually. Their natural asset value is estimated at USD 100 - 337 trillion, comparable to value of global real estate, assuming a relatively high social discount rate to account for future increased standard of livings. Considering environmental degradation, future generations may experience a lower living standard. Using a 0.1% discount rate, recognizing potential harm and aligning with indigenous values, raises the lakes’ value to USD 1,500 - 5,500 trillion which is at least equal to the global value of wealth created. This valuation is shared by all, unlike the skewed distribution of created wealth.

The relationship between biodiversity and ecosystem function (BEF) captivates ecologists, but the factors responsible for the direction of this relationship remain unclear. While higher ecosystem functioning at higher biodiversity levels (‘positive BEF’) is not universal in nature, negative BEF relationships seem puzzlingly rare. Here, we develop a dynamical consumer-resource model inspired by microbial decomposer communities in pitcher plant leaves to investigate BEF. We manipulate microbial diversity via controlled colonization and measure their function as total ammonia production. We test how niche partitioning among bacteria and other ecological processes influence BEF in the leaves. We find that a negative BEF can emerge from reciprocal interspecific inhibition in ammonia production causing a negative complementarity effect, or from competitive hierarchies causing a negative selection effect. Absent these factors, a positive BEF was the typical outcome. Our findings provide a potential explanation for the rarity of negative BEF in empirical data.

Whether individuals migrate or not is rapidly shifting in many populations. Exactly how and why environmental change alters migration propensity is not well understood. We conducted a systematic literature review to gain insights into the mechanisms that affect the propensity to migrate. Motivated by findings from our literature review, we constructed density-dependent structured population models to explore the coexistence of migrants and non-migrants, when they coexist, and when they do not. We find that carrying capacity in a seasonal environment determines the dominant type in the population. Partial migration can be maintained, or not, depending on where in the life cycle density-dependent operates. Bet-hedging also promotes partial migration. Our study disentangles density-dependence and density-independence in seasonal environments, providing insights into the coexistence of polymorphism, potentially explaining the rapid change in migration strategy observed.

Virus host shifts from managed honey bees, Apis mellifera, are thought to contribute to the decline of wild pollinators. However, data on the impact of such viruses on wild pollinators remain scarce, and how landscape structure may affect virus transmission is poorly understood. We experimentally deployed bumble bee colonies in an agricultural landscape to study changes in the bumble bee virome under varying habitat composition and configuration. The results show a decline in prevalence and viral loads of honey bee associated viruses, while viruses common in Bombus spp. increased during field exposure. Honey bee associated viruses had no effect on colony development, suggesting that immediate impacts are unlikely in the field. Notably, we further demonstrate that increased habitat diversity results in fewer viruses in Bombus colonies. To mitigate the decline of bumble bees and other wild pollinators, we suggest focusing conservation efforts on habitat diversification and restoration.