Competition among pollinators for floral resources is a phenomenon of both basic and applied importance. While competition is difficult to measure directly under field conditions, it can be inferred indirectly through the measurement of floral resource depletion. In this study, we conducted a pollinator exclusion experiment to calculate nectar depletion rates in summer across 16 grassland sites in the German regions of Franconia and Saxony-Anhalt. Overall depletion rates were estimated at 95% in Franconia and 79% in Saxony-Anhalt, indicating strong nectar limitation and, by implication, competition among pollinators. Despite being ubiquitous in our study regions, honey bees were scarce at our sites at the time of nectar sampling. This demonstrates that wild pollinators alone are capable of massive nectar depletion, and the addition of managed honey bees to wild pollinator communities may intensify already competitive conditions. Nevertheless, the manifest diversity of the pollinator communities at our sites indicates that other factors, such as non-trophic constraints or temporal variation in food limitation, can mitigate competitive exclusion despite immediate conditions of acute food scarcity.

Herbivores in the tundra interact with vegetation through several mechanisms, especially defoliation, trampling and nutrient addition through urine and faeces. Through these mechanisms, herbivores drive shifts in plant species composition, richness and diversity. As reindeer effects on vegetation accumulate over time, they might cascade to other trophic levels, but how and when this happens is poorly understood. Since it is methodologically demanding to measure biodiversity across spatial gradients, an alternative approach is to assess it indirectly via biodiversity indices of vascular plants. Values from the Index of Biodiversity Relevance were coupled with vegetation data from a network of 96 fenced and paired grazed plots across Fennoscandia. We analysed the role herbivory has on plant richness and diversity, and on the number of organisms that depend on the vegetation according to the index values. We also explored how herbivores affect the competitive effects of shrubs on other plants since the dominance of a vegetation type links directly to biodiversity. Vegetation richness and diversity did not present any differences between treatments, yet reindeer had an increasing effect on plant diversity when testing the interaction between grazing and herbaceous vegetation. Three out of six biodiversity indexes were higher in fenced plots indicating a higher number of interactions between plants and organisms from other trophic levels. Finally, herb abundance was negatively related to shrubs in both treatments but with a faster decline in the absence of herbivores, suggesting that herbivory increases plant diversity and decreases the diversity of other taxa by reducing shrub abundance. This study highlights the importance of maintaining herbivore populations in the Arctic to prevent the expansion of climate-driven biodiversity into the tundra. The effect of herbivores on ecological communities is not merely a product of plant diversity but can be quantitatively and qualitatively different.

Interactions between species, such as seed-dispersal interactions, can shape many aspects of those species' life, as well as ecological patterns and evolutionary dynamics. Yet, sampling interactions in the field is challenging. Even with extensive sampling efforts we can hardly obtain a comprehensive picture of which species interact with each other. Such missing interactions can produce important gaps that affect how we perceive and interpret the network formed by species interactions and the roles of individual species within those networks. In this study we propose two methods that combine data on species interactions with information on species traits and phylogenies to estimate potentially missing interactions. We use one of the largest datasets on plant-frugivore interactions, depicting thousands of interactions between birds and plants in the Atlantic Forest hotspot, to test those methods and analyze how adding newly estimated interactions change the structure and the topological importance of the species within the seed dispersal network. We show that estimated missing interactions more than tripled the number of interactions in the network and impact the general topological properties of the network increasing nestedness and reducing modularity. Both models generated networks with a similar structure and were effective in estimating new interactions, accurately predicting known interactions without overestimating interactions in place of true absences. More importantly, added interactions changed our perception on the topological role of species, with several under-sampled species earning several interactions and becoming more central to network structure. This shows that estimating interactions can be helpful to get a more complete idea of how a network may look like and may help inform which interactions should be focused on in further sampling efforts.

The importance of fine-root diameter for ecosystem functioning is increasingly recognized; yet, much remains to be learned about the variation in fine-root diameter at large scale. We conducted an analysis of fine-root diameter for 1,163 plant species to detect root diameter patterns in relation to resource availability (e.g. carbon, nitrogen and water), stress intensity (e.g. plant/soil biodiversity, soil bulk density) and temperature. First- to fourth-order root diameter showed non-linear relationships with latitude and/or mean annual temperature (except for first-order root diameter). The diameter of five root orders decreased with increasing mean annual precipitation, but increased with net primary production (NPP), which was the strongest determinant of fine-root diameter. Increasing soil biodiversity was associated with decreasing root diameter of fourth- to fifth-order roots while increased plant biodiversity was associated with decreasing diameter of first- to third-order roots. Total soil nitrogen had a positive effect on first-order root diameter, but a negative effect on fourth- and fifth-order root diameter. The patterns reversed for total soil phosphorus. First- to third-order and fifth-order root diameters increased with increasing soil bulk density. Second- to fourth-order root diameter increased with soil pH. Overall, the variables related to climate, biology and soil explained 44% to 63% of the total variance in the diameter of the different root orders. The unique patterns of plasticity observed in fine-root diameter across root orders in response to varying environmental conditions contributes to a diversification of strategies for nutrient/water acquisition and transport under climate change.

Phenological mismatch has been highlighted as a reason why climate change is causing declines of migratory populations. The likelihood of declines due to phenological mismatch might depend on what cues trigger migration. Migrants that use environmental cues (e.g. temperature, resource availability) to trigger migration are often considered to be less vulnerable than migrants that use temporal information (e.g. photoperiod). We develop a model to investigate how migration cue type determines the effects of phenological change of habitat quality on fitness. We show that which cue type performs better depends on the strength of seasonality in the habitats used by a migrant. We use our results to identify scenarios that align and contrast with the prediction that migrants using temporal cues are more vulnerable. We also recommend that future empirical and theoretical work on phenological mismatch more clearly distinguish between the accuracy and efficacy of cues. Similarly, we recommend considering both how the benefits available from migrating and the benefits that are captured by migrants are changing with phenological change. This work improves our understanding of the role of cue in determining migratory populations’ trajectories as climate changes.

Plant pathogens are important for ecosystem functioning and community assembly and respond to a variety of biotic and abiotic factors, which change along elevation gradients. Thus elevational gradients are a valuable model system for exploring how plant community, soil properties, and environmental factors influence pathogens. Yet, how these factors influence pathogens in nature remains poorly understood. We tested patterns and potential mechanisms of plant fungal pathogens along elevational gradients by combining a field survey in the Tibetan Plateau with a global meta-analysis. We found that increasing elevation was associated with a decrease in soil fungal pathogen richness but not foliar fungal disease symptoms. Elevation mainly related to soil fungal pathogen richness through abiotic factors. Whereas no evidence supported association between elevation and foliar fungal disease. The meta-analysis suggests some generality in the results of the field survey: elevation was associated with a decrease in soil fungal pathogen richness, but had no consistent relationship with foliar fungal disease or pathogens. Our study reveals distinct patterns of above- and belowground plant pathogen along elevation gradients and provides new insight into the potential mechanisms in shaping these patterns.

Growing evidence indicates that the tendency to synchronize community dynamics may be a general phenomenon in nature related to metaecosystem stability. Synchronized dynamics reduce stability since local variations in biomass or richness are directly propagated to variations in metacommunity dynamics. Asynchronous dynamics have a strong stabilizing effect because of the cancelling out of local variations. Synchronization of biodiversity dynamics may occur due to dispersal among communities and similar responses of different communities to correlated environmental variations---the generalized Moran effect. This congruent response of different communities to environmental dynamics depends on their similar functional composition, which is determined by the similarity in local conditions and the spatial distance between them. In a metacommunity of 51 temporary ponds that were surveyed for 14 years, we evaluated the existence of synchronized dynamics in plant richness and biomass among communities, and their association with temporal stability. A path analysis based on Mantel tests was used to evaluate the hypothesized determinants of synchrony and stability. Community-community matrices for Mantel tests were constructed with synchrony in biomass and richness, and with the Euclidean distance in geographic location, environmental conditions, and functional composition. Elements of the stability matrices were the inverse of variation in richness and biomass for each pair of ponds. A wide range of dynamics from asynchronous to synchronous rhythms was observed, and stability decreased with the coupling of community dynamics. Geographic, environmental, and functional distances between pairs of communities decoupled their dynamics in richness but weakly affected biomass synchrony. The role of rare species in richness dynamics and of dominant species in biomass dynamics may explain the observed discrepancies. While evidence for biodiversity synchrony is accumulating, evaluating the role of the proposed determinants becomes essential. Our results support the main hypotheses but also identify discrepancies that may devote further attention.

The Acoustic Complexity Index (ACI) is one of the most used metrics in ecoacoustics, demonstrating reliability across a broad range of environments and ecological conditions. However, this index requires specific procedures to be applied in the correct way. Based on the “Canberra metric,” the ACI is an unsupervised metric formulated to extract information from fast Fourier transform (FFT) sonic matrices. The ACI measures contiguous differences in acoustic energy of each frequency bin i along temporal steps (ACItf) and of a temporal interval j along the frequency bins (ACIft). The aggregation of data after an FFT using a clumping procedure allows for better scaling of the sonic signals before the computation of the ACI. The application of a filter to reduce the effects of non-environmental signals produced by microphone electrical noise is mandatory to avoid masking effects. Due to a singularity of the index for values equal to 0, ACIs require ad hoc procedures to exclude from the comparisons pairs of elements of which one is equal to 0. The spectral sonic signature and temporal sonic signature are vectors obtained from the sequence of ACItf and ACIft values, respectively. The comparison between sonic signatures using the chord distance index returns spectral and temporal sonic dissimilarities that allow the evaluation of sonic patterns emerging at different temporal and spatial resolutions. The number of frequency bins, sonic variability, and sonic evenness are further derivative metrics that help to interpret sonic heterogeneity by distinguishing the temporal and spatial heterogeneity of sonoscapes. A change of the name of the “Acoustic Complexity Index” to the “Sonic Heterogeneity Index” is recommended.

Understanding the factors influencing how fast populations can spread across the landscape will be crucial as species ranges shift due to climate change. While the role of abiotic factors in determining expansion speed has been well studied in theory and empirical research, how interspecific interactions such as competition impact speed has received far less attention. Here, we investigated how seed dispersal distances change in response to competition and how these changes to seed distributions impact expansion speed. We dispersed four genotypes of the annual plant Arabidopsis thaliana with variation in life history traits into greenhouse mesocosms of either empty habitat or habitat containing the annual grass competitor, Lolium multiflorum. We found that competition decreased both mean and maximum dispersal distance. We then built a simulation model of range expansion with experimental data from this and a prior experiment to understand whether competition slows species expansions primarily through decreasing dispersal or fecundity. We found that competition primarily slows expansion speed through decreases in dispersal, but that when competition impacts both dispersal and fecundity, expansions slow more than with dispersal alone. The genotype with traits associated with longer distance dispersal was the most affected by competition in both experimental dispersal and simulations. This research suggests that not only does competition slow range expansions through decreases in both fecundity and dispersal, but that there may be consequences for evolutionary processes at the leading edge.

Current workflows in academic ecology rarely allow an engagement of ecologists with philosophers, or with contemporary philosophical work. We argue that this is a missed opportunity for enriching ecological reasoning and practice, because many questions in ecology overlap with philosophical questions and with current topics in contemporary philosophy of science. One obstacle to a closer connection and collaboration between the fields is the limited awareness of scientists, including ecologists, of current philosophical questions, developments and ideas. In this article, we aim to overcome this obstacle and trigger more collaborations between ecologists and philosophers. First, we provide an overview of philosophical research relevant to ecologists. Second, we use examples to demonstrate that many ecological questions have a philosophical dimension and point to related philosophical work. We elaborate on one example -- the debate around the appropriate level of complexity of ecological models -- to show in more detail how philosophy can enrich ecology. Finally, we provide suggestions for how to initiate collaborative projects involving both ecologists and philosophers.

Resources play an important role in shaping the evolution of plant defensive strategies. Much research has focused on how resource availability impacts the overall concentration of specific defensive compounds, particularly among-species. Yet, how resource availability influences overall phytochemical diversity within species, and how this in-turn might affect herbivore damage is less well understood. Using Monarda fistulosa, a species that produces diverse terpene compounds and distinct chemotypes (i.e., thymol or carvacrol), we addressed three primary questions: 1) How do phytochemical components (i.e., total concentration, Shannon diversity, and chemotypes) vary between distinct populations from two large, widely separated regions that differ in climate and productivity? 2) How do these components influence attack by different herbivore species? 3) What are the growth costs of higher phytochemical levels in different chemotypes? Seeds were collected from 12 populations, six from a low-productivity/resource environment in Montana, and six from a high-productivity/resource environment in Wisconsin. Seedlings produced from these seeds were transplanted to a common garden in Wisconsin. Over two growing seasons, we analyzed terpene concentrations, quantified the number of herbivores damage, and measured plant above-ground biomass. Plants from Montana exhibited higher terpene concentrations but lower diversity, whereas those from Wisconsin displayed lower terpene concentrations but higher diversity. Total terpene concentration emerged as the primary predictor of herbivore damage, although some differences were observed between region of origin and with terpene richness. Herbivores exhibited mixed responses to phytochemistry; some herbivores were negatively affected, while one species, a specialized leaf galler, responded positively. Costs of producing defenses were evident, manifest by negative correlations between plant biomass and total terpene concentration (but not chemical richness or Shannon diversity). Our study revealed that regional differences in resource availability and productivity can influence the evolution of phytochemical concentration and diversity, which, in turn, affects plant damage and incurs growth-related costs.

Living in a seasonal environment poses challenges for small mammals, such as bats, reliant on insects as their primary food source. Bats may adeptly navigate these energetic challenges by reducing their metabolism and body temperature, entering a state of torpor. Particularly during the winter, bats remain torpid for extended periods, but are dependent on sufficient energy reserves to survive until spring. With the onset of autumn and declining temperature, bats face the challenge of building their fat deposits during a time of decreasing food availability. Bats may therefore transition to cooler roosts to initiate torpor, thereby reducing energy expenditure. However, little is still known about torpor use or roost selection by bats in autumn. This study explores the factors influencing roost selection and torpor use and --duration in two bat species during this critical transition period between the breeding and overwintering season. We show that date in autumn is a stronger driver of torpor use than prevailing ambient temperature, and that bats employ specific strategies in which they first increase daytime torpor use before also increasing the use of nighttime torpor during the pre-hibernation fattening period, most likely to facilitate rapid fat accumulation. Notably, bats commenced nighttime torpor use after spending entire days in torpor. These findings underscore the dynamic nature of torpor and the energy-saving strategies employed during the crucial pre-hibernation period, marking the transition from summer to winter.

There is an urgent need for woodland expansion to help mitigate climate change and biodiversity loss. However, the process of natural regeneration of forest ecosystems is often slow, requiring active reforestation approaches. Factors limiting regeneration are complex, but there is increasing evidence that natural expansion of woodlands onto sites that have been treeless for a long period of time may be limited by the loss of microbial woodland-soil properties. This study explored the potential role of mycorrhizal associations in facilitating obligate ectomycorrhizal (ECM) tree establishment. We determined the spatial distribution patterns of ECM tree seedlings – Pinus sylvestris and Betula spp. - outwith the existing woodlands, in relation to established dual-mycorrhizal Salix. There was very strong evidence that ECM tree seedlings were more likely to be found growing within groups around dual-mycorrhizal Salix than as isolated individuals, supporting the view that Salix drives the current spatial distribution patterns by supporting tree establishment. We suggest that the ability of Salix to form dual-mycorrhizal associations with both arbuscular (AM) and ECM fungi allows these plants to become established across the open AM dominated vegetation. Over time these plants can become colonised by ECM fungi via aerial spores and then act as a source of inoculum for obligate ECM tree seedlings, which land as seeds in the vicinity of Salix. This study highlights the potential role of dual-mycorrhizal Salix as a nurse plant in supporting secondary forest succession of obligate ECM boreal/temperate woodland species onto adjacent open areas through nucleation. Overall, we concluded that there is potential for existing ECM networks to aid tree establishment and propose a nature-based approach to maximize reforestation efforts by targeting existing symbiotic fungal networks as nucleation points for tree planting. Our findings contribute to understanding the ecological dynamics involved in woodland expansion and restoration.