Montane ecosystems contribute significantly to global diversity, serving as refuges for numerous species, many of which are entirely restricted to mountainous areas. These species are particularly vulnerable to anthropogenic stressors, which are expected to result in heterogeneous shifts in elevational distributions and potential range restrictions. Here, we resurveyed the elevational ranges of birds in Tianmu Mountain, eastern China, in 2021, 60 years after the original survey in the 1960s. We aimed to determine whether the elevational shifting trends of birds in the lowland and highland regions are asynchronous and whether these trends can be predicted by species traits. Over the past 60 years, we observed the upward shifts of the upper limit of lowland birds, exhibiting range expansion. However, highland birds have generally contracted their upper limits downward, resulting in decreased range. Upslope shifts and range expansions were more pronounced in species with smaller range sizes, while widely distributed species were more likely to move downward and lose occupancy of elevational areas. Our results illustrate the heterogeneous elevational range shifts between two lowland and highland bird assemblages, highlighting the complexity of avian responses to environmental changes and the need for caution when applying conventional patterns of elevational upslope shifts to species redistribution in montane ecosystems.

Museum specimens offer a unique and powerful tool for understanding the impact of anthropogenic change on populations over time. Morphological traits can be impacted by many different environmental variables that are difficult to separate from one another as potential driving factors. Comparative analyses among similar species jointly experiencing change in the same environmental variables can help pinpoint the selective pressures driving temporal morphological change. We assessed temporal change in bill size, tarsus length, and body size between six species of songbirds from the San Francisco Bay Area over the past 150 years. Proxies for body size (wing and tarsus length) exhibited idiosyncratic temporal changes among species. In contrast, we found a significant increase in bill surface area across all but one species. Quantile regression analyses on bill size variation additionally revealed that temporal increases over the past century have been driven by increases in the largest bill sizes in some species, but increases in the smallest bills over time in others. The climate variables best explaining temporal change in bill size also differed among species with some species responding more to changing summer variables (e.g. maximum annual temperature) and others in response to a changing winter climate. These results together suggest that different sympatric, resident bird species may be experiencing temporal morphological change in response to selective pressures experienced at different seasons. Our finding provides support for the season of critical thermal stress hypothesis that suggests variation in functional traits will be shaped by the season that imposes the greatest selective force on a population. Overall, this study has important implications for future research on the role of bills in thermoregulation and for conservation efforts based on the adaptive capacity of birds to respond to climate change.

Many investigations of plant defense theory fail to address how trajectories of trait evolution vary across levels of biological organization, even though the processes that shape trait correlations have the strong potential to shift within versus across species, as well as in different environmental and ecological contexts. In this work, we tested for correlations between multiple defensive traits (secondary chemistry, carbon to nitrogen ratio, domatia, leaf toughness, trichomes, and pearl bodies) across a common garden of twenty-one Vitis species and eighteen genotypes of the species Vitis riparia to identify when and where patterns of defense trait evolution persist or break down across biological scales. Additionally, we asked whether Vitis defense trait investment correlates with environmental variables as predicted by plant defense theory, using environmental metrics for each Vitis species and V. riparia genotype from the GBIF and WorldClim databases. We tested for correlations between defense trait investment, herbivore palatability, and environmental variables using phylogenetically informed models. Beyond a few likely physiological exceptions, we observed a lack of correlations between defense traits at both intra- and interspecific scales, indicating that these traits evolve independently of each other in Vitis rather than forming predictable defense syndromes. We did find that select traits vary with proximity to the equator, demonstrating support for plant defense theory’s prediction of higher investment in defenses at more equatorial environments for some, but not all, defense traits. Overall, our results challenge commonly held hypotheses about plant defense evolution, namely the concept of syndromes, by demonstrating that strong correlations between defense traits are not the prevailing pattern both across and within Vitis species. Our work also provides the first comprehensive evaluation of the evolutionary divergence in approaches that Vitis, a genus with significant agricultural value, have evolved to defend themselves against herbivores.

Biogeographical partitioning of ecological communities has been renewed in recent decades to illustrate broad distributional patterns. In the oceans, observational datasets have grown substantially and open new access to test bioregional patterns beyond the classical fixed thresholds of endemism to differentiate regions. This work combines a recently collated dataset of 29 different scientific bottom trawl surveys spanning 21 years with network-based clustering to illustrate biogeographical partitions of vast tracts of the northern hemisphere’s continental shelf seas. Our work contributes to testing bioregionalization patterns in demersal fishes using observational data, totaling >2.5 million species records and >2000 species, with bipartite network clustering weighted by species occurrence frequencies. We propose eight major bioregions across shelf seas which fall along the longest geographical axis in each shelf region and against continua of species richness gradients, endemicity, and phylogenetic turnover rates. These patterns capture known biogeographical boundaries (e.g., North Sea–Baltic Sea, Cape Hatteras) alongside potential transition areas deduced from uncertainty estimates based on shared network nodes between bioregions. The most species-rich areas include the Southeast US Shelf, Temperate Pacific, Northeast Atlantic Shelf, and the Outer European Shelf— corresponding to relatively high endemicity. However, the relatively species-poor partitions including the Baltic Sea and the North & Celtic Seas display comparatively low endemicity (<8%), illustrating apparent statistical differences in partitions captured by bipartite networks and occurrence frequencies that would otherwise be missed using a fixed endemic criterion. Our proposed bioregionalization can be compared against the growing availability of species occurrence data, dispersal limitations, or other quantitative observations of ecological communities.

Ecosystems may exist in alternative stable states and thereby extremely differ in ecosystem structure and functions, including gross primary productivity (GPP), which is crucial for assessing an ecosystem’s ability to capture atmospheric carbon dioxide, especially under the context of climate change. This study applied alternative stable states theory to evaluate GPP in global dryland forests, and analyzed multi-year average GPP data alongside environmental factors such as the Aridity Index and mean annual precipitation. Here, we found the existence of alternative stable states of GPP along the aridity gradient. Mean GPP were 893.12 gC/m²/year and 1539.86 gC/m²/year under lower and higher branches of alternative stable states, respectively, compared to the current mean value of 1203.02 gC/m²/year. Notably, we observed striking regional disparities in GPP, with Africa and Oceania predominantly in the higher alternative stable state, while North America and Asia were in the lower alternative stable state. However, GPP along mean annual precipitation did not exhibit alternative stable states, but a significant variation during the medium range of mean annual precipitation (241-402 mm year-1). The relationships between GPP data and environmental factors were consistent across different forest types. This study sheds light on dryland forest productivity and indicates adaptive management strategies that should be used to bolster ecosystem function in the context of climate change.

The global biodiversity loss is causing abrupt shifts in the structure and functioning of ecosystems with severe ecological and socio-economic consequences. Therefore, improving our understanding of ecosystem dynamics and regime shifts, as well as the stabilizing role of biodiversity across multiple scales is needed. Here we investigate the temporal dynamics and stability of marine ecosystems using high-resolution monitoring data on fish species composition, abundances and traits throughout European Seas. More specifically, we quantify and compare the direction and magnitude of community change at multiple spatial scales and levels of biological organization. Our results show less variability in community trajectories at larger spatial scales and higher levels of biological organization. The main underlying processes providing stability are statistical averaging arising from a larger pool of species, while at smaller spatial scales stability also emerge from functional complementarity channeled through the distribution of species traits within functional groups.

The relative importance of abiotic and biotic factors in determining species distributions has long been of interest to ecologists but is often difficult to assess due to the lack of spatially and temporally robust occurrence records. Furthermore, locating places where potentially highly competitive species co-occur may be challenging but would provide critical knowledge into the effects of competition on species ranges. We built species distribution models for two closely related species of small mammals (Neotoma) that are largely parapatric along mountainsides throughout the Great Basin Desert using extensive modern occurrence records. We hindcasted these models to the mid-Holocene to compare the response of each species to dramatic climatic change and used paleontological records to validate our models. Model results showed species co-occurrence at mid-elevations along select mountain ranges in this region. We confirmed our model results with fine-scale field surveys in a single mountain range containing one of the most extensive survey datasets across an elevational gradient in the Great Basin. We found close alignment of both species’ realized distributions to their respective abiotic species distribution model predictions, despite the presence of the congener, indicating that climate may be more influential than competition in shaping distribution at the scale of a single mountain range. Our models also predict differential species responses to historic climate change, leading to reduced probability of species interactions during warmer and dryer climatic conditions. Our results emphasize the utility of examining species distributions with regards to both abiotic variables and species interactions and at various spatial scales to make inferences about the mechanisms underlying distributional limits.

More species-rich communities are often assumed to contain more specialist species, typically characterized by narrower niche breadths or smaller ranges. Stronger interspecific competition in species-rich communities is thought to be a key mechanism explaining these patterns. Yet, the relationship between richness and specialization has so far only been studied for a few taxa, and characterizing the effects of interspecific competition on species niches and distributions is challenging. Thus, it remains unclear how general richness-specialization relationships are. Here, we assess relationships between specialization and interspecific competition along richness gradients of bats across four understudied global biodiversity hotspots. Using a novel, integrated species distribution modeling approach that combines expert range maps and occurrence records of 49 bat species, we produced fine-scale distribution and species richness maps, allowing us to assess environmental niche breadth and range sizes. Further, contrasting potential ranges obtained from traditional distribution models with realized ranges obtained through the integration of expert ranges, we assessed range filling and derived indicators of geographic exclusion that characterize how interspecific competition is limiting species' ranges. Our results highlight that the narrowest niche breadths and strongest geographic exclusion occur in species-poor, not species-rich bat communities, in contrast to what was found for other taxa. While niche breadth peaked at intermediate richness, range sizes decreased continuously with richness. These findings show that increasing bat species richness is not closely linked to environmental specialization across the entire richness gradient and that decreasing range sizes in species-rich communities could be driven by the number of interacting species, rather than by environmental specialization or individually stronger interactions. Our study shows how innovative distribution modeling approaches can shed new light on the interplay of species richness, interspecific competition, and community structure. More generally, our findings caution against generalizing relationships between richness and specialization across taxa and geographies.

Understanding how plant communities are assembled is critical to explaining the functioning of ecosystems and the maintenance of biodiversity. The phylogenetic distance among species in a community (community phylogenetic structure) has been used to infer deterministic and stochastic assembly processes, albeit with criticisms. However, the effect of the phylogenetic scale (old versus young lineages) and spatial scale on measures of community phylogenetic structure are rarely tested especially in the boreal biome, yet essential to unravel different assembly processes that might operate across species in a community. We examined lineage-specific phylogenetic structure of six plant communities defined at the habitat scale, and the phylogenetic structure of communities defined at a plot level scale (1m2). We obtained vascular plant species lists for six habitats (arctic-alpine barren, bog, fen, kalmia barren, limestone barren, and serpentine barren) on the island of Newfoundland, Canada, and 73 permanent vegetation plots within three of the above habitats to estimate their mean pairwise phylogenetic distance standardized for sample size (SES-MPD). Contrary to the expectation under the stress-dominance hypothesis of phylogenetic clustering in challenging boreal environments, the majority of clades had random phylogenetic structure. However, we observed a pattern consistent across most habitats of a shift from phylogenetic clustering at the deepest nodes of the angiosperms to no phylogenetic structure at shallower nodes, suggesting that different assembly processes may be operating at different phylogenetic scales within a habitat. As expected, all vegetation plot communities at a fine spatial scale showed strong phylogenetic overdispersion likely explained by biotic interactions. Our lineage-specific approach to estimate SES-MPD proved useful to outline testable hypotheses on the evolution and role functional traits play in community structure and assembly of boreal habitats

Alternative stable states refer to two or more stable states in an ecosystem under the same external conditions. Ecosystems with alternative stable states respond to external conditions changes nonlinearly and hysteretic, with forward and backward regime shifts occurring at different environmental levels (thresholds). The region between the two thresholds is unstable, and the eventual ecosystems state depends on the initial conditions. Alternative stable states mainly result from positive feedback generated by various biotic-biotic and biotic-abiotic interactions in the ecosystem. For degraded ecosystems with alternative stable state, the recovery trajectory is not the same as the collapse, and feedback makes it more difficult to restoration. In the context of global change, it is expected that the frequency of catastrophic regime shifts and alternative stable states under climate change and human disturbance may increase. Therefore, incorporating the frameworks of ASS into restoration practices, and understanding when, how, and why to apply them is increasingly important. Here, we summarized the alternative stable states in the different ecosystems, the field and theoretical work in generating, diagnosing, and evaluating alternative stable states. It is generally believed that hysteresis, threshold, and positive feedback are important characteristics of alternative stable states. When putting the alternative stable states framework into restoration, correctly identifying the recovery threshold is still needed. On this basis, disrupting the feedback reinforcing the degraded state or strengthening the restoration feedback artificially to restore the ecosystem to the ideal state is a direction that restoration ecology should make efforts.

Saltmarsh habitats sequester significant amounts of carbon from the atmosphere and provide vital habitats for various bird species but are eroding at increasingly rapid rates due to ongoing sea level rise. Yet, in some regions where space and topography permit, saltmarshes are transgressing into adjacent uplands, counterbalancing the lost area. In these areas, a greater proportion of saltmarsh is relatively young but it remains uncertain whether younger marshes support the same plant and animal communities as older ones. We compared soil organic matter (SOM), plant communities, and bird occupancy at 133 marsh patches on the Delmarva Peninsula, Virginia, USA. Marshes that converted from uplands since the early to mid-20th century exhibited lower SOM levels, were more closely situated to trees and snags, and were less likely to support obligate saltmarsh nesting bird species. Areas with past agricultural activity, characterized by features like berms and ditches, exhibited higher SOM levels, supported fewer of the most salt-tolerant plants and more of the least salt-tolerant species, and were more likely to support saltmarsh obligate bird species. We expect areas where a high proportion of relatively young marsh to shift away from the most salt-tolerant plants and birds, especially where an agricultural legacy can be found. We hypothesize that elevated organic carbon content found in formerly farmed fields may result from decreased inorganic sediment input, facilitated by restricted tidal flooding, rather than an enhanced capacity for carbon sequestration. However, further investigation is necessary to conclusively address this issue.

Species distribution modeling is increasingly used to describe and anticipate consequences of a warming ocean. These models often identify statistical associations between distribution and environmental conditions such as temperature and oxygen, but rarely consider the mechanisms by which these environmental variables affect metabolism. Oxygen and temperature jointly govern the rate of oxygen supply to oxygen demand, and theory predicts thresholds in these rates below which species population densities are diminished. However, parameterizing models with this joint dependence is challenging because of the paucity of experimental work for most species, and the limited applicability of experimental findings in situ. Here we ask whether the joint effects of temperature and oxygen can be reliably inferred from species distribution observations in the field, using the U.S. Pacific Coast as a model system. Through simulation testing, we found that our statistical model—which adapted the metabolic index to jointly consider oxygen and temperature by applying an Arrhenius equation and used a non-linear threshold function to link the index to fish distribution—could not precisely estimate the parameters due to inherent features of the distribution data. However, the model reliably estimated an overall metabolic index threshold effect, and provided a better fit to sablefish (Anoplopoma fimbria) spatial distribution than previously used models. This mechanistic approach may improve predictions of species distribution, even in novel environmental conditions. Further efforts to combine insights from mechanistic responses and realized species distributions will improve forecasts of species’ responses to future environmental changes.

not-yet-known not-yet-known not-yet-known unknown Projecting how climate change will reshape global patterns of forest carbon storage is paramount to investigate the future of the global carbon cycle. Advances in machine learning and the proliferation of remote-sensing missions have stimulated the development of statistical models for the estimation of carbon storage on a global scale. However, existing models present two major limitations. First, they are not suitable for forecasting because they are trained on variables that cannot be projected. Second, they are based on large numbers of predictors, which hinders the interpretability and explainability of their results from a biological and ecological perspective. In this manuscript, we present a machine learning model for the global mapping of potential Aboveground Biomass Density that overcomes the above mentioned limitations. On the one hand, our model is based exclusively on bioclimatic variables and is therefore suitable for forecasting and interpretable from a biological perspective. On the other hand, we calibrated our model with a state-of-the-art predictor selection process to identify the optimal subset of predictors for the maximization of model accuracy. We found that a minimal model based solely on four bioclimatic variables performed the best. Furthermore, our model reproduces field measurements from experimental forest plots equally well than a state-of-the-art model trained on $190$ predictors. In conclusion, we provide a simple and computationally cheap model that can be coupled with climate projections to investigate how climate change will reshape carbon storage on a global scale.

Forest bird populations in Europe have remained stable overall, unlike the drastic decline in the populations of farmland species. However, this apparent overall stability may hide large variation among species. We aimed to determine if forest bird species with varying life histories and biome distributions show different population trends. We used functional traits and specialisation indices to study changes in abundance and distribution of European forest bird populations, and to identify “winner”, “loser”, and stable species. We defined change in abundance as the population trend of each species over the last 40 years, and change in distribution as two components: range change (i.e., area shrinkage or expansion) and range shift (i.e., latitudinal adjustments), both over the last 30 years. We also considered specialist groups of different biomes (i.e., boreal, temperate, Mediterranean and biome generalists) separately. We show that while Mediterranean and temperate species have increased in abundance and range, probably as the result of warmer temperatures and forest expansion in these regions, boreal forest species have declined in abundance and range area. This probably results from changes in forest structure and composition due to forestry practices, increasing temperatures, and colonisation of warm-dwelling species. Among boreal species, the ones related to mixed forest (i.e., mix of broadleaf and coniferous trees) declined the most, both in abundance and range, and shifted northwards. In contrast, for vertebrate carnivores (i.e., birds of prey), we observed abundance increase among Mediterranean species and southward expansion among all species. We conclude that forest bird species in Europe are sensitive to the combined effects of land use and climate change, and these effects vary among the different biomes. Our results highlight the necessity of maintaining and restoring key forest habitats (e.g. through increased protected areas and extensive management) and halting or limiting climate change, especially regarding boreal species.

The spatial pattern and community assembly of soil microbial taxa have notable meanings for biodiversity shaping and maintaining mechanisms. Important for ecosystem functionality and equilibrium, the microbial rare taxa may have distinct spatial patterns and community assembly mechanisms from those of abundant taxa. However, such information is lacking, especially for rare fungal taxa at large scales. Here, we investigated distance-decay patterns and underlying assembly mechanisms for abundant and rare fungal taxa in 129 soil samples collected across 4,000 km in Chinese Northern grasslands, based on high-throughput sequencing data. A total of 208 abundant OTUs (relative abundance > 0.1%) and 5,779 rare OTUs (relative abundance < 0.01%) were obtained, accounting for 2.73% and 75.85% of entire OTUs, respectively. Community similarities of abundant and rare fungal taxa both declined significantly (P < 0.001) with the increasing geographic distance, following the distance-decay relationship. However, the turnover rate for rare fungal taxa (0.0024 per 100 km) was almost half of that for the abundant taxa (0.0054 per 100 km) based on the binary Bray-Curtis distance. Such lower turnover for rare fungal taxa was likely due to their community assembly mechanism dominated by stochastic processes, which were less influenced by environmental variance along the geographic distance. In contrast, the assembly of abundant fungal taxa was dominated by deterministic factors including soil variables and plant traits, which changed greatly along the geographic distance. Consistently, the rare fungal taxa were less sensitive to environmental changes spatially since their turnover rate by the environmental distance was much lower than that of abundant taxa (0.0027 Vs 0.0099). In summary, our findings revealed that rare fungal taxa shaped mainly by stochastic processes had lower spatial turnover than abundant fungal taxa shaped by deterministic processes, which enhanced our understanding of the biogeography for rare microbial taxa.

In alpine ecosystems, greater overlap in flowering phenology among species at higher elevations could be due to evolutionary convergence among lineages or environmental filtering for taxa preadapted to colder conditions. We hypothesize that the flowering phenology of high alpine communities, subjected to colder and shorter reproductive seasons, is the result of convergence due to strong selective pressure imposed by the environment rather than environmental filtering for conservated traits. To test this hypothesis, we analyzed phylogenetic signal for first flowering date, peak flowering date, flowering duration and thermal sums to first and peak flowering and community phylogenetic structure considering Mean Nearest Taxon Distance (MNTD) and Mean Pairwise Distance (MPD) on four sites encompassing a total of 86 species derived from the subalpine and high alpine in the central Chilean Andes. After discarding possible richness effects on phylogenetic signal, the high alpine sites continued to show significant phylogenetic signal for a smaller number of floral traits than the subalpine sites. This was particularly evident for thermal sums. The two high elevation communities show significant values of SES(MNTD) but not for SES(MPD), indicating clustering related to the tips of the phylogeny. Overall, results suggest that environmental filtering for preadapted lineages is not the main driver of the phylogenetic structure and composition in high alpine communities. Rather, species at higher elevation have been subjected to greater environmental pressures leading to trait convergence. We conclude that phylogenetic conservatism in floral phenology has been overridden by the harsh environmental conditions in the high Andes. The high alpine environment can be seen as an evolutionary promoter rather than a gatekeeper of lineages preadapted to cold conditions.

Successful plant invasions are often explained by adaptation to novel environments. However, invasive species usually occupy broad niches within their native and introduced ranges. A true understanding of microevolution during invasion therefore requires a wide sampling of ranges, ideally with a knowledge of introduction history. We tested for genetic differentiation in herbivore resistance among 128 introduced (European, North American) and native (Chinese, Japanese) populations of the invasive Japanese knotweed (Reynoutria japonica) in two common gardens in the native range. In both common gardens, we found that the resistance traits of the introduced populations differed from most Chinese native populations but not from native populations in Japan, which are the two putative sources of introduction. Compared to Chinese populations, introduced European populations had thicker leaves in both common gardens with a lower C: N ratio but higher flavonoids content in the Shanghai garden. In the native range, variation in herbivore resistance was much more strongly associated with climate of origin than in introduced populations. Our results support that introducing particular resistance phenotypes from Japan played a key role in the invasion of knotweed into Europe and North America. Our study demonstrates how knowledge of introduction history can avoid misinterpretations of observed biogeographic divergence.

Feedbacks are the basic linkages of living systems. In living organisms, feedbacks regulate the processes of growth and homeostasis, as well as their interactions with their world. Feedbacks are equally important in ecological systems, which is why ‘feedback in ecology’ gets more than 2 million hits on Google. The ecological literature is rich in papers dealing with the role of feedback in various phenomena. However, attempts to embrace the subject of feedbacks as a whole in ecology are rare. Pichon et al. (in press) has done that, with skill and comprehensiveness. The paper succeeds in bringing the array of different types of feedbacks into a manageable order that makes this a valuable synthesis of the subject.