Ecological Monographs最新文献

Climate change has led to pronounced shifts in phenology, varying across taxa. The Arctic is experiencing particularly rapid warming, but long-term data on phenological changes are rare in this region, especially for arthropods—a diverse taxonomic group that form important links to other trophic levels. Understanding the environmental drivers of arthropod phenological variation is necessary for predicting future trends across taxa and habitats to climate change. Here, we analyze temporal trends and climate associations in arthropod phenology using 25 years of standardized monitoring data from four habitat types in high-Arctic Greenland. We observed earlier peak activity in the arthropod community, with responses varying considerably among families and habitats. Snowmelt timing was a key driver of peak activity, especially for late-active taxa, while temperature was a less important driver, but arthropods generally exhibited earlier activity with warming. Responses in the duration of activity were more complex, with family- and habitat-specific responses to climate variation. Notably, taxa in habitats with late snowmelt responded strongly to snowmelt timing, while those in the pond habitat responded strongly to temperature. Mixed feeders and parasitoids showed rapid peak phenological shifts to earlier snowmelt and warming; however, mixed feeders shortened their activity periods, while parasitoids extended theirs. Our findings highlight the complexity of arthropod community phenological responses to climate change, with potential implications for trophic interactions dependent on temporal overlap. By analyzing phenological metrics across entire activity seasons for taxa with different functional and life-history traits, we identify general trends and consistent patterns that enhance our understanding of arthropod responses to climate change.

Changing global climate and wildfire regimes are threatening forest resilience (i.e., the ability to recover from disturbance). Yet distinguishing areas of “no” versus “slow” postfire forest recovery is challenging, and consequences of sparse tree regeneration for plant communities and carbon dynamics are uncertain. We studied previously forested areas where tree regeneration remained sparse 34 years after the large, stand-replacing 1988 Yellowstone fires (Wyoming, USA) to ask the following questions: (1) What are the recovery pathways in areas of sparse and reduced forest recovery and how are they distributed across the landscape? (2) What explains variation in postfire tree regeneration density (total and by species) among sparse recovery pathways? (3) What are the implications of sparse recovery for understory plant communities? (4) How diminished are aboveground carbon stocks in areas of sparse postfire forest recovery? Tree densities and species-specific age distributions, understory plant communities, and carbon stocks were sampled in 55 plots during summer 2022. We detected three qualitatively distinct sparse recovery pathways (persistent sparse or non-forest, continuous tree infilling, and recent seedling and sapling establishment). Nearly half of the plots appeared “locked in” as persistently sparse or non-forest, while the remaining may be on a slow path to forest recovery. Plots with nearby upwind seed sources as well as in situ seed pressure from young postfire trees appear likely to recover to forest. Where trees were sparse or absent, plant communities resembled those found in meadows, capturing compositional changes expected to become more common with continued forest loss. However, forest-affinity species persisted in mesic locations, indicating mismatches between some plant communities and future forest change. Aboveground carbon stocks were low owing to minimal tree reestablishment. Almost all (96%) carbon was stored in coarse wood, a sharp departure from C storage patterns where forests are recovering. If not offset by future tree regeneration, decomposition of dead biomass will protract postfire aboveground carbon stock recovery. As global disturbance regimes and climate continue to change, determining the drivers of ecosystem reorganization and understanding how such changes will cascade to influence ecosystem structure and function will be increasingly important.

Host personality can markedly affect parasite transmission. Especially for parasites with indirect transmission through the environment, the effects of consistent among-individual differences in behavior may have both direct and indirect components. For example, personality may mediate both how hosts respond to infected individuals and the likelihood that hosts indirectly interact with infected conspecifics (e.g., by visiting patches infected hosts have previously contaminated). Integrating parasites, personality, and these different kinds of interaction networks constitutes a key step toward understanding transmission in natural systems. We evaluated these elements using a 5-year field study of a wild population of sleepy lizards, Tiliqua rugosa, and their tick parasites, which transmit among lizards through lizards' shared use of refuges. Using Bayesian models, we evaluated (1) predictors of lizard infestation probability and intensity (i.e., average tick count when infested) and (2) relationships among the predictors. We used the latter set of models to assess indirect relationships between the predictors and the infestation metrics. As predictors, we used lizards' infestation “risk” (derived from a time-lagged refuge sharing transmission network), traits (sex, mass, and the personality axes aggression and boldness), space use (number of unique refuges used and home range overlap with other lizards), and measures of synchronous social interactions (i.e., edge weight and degree). We found both indirect and direct connections between our predictors and tick infestation. For example, boldness was positively directly associated with infection intensity and indirectly positively associated with both infestation probability and intensity via intermediary connections with social network interaction and risk. Using more unique refuges, on the other hand, was indirectly negatively associated with infestation probability (via reduced risk), but directly positively associated with infestation probability, indicating a potential trade-off in the anti-parasite benefits of using more refuges. Our results emphasize that (1) multiple aspects of host behavior may associate with parasite infection, (2) these components may proceed through both direct and indirect pathways, and (3) multiple pathways should be considered together because the pathways may have compounding or counteracting effects.

Climate change and river regulation alter environmental controls on riparian plant occurrence and cover worldwide. Simultaneous changes to river flow and air temperature could result in unanticipated plant responses to novel environmental conditions. Increasing temperature could alter riparian plant response to hydrology and other factors, while river regulation may exacerbate environmental stress through novel flows like those resulting from power generation. Further, plant establishment and growth may require differing conditions, which may be decoupled by novel conditions. Using a large dataset that spans a natural 5°C mean annual temperature (MAT) gradient and a Bayesian model that integrates plant occurrence and cover, we address four questions: (1) Does hotter MAT modify plant response to hydrology, substrate composition, topography, and cover of co-occurring plant species? (2) Does the timing of hydropower tides benefit some species over others? (3) Does dam-induced erosion hinder riparian species more than upland species? (4) Do occurrence and cover respond to different environmental variables, allowing for decoupling of life history processes? We addressed these questions with data collected along 364 km of the Colorado River downstream of Glen Canyon Dam, Arizona, United States of America. Occurrence and cover class were recorded in >10,000 plots from 2016 to 2020, along with environmental covariates that repeat across the climate gradient. For 36 species, plant occurrence and cover were modeled with respect to MAT, hydrology, substrate, topography, other plant cover, and their interactions with MAT. There were four key results. (1) Increasing MAT will not only directly influence plants but will mediate their responses to the environment, including greater dependence on stable water supplies. (2) The timing of hydropower tides shapes plant community composition. (3) Dam-related erosion has an outsized effect on riparian species, which could lead to a loss of regionally unique plant species. (4) For all species, the most important covariates driving occurrence differed from those for cover, suggesting the potential for these life stages to be decoupled. Not only will climate change and river regulation independently alter plant distributions, interactions among hotter temperature, dam-controlled flow patterns, and limited fine sediments will determine which species flourish or perish under future conditions.

Natural and anthropogenic stressors alter the composition, biomass, and nutritional quality of primary producers and microorganisms, the basal organisms that synthesize the biomolecules essential for metazoan growth and survival (i.e., basal resources). Traditional biomarkers have provided valuable insight into the spatiotemporal dynamics of basal resource use, but lack specificity in identifying multiple basal organisms, can be confounded by environmental and physiological processes, and do not always preserve in tissues over long timescales. Carbon stable isotope ratios of essential amino acids (δ¹³C-EAA) show remarkable promise in identifying and distinguishing clades of basal organisms with unique δ¹³C-EAA fingerprints that are independent of trophic processing and environmental variability, providing unparalleled potential in their application. Understanding the biochemical processes that underpin δ¹³C-AA data is crucial, however, for holistic and robust inferences in ecological applications. This comprehensive methodological review, for the first time, conceptualizes these mechanistic underpinnings that drive δ¹³C-EAA fingerprints among basal organisms and incorporates δ¹³C values of non-essential amino acids that are generally overlooked in ecological studies, despite the gain of metabolic information. We conduct meta-analyses of published data to test hypothesized AA-specific isotope fractionations among basal organism clades, demonstrating that phenylalanine separates vascular plant δ¹³C-EAA fingerprints, which strongly covaries with their phylogeny. We further explore the utility of non-essential AAs in separating dietary protein sources of archaeological humans, showing the differences in metabolic information contained within different NEAAs. By scrutinizing the many methodologies that are applied in the field, we highlight the absence of standardized analytical protocols, particularly in sample pretreatments leading to biases, inappropriate use of statistical methods, and reliance on unsuitable training data. To unlock the full potential of δ¹³C-EAA fingerprints, we provide in-depth explanations on knowledge gaps, pitfalls, and optimal practices in this complex but powerful approach for assessing ecosystem change across spatiotemporal scales.

Variance partitioning is a common tool for statistical analysis and interpretation in both observational and experimental studies in ecology. Its popularity has led to a proliferation of methods with sometimes confusing or contradicting interpretations. Here, we present variance partitioning in a model-based Bayesian framework as a general tool for summarizing and interpreting regression-like models to produce additional insight on ecological studies compared with what traditional parameter inference of these models on its own can reveal. For example, we propose predictive variance partitioning as a tool to extend sample-based analyses to analyses of whole populations or predictive scenarios. We also extend variance partitioning to encompass partitioning of variance within and between ecologically relevant subgroups of the observations, or the whole population of interest, to provide information on how the relative roles of processes underlying the study system may vary depending on the environmental or ecological context. We discuss the role of correlated covariates and random effects and highlight uncertainty quantification in variance partitioning. To showcase the utility of our approach, we present a case study comprising a simple occupancy model for a metapopulation of the Glanville fritillary butterfly. As a result, we demonstrate model-based variance partitioning as a general and rigorous statistical tool to gain more insight from ecological data.

Identifying the specific environmental features and associated density-dependent processes that limit population growth is central to both ecology and conservation. Comparative assessments of sympatric species allow for inference about how ecologically similar species differentially respond to their shared environment, which can be used to inform community-level conservation strategies. Comparative assessments can nevertheless be complicated by interactions and feedback loops among the species in question. We developed an integrated population model based on 61 years of ecological data describing the demographic histories of Canvasbacks (Aythya valisineria) and Redheads (Aythya americana), two species of migratory diving ducks that utilize similar breeding habitats and affect each other's demography through interspecific nest parasitism. We combined this model with a transient life table response experiment to determine the extent that demographic rates, and their contributions to population growth, were similar between these two species. We found that demographic rates and, to a lesser extent, their contributions to population growth covaried between Canvasbacks and Redheads, but the trajectories of population abundances widely diverged between the two species during the end of the twentieth century due to inherent differences between the species life histories and sensitivities to both environmental variation and harvest pressure. We found that annual survival of both species increased during years of restrictive harvest regulations; however, recent harvest pressure on female Canvasbacks may be contributing to population declines. Despite periodic, and often dramatic, increases in breeding abundance during wet years, the number of breeding Canvasbacks declined by 13% whereas the number of breeding Redheads has increased by 37% since 1961. Reductions in harvest pressure and improvements in submerged aquatic vegetation throughout the wintering grounds have mediated the extent to which populations of both species contracted during dry years in the Prairie Pothole Region. However, continued degradation of breeding habitats through climate-related shifts in wetland hydrology and agricultural conversion of surrounding grassland habitats may have exceeded the capacity for demographic compensation during the nonbreeding season.

Anthropogenic land use change facilitates disease emergence by altering the interface between humans and pathogen reservoirs and is hypothesized to drive pathogen evolution. Here, we show a positive association between land use change and the evolution and dispersal of Zaire ebolavirus (EBOV) and Sudan ebolavirus (SUDV). We update the phylogeographies of EBOV and SUDV, which reveal that the most recent common ancestor of EBOV was circulating around 1960 in the forests of what is now the northwestern Democratic Republic of the Congo, while the most recent common ancestor of SUDV was circulating around 1958 in the southern Sudanese savanna. Both landscapes underwent significant anthropogenic fragmentation between 1940 and 1960, associated with specific colonial “schemes,” which substantially altered local human settlement patterns and the surrounding vegetation to support intensive cash crop agriculture. Since these disturbances, landscape fragmentation was spatiotemporally associated with the divergence and dispersal of new variants of both viruses into new ecoregions of Africa. These variants segregated geographically along ecoregion boundaries, resembling a pattern observable for other bat-borne viruses. The amino acid changes which characterized each variant disproportionately involved glycosylation-sensitive amino acids in the surface glycoprotein domain responsible for immune evasion and attachment to host cells, suggesting adaptation to new hosts amidst changing landscapes. Our results show that land use change not only increases the risk of spillover, but also impacts the evolution of viruses themselves.

All populations are affected by multiple environmental drivers, including climatic drivers such as temperature or precipitation and biotic drivers such as herbivory or mutualisms. The relative response of a population to each driver is critical to prioritizing threat mitigation for conservation and to understanding whether climatic or biotic drivers most strongly affect fitness. However, the importance of different drivers can vary dramatically across species and across populations of the same species. Theory suggests that the response to climatic versus biotic drivers can be affected by both the species' fundamental niche breadth and the latitude of the population at which the response is measured. However, we have few tests of how these two factors affect relative response to drivers separately, let alone tests of how niche breadth and latitude together influence responses. Here, we use a meta-analysis of published studies on population response to climatic and biotic drivers in terrestrial plants, combined with estimates of climatic niche breadth and position within climatic niche derived from herbarium records, to show that species' niche breadth is the primary determinant of response to climatic versus biotic drivers. Namely, we find that response to climatic drivers changes only minimally with increasing niche breadth, while response to biotic drivers increases with niche breadth. We see similar relationships when considering range size instead of niche breadth. Surprisingly, we find no effects of latitude on the relative effect of climatic versus biotic drivers. Our work suggests that populations of species with small and large ranges experience similar extirpation risks due to the negative impacts of climate change. By contrast, populations of species with large (but not small) ranges may be highly susceptible to changes in densities or distributions of interacting species.

Wet tropical forests play an important role in the global carbon (C) cycle, but given current rates of land-use change, nitrogen (N) and phosphorus (P) limitation could reduce productivity in regenerating forests in this biome. Whereas the strong controls of climate and parent material over forest recovery are well known, the influence of vegetation can be difficult to determine. We addressed species-specific differences in plant traits and their relationships to ecosystem properties and processes, relevant to N and P supply to regenerating vegetation in experimental plantations in a single site in lowland wet forest in Costa Rica. Single-tree species were planted in a randomized block design, such that climate, soil (an Oxisol), and land-use history were similar for all species. In years 15–25 of the experiment, we measured traits regarding N and P acquisition and use in four native, broad-leaved, evergreen tree species, including differential effects on soil pH, in conjunction with biomass and soil stocks and fluxes of N and P. Carbon biomass stocks increased significantly with increasing soil pH (p = 0.0184, previously reported) as did biomass P stocks (p = 0.0011). Despite large soil N pools, biomass P stocks were weakly dependent on traits associated with N acquisition and use (N₂ fixation and leaf C:N, p < 0.09). Mass-balance budgets indicated that soil organic matter (SOM) could supply the N and P accumulated in biomass via the process of SOM mineralization. Secondary soil P pools were weakly correlated with biomass C and P stocks (R = 0.47, p = 0.08) and were large enough to have supplied sufficient P in these rapidly growing plantations, suggesting that alteration of soil pH provided a mechanism for liberation of soil P occluded in organo-mineral soil complexes and thus supply P for plant uptake. These results highlight the importance of considering species' effect on soil pH for restoration projects in highly weathered soils. This study demonstrates mechanisms by which individual species can alter P availability, and thus productivity and C cycling in regenerating humid tropical forests, and the importance of including traits into global models of element cycling.