Ecology最新文献

Mutualisms are complex, interspecific relationships, which sometimes create “selfish-herds” as individuals of each species compete to maximize their own fitness. Nest association, where individuals of different species spawn on a nest created by a host species, is a reproductive interaction characteristic of some minnows (Leuciscidae) and is considered mutualistic despite mimicking the behavior labeled “brood parasitism.” We studied the spawning behaviors of bluehead chub (Nocomis leptocephalus) and its nest associates, testing the hypothesis that bluehead chub exploits the selfish-herd dynamic in a novel manner by arranging embryos within its nest to maximize the survival of its own offspring at the expense of the nest associates' offspring. Our results show that embryos were not uniformly distributed within a nest, as one section representing one-sixth of the nest's total volume contained a disproportionate percentage of embryos (x¯ = 40.0% ± 6.1% SE). We found three-quarters of host embryos within deeper nest sections safer from embryo predators, whereas only a third of all associate embryos were found in the same sections. These results support our hypothesis that male Nocomis leptocephalus create “embryonic selfish-herds” within their nests. This is the first study to document the existence of embryonic selfish-herds, a phenomenon that warrants the reexamination of some vertebrate reproductive interactions labeled as brood parasitism.

Priority effects, where species that arrive first influence later arriving species, are often considered in terms of seed arrival time. However, the timing of seedling emergence may play a more critical role, as this defines when plants start interacting. Further, initial seed density may also be important, allowing early-arriving species with low initial seed density to overcome seed limitation, while also potentially allowing late-arriving high-density species to overcome the disadvantage of arriving late. In this large-scale, multi-site field experiment, we manipulated species arrival and emergence timing by sowing fast- and slow-germinating meadow species in various arrival orders and seed densities across two climatically contrasting sites in Sweden. Our findings demonstrate that germination speed modulates the strength and direction of priority effects: fast-germinating species were less affected by both early- and late arrival. Conversely, slow-germinating species were disadvantaged by late arrival and benefited significantly from early arrival, particularly at the more productive, northern site with shorter growing seasons. Contrary to expectations, initial sowing density had limited and inconsistent effects on priority effect outcomes. These results highlight that emergence timing, not just seed arrival, is a key aspect of priority effects, influencing plant competition and community structure. Furthermore, the context dependency across sites emphasizes the importance of environmental conditions in modulating priority effects, with implications for predicting vegetation dynamics under climate change.

Characterizing the processes that drive microbial community assembly remains a key challenge in ecology. Several recent studies have argued that pairwise interactions may be insufficient to explain co-occurrence patterns in complex microbial communities, but most such studies have focused on synthetic communities not found in nature or microbes grown in contexts that differ widely from their natural environment. Moreover, most models of pairwise interactions rely on equilibrium assumptions that are not relevant to all natural communities, such as gut microbiomes or species in fluctuating environments. Inclusion of appropriate demographic factors into models of pairwise interactions could be a potential approach to better capture patterns of community assembly. In this study, we investigated whether multispecies co-occurrence patterns can be predicted from pairwise interactions for microbes isolated from sourdough starters. Interaction parameters inferred from pairwise growth trajectories were suggestive of widespread coexistence between pairs of microbes in our species pool. In communities of up to nine species, most species' presence and relative abundance could be reliably predicted based on a model of pairwise interactions. The inclusion of nonequilibrium demography in our model further improved the accuracy of our pairwise model. Our work contributes to the broader debate on the processes underlying community assembly by showing that pairwise interactions are predictive of community structure in a system of moderate species complexity.

As ecology becomes a more predictive discipline, identifying the intrinsic predictability, or stochasticity, of ecosystem variables across space and time is needed to help guide the development of ecological models and forecasts. For example, if an ecological time series has high intrinsic predictability, then a high-performing model should presumably be able to replicate its dynamics. Conversely, if an ecological variable has low intrinsic predictability, then no model—regardless of its performance—will be able to replicate its dynamics. However, despite the proliferation of ecological models and forecasts, the intrinsic predictability of ecological variables remains largely unknown. To bridge this gap, we analyzed a >4-year time series of high-frequency sensor data collected from replicate freshwater ecosystems to determine how intrinsic predictability (quantified as permutation entropy) differs among ecological variables, seasons, and ecosystems. We observed greater differences in predictability among ecological variables and days of year than between ecosystems. Although intrinsic predictability was generally low for all variables, it was still significantly higher than white noise, indicating complex yet predictable dynamics. We observed the highest predictability for physical ecosystem variables (e.g., water temperature) and the lowest predictability for biological variables (e.g., phytoplankton biomass), with chemical variables (e.g., dissolved oxygen) intermediate. We observed substantial seasonal differences in predictability among variables: surface water temperature and dissolved organic matter exhibited their highest levels of predictability in autumn, whereas surface chlorophyll and bottom-layer dissolved oxygen and temperature exhibited highest predictability in summer. Periods of anoxia (low oxygen) were associated with the highest levels of predictability in dissolved oxygen over the time series. Altogether, our analysis highlights how intrinsic predictability data can both guide ecological model development and improve our understanding of how ecological predictability varies across space and time.

The proportion of individuals that are found to have empty stomachs during a survey of a predator population's diet has been used as an indicator of the average individual's state of energy balance and of the degree to which its feeding rate (i.e., its functional response) is saturated with respect to prey availability. As such, the proportion of empty stomachs provides insights into the effects of prey on predators and vice versa, although it is typically unreported in deference to descriptions of the contents of the non-empty stomachs. The FracFeed database is an ongoing compilation of the proportions of empty and non-empty stomachs (for gut content surveys) and of feeding and not feeding individuals (for direct observation surveys) reported in publications of predator diet surveys. FracFeed contains data from 4920 diet surveys on 1507 taxa (>4.3 million individuals) spanning cnidarians, ctenophores, chaetognaths, birds, annelids, amphibians, arthropods, mammals, mollusks, reptiles, echinoderms, and fishes that were surveyed in terrestrial, marine, and freshwater ecosystems across the globe over more than 135 years (1887–2023). For most surveys, covariate data include information on the spatial and temporal extent of the diet survey, its central geographical coordinates, the method by which the survey was performed (lethal gut contents, lavage, or direct observation), as well as each predator's standardized taxonomic name and identifier in the Open Tree of Life, its body mass (compiled mostly from independent compilations and additional publications), and its apparent diet's taxonomic richness and resolution. We appeal to more researchers who perform diet surveys to report on the number of empty stomachs they find and encourage additional contributions to the database—particularly from underrepresented geographic regions (e.g., North and Central Asia, North and Central Africa)—to help grow its scope and utility. The database is provided under a CC-BY-NC-S4 4.0 license. Users are requested to cite this data paper when using the data.

Biologists often use organismal thermal tolerance to help explain or forecast responses of populations to climate change. Yet many studies quantify thermal tolerance under isolated laboratory conditions despite extreme events, such as heatwaves, often coinciding with other stressors such as nutrient or food limitation. These oversights may be consequential as recent theory suggests thermal tolerance itself can be fundamentally altered by food limitation. Here, we experimentally test how food limitation (500–10,000 cells mL⁻¹) affects long-term survival, development, and growth across a present-day range of temperatures (10–20°C) in the most sensitive life stages of an important marine herbivore, purple sea urchins (Strongylocentrotus purpuratus). We show food limitation substantially erodes thermal tolerance in terms of survival, but when provided ample food, larvae exhibited robust survival across temperatures currently experienced by larvae in nature. Reductions in food however lowered optimal survival temperatures and shifted survival thresholds to those conditions observed during recent marine heatwaves. These results are consistent with the “metabolic meltdown” hypothesis—shifting optima and upper limits to cooler temperatures—and illustrate how present-day warming coupled with lower productivity may lead to substantial, unexpected declines in larval survival and recruitment. In contrast to survival, developmental rates and time to metamorphic competency, which ranged from 21 to 61 days, were driven largely by temperature with little impact of food concentration. Our findings relate to historical observations of declines in larval supply at the southern edge of the species range. Overall, these results have broad-reaching implications beyond sea urchin populations as sea urchin herbivory is known to control productivity of kelp forest communities. We provide evidence of how laboratory derived thermal reaction norms can be coupled with ecologically relevant food concentrations to inform unexpected vital rate declines of sensitive life stages in a changing climate.

This dataset enriches the ongoing project “The European plethodontid salamanders' trophic niche project,” which focuses on studying the trophic niche of the strictly protected European plethodontid species of the genus Speleomantes. We provide here a dataset that collects dietary data from 36 populations belonging to seven of the eight Speleomantes species (S. strinatii, S. ambrosii, S. italicus, S. flavus, S. imperialis, S. sarrabusensis, S. genei) and the natural hybrid zone S. italicus × S. ambrosii. Eleven populations were sampled in natural and artificial subterranean environments for a total surveyed area of 4667 m². Twenty-five surface populations were sampled in woodlands, garrigues, and dry-stone walls for a total surveyed area of 34,640 m². Data collection took place from 2021 to 2024. Twenty-seven populations were surveyed only once; the other nine were surveyed twice during different seasons/years. The dataset contains information on a total of 1108 captured salamanders. Captured individuals were weighed using a digital scale and photographed in a portable photo studio to obtain high-quality images used for post hoc measurements. This allows us to assess potential variation in the body condition of individuals over time (e.g., during different years or seasons) and identify potential divergences between conspecific populations. We used stomach flushing to obtain the stomach contents of the salamanders, which were assessed qualitatively and quantitatively using the stereomicroscope. In 930 salamanders, we could recognize 8899 consumed prey items belonging to 50 different prey categories (e.g., order level or lower). These data, in addition to adding new populations to the overall Speleomantes dataset, allow us to compare aboveground and subterranean Speleomantes populations to identify potential variations in trophic niche breadth that have occurred in populations that have colonized subterranean environments. Furthermore, the large number of samples performed on S. italicus allows for in-depth analysis of potential variability among conspecific populations. The dataset is released under the Creative Commons Attribution 4.0 International license (CC BY 4.0).