Ecology最新文献

Demographic processes that ensure the recovery and resilience of marine populations are critical as climate change sends an increasing proportion on a trajectory of decline. Yet for some populations, recovery potential remains high. We conducted annual monitoring over 9 years (2012–2020) to assess the recovery of coral populations belonging to the genus Pocillopora. These populations experienced a catastrophic collapse following a severe typhoon in 2009. From the start of the monitoring period, high initial recruitment led to the establishment of a juvenile population that rapidly transitioned to sexually mature adults, which dominated the population within 6 years after the disturbance. As a result, coral cover increased from 1.1% to 20.2% during this time. To identify key demographic drivers of recovery and population growth rates (λ), we applied kernel-resampled integral projection models (IPMs), constructing eight successive models to examine annual change. IPMs were able to capture reproductive traits as key demographic drivers over the initial 3 years, while individual growth was a continuous key demographic driver throughout the entire monitoring period. IPMs further detected a pulse of reproductive output subsequent to two further Category 5 typhoon events during the monitoring period, exemplifying key mechanisms of resilience for coral populations impacted by disturbance. Despite rapid recovery, (i.e., increased coral cover, individual colony growth, low mortality), IPMs estimated predominantly negative values of λ, indicating a declining population. Indeed, while λ translates to a change in the number of individuals, the recovery of coral populations can also be driven by an increase in the size of surviving colonies. Our results illustrate that accumulating long-term data on historical dynamics and applying IPMs to extract demographic drivers are crucial for future predictions that are based on comprehensive and robust understandings of ecological change.

越來越多物種的族群數因氣候變遷而日益下降，故海洋物種復原力與韌性的族群統計過程至關緊要。話雖如此，某些物種仍舊充滿復原潛力。在2009年，鹿角珊瑚屬珊瑚族群在威力強大的颱風襲擊之下而嚴重崩壞，我們針對此族群進行長達9年的(2012–2020)年度監控，評估復原情況。在監控初期，大量的入添建立了幼年珊瑚族群。這些幼年珊瑚快速進入性成熟期，在干擾事件後的6年內成為主導族群，珊瑚覆蓋率也從1.1% 成長至20.2%。為獲取珊瑚礁復原力和韌性的關鍵族群驅動因素以及族群成長率(λ)，我們應用核心重採樣積分投影(IPMs)，並建立8組連續模型以檢視每一年的變化。IPMs結果指出，繁殖性狀為首3年的關鍵族群驅動因素，而個體成長則是整段監測期間持續性的關鍵族群驅動因素。在研究期間，IPMs更近一步檢測到此族群在2次五級颱風侵襲後分別有短促的繁殖輸出，體現珊瑚族群在干擾事件後的關鍵復原調節機制。即便族群快速恢復(珊覆蓋率增加、個體族群成長、低死亡率)，IPMs估算的λ卻多為負值，象徵族群正在縮減。的確，λ代表個體數量改變，但倖存珊瑚殖民地的擴張也能驅動珊瑚族群的復原。若要做出以完善生態變遷認知為基礎的預測，長期搜集歷史動態資料以及應用IPMs提取族群驅動因素，至關重要。

For many drylands, both long- and short-term drought conditions can accentuate landscape heterogeneity at both temporal (e.g., role of seasonal patterns) and spatial (e.g., patchy plant cover) scales. Furthermore, short-term drought conditions occurring over one season can exacerbate long-term, multidecadal droughts or aridification, by limiting soil water recharge, decreasing plant growth, and altering biogeochemical cycles. Here, we examine how experimentally altered seasonal precipitation regimes in a mixed shrub grassland on the Colorado Plateau impact soil moisture, vegetation, and carbon and nitrogen cycling. The experiment was conducted from 2015 to 2019, during a regional multidecadal drought event, and consisted of three precipitation treatments, which were implemented with removable drought shelters intercepting ~66% of incoming precipitation including: control (ambient precipitation conditions, no shelter), warm season drought (sheltered April–October), and cool season drought (sheltered November–March). To track changes in vegetation, we measured biomass of the dominant shrub, Ephedra viridis, and estimated perennial plant and ground cover in the spring and the fall. Soil moisture dynamics suggested that warm season experimental drought had longer and more consistent drought legacy effects (occurring two out of the four drought cycles) than either cool season drought or ambient conditions, even during the driest years. We also found that E. viridis biomass remained consistent across treatments, while bunchgrass cover declined by 25% by 2019 across all treatments, with the earliest declines noticeable in the warm season drought plots. Extractable dissolved inorganic nitrogen and microbial biomass nitrogen concentrations appeared sensitive to seasonal drought conditions, with dissolved inorganic nitrogen increasing and microbial biomass nitrogen decreasing with reduced soil volumetric water content. Carbon stocks were not sensitive to drought but were greater under E. viridis patches. Additionally, we found that under E. viridis, there was a negative relationship between dissolved inorganic nitrogen and microbial biomass nitrogen, suggesting that drought-induced increases in dissolved inorganic nitrogen may be due to declines in nitrogen uptake from microbes and plants alike. This work suggests that perennial grass plant–soil feedbacks are more vulnerable to both short-term (seasonal) and long-term (multiyear) drought events than shrubs, which can impact the future trajectory of dryland mixed shrub grassland ecosystems as drought frequency and intensity will likely continue to increase with ongoing climate change.

For their service as ad hoc editors of one or more manuscripts for Ecology, Ecological Applications, Ecological Monographs, Ecosphere, and Frontiers in Ecology and the Environment during the past year (1 January 2023 through 31 December 2023) the Society is especially grateful to:

Leticia Avilés

Christopher P. Catano

Eliana Cazetta

Jin Chen

Christos Damalas

Rachel Germain*

Michelle Gierach

Niall Hanan

Paul Hessburg

Heather Kharouba

Jesse Kreye

Xuan Liu*

Yanjie Liu

Katie Marshall*

R. Chelsea Nagy

Ed Parnell

Adam Smith

Gina Wimp*

Aibin Zhan*

Contemporary symbioses in extreme environments can give an insight into mechanisms that stabilize species interactions during environmental change. The intertidal sea anemone, Anthopleura elegantissima, engages in a nutritional symbiosis with microalgae similar to tropical coral, but withstands more intense environmental fluctuations during tidal inundations. In this study, we compare baseline symbiotic traits and their sensitivity to thermal stress within and among anemone aggregations across the intertidal using a laboratory-based tank experiment to better understand how fixed genotypic and plastic environmental effects contribute to the successful maintenance of this symbiosis in extreme habitats. High intertidal anemones had lower baseline symbiont-to-host cell ratios under control conditions, but their symbionts had higher baseline photosynthetic efficiency compared to low intertidal anemone symbionts. Symbiont communities were identical across all samples, suggesting that shifts in symbiont density and photosynthetic performance could be an acclimatory mechanism to maintain symbiosis in different environments. Despite lower baseline symbiont-to-host cell ratios, high intertidal anemones maintained greater symbiont-to-host cell ratios under heat stress compared with low intertidal anemones, suggesting greater thermal tolerance of high intertidal holobionts. However, the thermal tolerance of clonal anemones acclimatized to different zones was not explained by tidal height alone, indicating additional environmental variables contribute to physiological differences. Host genotype significantly influenced anemone weight, but only explained a minor proportion of variation among symbiotic traits and their response to thermal stress, further implicating environmental history as the primary driver of holobiont tolerance. These results indicate that this symbiosis is highly plastic and may be able to acclimatize to climate change over ecological timescales, defying the convention that symbiotic organisms are more susceptible to environmental stress.

Leapfrog migration is a common migration pattern in birds where the breeding and wintering latitudes between populations are in reversed latitudinal sequence. Competition for wintering and breeding sites has been suggested to be an ultimate factor, and several competitor-based hypotheses have been proposed to explain this pattern. If wintering sites close to the breeding sites are favored, competitive exclusion could force subdominant individuals to winter further away. Competitive exclusion could be mediated either through body size or by prior occupancy. The alternative “spring predictability” hypothesis assumes competition for sufficiently close wintering areas, allowing the birds to use autocorrelated weather cues to optimally time spring migration departure. To test predictions and assumptions of these hypotheses, we combined morphometrics, migration, and weather data from four populations of common ringed plover breeding along a latitudinal (56–68° N) and climatic gradient (temperate to Arctic). Critical for our evaluation was that two populations were breeding on the same latitude in subarctic Sweden with the same distance to the closest potential wintering site, but differed in breeding phenology, and wintered in West Africa and Europe, respectively. Thus, while breeding on the same latitude, their winter distribution overlapped with that of an Arctic and temperate population. Body size was largest within the temperate population, but there was no size difference between the two subarctic populations. Populations wintering in Europe arrived there before populations wintering in Africa. The largest variation in the arrival of meteorological spring occurred at the temperate breeding site, while there was almost no difference among the other sites. In general, temperatures at the northernmost wintering area correlated well with each breeding site prior to breeding site-specific spring arrival. Based on these observations, we conclude that competitive exclusion through body-size-related dominance cannot explain leapfrog migration. Furthermore, the assumptions on which the “spring predictability” hypothesis is based did not match the observed wintering ranges either. However, we could not reject the hypothesis that competitive exclusion mediated by prior occupancy in the wintering area could lead to leapfrog migration, and therefore, this hypothesis should be retained as working hypothesis for further work.

Understanding the drivers of community assembly is critical for predicting the future of biodiversity and ecosystem services. Ecological selection ubiquitously shapes communities by selecting for individuals with the most suitable trait combinations. Detecting selection types on key traits across environmental gradients and over time has the potential to reveal the underlying abiotic and biotic drivers of community dynamics. Here, we present a model-based predictive framework to quantify the multidimensional trait distributions of communities (community trait spaces), which we use to identify ecological selection types shaping communities along environmental gradients. We apply the framework to over 3600 boreal forest understory plant communities with results indicating that directional, stabilizing, and divergent selection all modify community trait distributions and that the selection type acting on individual traits may change over time. Our results provide novel and rare empirical evidence for divergent selection within a natural system. Our approach provides a framework for identifying key traits under selection and facilitates the detection of processes underlying community dynamics.

Mediterranean ecosystems are predicted to undergo longer and more intense summer droughts. The mechanisms underlying the response of herbaceous communities to such drier environments should be investigated to identify the resilience thresholds of Mediterranean rangelands. A 5-year experiment was conducted in deep and shallow soil rangelands of southern France. A rainout shelter for 75 days in summer imposed drier and warmer conditions. Total soil water content was measured monthly to model available daily soil water. Aboveground net primary production (ANPP), forage quality, and the proportion of graminoids in ANPP were measured in spring and autumn. Plant senescence and plant cover were assessed in summer and spring, respectively. The experimental years were among the driest ever recorded at the site. Therefore, manipulated summer droughts were drier than long-term ambient conditions. Interactions between treatment, community type, and experimental year were found for most variables. In shallow soil communities, spring plant cover decreased markedly with time. This legacy effect, driven by summer plant mortality and the loss of perennial graminoids, led to an abrupt loss of resilience when the extreme water stress index exceeded 37 mm 10 day⁻¹, characterized by a reduction of spring plant cover below 50% and a decreased ANPP in rainy years. Conversely, the ANPP of deep soil communities remained unaffected by increased summer drought, although the presence of graminoids increased and forage nutritive value decreased. This study highlights the role of the soil water reserve of Mediterranean plant communities in modulating ecosystem responses to chronically intensified summer drought. Communities on deep soils were resilient, but communities on shallow soils showed a progressive, rapid, and intense degradation associated with a loss of resilience capacity. Notably, indexes of extreme stress were a better indicator of tipping points than indexes of integrated annual stress. Considering the role of soil water availability in other herbaceous ecosystems should improve the ability to predict the resilience of plant communities under climate change.

Conspecific negative density dependence (CNDD) is thought to be a key process in maintaining plant diversity. However, the strength of CNDD is highly variable in space and time as well as among species, and correlates of this variation that might help to understand and explain it remain largely unquantified. Using Bayesian hierarchical models, we took advantage of 10-year seedling monitoring data that were collected annually in every dry and rainy season in a seasonal tropical forest. We quantified the interspecific variation in the strength of CNDD and its temporal variation. We also examined potential correlates of this interspecific and temporal variation, including species functional traits (such as drought-tolerant traits, defense-related traits, and recourse acquisition traits) and species abundances. In the dry season, we found a negative relationship between the density of neighboring conspecific seedlings on seedling survival, while in the rainy season, there was a negative relationship between the density of neighboring conspecific adults on seedling survival. In addition, we found that interspecific variation in CNDD was related to drought-tolerant traits in the dry season but not in the rainy season. Across years, we found that drought-intolerant species suffer less CNDD during the dry seasons that have higher rainfall, whereas drought-tolerant species suffer less CNDD when the dry season has lower rainfall. We also found that rare species suffered stronger CNDD in the dry season. Overall, our study highlights that CNDD is highly variable among species and through time, necessitating a deeper appreciation of the environmental and functional contexts of CNDD and their interactions.

The scaling exponent relating the mean and variance of the density of individual organisms in space (i.e., Taylor's slope: z_space) is well studied in ecology, but the analogous scaling exponent for temporal datasets (z_time) is underdeveloped. Previous theory suggests the narrow distribution of z_time (e.g., typically 1–2) could be due to interspecific competition. Here, using 1694 communities time series, we show that z_time can exceed 2, and reaffirm how this can affect our inference about the stabilizing effect of biodiversity. We also develop a new theory, based on temporal change in the ranks of species abundances, to help account for the observed z_time distribution. Specifically, we find that communities with minimal turnover in species' rank abundances are more likely to have higher z_time. Our analysis shows how species-level variability affects our inference about the stability of ecological communities.