Ecology最新文献

Earth's lower atmosphere is a vital ecological habitat, home to trillions of organisms that live, forage, and migrate through this medium. Despite its importance, this space is seldom considered a primary habitat for ecological or conservation prioritization, making it one of the least studied environments. However, it plays a crucial role as a global conduit for the transfer of biomass, weather, and inorganic materials. Fundamental research is essential to address core ecological questions related to the ecological consequences of this habitat's intricate spatial and temporal structure. To advance our understanding of airspace use by migratory animals, we analyzed over 108 million 5-min radar observations from 143 NEXRAD sites, focusing on 24-h diel cycles across the contiguous United States. This extensive dataset, spanning from 1995 to 2022, allowed us to quantify aerial space use by systematically identifying peak activity times, the portion of the airspace that contained the majority of migration activity, and the percentage of migrants passing across diurnal and nocturnal diel cycles. We found that airspace is used predominantly during nocturnal periods in both spring and autumn (88%), while summer exhibited a more balanced distribution (54% nocturnal). Additionally, the percentage of nocturnal activity increased with latitude in spring and autumn but decreased in summer. Peak aerial activity typically occurred about 4 h after local sunset in both spring and autumn, with variations based on latitude and longitude. During these peak times, on average, half of the aerial movement was confined within a vertical band of 516 meters, starting around 355 m above ground level. Our research underscores the need to view the lower atmosphere as a structured habitat with significant ecological importance.

Many plant species alter both the timing and duration of their flowering in response to changing climate and often differ with respect to the magnitudes or directions of their phenological responses to climate changes. These shifts may have cumulative effects on the diversity of species simultaneously in flower throughout a given flowering season, resulting in periods of disproportionately high or low species richness of actively flowering community members relative to historical conditions. Although the potential for such changes to occur is well appreciated, few studies have assessed how climate trends have affected patterns of co-flowering synchrony due to a scarcity of long-term datasets documenting flowering duration across species in a community. In this study, we leveraged 1,908,706 plant specimens collected in flower to model the effects of warming throughout the past century on the daily species richness of actively flowering species by developing species-specific phenoclimate models for 1848 plant species inhabiting 16 well-documented plant communities across California. These communities are located across a variety of ecoregions, ranging from coastal marshes and grasslands to deserts, chaparral shrublands, and coniferous forests. The recurring patterns in the modeled community-level flowering displays indicate that recent warming has consistently shortened the period during which many species flower concurrently, and that the bloom season has advanced by nearly 5 days on average. Accordingly, within every flora, recent warming was predicted to increase the daily species richness of flowers early in the local growing season, with corresponding reductions in species richness of flowers later in the growing season. Notably, patterns of change in community-level bloom displays were driven primarily by differences among species in the timing of flowering onset, as termination dates tended to advance in unison with onset dates, resulting in minor changes to flowering duration among species.

Biological interactions, disturbances, and demographic stochasticity often drive population declines and local extinctions. Dispersal can counterbalance these drivers by rescuing small populations or facilitating recolonization. Using freshwater zooplankton in experimental mesocosms, we tested three hypotheses: (1) isolated sites would experience declines in species richness, with ecological drift causing communities to lose different species and become more dissimilar over time; (2) communities connected by dispersal from similar habitats would maintain their species richness and composition, as arriving species balance losses through rescue effects and recolonization, thereby halting community differentiation; and (3) dispersers originating from different sources may establish themselves in recipient communities through mass effects, resulting in higher species richness compared to communities receiving dispersers from similar habitat sources. Thirty 500-L tanks were initially colonized with zooplankton from lake A, and 10 tanks with colonizers from lake B, which had partially distinct species composition. Tanks were kept isolated for 50 days, after which 10 tanks initially colonized by lake A began receiving dispersers from paired tanks also colonized by lake A (treatment Aa). Another 10 tanks colonized by lake A received dispersers from paired tanks colonized by lake B (Ab). We found that isolated communities (A0, B0) tended to lose species over time and differentiate from one another, indicating differential local extinctions. Communities receiving dispersers from the same habitat (Aa) halted species losses and maintained their species richness, whereas those receiving species from a different habitat (Ab) not only halted species losses but also accumulated additional species over time. Treatments receiving dispersers (Aa, Ab) exhibited beta diversity (among replicates within treatments) similar to levels observed prior to dispersal events. Comparisons of paired source-recipient tanks (A0–Aa, B0–Ab) further supported the finding of differential extinctions in isolated communities. Our results demonstrate that dispersal counteracts declining species richness and increasing differentiation caused by differential local extinctions in isolated communities, either through rescue or mass effects.

The spatial scale of adaptation is fundamental to our understanding of evolutionary ecology. Traditionally, strong gene flow and weak selection were expected to prevent adaptive evolution at finer spatial scales, but instances of microgeographic adaptation challenge this assumption. We evaluated four alternative predictions about the scale of adaptation to divergent selection from predators for two pond-breeding amphibians. Common garden experiments revealed that wood frogs developed larger tailfins and higher survival along a spatial cline, indicating the importance of selection and gene flow between and within habitats. Spotted salamanders displayed defensive behaviors and higher survival between ponds. Results suggest that adaptation occurs both between and within habitats such as ponds. Evidence for adaptations within traditional habitats contradicts the traditional notion of the habitat patch as a population. Overall, results compel a greater appreciation of fine-scaled adaptation in nature, suggest the need for spatially explicit genetic sampling designs, and reject the assumption that populations are always panmictic within habitat patches.

Source-sink dynamics are a cornerstone of theory for spatially structured populations. Despite long-standing interest, understanding temporal variation in source-sink dynamics in wild populations remains rare. Biological invasions have the potential to alter source-sink dynamics for native species, which may change over time as invasions proceed. We used 28 years of data on reproduction, movement, and survival to estimate annual source-sink dynamics across the entire range of the endangered Everglade snail kite (Rostrhamus sociabilis plumbeus) during the invasion of a novel prey species, the island apple snail (Pomacea maculata). Snail kite populations underwent striking changes in source-sink dynamics with time since invasion, and no population was consistently a source or sink over time. Some initial benefits of increased prey availability on snail kite demography were diminished in the long term. Populations invaded by P. maculata impacted uninvaded populations via changes in snail kite retention (i.e., lack of movement) and emigration across the metapopulation. Our findings illustrate how effects of biological invasions can change over time and may take decades to fully emerge, and they emphasize how an invasive species can have distant impacts on uninvaded populations via fluctuations in native species' local retention and emigration. In addition, our results demonstrate how fluctuating emigration and retention alter long-term interpretations of source-sink dynamics through variation in local versus landscape contributions of populations to the metapopulation, highlighting that the status of “source” or “sink” can be highly variable through time.

Resource utilization is considered a crucial determinant of alien plant species in terrestrial ecosystems under abiotic and biotic conditions of global change. Alien plants are often favored over natives in stress-free or resource-rich ecosystems. However, certain resource-poor ecosystems have also been heavily invaded, particularly by legume woody species. How alien and native woody species compete in various abiotic and biotic stress environments and whether the functional traits associated with resource utilization promote their performance remain unknown. To test this, we grew six naturalized alien and six native woody species, grouped into three pairs of legumes and three pairs of nonlegumes, individually or in competition, under benign and two abiotic stress (drought, limited nutrients) and two biotic stress (aboveground enemies, belowground enemies) conditions. Overall, the four stress conditions had more negative effects on native plants than on alien ones, especially for nonlegumes under abiotic stresses. Moreover, when grown in competition, the presence of stress increased the growth asymmetry between alien and native plants in favor of the alien plants, but this was less pronounced in the legume group than in the non-legume group. Our study suggests that alien woody plants may have a competitive advantage over native ones under diverse abiotic and biotic stress conditions, but that this depends on their nitrogen-fixing ability. This is likely to affect the coexistence of alien and native woody species and may facilitate the spread of alien plants into stressful habitats.

Hibernation is an important strategy used by many endotherms to conserve energy and water. Global warming is changing species' phenology and hibernation patterns, but whether such changes are beneficial or harmful depends on the species' life history traits, physiology, morphology, and behavior. Mechanistic niche models can be used to make strong inferences on such responses by explicitly quantifying the consequences of changed hibernation patterns for energy and water requirements. However, they have yet to be adapted to heterothermic species. Here, we address this problem by extending the endotherm biophysical model of the NicheMapR package to encompass torpor. This model accurately predicts the energy requirements of hibernating mammals over a broad size range from microbats to bears. We then used this approach to assess the effect of climate change on a Critically Endangered hibernator, the Australian mountain pygmy possum (Burramys parvus). Specifically, we contrasted conditions for the year 2010 with two future climate-change scenarios (2or 4°C of average warming) to identify: (i) the projected changes in energy and water requirements; (ii) the advantage conferred by hibernating for the species' energy and water requirements; and (iii) the areas across southeastern Australia that could continue to support hibernation. We projected an 11%–43% reduction in hibernation hours for the mountain pygmy possum under our two climate-change scenarios. In consequence, requirements for energy increased by 4%–21%, and for water by 10%–34%. Under current conditions, hibernation reduces annual energy requirements by 44%–52% and annual water requirements by 32%–42%, but in our projections, this energetic and hydric benefit of hibernation will decline due to climate change. The total area where hibernating and not hibernating is energetically equivalent is projected to increase by 60% under 4°C warming, preventing recovery from the species' severely restricted distribution at present. Our results show that climate change will have a profound impact on the duration and patterns of hibernation, a key survival strategy, for Burramys. Our framework for analyzing changing hibernation patterns provides a new and general way to test the vulnerability and plasticity of hibernating endotherms under global change.

Global biodiversity loss is threatening ecosystem functioning and human well-being. Arthropods above the ground have substantially decreased in abundance and diversity during the last 15–20 years. However, changes in belowground biodiversity, particularly in forests, received little attention. Here, we analyzed a comprehensive dataset of soil-living meso- and macrofauna in forests differing in land-use intensity within the framework of the open research platform “Biodiversity Exploratories” in Germany. The abundance of soil animal species was analyzed at 3-year intervals, covering 12 years from 2008 to 2020. Neither species richness nor γ-diversity of both soil meso- and macrofauna declined, suggesting contrasting dynamics of biodiversity above and below the ground. The density and diversity of soil mesofauna varied significantly between years within regions. These variations were closely related to the precipitation levels in the previous winter and during the sampling period. However, there was no consistent long-term downward trend, as declines in some years were offset by full recoveries. Temporal trends of soil macrofauna taxa densities were inconsistent and depended on regions and forest management intensity. The stability of many soil taxa was related to effective diversity and asynchrony of species fluctuations, supporting the portfolio effect. However, variance ratios not different from null communities and a negative impact of temporal species turnover on stability suggest a minor influence of compensatory dynamics as predicted by the insurance hypothesis. Instead, strong abiotic control resulted in synchronous species dynamics. Species densities, particularly those of soil mesofauna, depended heavily on abiotic conditions, such as soil moisture. While influencing the density and richness of soil fauna and modulating the effects of precipitation, forest management did not directly affect the stability of soil fauna communities. While our findings demonstrate a remarkable resilience of soil animal communities in temperate German forests amidst ongoing biodiversity decline, they are based on a limited temporal window and forests in central Europe. As such, caution is needed when extrapolating these results to longer timescales or wider spatial scales. Nonetheless, our study provides valuable insights into the temporal dynamics of soil faunal density and diversity, and the key drivers underlying their community stability.

Darwin's theory of natural selection provides two seemingly contradictory hypotheses for explaining the success of biological invasions: (1) the pre-adaptation hypothesis posits that introduced species that are closely related to native species will be more likely to succeed due to shared advantageous characteristics; (2) the limiting similarity hypothesis posits that invaders that are more similar to resident species will be less likely to succeed due to competitive exclusion. Previous studies assessing this conundrum show mixed results, possibly stemming from inconsistent study spatial scales and failure to integrate both functional and phylogenetic information. Here, we address these limitations using a 33-year grassland successional survey at Cedar Creek Ecosystem Science Reserve (USA). We incorporate functional dissimilarities, phylogenetic distances, environmental covariates, and species origin data for 303 vascular plant taxa (256 native, 47 introduced), collected from 2700 plots. In contrast with other studies, we test both hypotheses at two fine spatial scales—neighborhood (0.5 m²) and site (~40 m²)—to better capture competition and environmental filtering, respectively. Findings related to Darwin's naturalization conundrum depended on spatial scale and dissimilarity metric. Our results agreed with the pre-adaptation hypothesis at site scale (40 m²)—a much finer resolution than typically used to test the pre-adaptation hypothesis—highlighting the role of environmental filtering. At the neighborhood scale (0.5 m²), support for the limiting similarity hypothesis emerged when using functional dissimilarity, while phylogenetic distance aligned with the pre-adaptation hypothesis, demonstrating that different dissimilarity metrics can yield contrasting conclusions. In addition, native and introduced species showed different abundance patterns in relation to functional ranked dissimilarities, with introduced species reaching higher cover when they were taller than co-occurring species, had higher leaf dry matter content (LDMC) and lower seed mass. Introduced species also reached high cover with higher soil N concentrations and a shorter time after colonization, relative to native species. Our results suggest that inconsistent findings related to Darwin's naturalization conundrum may arise from an overreliance on single dissimilarity metrics and the use of spatial scales failing to capture underlying ecological processes. This highlights the need for more nuanced methodologies when testing the pre-adaptation and limiting similarity hypotheses.