Ecology最新文献

Sex differences are predicted to play an important role in the spread and evolution of pathogens. However, attempts to generalize the “sicker” sex have been challenged by intraspecific variability of sex biases across the infection process. Sex-specific plasticity provides a framework to resolve this by elucidating how infection is shaped at the sex-pathogen-environment interface. Using the Daphnia magna and Pasteuria ramosa system, we measure infection outcomes for males and females across three temperatures and seven pathogen densities to quantify how sex-specific plasticity shapes susceptibility, pathogen loads, and ultimately transmission. We find unique forms of plasticity at each stage of infection – including equivalent, sex-specific, and divergent plasticity. Integrating these into a single estimate of transmission reveals a clear pattern—male-biased transmission at cold temperatures, and female-biased transmission at warm temperatures. Sex-specific thermal plasticity can thus determine the “sicker” sex, with implications for pathogen spread and evolution in a warming world.

Mutualisms confer both benefits and costs to participants, but costs have been largely ignored when considering how mutualisms function and evolve. Plants that are dispersed by ants produce seeds with attached nutrient-rich food rewards (elaiosomes). When ants approach a seed, they likely assess both the benefits (elaiosome mass) and costs (mass of the inedible seed) of moving it. We hypothesized that the masses of both the seed and elaiosome would affect diaspore removal rate, and predicted that when given a choice, ants would remove diaspores with higher benefits and diaspores with lower costs more quickly. To test these hypotheses, we manipulated the elaiosomes of Datura wrightii and Datura discolor (Solanaceae) and conducted choice experiments where we presented diaspores with variable benefits and costs to colonies of the seed-dispersing ant Novomessor cockerelli (Formicidae). D. discolor has a larger elaiosome-to-seed ratio since its seeds are half the mass of D. wrightii. Consistent with our hypotheses, ants removed seeds with heavier elaiosomes (larger rewards) and lighter seeds (lower costs) more quickly. Our study provides new evidence for seed dispersal costs by quantifying a cost of seed dispersal to ants and underscores the necessity of measuring both the benefits and costs of mutualistic interactions.

More widespread species tend to be more locally abundant. This hypothesis has received support when considering single species abundance (mean density of individuals across sites) and occupancy (fraction of occupied sites) through time (intraspecific relationship) and comparing different species sampled at a single point in time (interspecific relationships). But while abundance-occupancy relationships are fairly well supported in observational studies, the underlying factors driving them are less clear. For instance, variation in demographic rates, dispersal, and spatial network structure could all influence resulting abundance-occupancy relationships. We used a simulation model to explore these relationships in spatial networks of variable size and dispersal connectivity. We simulated population dynamics on spatial networks by starting from entirely neutral communities and then systematically incorporated complexity in the form of (co)variation in species demographic rates and dispersal processes. The effect of spatial network structure on abundance-occupancy relationships was dependent on the community dynamics and the covariation imposed on demographic and dispersal parameters. Together, we demonstrate the interplay between the spatial network and variation in demographic and dispersal rates, generating testable hypotheses for when abundance-occupancy relationships would be more likely to be observed, as well as how these relationships may change with habitat fragmentation and shifts in community composition.

Plant ionomes—the suite of chemical elements making up plant tissue—constrain plant performance and the nutrition of consumers. The possible mechanisms driving Nutrient Dilution—the globally distributed decline of essential element density (parts per million [ppm]) in plant tissue—are rarely evaluated together. Toward a remedy, we explored a 30+ year record of 17 elements in the grasses, forbs, and woody plants across three burn frequencies on Konza, a North American tallgrass prairie. About one quarter of ionomic variation arose among Konza's three plant functional groups, which differed in ppm and its regulation over three decades. Nutrient-poor grass biomass increased steadily with CO₂, encroaching woody plant biomass accelerated over the same period, and nutrient-rich forb biomass decreased. Each functional group revealed its own pattern of nutrient dilution across the ionome, where it was more widespread in grasses (12/17 elements) than forbs (5/17) or woody plants (2/17). Competition with other functional groups regularly depleted the ionome ppm of grasses (9 elements) and forb and woody plants (4 elements). Unexpectedly, nutrient densities often increased in response to higher CO₂ (especially in forbs), suggesting photosynthate was invested in nutrient harvest. Fire suppression had fewer, and more idiosyncratic effects. In an era of herbivore declines, grass-feeding herbivores in this tallgrass prairie are experiencing more abundant but lower quality food. Forb feeders, in contrast, must search for less abundant but sometimes enriched food.

Poleward shifts in tropical cyclone (TC) activity have introduced unprecedented disturbances to Northeast Asia's boreal and temperate-boreal ecotone forests. As TCs migrate northward, they increasingly influence previously unaffected regions, yet their impacts on forest structure and species composition remain poorly understood. This study examines TC Maysak (2020), the most intense cyclone recorded in the ecotone forests near the Chinese–Russian border, and its effects on tree vulnerability and canopy structure. Using high-resolution drone-based orthophotographs, we analyzed fallen tree dimensions across four affected sites within protected forests, identifying key differences between coniferous and broadleaf species. Tall emergent conifers, including Manchurian fir (Abies holophylla) and Korean pine (Pinus koraiensis), were disproportionately susceptible to windthrow, with mean fallen heights exceeding the average canopy height by 4.88 ± 0.20 m (13.62 m maximally). In contrast, broadleaf species such as Mongolian oak (Quercus mongolica) exhibited minimal height variation relative to the canopy average. Our findings highlight TCs as emerging disturbance agents in Northeast Asia's temperate-boreal ecotone, preferentially removing emergent conifers, simplifying canopy structure, and promoting broadleaf dominance. As TC activity intensifies under global climate change, these disturbances may accelerate forest transitions in climatically sensitive ecotone forests.

Invasive predators can reshape native predator assemblages, triggering cascading changes in broader wildlife communities. In western North America, the barred owl (Strix varia) is an invasive apex predator with well-documented negative impacts on congeneric northern spotted owls (Strix occidentalis caurina), but impacts on other native forest owls are poorly understood. We coupled a large-scale removal experiment with a passive acoustic monitoring network to quantify species-specific and community-level responses of a five-species assemblage of native forest owls to the lethal removal of invasive barred owls. Our results supported predictions of intraguild predation theory, where smaller bodied, nocturnal species most susceptible to predation and resource competition from larger barred owls benefitted from removal, whereas a diurnally active owl species and a larger bodied species showed little to no response. We conclude that focused management actions limiting the occurrence of barred owls can provide spatial refugia for spotted owls and other sympatric native owl species, thereby promoting forest biodiversity.

Antipredator defenses typically act at distinct stages of the predation sequence—encounter, identification, approach, and subjugation. However, their effectiveness has rarely been quantified and compared simultaneously in wild predator–prey systems. We conducted a study in Peru, where we installed aviaries at two localities and recorded the responses of wild avian predators to three types of antipredator defenses—crypsis, aposematism, and evasiveness—expressed by three butterfly prey types. The study included both immature and adult birds from forest and urban environments, representing the present community of insectivorous birds. We tested the theoretical expectations that cryptic butterflies (Nymphalidae: Euptychiina) were rarely detected, aposematic Heliconius (Nymphalidae: Heliconiinae) were often sighted but seldom attacked, and evasive Spicauda (Hesperiidae: Eudaminae) were frequently detected and attacked but evaded capture at higher rates. Despite these distinct defensive strategies, mortality rates among prey types were largely similar, but predator life stage strongly influenced defense effectiveness, with immature birds tending to attack Heliconius more frequently. Additionally, predator family influenced predation patterns, with more skilled insectivores (e.g., Vireonidae) showing higher capture success against defended prey. These findings illuminate the evolutionary pressures that shape predator behavior and prey defenses in tropical ecosystems. The similar mortality rates underscore the adaptive value of these defenses, which collectively distribute the total predation pressure across prey species.

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.