Ecology最新文献

Biological communities are facing profound upheaval induced by global environmental change. While changes in community composition over time are now well documented, much less is known about whether concomitant shifts in trophic structure also manifest. Here, we leveraged a 10-year dataset of freshwater fish communities and stable isotope compositions in nine lakes to test whether compositional changes (i.e., changes in community structure) and local environmental factors drove trophic trajectories over time. We found marked changes in the trophic structure of fish communities across all lakes, with a general tendency toward narrower trophic niches dominated by trophically redundant species. The variations in trophic trajectories among lakes were primarily linked to differences in the temporal pace and directionality of change. Specifically, lakes exhibiting greater compositional changes displayed more irregularity in their trajectory, and communities dominated by non-native species displayed elevated trophic stability over time. Our findings reveal species turnover as the dominant factor shaping trophic dynamics, through the addition or removal of predatory species and trophic turnover. The trophic stability observed in communities that were already invaded at the start of the study could be driven by their reduced susceptibility to compositional change caused by subsequent invasions. These findings highlight the existence of strong changes in trophic niches and unveil the intricate interplay between compositional changes and biological invasions in governing the trophic trajectories of communities and food web architecture, with subsequent implications for ecosystem functioning.

As the oceans change, the abundance of parasites and the risk of infection to marine mammals may also be changing. Nematodes in the family Anisakidae can harm marine mammals, and recent studies have revealed a global increase in these parasites, but the cause is unknown. We sought to determine how anisakid risk in Puget Sound had changed over 98 years by conducting a parasitological analysis of museum specimens of the prey species of marine mammals. We dissected Pacific Herring, Walleye Pollock, Surf Smelt, Pacific Hake, and Copper Rockfish collected between 1920 and 2018. We found that the larval anisakid Contracaecum spp. was the most abundant marine mammal parasite in these prey fish. We used a state-space model to assess the relationship between Contracaecum spp. abundance and time, with harbor seal abundance and sea surface temperature as potential correlates. We detected an overall decline in Contracaecum spp. abundance with a recent uptick starting in 1989, which was correlated with increasing harbor seal abundance. While these data reveal a regional trend, increases in marine mammal parasites in response to marine mammal protection have occurred elsewhere and suggest that the phenomenon might be more widespread than is currently appreciated. Marine mammals in Puget Sound are probably less burdened by anisakids than they were historically, but the recent recovery of anisakids could impact the health of these hosts, which today face very different stressors than they did in the past.

The ongoing decline in the American tropical forest carbon sink has serious ramifications for atmospheric carbon levels and global climate change. Increasing liana abundance may explain the decaying carbon sink because lianas reduce canopy tree growth and survival, which limits forest carbon storage. However, canopy lianas, not solely understory lianas, would have to be increasing for this hypothesis to be credible because canopy lianas compete especially intensely with canopy trees. We examined the change in canopy lianas over 10 years on Barro Colorado Island (BCI), Panama to test two main hypotheses. (1) Canopy lianas are increasing on BCI. (2) Increasing canopy lianas decrease aboveground canopy tree and forest carbon storage. We found that canopy liana density increased 8.3% over the 10-year period, and canopy lianas outnumbered canopy trees 3.59–1. There was a clear negative relationship between increasing canopy liana density and decreasing canopy tree carbon storage. Where liana density increased, tree carbon decreased, and where canopy lianas decreased, canopy tree carbon increased. Our findings indicate that lianas are the numerically dominant and diverse woody plant group in the BCI canopy, and this dominance is increasing, reducing forest-level carbon storage and possibly explaining the decaying American tropical forest carbon sink.

NOTIFICATION: R. Klink, D. E. Bowler, O. Comay, M. M. Driessen, S. K. M. Ernest, A. Gentile, F. Gilbert, K. B. Gongalsky, J. Owen, G. Pe'er, I. Pe'er, V. H. Resh, I. Rochlin, S. Schuch, A. B. Swengel, S. R. Swengel, T. J. Valone, R. Vermeulen, T. Wepprich, J. L. Wiedmann, J. M. Chase, “ InsectChange: a Global Database of Temporal Changes in Insect and Arachnid Assemblages,” Ecology 102(6):e03354, https://doi.org/10.1002/ecy.3354.

This notification is for the above article, published online on 2 April 2021 in Wiley Online Library (wileyonlinelibrary.com), and has been issued by agreement between the journal Editor-in-Chief, Kathryn L. Cottingham; the Ecological Society of America; and John Wiley & Sons, Inc.

The Ecological Society of America and Ecology's editorial team would like to alert potential users of the InsectChange dataset that updates were made to the dataset residing at the Knowledge Network for Biocomplexity (KNB) in 2023: see https://knb.ecoinformatics.org/view/urn%3Auuid%3A9c946111-05e2-48c9-afb1-2783ee43d0ed for the updated data. As such, the material provided in the DataS1.zip file with this 2021 Data Paper may be out of date. We encourage interested readers to check for further updates at the KNB website.

Additionally, we note the many concerns raised about errors in this dataset detailed by (Gaume & Desquilbet, 1). As with any project involving reuse of an existing dataset, we urge potential data users to (1) ensure that they are using the most recent version of dynamic datasets and (2) evaluate whether the dataset meets appropriate quality assurance/quality control standards for their ecological question before proceeding with analyses. R. van Klink agrees with the Notification, stating that the authors are in the process of updating the database and for the most recent version, readers are encouraged to contact the corresponding author. Authors D. E. Bowler and T. Wepprich agree with the Notification. All other authors were informed of the Notification.

Food web theory has illustrated that mobile top predators, such as lake trout (Salvelinus namaycush), can be potent stabilizers of food webs due to their ability to shift foraging behaviors in response to changing conditions. Consistent with this, research has demonstrated that mean lake trout food web attributes (i.e., trophic position and nearshore coupling) structurally change across environmental gradients; however, intraspecific variation in these attributes across gradients has not been fully explored. Here, we used stable isotope-based food web metrics to investigate how both mean and intraspecific variation in trophic structure changes in Canadian boreal shield lakes across gradients in ecosystem size, temperature, and competition. Consistent with earlier findings, we find nearshore coupling decreases and trophic position increases with warmer summer climate. In contrast to previous findings, increasing lake area predicted increased nearshore coupling and was not associated with lake trout trophic position. Our results show that warmer temperatures and smaller ecosystem sizes reduce the expression of intraspecific variation in food web structures. Specifically, larger lakes increased variation in nearshore coupling and trophic position, resulting in larger niche areas, and warmer lakes reduced variation in nearshore coupling and tended to generate smaller niche areas. Interestingly, we found little evidence for the relative abundance of lake trout or other predator taxa (surrogates of intra- and interspecific competition) influencing mean and variance in lake trout trophic structure. Intraspecific variation can promote ecosystem resilience by enabling diverse individual responses that help buffer populations against environmental change. Therefore, reduction in intraspecific variation in smaller, warmer lakes may have undesirable consequences for lake trout and the biota in these Canadian boreal shield lakes, leaving these ecosystems less able to adjust to future perturbations.

Arctic ecosystems present unique opportunities for community-wide monitoring, in part due to their relatively low species richness. However, conducting research in these remote environments poses significant logistical challenges, resulting in long-term monitoring being exceedingly rare. Here, we focus on the long-term, intensive ecological monitoring efforts conducted on the south plain of Bylot Island (~400 km², Nunavut, Canada), which has generated a remarkable dataset spanning up to 30 years, a rarity in tundra ecosystems. Our goals are to (1) provide long-term time-series of annual vertebrate density measured at various spatial scales and for the broadest possible range of species and years, to allow the assessment of interannual variability and trends in species density; and (2) upscale annual vertebrate abundance or sometimes long-term averages to the landscape scale (400 km²) to allow food web modeling. Monitoring data include intensive capture–mark–recapture density estimates of lemmings on trapping grids, systematic or opportunistic nest monitoring conducted across the entire study area or within specific plots for all bird species, transects of vertebrate counts distributed throughout the study area, daily incidental observations of vertebrates, and satellite tracking of foxes. We standardized data obtained with different field methods to provide a readily usable dataset for community ecologists. Long-term time-series of vertebrate densities span 3–27 years, with a median of 16.5 years for 22 species. We estimated landscape-scale abundance for all 35 species of the community based on annual time-series for 15 of them and average abundance for the remaining 20 species. Furthermore, we provide body mass data for each species, based on empirical onsite measurements for 18 species and from the literature for the remaining species. Body mass is essential to convert species abundance into biomass for studies of trophic fluxes and ecosystem processes. Daily climatic data recorded since 1992 from weather stations within the study area are also available and complement the vertebrate dataset. The ecological data presented offer a rare opportunity for holistic empirical studies of community structure and dynamics. Considering that the study site is a pristine and protected area that has experienced minimal direct anthropogenic impact, it also provides an ideal baseline for investigating the impacts of global changes on high-latitude terrestrial ecosystems. There are no copyright restrictions on the data or code, and this data paper should be cited when these items are reused.

Juvenile survival and growth rates are commonly studied demographic rates with consequences for population growth. For species that can achieve a size refuge from juvenile predators, the time spent at smaller vulnerable sizes is expected to affect population dynamics. But the interactive effects of juvenile growth and survival on population growth are rarely illustrated theoretically, and most studies of these concepts have been in experimental settings. The interactive effects of the two rates have applications to field studies of recruitment variation for a diversity of species that could be assessed with demographic models and isoclines. We conceptually illustrate the potential use of demographic isoclines for marine, terrestrial, and freshwater examples in the literature, and then demonstrate the use of a demographic isocline for an annual freshwater gastropod (Florida Apple Snail, Pomacea paludosa). Using a published size-indexed demographic model, we constructed a zero-population growth isocline for theoretical combinations of juvenile growth and survival rates. We then quantified daily juvenile survival and growth in two wetlands twice during the recruitment period, incorporating variable predator assemblages and seasonal environmental conditions (i.e., water depth and temperature). Daily juvenile survival rates were lower in the cooler dry season and juvenile growth was faster in the warmer wet (rainy) season. Parameter combinations of juvenile growth and survival in the dry season predicted declining populations (λ < 1), while rates from the wet season predicted populations at replacement (λ = 1) or increasing. When parameters were combined for the full annual recruitment window, populations were projected to decline in both wetlands. The qualitative predictions were robust to variation in hydrologic conditions affecting reproductive rates, but with better hydrologic conditions, one population was near replacement. Our demographic isocline approach provided population-dynamic context to field-measured demographic rates, identified important temporal variation in survival and growth for the population, and generated new hypotheses for future investigation and management. We encourage others to consider developing demographic isoclines to interpret variation of early life stage demographic rates across spatially and temporally variable environmental conditions.

Climate change is altering habitat suitability and driving shifts in species distributions. To understand potential responses by mobile animals, it is essential to assess levels of plasticity in habitat use, ranging from transience to long-term fidelity. Here, we evaluate the fidelity of hawksbill sea turtles (Eretmochelys imbricata) to habitats used while foraging (our primary focus), migrating, and nesting. After satellite tracking 17 adult females from three Western Atlantic nesting areas, we then re-tracked them in a subsequent year. Of 15 turtles with sufficient data to assess interannual foraging area fidelity, 14 returned to the same home range, exhibiting overlap between successive 50% utilization distributions (UDs); the 15th individual shifted <10 km. Mean precision of fidelity, here expressed as the distance between centroids of successive foraging UDs, was 1.45 ± SD 2.3 km—less than the error associated with many satellite fixes. We also observed fidelity to inter-nesting home ranges and migratory pathways, though distinct deviations in migratory routes occurred. A paradigm of precise habitat fidelity is likely appropriate for adult hawksbills, yet merits further investigation across life history stages and global populations. Our results suggest that adult transience may have limited potential to contribute to projected distributional shifts.

Nutrient limitation of forest growth has been difficult to predict, and in temperate forests, long-term tests of single-nutrient versus multiple-element limitation are few. Nutrient co-limitation is the expected outcome of the ability of plants to adjust allocation to minimize limitation by any single resource. Nutrient limitation of productivity in northern hardwood forests was predicted by the Multiple Element Limitation (MEL) model to shift over time since harvest from single limitation by N to P at ~30 years and then, in mature forests, to co-limitation by N and P. Our work tested those predictions for tree growth in a fully factorial N and P addition experiment in 13 forest stands that we grouped in young (20–30 years), mid-age (40–50 years), and mature (>100 years old) age classes in New Hampshire, USA. Over 8 years of treatment, we found evidence of additive co-limitation of tree growth by N and P. We did not find evidence that limitation varied with time since disturbance. Our results suggest that processes contributing to co-limitation in these northern hardwood forests are effective across stands that vary widely in N status and are not sensitive to disturbance by forest harvest over time periods of several decades.