Ecology最新文献

As a mechanism of the dilution effect, predation and filter feeding on parasitic propagules are hypothesized to reduce transmission to susceptible hosts and alter host–parasite interactions. In marine systems, the effect of other community members on the disease dynamics of microparasites in their suitable hosts is poorly known. In a coastal estuarine host–parasite system, we examined how eastern oysters, Crassostrea virginica, affect the transmission of a parasitic dinoflagellate, Hematodinium perezi, to juvenile blue crabs, Callinectes sapidus. We deployed juvenile blue crabs in custom mesh bags that were sandwiched by oysters into holo-endemic areas, or areas with high endemic transmission for the parasite in juvenile hosts. Controls consisted of juvenile crabs deployed with an equivalent number of oyster shells to test for the effect of rugosity on transmission and crabs deployed alone. Deployments lasted 7–13 days and were done over different temporal and spatial scales. Results from the field deployments suggest that oysters, not shells, reduced the probability of infection to crab hosts. To investigate consumption in the laboratory, single oysters in 1 L aquaria were fed dinospores of H. perezi released from infected crabs. Oysters reduced parasite densities in the water at rates similar to those observed for a common phytoplankton, Tetraselmis chui, that is grown specifically as oyster food. Our results jointly support that oysters benefit adjacent community members through feeding on transmissive stages of their pathogens and highlight the need for additional field-based approaches addressing environmental heterogeneity in pathogen transmission.

Understanding critical transitions in ecological systems is fundamental for addressing various natural phenomena, from population outbreaks to sudden ecosystem collapses. Ecological interactions are key drivers of these transitions, and theory suggests that the networks formed by these interactions can undergo their own critical transition. By examining interactions between plant individuals and insect species in a tropical forest, we first identified a critical network structural transition between the rainy and dry seasons. Next, we showed that seasonal changes and the phytochemical diversity of plants are associated with this transition. Finally, we quantified the consequences of the critical transition, which significantly increases the number of pathways and the potential for cascading effects among plants and herbivores in the network. Our findings reveal that ecological networks can experience abrupt changes on shorter timescales than previously recognized, with profound implications for cascading effects and the impacts of human-induced perturbations on the stability of ecological assemblages.

Urban areas are altered from natural landscapes in several ways that can impact wildlife. Birds are widespread in urban areas, and it is well documented that there are phenotypic differences between urban and non-urban conspecifics. However, little is known about which characteristics of the urban environment are driving differences. We used 9 years of data from nest boxes spread across 20 sites along a 40-km urban–non-urban gradient in Scotland to test whether characteristics of the urban environment (native, non-native, native oak (Quercus spp.), birch (Betula spp.) foliage availability, temperature and human population density, and the interaction between foliage and temperature) influenced phenology and reproductive success in blue tits (Cyanistes caeruleus). We found that higher foliage availability of native foliage, and specifically of the most common native genus, oak, was associated at the territory level with earlier first egg laying date. Higher non-native foliage availability at both a site and territory level was negatively related to clutch size. The number of fledglings produced was reduced at sites with higher levels of non-native foliage and increased at sites with greater amounts of native oak foliage present. We also found territories with a higher human population density had reduced fledging success. Temperature was negatively related to first egg laying date, clutch size and the number of fledglings produced. Moreover, the number of Lepidopteran larvae, blue tits' preferred prey, that were collected over the breeding season was positively related to native oak foliage availability. Our results strongly indicate that the presence of native trees, such as oak, are beneficial to breeding insectivores by increasing the number of fledglings they can successfully raise, likely due to the increased availability of invertebrate prey. We suggest that urban planting regimes should be carefully considered, selecting tree species that are native or non-native congeneric species, and most importantly that will host Lepidoptera larvae. This will not only help to support complete food chains, but also to maximize biodiversity and ecosystem services of urban green spaces.

Over the past decades, our understanding of the vital role microbes play in ecosystem processes has greatly expanded. However, we still have limited knowledge about how microbial communities interact with larger organisms. Many existing representations of microbial interactions are based on co-occurrence patterns, which do not provide clear insights into trophic or non-trophic relationships. In this study, we untangled trophic and non-trophic interactions between macroscopic and microscopic organisms on a marine rocky shore. Five abundant mollusk grazers were selected, and their consumptive (grazing) and nonconsumptive (grazer pedal mucus) interactions with bacteria in biofilms were measured using 16S rRNA-gene amplicon sequencing. While no significant effects on a commonly used measure of biofilm grazing (chlorophyll a concentration) were observed, detailed image analysis revealed that all grazers had a detrimental impact on biofilm cover. Moreover, different grazers exhibited distinct effects on various bacterial groups. Members of the Alteromonadaceae, Burkholderiaceae, Flavobacteriaceae, Halieaceae, Phycisphaeraceae, Rhodobacteraceae, Rickettsiaceae, Saprospiraceae, and Vibrionaceae families experienced positive trophic effects from specific grazers. In contrast, members of the Flavobacteriaceae, Pirellulaceae, Rhodobacteraceae, Rubritaleaceae, and Saprospiraceae families were negatively affected by trophic interactions with other grazers. Some members of the Gammaproteobacteria, Flavobacteriaceae, Ilumatobacteraceae, Pirellulaceae, Rickettsiales, Rhodobacteraceae, and Rubritaleaceae families exhibited non-trophic positive interactions with specific grazers. Meanwhile, members of the Family DEV007 (Verrucomicrobiales), Flavobacteriaceae, Ilumatobacteraceae, Legionellaceae, Rickettsiales, Rhodobacteraceae, Saprospiraceae, and Xanthobacteraceae families exhibited non-trophic negative interactions with particular grazers. Both trophic and non-trophic interactions shift the microbial community toward enhanced recycling, energy efficiency, and stress resilience. Grazer activity, through biomass removal and exudates like pedal mucus, reduces photosynthetic groups like diatoms, halting dimethylsulfoniopropionate (DMSP) production and negatively impacting sulfur-cycling bacteria and associated parasites. This research complements the ecological network of the intertidal rocky shore in central Chile and represents the first attempt to construct an interaction network between macroorganisms and bacteria. It reveals that the strength of trophic and non-trophic interactions varies depending on the grazer and bacterial group involved. While some bacterial groups responded broadly, others showed specialized responses to specific macroorganisms. Overall, this study highlights the potential for integrating microbes into ecological networks, offering valuable insights methodologies for quantifying interactions across domains.

Understanding the mechanisms shaping food chain length (FCL) has long been central to food web ecology. FCL is a key determinant of stability, energy flow efficiency, and biodiversity maintenance, but there is an ongoing debate about its underlying drivers. It is particularly important in meta-ecosystems, where predator trophic position (TP) is influenced by multiple energy channels. In this study, we focused on spiders in riparian ecosystems, which rely on resources linked to distinct energy channels: blue (algal herbivory), green (terrestrial herbivory), and brown (terrestrial detritivory). We applied nitrogen isotope analysis of amino acids to estimate the TP of both spiders and their prey. This method is a powerful tool for determining TP from a single sample and even allows for capturing decomposer trophic steps. However, the TP estimate requires special care for riparian spiders, as spiders show a specific trophic discrimination factor (TDF_Glx-Phe), and that energy channel use can confound the TP estimate. Our detailed food web resolution supports the use of specific parameters for spiders, particularly the low trophic discrimination factor (TDF_Glx-Phe ~ 2‰), and raises caution about the importance of estimating resource use of predators to estimate their TP. We show that the primary factor driving variation in spider TP is the energy channel they utilize, from blue (TP ~ 2.9) to green (TP ~ 3.6) to brown (TP ~ 4.1). This increase was largely due to prey omnivory in green channels, and microbial and fungal decomposers serving as an initial trophic step between litter and invertebrate detritivores in brown channels. We propose that this pattern is likely influenced by differences in basal nutritional quality, which increases from brown (low) to green (medium) and to blue (high) sources. This suggests that shifts in energy channels within meta-ecosystems in the course of global change (e.g., climate warming, eutrophication and land-use change) may significantly impact FCL, with significant consequences for trophic interactions, nutrient fluxes, and biomagnification processes.

A fundamental question in ecology is why plant communities have large trait space yet strong coordination among those traits across large scales, despite these patterns seeming contradictory. Answering this question requires quantitatively linking the geographic distribution of trait space and coordination with gross primary productivity (GPP). We leveraged an unprecedented large-scale dataset of nine leaf traits for 5718 species-site combinations with simultaneous field measurements of plant community composition in 64 naturally assembled communities to investigate trait spaces (hypervolume, quantity dimension) and trait compactness (coordination, efficiency dimension) and their influence on GPP. Trait space and compactness combined explained 72% of the variation of GPP. Interestingly, a larger trait space (more diverse trait combinations) drove higher GPP in resource-poor communities, while higher trait compactness (greater coordination of traits) determined higher GPP in resource-rich communities. Our findings provide a new perspective that natural plant communities increase both trait space and compactness to improve GPP, shedding light on the development of multidimensional functional ecology.

The enemy release hypothesis posits that introduced species escape some of their predators, pathogens, and parasites when they move to a new range. We used a systematic review to compile data from 691 contrasts of enemy release spanning plants, animals, and algae in aquatic and terrestrial systems worldwide. Data from 311 biogeographic contrasts (between home and new range) revealed that on average, a species experiences only 43% as much enemy pressure in their introduced range as they experience in their native range. Data from 380 community contrasts (between native and introduced species) revealed that introduced species experience on average 70% of the enemy pressure that their native congeners endure. Interestingly, one third (36%) of contrasts showed higher, rather than lower, enemy pressure on the introduced population. Enemy release was well supported in contrasts of the diversity of enemies and enemy damage but not significant in contrasts of host fitness, suggesting that while introduced populations are attacked by fewer enemies, this does not always result in higher fitness. We also found that biogeographic enemy release was higher in mollusks and fish but lower in insects and algae, indicating that certain taxa may be favored by enemy release. We hope that an improved understanding of the extent to which introduced species are released from enemy pressures will help managers to identify good opportunities for biocontrol and to understand the factors likely to be affecting the success of invasive species.

Thermophilization of communities, or shifts in composition favoring more warm-adapted species, over time and space is a common response to warming from global climate change and localized effects of land-use change. However, the interplay between community thermophilization driven by temporal warming in global climate and spatial warming in local climate is not well explored empirically. Here, we use long-term ecological monitoring of ground-dwelling arthropod communities over twenty years, sited in desert and urbanized habitats, to address the joint effects of spatiotemporal warming on community thermophilization. We found spatial convergence of high community thermophily among warm desert and highly urbanized sites, implicating temperature as a major driver of community composition. However, we found unexpected temporal declines in community thermophily, the magnitude of which depended upon space. Declines were found in urbanized sites, but not desert sites. There was evidence of both increases in occurrence of heat-intolerant taxa and decreases in heat-tolerant taxa from urban sites. Our study demonstrates the contingency of responses to recent climate change based on contemporary land-use change.

Trait-based approaches can improve ecological understanding by linking fitness to the environment. The trilateral life history model is an expansion of r- and K-selection theory that reflects trade-offs between juvenile survival, fecundity, and generation time and describes differential survival of species across environmental gradients. We used this framework to generate and test hypotheses regarding community assembly and the validity of such a model in two disparate taxonomic groups, freshwater mussels and fish. We assessed the distribution of mussel and fish life history strategies across 80 sites spanning aspects of the river continuum concept within the Ouachita Highlands (USA) and asked if their distributions are predicted by a similar life history strategy framework. Because mussel and fish assemblages should both be structured by selective forces in an up- to downstream trajectory, we expected both taxa to converge on more species-rich assemblages with a greater proportion of equilibrium strategists in larger, more stable downstream habitats. We found that both mussel and fish species richness increased with watershed area as well as the proportion of equilibrium strategists in the assemblages. Our study validates the use of the trilateral life history model to test hypotheses about the distribution patterns of two coevolved taxonomic groups.

Algal dynamics are fundamental drivers of lotic ecosystem processes. Although rivers tend to be heterotrophic and have low standing stocks of autotrophic biomass, filamentous algae can cause nuisance algal blooms that alter the structure of the autotrophic assemblage. Still, the influence of these blooms on ecosystem processes can be variable. Here, we examined the structural and functional contribution of filamentous and epilithic algae by linking algal biomass measurements to daily primary production fluxes throughout two growing seasons in six sites along the Upper Clark Fork River, an open canopy, snow melt river in western Montana, USA. We partitioned daily productivity estimates across different algal groups using the spatial and temporal variability in algal assemblages across our six sites. By using reach-scale metabolism estimates, we assessed the in situ functional rates of individual algal groups. Throughout two growing seasons, we measured high fluxes of ecosystem productivity and spatially variable filamentous algal blooms. We found that the filamentous algal blooms determined the ecosystem structure in terms of total biomass and algal turnover times, but not the ecosystem functions of gross primary productivity, ecosystem respiration, or net production. Whole-reach estimates of epilithic and filamentous algae growth rates were 0.30 and 0.026 day$��{\hspace{0.17em}}^{�-�1�}�$ respectively, which are similar to rates measured in mesocosms. The epilithic algae grew and turned over rapidly, dominating total biomass production and driving ecosystem function while filamentous algae grew slowly and built up large amounts of biomass during a growing season, shaping the structure, but not function, of the ecosystem.