Niche differentiation among species is a key mechanism by which biodiversity may be linked to ecosystem function. We tested a set of widely invoked hypotheses about the extent of niche ...differentiation in one of the most diverse communities on Earth, decomposer microorganisms, by measuring their response to changes in three abundant litter resources: lignin, cellulose, and nitrogen (N). To do this, we used the model system Arabidopsis thaliana to manipulate lignin, cellulose, and N availability and then used high-throughput sequencing to measure the response of microbial communities during decay. Resequencing the decomposer communities after incubation of decomposed litter with pure substrates showed that groups of species had unique substrate use profiles, such that species organized into functional "guilds" of decomposers that were associated with individual litter chemicals. Low concentrations of lignin, cellulose, or N in the litter caused unique shifts in decomposer community composition after 1 yr of decay. Low cellulose plants had low levels of fungi in all decomposer guilds, low lignin plants had high levels of fungi in all decomposer guilds, and low N plants had low levels of fungi in decomposer guilds associated with sucrose and lignin. The relative abundance of decomposer guilds correlated with the total loss of individual litter chemicals during litter decay in the field. In addition, N fertilization shifted decomposer communities during both the early and later stages of decay to those dominated by decomposers in the cellulose guild. Our results contrast the assumption that major carbon (C) and N degradation mechanisms are uniform across whole decomposer communities and instead suggest that decomposition arises from complementarity among groups of metabolically distinct taxa.
Late medieval and early modern cities are often depicted as cradles of artistic creativity and hotbeds of new material culture. Cities in renaissance Italy and in seventeenth and eighteenth-century ...northwestern Europe are the most obvious cases in point. But, how did this come about? Why did cities rather than rural environments produce new artistic genres, new products and new techniques? How did pre-industrial cities evolve into centres of innovation and creativity? As the most urbanized regions of continental Europe in this period, Italy and the Low Countries provide a rich source of case studies, as the contributors to this volume demonstrate. They set out to examine the relationship between institutional arrangements and regulatory mechanisms such as citizenship and guild rules and innovation and creativity in late medieval and early modern cities. They analyze whether, in what context and why regulation or deregulation influenced innovation and creativity, and what the impact was of long-term changes in the political and economic sphere.
• In the processes controlling ecosystem fertility, fungi are increasingly acknowledged as key drivers. However, our understanding of the rules behind fungal community assembly regarding the effect ...of soil fertility level remains limited.
• Using soil samples from typical tea plantations spanning c. 2167 km north-east to south-west across China, we investigated the assemblage complexity and assembly processes of 140 fungal communities along a soil fertility gradient.
• The community dissimilarities of total fungi and fungal functional guilds increased with increasing soil fertility index dissimilarity. The symbiotrophs were more sensitive to variations in soil fertility compared with pathotrophs and saprotrophs. Fungal networks were larger and showed higher connectivity as well as greater potential for inter-module connection in more fertile soils. Environmental factors had a slightly greater influence on fungal community composition than spatial factors. Species abundance fitted the Zipf–Mandelbrot distribution (niche-based mechanisms), which provided evidence for deterministic-based processes.
• Overall, the soil fungal communities in tea plantations responded in a deterministic manner to soil fertility, with high fertility correlated with complex fungal community assemblages. This study provides new insights that might contribute to predictions of fungal community complexity.
Ingestion of microplastics by fishes could be an emerging environmental crisis because of the proliferation of plastic pollution in aquatic environments. Microplastics in marine ecosystems are well ...documented, however only one study has reported percent occurrence of microplastics in freshwater fishes. The purpose of this study was to quantify the occurrences and types of microplastics ingested by fishes within several freshwater drainages of the Gulf of Mexico and an estuary of the Gulf of Mexico. Among 535 fishes examined in this study, 8% of the freshwater fishes and 10% of the marine fishes had microplastics in their gut tract. Percentage occurrence of microplastics ingested by fishes in non-urbanized streams (5%) was less than that of one of the urbanized streams (Neches River; 29%). Percent occurrence of microplastics by habitat (i.e., benthic, pelagic) and trophic guilds (herbivore/omnivore, invertivore, carnivore) were similar. Low but widespread occurrences among drainages, habitat guilds, and trophic guilds indicate proliferation of plastic pollution within watersheds of the Gulf of Mexico, but consequences to fish health are unknown at this time.
•8% of the freshwater fishes and 10% of marine fishes had microplastic in their gut tract.•Fishes from freshwater and marine environments in Texas ingest microplastics ubiquitously across habitat and trophic guilds.•Significantly more fishes taken from one of the urbanized streams had ingested microplastic.•A subsample of plastic fragments, filaments and film was analyzed using FT-IR spectroscopy.
ABSTRACT
Increased frequency and severity of drought, as a result of climate change, is expected to drive critical changes in plant–insect interactions that may elevate rates of tree mortality. The ...mechanisms that link water stress in plants to insect performance are not well understood. Here, we build on previous reviews and develop a framework that incorporates the severity and longevity of drought and captures the plant physiological adjustments that follow moderate and severe drought. Using this framework, we investigate in greater depth how insect performance responds to increasing drought severity for: (i) different feeding guilds; (ii) flush feeders and senescence feeders; (iii) specialist and generalist insect herbivores; and (iv) temperate versus tropical forest communities. We outline how intermittent and moderate drought can result in increases of carbon‐based and nitrogen‐based chemical defences, whereas long and severe drought events can result in decreases in plant secondary defence compounds. We predict that different herbivore feeding guilds will show different but predictable responses to drought events, with most feeding guilds being negatively affected by water stress, with the exception of wood borers and bark beetles during severe drought and sap‐sucking insects and leaf miners during moderate and intermittent drought. Time of feeding and host specificity are important considerations. Some insects, regardless of feeding guild, prefer to feed on younger tissues from leaf flush, whereas others are adapted to feed on senescing tissues of severely stressed trees. We argue that moderate water stress could benefit specialist insect herbivores, while generalists might prefer severe drought conditions. Current evidence suggests that insect outbreaks are shorter and more spatially restricted in tropical than in temperate forests. We suggest that future research on the impact of drought on insect communities should include (i) assessing how drought‐induced changes in various plant traits, such as secondary compound concentrations and leaf water potential, affect herbivores; (ii) food web implications for other insects and those that feed on them; and (iii) interactions between the effects on insects of increasing drought and other forms of environmental change including rising temperatures and CO2 levels. There is a need for larger, temperate and tropical forest‐scale drought experiments to look at herbivorous insect responses and their role in tree death.
1. Interspecific social information transfer can play a key role in many aspects of animal ecology from foraging to habitat selection to predator avoidance. 2. Within scavenging communities, avian ...scavengers often act as producers and mammalian scavengers act as scroungers, but we predict that species-specific cueing will allow for mammalian scavengers to utilize particular avian scavenger species using preferred food sources similar to their own preferences. 3. We use empirical and theoretic approaches to assess interactions between mammalian and avian scavengers in one of the most diverse scavenging guilds in Masai Mara National Reserve, Kenya. 4. Using a spatially explicit model and data from experimental carcasses, we found evidence that mammals benefit from local enhancement provided by vultures and that mammalianavian following patterns are consistent with the idea that species-specific cueing is occurring. 5. Results suggest that ongoing population declines in avian scavengers may have significant impacts on mammalian scavengers and potentially create trophic cascades.
This study aims to identify, classify, quantify the ingested microplastic by marine teleost fish, in order to analyze the relationship between microplastic and trophic guilds. Food items of 214 ...individuals of Opisthonema oglinum, Bagre marinus, Cathorops spixii, Sciades herzbergii, Chloroscombrus chrysurus, Conodon nobilis, Haemulopsis corvinaeformis were analyzed. The species were classified according to their trophic guilds (zoobenthivorous or opportunistic/omnivorous). All species ingested microplastic and contamination occurred independently of the trophic guild. Of the sampled fish, 55% were contaminated by microplastic. The most consumed categories were blue (28%) and transparent filaments (20%). Raman spectroscopy measurements detected that most sampled filament corresponds to blue synthetic fiber (polyester). This study can contribute by filling gaps in knowledge regarding sandy beach impacts, which are environments so highly threatened by human activities around the world and are neglected in terms of use and conservation plans.
•All species have ingested microplastic.•Microplastic contamination occurred regardless of trophic guild.•The species that most ingested microplastic was Cathrops spixii.•The most recorded microplastic in fish stomach content was the blue filament.
Despite the growing number of dam removals, few have been studied to understand their impacts on stream fish communities. An even smaller proportion of dam removal studies focus on the impacts of ...low‐head dam removals, although they are the most common type of dam. Instead, the majority of removal studies focus on the impacts of larger dams. In this study, two previously impounded Illinois Rivers were monitored to assess the impacts of low‐head dam removal on the functional assemblage of stream fishes. Study sites were sampled each fall from 2012–2015 (pre‐dam removal) and 2018–2020 (post‐dam removal) in three locations: the tailrace, impoundment, and river channel. Fishes were aggregated into habitat and reproductive guilds, relating community changes to habitat, environmental metrics, and stream quality. Prior to removal, the slackwater guild was the most prevalent habitat guild throughout both rivers, while nest builders and benthic spawners were the most abundant reproductive guilds. During the two years following removal, fish assemblage throughout both rivers shifted to a more evenly distributed representation of habitat and reproductive guilds, while restoration of lotic habitat conditions increased, as surface water temperatures decreased and QHEI, IBI, and dissolved oxygen increased. This shift in environmental metrics and increase in overall stream quality increased, particularly in the formerly impounded reaches, indicate diminished habitat homogeneity, and a shift towards natural habitat diversity. This habitat diversification likely led to the restoration of a range of potential niches, thereby increasing the array of guild types inhabiting these rivers, while simultaneously preventing single‐guild dominance.
PDF
