Seventy‐five percent of Madagascar is treeless C4‐grassland adapted to human‐lit fire, which likely succeeded pre‐human mosaics of forest, ericoids, grassy‐woodlands and some smaller ...treeless‐grasslands. In support of pre‐settlement Malagasy grasslands having evolved with many grassland specialist faunal elements, Bond et al. (2022) cite “considerable overlap” in African and Malagasy hippo diets, and suggest time‐scale hampered mammal radiation into treeless‐grasslands. We find, however, that faunal elements referenced are predominantly habitat generalists (not grassland specialists), that African and Malagasy hippos occupy significantly different feeding‐niches, and that despite shared Miocene timeframes, Malagasy non‐arboreal mammals remained forest‐adapted whilst species that share ancestry with them on the African mainland radiated into open habitats.
Résumé
Soixante‐quinze pour cent de Madagascar présente des prairies C4 sans arbres adaptées au feu allumé par l’homme, prairies qui ont probablement succédé à des mosaïques préhumaines de forêts, d’éricoïdes, de forêts herbeuses et de quelques prairies plus petites sans arbres. À l’appui de l’hypothèse que les prairies malgaches d’avant la colonisation par les humains auraient évolué avec de nombreux éléments fauniques spécialistes de ces prairies, Bond et al. (2022) ont cité un “chevauchement considérable” dans les régimes alimentaires des hippopotames africains et malgaches, et ont suggéré que trop peu de temps à l’échelle évolutive avait passé pour permettre le rayonnement des mammifères de Madagascar dans les prairies sans arbres. Nous trouvons, cependant, que les éléments fauniques dans les prairies malagaches référencés sont principalement des généralistes de l’habitat (et non des spécialistes des prairies), que les hippopotames africains et malgaches occupent des niches alimentaires significativement différentes, et que malgré l’échelle de temps partagés du Miocène, les mammifères malgaches non arboricoles sont restés adaptés à la forêt tandis que les espèces du continent africain qui partagent avec eux des ancêtres présentent une radiation dans des habitats ouverts.
The worldwide increase in human outdoor activities raises concerns for wildlife. Human disturbances, even at low levels, are likely to impact species during sensitive periods of the annual cycle. ...However, experimental studies during the putative sensitive period of territory establishment of birds which not only investigate low disturbance levels, but which also exclude the effect of habitat modification (e.g. walking trails) are lacking. Here, we experimentally disturbed birds in forest plots by walking through twice a day during territory establishment. Later we compared the breeding bird community of experimentally disturbed plots with that of undisturbed control plots. We discovered that the number of territories (−15.0%) and species richness (−15.2%) in disturbed plots were substantially reduced compared with control plots. Species most affected included those sensitive to human presence (assessed by flight-initiation distances), open-cup nesters and above-ground foragers. Long-distance migrants, however, were unaffected due to their arrival after experimental disturbance took place. These findings highlight how territory establishment is a sensitive period for birds, when even low levels of human recreation may be perceived as threatening, and alter settlement decisions. This can have important implications for the conservation of species, which might go unnoticed when focusing only on already established birds.
Collembola are among the most abundant, diverse and functionally important groups of soil animals. Collembolans inhabit different litter and soil layers and their food objects are intimately related ...to their habitat. Morphological differences that separate high rank taxa of collembolans have clear functional meaning in relation to life style and habitat requirements (including position in the soil profile). However, no study has tested the hypothesis that the species within the major functional groups also differ in terms of trophic positions. This hypothesis was tested for the first time using stable isotope analysis. We compiled original and published data on the stable isotope composition of 82 collembolan species in temperate forest ecosystems. The δ13C and δ15N values of collembolans were found related to their life forms, reflecting a shift in available food objects across different habitat layers and matching the vertical isotopic gradient of soil organic matter. The trophic niche of species varied among different collembolan orders and families, indicating a pronounced phylogenetic signal and supporting the trophic niche conservatism hypothesis. Considering stable isotope compositions, as well as the taxonomic identity and life form of species, we outlined four collembolan functional guilds that use different types of food and perform different ecosystem functions.
•Trophic differentiation of collembolans was studied using stable isotope analysis.•Trophic niches are related to life forms reflecting a strong connection to habitat.•Trophic niches are related to taxonomy supporting niche conservatism hypothesis.•Supraspecific taxa in Collembola can be considered as functional units.•Four collembolan functional leagues are outlined.
Stover mulching as a conservation and sustainable agricultural practice is beneficial for maintaining soil nitrogen (N) requirements and plant health. The microbial functional guilds of the root and ...rhizosphere are important factors in the soil nitrogen cycle. However, it is unclear how the frequency and amount of stover mulching influence microbial functional guilds in the root and rhizosphere. Therefore, we investigated the responses of the microbial functional guilds in the endosphere and rhizosphere to maize stover mulching amounts (0, 1/3, 2/3, and total stover mulching every year) and frequencies (once every 3 years and twice every 3 years) under 10-year no-till management. The bacterial functional guilds of nitrogen fixation, nitrification, and anaerobic nitrate oxidation displayed the significantly correlation with C/N, total nitrogen, NO
3
−
, and NH
4
+
. The fungal functional guilds of plant pathogens and saprotrophs showed significantly correlations with C/N, total nitrogen, and NO
3
−
. Moreover, we found that bacterial guilds play a pivotal role in maintaining N requirements at the jointing stage, whereas root endophytic fungal guilds play a more important role than bacterial guilds in regulating plant health at the mature stage. The frequency and amount of stover mulching had significant effects on the microbial functional guilds in the root and rhizosphere. Our data suggest that stover mulch application twice every 3 years is the optimal mulching frequency because it yielded the lowest abundance of nitrifying and anaerobic nitrate-oxidising bacteria and the highest abundance of nitrogen-fixing bacteria at the jointing stage, as well as the lowest abundance of fungal plant pathogens in roots at the mature stage.
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•Woody species richness played a vital role in driving soil fungal community structure.•Higher ectomycorrhizal fungi abundance accompanied by lower undefined saprotrophic fungal ...abundance.•Change of ericoid mycorrhizal fungi abundance was dependent on understory species composition.•Endophytic fungal abundance increased with the forest secondary succession.
Forest secondary succession alters plant diversity and soil properties in the forest ecosystems; however, effects of this process on the soil fungal community structure are poorly understood. We used Illumina high-throughput sequencing to identify soil fungal community during forest secondary succession (including 30-, 45-, 60-, and 80-year-old stands) in the Pinus yunnanensis forest. The aims were to explore how plant diversity and soil properties drive soil fungal community structure and elucidate the role of fungal guilds in integrating the linkages of plant diversity and soil properties with forest secondary succession. Our study found that forest secondary succession changed woody species composition, richness, and soil properties, furthermore, this also affected significantly soil fungal diversity, community composition, and the abundances of the different functional guilds along the forest secondary succession. Soil fungal diversity initially increased up to the 60-year-old stand, and then decreased with forest secondary succession. The main phyla included Agaricomycetes, Leotiomycetes, Mortierellomycetes, and Eurotiomycetes, and indicator phyla varied differently with forest secondary succession. Soil fungal community could be clearly divided into the four successional stages. Forest secondary succession affected significantly soil fungal diversity via altering woody species richness and soil properties. Mycorrhizal, saprotrophic, and endophytic fungi interacted differently with forest secondary succession. Ectomycorrhizal fungi (ECM) played a vital role in driving forest secondary succession, and greater ECM fungal abundance could drive the forest secondary succession process through changes in the ECM plant composition. ECM plant community composition displayed different effects on ECM fungal abundance. As a result, ECM fungal abundance increased with a higher abundance of Castanopsis orthacantha, and decreased with a higher abundance of P. yunnanensis. Ericoid mycorrhizal fungal abundance reached its maximum in the 45-year-old stand and then decreased, which could provide valuable information for understory restoration. Undefined saprotrophic fungal abundance decreased with increasing forest secondary succession, accompanied by an increase of ECM fungal abundance, while endophytic fungi increased with forest secondary succession. Our findings suggested that plant-fungal symbionts and environmental selection posed an important constraint in assembly of soil fungal community and functional guild abundances. Altogether, these results provided new insights for predicting shifts in plant and soil fungal community strategies with the forest secondary succession in the P. yunnanensis forest.
Despite the potential emissions of heavy metal pollution in Lake Caizi due to extensive agriculture, urban growth and fishing activities, the risk posed by metal concentrations to aquatic ...environments and human populations has not yet been studied. In this study we compared the concentrations of Hg, As, Pb, Cd, Cr, Cu and Zn in water, sediment, and economic fish species with different habitat preferences and trophic guilds across important fishery areas in Lake Caizi, located on the northern shore of the Yangtze River, Southeast China. The concentrations of Cr in water were found approximately 6 times higher than the safety thresholds established by international legislation. Cr, Zn, As and Cd concentrations in sediments surpassed the background values for Yangtze River basin in Anhui Province. However, all the studied fish species in Lake Caizi had metal concentrations lower than legislation thresholds established by China and international organizations. Heavy metal concentrations were found to be significantly higher in demersal (inhabiting near the sediments) and piscivorous (possessing higher trophic level) fishes than in pelagic/benthopelagic (inhabiting the upper and lower water column) and herbivorous/planktivorous (possessing lower trophic level) fishes. Our finding demonstrated that the metal concentrations in fishes are simultaneously influenced by the habitat and bio-accumulation through the food chain. According to target hazard quotient (THQ) calculations for heavy metal contents in the muscles of fish species, all the determined heavy metals gave THQ values lower than 1, suggesting the inexistence of health risks from the intake of fishes from Lake Caizi.
•Cr content in the water of Lake Caizi exceeded international safety thresholds.•High levels of Cr, Zn, As and Cd were found in sediments from Lake Caizi.•Fishes located in higher trophic level showed higher accumulation of heavy metals.•Demersal fishes accumulate more heavy metals than pelagic and benthopelagic fishes.
Fungi typically live in highly diverse communities composed of multiple ecological guilds. Although high-throughput sequencing has greatly increased the ability to quantify the diversity of fungi in ...environmental samples, researchers currently lack a simple and consistent way to sort large sequence pools into ecologically meaningful categories. We address this issue by introducing FUNGuild, a tool that can be used to taxonomically parse fungal OTUs by ecological guild independent of sequencing platform or analysis pipeline. Using a database and an accompanying bioinformatics script, we demonstrate the application of FUNGuild to three high-throughput sequencing datasets from different habitats: forest soils, grassland soils, and decomposing wood. We found that guilds characteristic of each habitat (i.e., saprotrophic and ectomycorrhizal fungi in forest soils, saprotrophic and arbuscular mycorrhizal fungi in grassland soils, saprotrophic, wood decomposer, and plant pathogenic fungi in decomposing wood) were each well represented. The example datasets demonstrate that while we could quickly and efficiently assign a large portion of the data to guilds, another large portion could not be assigned, reflecting the need to expand and improve the database as well as to gain a better understanding of natural history for many described and undescribed fungal species. As a community resource, FUNGuild is dependent on third-party annotation, so we invite researchers to populate it with new categories and records as well as refine those already in existence.
Methlymercury is a significant risk to environmental health globally. We examined the ecological drivers of methylmercury bioaccumulation in songbirds and its effect on body condition while ...experimentally removing the potentially confounding and predominant effects of site and habitat. We measured blood and feather mercury concentrations and body condition in nearly 1200 individuals representing resident or migrant songbirds of 52 species and 5 foraging guilds. Songbird mercury concentrations differed among species, foraging guilds, residency status, dates, and ages, but not sexes. Blood mercury concentrations 1) ranged from 0.003 in house finch to 0.85 μg/g ww in American robin, 2) were 125 times greater in insectivores than granivores and 3.6 times greater in insectivores than omnivores, 3) were 3.3 times greater in summer residents than in migrating songbirds, 4) increased by 25% throughout spring and summer, and 5) were 45% higher in adults than juveniles. Songbird mercury concentrations were negatively correlated with body condition, with blood mercury concentrations decreasing by 44% and 34% over the range of standardized body masses and fat scores, respectively. Our results highlight the importance of foraging and migration ecology in determining methylmercury contamination in birds, and the potential for reduced body condition with methylmercury exposure in songbirds.
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•We examined ecological drivers of methylmercury in songbirds and effects on condition.•We measured 1200 resident or migrant songbirds of 52 species and 5 foraging guilds.•Mercury varied among species, foraging guilds, residency status, dates, and ages.•Songbird mercury concentrations were negatively correlated with body condition.•Results highlight ecological drivers of bird contamination and effects on condition.
Foraging and migration ecology are important determinants of methylmercury contamination in birds, and methylmercury exposure in songbirds may result in reduced body condition.
The pathogenic mechanisms underlying distal symmetric polyneuropathy (DSPN), a common neuropathy in patients with diabetes mellitus (DM), are not fully understood. Here, we discover that the gut ...microbiota from patients with DSPN can induce a phenotype exhibiting more severe peripheral neuropathy in db/db mice. In a randomized, double-blind, and placebo-controlled trial (ChiCTR1800017257), compared to 10 patients who received placebo, DSPN was significantly alleviated in the 22 patients who received fecal microbiota transplants from healthy donors, independent of glycemic control. The gut bacterial genomes that correlated with the Toronto Clinical Scoring System (TCSS) score were organized in two competing guilds. Increased guild 1, which had higher capacity in butyrate production, and decreased guild 2, which harbored more genes in synthetic pathway of endotoxin, were associated with improved gut barrier integrity and decreased proinflammatory cytokine levels. Moreover, matched enterotype between transplants and recipients showed better therapeutic efficacy with more enriched guild 1 and suppressed guild 2. Thus, changes in these two competing guilds may play a causative role in DSPN and have the potential for therapeutic targeting.
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•Gut microbiota from patients with DSPN induce severe peripheral neuropathy in db/db mice•In a randomized clinical trial, FMT from healthy donors significantly alleviated DSPN•Two competing guilds of gut microbiota were associated with FMT-induced alleviation of DSPN•Matched enterotype between transplants and recipients linked to better FMT efficacy
Yang et al. discover that transferring dysbiotic gut microbiota from patients with DSPN to db/db mice can promote the progression of peripheral neuropathy. In a randomized clinical trial, gut microbiota transplanted from healthy donors significantly alleviated DSPN in patients. The bacterial genomes that correlated with DSPN’s severity were organized into two competing guilds.
In consumer communities, intra-guild predation (IGP) is a commonly observed interaction that is widely believed to increase resource density. However, some recent theoretical work predicts that ...resource density should first decrease, and then increase as the strength of IGP increases. This occurs because weak to intermediate IGP increases the IG predator density more than it reduces the IG prey density, so that weak to intermediate IGP leads to the lowest resource density compared to weak or strong IGP. We test this prediction that basal resource density would first decrease and then increase as the strength of IGP increase. We used a well-studied system with two protozoa species engaged in IGP and three bacteria species as the basal resources. We experimentally manipulated the percentage of the IG prey population that was available to an IG predator as a proxy for IGP strength. We found that bacterial density first decreased (by ~25%) and then increased (by ~30%) as the strength of IGP increased. Using a modified version of a published IGP model, we were able to explain ~70% of the variation in protozoa and bacterial density. Agreement of the empirical results with model predictions suggests that IGP first increased the IG predator density by consuming a small proportion of the IG prey population, which in turn increased the summed consumer density and decreased the bacterial resource density. As IGP strength increased further, the IG predator became satiated by the IG prey, which then freed the bacterial resource from predation and thus increased bacterial density. Consequently, our work shows that IGP can indeed decrease or increase basal resource density depending on its strength. Consequently, the impacts of IGP on resource density is potentially more complex than previously thought.
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