Prey Spectrum Research Articles

Food Web Trophic Structure at Marine Ranch Sites off the East Coast of Korea

Understanding the trophic ecology of the giant Pacific octopus Enteroctopus dofleini is challenging in developing marine ranches and in reestablishing its regional stocks against the severe stress of fishing. We adopted carbon and nitrogen stable isotope techniques (termed δ13C and δ15N, respectively) to identify the trophic niche (i.e., pathways and positions) of this species systematically in the entire food webs of two marine ranches off the east coast of the Korean peninsula. While a slight spatial shift in the isotopic nestedness of faunal communities was observed, the δ13C and δ15N values of consumers were distinct and separate among functional groups at both ranches. The consumer δ13C values spanned a broad range between pelagic and benthic sources of organic matter, and their δ15N values recorded a stepwise trophic-level enrichment, indicating that suspension feeders and herbivore-deposit feeders served as baselines of pelagic- and benthic-based trophic pathways, respectively. The δ13C values of predators, including E. dofleini, were arrayed between the two primary consumer groups. Neither δ13C nor δ15N values showed any remarkable variations with increasing octopus weight. Dietary mixing-model calculations indicated that E. dofleini is a generalist predator relying on both benthic- and pelagic-affinity prey, similar to some teleost species that consume a diverse spectrum of prey. In contrast, other teleost groups showed prevalent trophic links with either pelagic- or benthic-based pathways. The trophic-level estimations revealed that E. dofleini occupies an intermediate position slightly below the teleosts. A lack of discrete trophic positions between E. dofleini and teleosts seemed to be indicative of the released teleost predation but instead reflects the imposed food competition. Overall, the results demonstrated that despite compositional changes in the taxa constituting individual trophic groups, E. dofleini occupied a very similar trophic niche in both ranching systems. Finally, as extracted from information based on octopus marine ranches launched on natural rocky bottoms, our isotopic evidence provides a greater understanding of the trophic ecology of this octopus species in nearshore natural habitats along the southwestern margin of its distribution range.

Trophic ecology of yellowtail rockfish (Sebastes flavidus) during a marine heat wave off central California, USA.

The yellowtail rockfish, Sebastes flavidus, is a widespread and abundant mesopredator in the California Current Large Marine Ecosystem. We utilized stomach content and stable isotope analyses to investigate the trophic ecology of this species at three sites off central California just before (August–October 2013) and during (August and October 2014) a marine heat wave. Sebastes flavidus largely consumed pelagic prey (zooplankton and micronekton). Diets were dominated by tunicates (salps and pyrosomes), pelagic crustaceans (euphausiids, hyperid amphipods, larval decapods), and fishes, with the relative contribution of these prey taxa varying spatially (sample location, longitude, depth) and temporally (year, month), based on complementary multivariate analyses. Prey-specific indices demonstrated that individual S. flavidus diet composition typically was dominated by one of these prey groups, and that prey switching occurred based on the relative availability of prey and their energetic importance. Stable isotope analysis of δ15N indicated that the S. flavidus populations sampled in 2014 had been feeding at an elevated trophic position and more variable prey spectrum relative to 2013, probably as a consequence of greater piscivory and the incorporation of temporal changes in diet composition. Because its opportunistic feeding behavior reflects the dynamism and heterogeneity of the pelagic forage preyscape, S. flavidus may be an important ecosystem indicator species. For example, the novel incorporation of pyrosomes as a large portion of the diet of S. flavidus during 2013–2014 directly related to the massive increase in pyrosome abundance in the California Current during the 2014 marine heat wave.

The diet of major predators of forest soils: A first analysis on syntopic species of Chilopoda through DNA metabarcoding

Centipedes (Chilopoda) represent a dominant group of predators in temperate forest soils, where multiple species often coexist in syntopy. However, their trophic ecology is largely unknown because traditional methodologies are hindered by the secretive habits of these animals and their partial fluid-feeding. We applied a DNA-metabarcoding approach with COI to assess and compare the prey spectrum of three centipede species (Clinopodes flavidus, Eupolybothrus tridentinus, Lithobius validus) living in a forest plot in the Southern Alps. We obtained DNA sequences from the guts of 79 specimens through Next-Generation Sequencing technology and applied a suite of stringent criteria of data filtering and taxonomic assignment. We found evidence for a similar rate of prey detection between predator species and for a broad prey spectrum, including most taxa of invertebrates living in the local soil biocoenosis and having subduable body size. We did not find evidence of diet variation in relation to sex and annual season, and instead slight but significant differentiation of diet between the geophilomorph C. flavidus and the other two lithobiomorph species.

Snapshot prey spectrum analysis of the phylogenetically early-diverging carnivorous Utricularia multifida from U. section Polypompholyx (Lentibulariaceae).

Utricularia multifida is carnivorous bladderwort from Western Australia and belongs to a phylogenetically early-diverging lineage of the genus. We present a prey spectrum analysis resulting from a snapshot sampling of 17 traps-the first of this species to our knowledge. The most abundant prey groups were Ostracoda, Copepoda, and Cladocera. The genus cf. Cypretta (Cyprididae, Ostracoda) was the predominant prey. However, a high variety of other prey organisms with different taxonomic backgrounds was also detected. Our results indicate that U. multifida may potentially be specialized in capturing substrate-bound prey. Future approaches should sample plants from different localities to allow for robust comparative analyses.

Behavior notes and prey spectrum of three species of the bee-hunting wasp Trachypus Klug (Hymenoptera: Apoidea)

Trachypus Klug is a Neotropical genus of crabronid wasps comprising 31 ground-nesting species. Its species can be solitary or communal, and two diet ranges are known: they can forage on several bee subfamilies and wasps; or can be specialists on stingless bees. Natural history observations are scarce nowadays but are essential to contextualize ecological and evolutionary studies. Here we report new records and give biological notes for Trachypus elongatus (Fabricius, 1804), Trachypus taschenbergi Rubio-Espina, 1975, and Trachypus varius (Taschenberg, 1875). Observations and samplings were carried out twice a month, during one year in the city of Curitiba, southern Brazil. Besides field observations, circular statistics were used to analyze seasonality. All species nest in sloped soil and are solitary. Trachypus elongatus and T. taschenbergi were active during most of the year with marked seasonality in the late spring and early summer. Both species were observed hunting only stingless bees, with T. elongatus specialized on Trigona spinipes (Fabricius, 1793), and T. taschenbergi specialized on Paratrigona subnuda Moure, 1947 drones. Trachypus varius was observed only in January and one female was recorded foraging on a Paratrigona subnuda worker. Our observations provide additional data for understanding the biology of bee-hunting wasps, and this is the first study to bring information for T. taschenbergi and T. varius. Our data corroborate that some species of the genus Trachypus are specialized on stingless bees.

The soil microbial food web revisited: Predatory myxobacteria as keystone taxa?

Trophic interactions are crucial for carbon cycling in food webs. Traditionally, eukaryotic micropredators are considered the major micropredators of bacteria in soils, although bacteria like myxobacteria and Bdellovibrio are also known bacterivores. Until recently, it was impossible to assess the abundance of prokaryotes and eukaryotes in soil food webs simultaneously. Using metatranscriptomic three-domain community profiling we identified pro- and eukaryotic micropredators in 11 European mineral and organic soils from different climes. Myxobacteria comprised 1.5–9.7% of all obtained SSU rRNA transcripts and more than 60% of all identified potential bacterivores in most soils. The name-giving and well-characterized predatory bacteria affiliated with the Myxococcaceae were barely present, while Haliangiaceae and Polyangiaceae dominated. In predation assays, representatives of the latter showed prey spectra as broad as the Myxococcaceae. 18S rRNA transcripts from eukaryotic micropredators, like amoeba and nematodes, were generally less abundant than myxobacterial 16S rRNA transcripts, especially in mineral soils. Although SSU rRNA does not directly reflect organismic abundance, our findings indicate that myxobacteria could be keystone taxa in the soil microbial food web, with potential impact on prokaryotic community composition. Further, they suggest an overlooked, yet ecologically relevant food web module, independent of eukaryotic micropredators and subject to separate environmental and evolutionary pressures.

Wrasse fishery on the Swedish West Coast: towards ecosystem-based management

Abstract Fishing and translocation of marine species for use in aquaculture is widespread. Corkwing, goldsinny, and ballan wrasse (Symphodus melops, Ctenolabrus rupestris, and Labrus bergylta) are fished on the Swedish west coast for use as cleaner-fish in Norwegian salmon farms. Here, we aim to provide knowledge and recommendations to support ecosystem-based management for wrasse fisheries in Sweden. We compared fished and non-fished areas to test if current fishery levels have led to stock depletion. To gain insight on the role of wrasse in the algal belt trophic chain, we analysed the gut contents of goldsinny and corkwing using metabarcoding. Finally, we analysed the trophic interactions of wrasse and potential prey in a mesocosm study. We could not detect any signs of stock depletion or altered size structure in fished areas compared to the protected control area. Gut analyses confirmed both goldsinny and corkwing as non-specialized, omnivorous opportunists and revealed, with 189 prey taxa detected, a broader spectrum of prey than previously known. Common prey items included mesoherbivores such as small gastropods and crustaceans, but also insects and algae. We conclude that there are no visible signs of stock depletion at the current removal level of wrasses by the fishery. However, this emerging fishery should be closely monitored for potential cascading effects on the algal belt ecosystem, and our study could provide a baseline for future monitoring.

Seasonal variation in the diet of two predators in an agroecosystem in southern–central Chile

In ecosystems, seasonal fluctuations in the availability of resources can promote effects on species with similar trophic requirements, increasing the probability of interspecific competition. This scenario becomes more evident in human–dominated landscapes where homogenization of space can contribute to the shortage of resources, modifying species feeding behavior to an uncertain degree. Understanding how these species modify their feeding habits within the context of habitat transformation is of special interest. We evaluated the diversity of prey and overlap for two predators, the chilla fox Lycalopex griseus and the barn owl Tyto alba, during three seasons in 2018 (winter, spring and summer). The study was based on the analysis of feces and pellets in a landscape with agricultural predominance in Southern–central Chile. We found the chilla fox had a generalist dietary profile, feeding on a broad spectrum of prey, with predominance of lagomorphs and, to a lesser extent, rodents. In contrast, the diet of the barn owl mainly consisted of small rodents, with little variation across seasons. Analyses of dietary overlap showed fluctuations during the periods surveyed, with a maximum value in winter and a minimum value in spring. Variations in the consumption of prey based on their size could facilitate their coexistence in the study area.

Not just honeybees: predatory habits of Vespa velutina (Hymenoptera: Vespidae) in France

Summary Understanding the impact of a predatory invasive alien species requires data on its diet. Vespa velutina Lepeletier, 1836, is a notorious bee-hawking hornet accidentally introduced in France before 2004 which spread across the European continent. Despite numerous studies and the impact on beekeeping activities, there are very few data on the diet of this species in its invaded range in Europe. To fill this knowledge gap, we studied 16 nests in the south-west of France between 2008 and 2010. Using a combination of morphological and barcoding approaches, we identified 2151 prey pellets showing that V. velutina acts as a generalist predator, preying on honeybees (38.1%), flies (29.9%) and social wasps (19.7%), as well as a wide spectrum of animal organisms (no less than 159 species identified). The prey spectrum is influenced by the nest surroundings, urban colonies preying more on honeybees and forest colonies preying more on social wasps. The predation intensity reaches its peak in early October. By comparing the dry weight of prey pellets to that of V. velutina larvae and considering the colony dynamics, we estimated that a single hornet nest can consume on average 11.32 kg of insect biomass in one season. Overall, our results suggest that V. velutina is a generalist opportunistic predator targeting mostly locally abundant prey. While the species may have an impact on honeybees, its generalist, opportunistic behaviour on abundant insects suggests a minor impact on wild species. Instead, attempts to manage this species using non-selective traps have a much greater impact on wild and domesticated entomofauna than the hornet itself.

Prey preferences of modern human hunter-gatherers

Understanding traditional hunter-gatherer lifestyles in our modern world is fundamental to our understanding of their viability, as well as the role of humans as predators in structuring ecosystems. Here, we examine the factors that drive prey preferences of modern hunter-gatherer people by reviewing 85 published studies from 161 tropical, temperate and boreal sites across five continents. From these studies, we estimated Jacobs' selectivity index values (D) for 2243 species/spatiotemporal records representing 504 species from 42 vertebrate orders based on a sample size of 799,072 kill records (median = 259). Hunter-gatherers preferentially hunted 11 large-bodied, riskier species, and were capable of capturing species ranging from 0.6 to 535.3 kg, but avoided those smaller than 2.5 kg. Human prey preferences were driven by whether prey were arboreal or terrestrial, the threats the prey afforded hunters, and prey body mass. Variation in the size of prey species pursued by hunter-gatherers across each continent is a reflection of the local size spectrum of available prey, and historical or prehistorical prey depletion during the Holocene. The nature of human subsistence hunting reflects the ability to use a range of weapons and techniques to capture food, and the prey deficient wildlands where people living traditional lifestyles persist.

EDNA metabarcoding reveals a core and secondary diets of the greater horseshoe bat with strong spatio‐temporal plasticity

AbstractDietary plasticity can be a determining factor allowing species to cope with environmental changes. Consequently, it is an important issue to consider in conservation biology. Despite this, it remains rarely addressed in the literature, potentially due to methodologies which were until recently rather limited. The advent of molecular approaches now makes it possible to get a precise picture of diet and its plasticity, even for endangered and elusive species. Here, we focused on the greater horseshoe bat (Rhinolophus ferrumequinum) in Western France, where this insectivorous species has been classified as “Vulnerable” on the Regional Red List in 2016. We applied an eDNA metabarcoding approach to 1986 fecal samples collected in six maternity colonies on three sampling dates. We described the diet and investigated whether the landscape surrounding colonies and the different phases of the maternity cycle influenced the diversity and the composition of this diet. We showed that R. ferrumequinum feed on a much more diverse prey spectrum than expected from previous studies, highlighting how eDNA metabarcoding can improve our knowledge on the dietary habits of elusive species. Our approach also revealed that the diet of R. ferrumequinum seems to be composed of two distinct features: the core diet consisting of a few preferred taxa shared by all the colonies (25% of the occurrences) and the secondary diet consisting of numerous rare prey taxa that were highly different between colonies and sampling dates (75% of the occurrences). Constraints associated with the greater horseshoe bat life cycle, as well as insect phenology and landscape features, strongly influenced the diversity and composition of both the core diet and the diet as a whole. Further research should now explore the relationships between R. ferrumequinum dietary plasticity and fitness, to better assess the impact of core prey decline on R. ferrumequinum population viability.

An insight into the prey spectra and livestock predation by cheetahs in Kenya using faecal DNA metabarcoding

Dietary composition is a fundamental part of animal ecology and an important component of population dynamics. Therefore, obtaining accurate information on what an animal consumes is important for conservation planning, especially for wild large carnivores that exist in human-dominated landscapes where they are prone to direct conflicts with local people. We used faecal DNA metabarcoding to identify the vertebrate taxa commonly predated on by cheetahs (Acinonyx jubatus) with an emphasis on domestic taxa and determine the drivers of livestock predation by cheetahs residing in the Maasai Mara and Amboseli ecosystems which are important population strongholds in southern Kenya. From 84 cheetah faeces that we analysed, a total of 14 prey taxa were identified, including birds, wild and domestic mammals. The livestock taxa identified in cheetah faeces occurred at moderate frequency (12.8%) and the results showed that livestock predation was influenced neither by the sex of the cheetah nor by season. In general, our study shows that cheetahs prey on a diverse range of prey taxa including birds, wild ungulates of various sizes and occasionally on domestic animals, and that the faecal DNA metabarcoding approach represents a valuable complement to traditional dietary analysis methods.

Reconstructing marine plankton food web interactions using DNA metabarcoding.

Knowledge of zooplankton in situ diet is critical for accurate assessment of marine ecosystem function and structure, but due to methodological constraints, there is still a limited understanding of ecological networks in marine ecosystems. Here, we used DNA-metabarcoding to study trophic interactions, with the aim to unveil the natural diet of zooplankton species under temporal variation of food resources. Several target consumers, including copepods and cladocerans, were investigated by sequencing 16S rRNA and 18S rRNA genes to identify prokaryote and eukaryote potential prey present in their guts. During the spring phytoplankton bloom, we found a dominance of diatom and dinoflagellate trophic links to copepods. During the summer period, zooplankton including cladocerans showed a more diverse diet dominated by cyanobacteria and heterotrophic prey. Our study suggests that copepods present trophic plasticity, changing their natural diet over seasons, and adapting their feeding strategies to the available prey spectrum, with some species being more selective. We did not find a large overlap of prey consumed by copepods and cladocerans, based on prey diversity found in their guts, suggesting that they occupy different roles in the trophic web. This study represents the first molecular approach to investigate several zooplankton-prey associations under seasonal variation, and highlights how, unlike other techniques, the diversity coverage is high when using DNA, allowing the possibility to detect a wide range of trophic interactions in plankton communities.

Size matters: trap size primarily determines prey spectra differences among sympatric species of carnivorous sundews

AbstractEven though carnivorous plants (CPs) are a popular focus of ecological research, surprisingly few studies have investigated their prey spectra (the number and composition of captured prey). This knowledge gap has important implications for our understanding of sympatric speciation processes in CPs and may potentially hinder effective conservation and ecological restoration efforts. We applied a novel photography‐based analysis method to characterize the in situ prey spectra of eight species from Drosera sect. Arachnopus, including five species that were studied across multiple populations in northern Australia. The prey spectra of all studied species predominantly comprised of flying insects, with small Nematocera (Diptera) being the most common prey group across all species. While the prey spectra of most species varied significantly among locations, differences in prey spectra among sympatric species were most strongly determined by trap size. The number of prey captured per plant and per centimeter of trapping leaf was strongly associated with increasing leaf length, and species with larger trapping leaves also captured comparatively greater numbers of large prey items than species producing smaller trapping leaves. Although niche segregation in prey spectra was not observed at any of the study sites, at one location D. fragrans (a species producing a strong, honey‐like scent from trapping leaves) was found to capture significantly more winged Hymenoptera than the unscented sympatric D. aquatica, potentially indicating selective prey attraction in D. fragrans. Small species (such as D. nana) captured a disproportionally low amount of prey, despite being relatively widespread over large areas of northern Australia. Results indicate that carnivory may not have been a primary driver of diversification in D. sect. Arachnopus.

Carbon δ13C Isotopic Marker Values Correlate with Carotenoid-Based Bill Colouration in Adult Yellow-Legged Gulls Larus michahellis

La coloracion basada en carotenoides que presentan muchas aves puede reflejar honestamente la calidad del individuo, ya que deben ser obtenidos mediante la dieta. Estos pigmentos son importantes para varias funciones fisiologicas y los individuos pueden buscar compensar entre la distribucion de los carotenoides para estos usos y su acumulacion para atributos sexuales secundarios y sociales. La gaviota patiamarilla Larus michahellis es una especie oportunista que se alimenta de una gran variedad de presas. En este trabajo hemos estudiado si la coloracion basada en carotenoides (pico, mancha roja, anillo orbital) esta relacionada con la ecologia trofica inferida a partir de la composicion isotopica de plumas de aves adultas en tres colonias de esta especie. El marcador isotopico del δ13C correlaciono negativamente con la coloracion basada en carotenoides (area de la mancha roja). Contrariamente a la prediccion hecha a priori, el marcador indica que un mayor consumo de presas terrestres y recursos de vertedero podria ayudar a generar una mancha roja del pico mayor en gaviotas de cualquier sexo. En hembras, no se detecto ninguna correlacion entre las signaturas isotopicas y el volumen de los huevos. El resultado de que un consumo mayor de presas marinas implica una mancha roja menor apoya otros descritos en estudios anteriores que muestran efectos aparentemente positivos de comer en ambientes terrestres humanos sobre el fenotipo de aves adultas. Los resultados pueden sugerir que un mayor consumo de presas marinas puede no ser tan positivo como el presentado en estudios previos. Sin embargo, el efecto de los componentes toxicos potenciales que se pueden obtener de algunas fuentes de alimentacion deberia ser estudiado mas a fondo. Deberiamos de considerar tambien los probables efectos subletales retardados asociados a estos habitats y que se ejercerian sobre los adultos y, probablemente tambien, sobre los pollos.

No ontogenetic shift in the realised trophic niche but in Batesian mimicry in an ant-eating spider

In predators an ontogenetic trophic shift includes change from small to large prey of several different taxa. In myrmecophagous predators that are also mimics of ants, the ontogenetic trophic shift should be accompanied by a parallel mimetic change. Our aim was to test whether ant-eating jumping spider, Mexcala elegans, is myrmecomorphic throughout their ontogenetic development, and whether there is an ontogenetic shift in realised trophic niche and their mimetic models. We performed field observations on the association of Mexcala with ant species and investigated the natural prey of the ontogenetic classes by means of molecular methods. Then we measured the mimetic similarity of ontogenetic morphs to putative mimetic models. We found Mexcala is an inaccurate mimic of ants both in the juvenile and adult stages. During ontogenesis it shifts mimetic models. The mimetic similarity was rather superficial, so an average bird predator should distinguish spiders from ants based on colouration. The realised trophic niche was narrow, composed mainly of ants of different species. There was no significant difference in the prey composition between ontogenetic stages. Females were more stenophagous than juveniles. We conclude that Mexcala is an ant-eating specialist that reduces its prey spectrum and shifts ant models during ontogenesis.

Changes in life history traits and transcriptional regulation of Coccinellini ladybirds in using alternative prey

BackgroundLadybird beetles (Coleoptera, Coccinellidae) are highly diverse in their feeding habits. Most of them are specialist feeders, while some can have a broad spectrum of prey. As a representative group of generalists, the tribe Coccinellini includes many aphidophagous species, but members of this tribe also feed on other hemipterous insects including coccids, psyllids and whiteflies. As a result, several species are effective biological control agents or invasive species with serious non-target effects. Despite their economic importance, relatively little is known about how they adapt to new prey.ResultsIn this study, comparisons of the life history traits and transcriptomes of ladybirds fed initial (aphids) and alternative prey (mealybugs) were performed in three Coccinellini species. The use of alternative prey greatly decreased performance, implied by the significantly prolonged development time and decreased survival rate and adult weight. Prey shifts resulted in a set of differentially expressed genes encoding chemosensory proteins and digestive and detoxifying enzymes.ConclusionsOur results suggest that these generalists do not perform well when they use alternative prey as the sole nutrition source. Although their capacity for predation might have created an opportunity to use varied prey, they must adapt to physiological obstacles including chemosensing, digestion and detoxification in response to a prey shift. These findings challenge the effect of Coccinellini predators on the biological control of non-aphid pests and suggest the possibility of non-target attacks by so-called specialists.

Food habits of wolves and selection of wild ungulates in a prey-rich Mediterranean coastal area

Large carnivores are increasing throughout the western Holarctic, re-colonising large parts of their former ranges. Ecological (e.g., predator-prey relationships) and socio-economic (e.g., livestock depredation) consequences of this process need to be monitored to identify suitable management/conservation actions. We studied food habits and selection of main prey by wolves in a Mediterranean protected coastal area (Uccellina Hills in the Maremma Regional Park, c. 70 km2, central Italy, May 2016- April 2018), including sclerophyllic scrubwood, pinewood, wetlands and mixed rural-wood habitats. Potential prey include wild boar, fallow deer and roe deer (c. 25–30 individuals/100 ha, in summer, all species together), livestock (mainly cattle and sheep, c. 20 heads/100 ha, overall) and several species of meso-mammals. Overall, wild ungulates dominated the diet (c. 90% of absolute occurrence, relative occurrence or volume), with the fallow deer being the main prey (absolute occurrence, AO: 55%; relative occurrence, RO: 42%; estimated volume, V: 44%) followed by the wild boar (AO: 48%; RO: 36% V: 33%). Livestock was rarely used (2%, both AO and V); the coypu (AO: 8%; RO: 6%; V: 6%) was another important food item. Fallow deer and wild boar dominated summer diet, whereas the use of alternative prey increased in winter. Fallow deer were selected, wild boar were used according to their availability, whereas roe deer were used less than availability. Prey selection was probably driven by the greater accessibility and detectability of fallow deer, which are gregarious and attended mainly open habitats on lower ground, in respect to wild boar/roe deer. Most likely, availability of a diverse spectrum of meso-large prey and a comparatively lower accessibility of livestock were key-factors to limit livestock consumption.

A food spectrum analysis of three bufonid species (Anura: Bufonidae) from Uttarakhand region of the western Himalaya, India

The ecological diversity of insects and its predators like amphibians are important determinants in ecological balance. A total of 1,222 prey items in 84 specimens were examined to contribute the understanding of the diets of three Duttaphrynus species, viz., himalayanus, melanostictus, and stomaticus from Uttarakhand, the western Himalaya, India. Gut content analysis of three bufonids revealed acceptance of a wide range of terrestrial insects and other invertebrates as their food. The index of relative importance indicated that the most important preys were Formicidae, Coleoptera and Orthoptera. Duttaphrynus melanostictus had the broadest dietary niche breadth, followed by D. himalaynus and D. stomaticus. The wide prey spectrum well indicates that these species are the generalist and opportunist invertebrate feeder. Information pertaining to the food spectrum analysis contributes to understanding the ecological roles and used as a baseline data for future successful amphibian conservation and management programs in the Himalayan ecosystem.

Predatory Myxococcales are widely distributed in and closely correlated with the bacterial community structure of agricultural land

Predation is commonly considered a key factor in regulating community structure or function. Although predation has been extensively explored in animals and microbial eukaryotes, predation by bacteria in agricultural land is poorly understood. Therefore, the objective was explored the community structure and abundance of predatory bacteria and their potential effects on other bacteria in agricultural land. Accordingly, six paired organic and conventional management crop soils were collected to compare typical predatory bacteria abundance information using the 16S rRNA gene high-throughput sequencing. The results revealed that 10 groups of predatory bacterial species accounted for 0.53–16.27% of the soil bacterial community. Soil pH was positively correlated with more than half of the predatory bacteria (P < 0.05, including Myxococcales). Myxococcales exhibited high abundance and widespread distribution in all of the soil samples, with a relatively uniform distribution in the three soil types. Myxococcales were significantly positively correlated with eight other predatory bacteria and with bacterial community Shannon and Abundance-based and Coverage Estimator (ACE) indices. Network analysis indicated that predatory bacteria, especially Myxococcales, co-occur with other nutrition-related bacteria. Under organic conditions, the abundance of Myxococcales significantly increased. Considering that Myxococcales have a higher adaptive potential and broader prey spectrum, we conclude that members of this bacterial order are important and active predators regulating bacterial communities in agricultural land. However, additional direct evidence is required to illustrate how Myxococcales alter bacterial community structure.