Taxonomic Compositions and Co-occurrence Relationships of Protists in Bulk Soil and Rhizosphere of Soybean Fields in Different Regions of China

As the main consumers of bacteria and fungi in farmed soils, protists remain poorly understood. The aim of this study was to explore protist community assembly and ecological roles in soybean fields. Here, we investigated differences in protist communities using high-throughput sequencing and their inferred potential interactions with bacteria and fungi between the bulk soil and rhizosphere compartments of three soybean cultivars collected from six ecological regions in China. Distinct protist community structures characterized the bulk soil and rhizosphere of soybean plants. A significantly higher relative abundance of phagotrophs was observed in the rhizosphere (25.1%) than in the bulk soil (11.3%). Spatial location (R2 = 0.37–0.51) explained more of the variation in protist community structures of soybean fields than either the compartment (R2 = 0.08–0.09) or cultivar type (R2 = 0.02–0.03). The rhizosphere protist network (76 nodes and 414 edges) was smaller and less complex than the bulk soil network (147 nodes and 880 edges), indicating a smaller potential of niche overlap and interactions in the rhizosphere due to the increased resources in the rhizosphere. Furthermore, more inferred potential predator-prey interactions occur in the rhizosphere. We conclude that protists have a crucial ecological role to play as an integral part of microbial co-occurrence networks in soybean fields.

Do Odontomachus brunneus nestmates request for help and are taken care of when caught?

In social insects, situations can arise that threaten an individual or an entire colony. When the call for help goes out, different behavioral responses are elicited by signals emitted from nestmates. In ants, the response can be one of redemptive behavior by the worker receiving it. However, little is known about the evolution of this behavior and in which group of ants it manifests. Therefore, this study investigates whether workers of Odontomachus brunneus Patton can act as rescuers, able to detect and respond to calls for help from nestmates. Laboratory experiments were carried out in which the legs of ants were trapped by tape, simulating capture by a predator. Nearby were nestmates able to receive and respond to a request for help. Two experiments were performed: 1. Calls for help were made at different distances, in order to test the response latency. 2. Evaluation of whether rescuers would respond differently to calls for help from nestmates, non-nestmates of the same species, and ants of another species. Finally, evaluation was made of the behaviors of the rescuers when they responded to requests for help from nestmates and ants of another species. It could be concluded from the results that O. brunneus workers respond to signals emitted by workers who may have been captured by a potential predator, prompting the performance of behaviors related to rescue attempts. The signals involved appear to have an optimal range and are species-specific. When exposed to a capture situation, this species transmits audible signals by stridulation, so it is possible that this type of signal may be involved, in addition to chemical signaling.

Potential predators of Dolichotis patagonum in the surroundings of its burrows, in Sierra de las Quijadas National Park, San Luis, Argentina

Dolichotis patagonum (common name: mara) is a large sized rodent, endemic of Argentina, which raises its juveniles in burrows. It has recently been categorized as vulnerable. This is the first study to evaluate D. patagonum interactions with potential predators in the surroundings of the dens. We monitored 20 burrows, using camera-traps, with a total of 5644 camera-days, obtained over two years (2015 and 2016). Five potential predator species were detected (Lycalopex griseus, Puma concolor, Leopardus geoffroyi, Salvator sp. and Chaetophractus villosus). L. griseus and L. geoffroyi were the species with the highest frequency of visits. Both species were photographed attacking the juveniles. Four out of five potential predator species registered presented agonistic interactions with adults of mara. Overlap between all species analyzed and mara was low to moderate, and potential predator visits to the surrounding of the burrows did not vary according to the presence of juveniles. Our results suggest that in this system, predators behave as opportunistic predators of mara’s juveniles. Mara’s social and reproductive behavior varies along the distribution range of the species, therefore it is of great ecological value to analyze and understand the variations of its interactions with predators in different regions and environments.

Seasonal trend of Eutetranychus orientalis in Moroccan citrus orchards and its potential control by Neoseiulus californicus and Stethorus punctillum

Citrus brown mite, Eutetranychus orientalis (Klein), known as major pest of citrus crops in different countries, was considered as a quarantine pest in Morocco. This pest is currently among the most potential enemies of Moroccan arboriculturists following the increasing ineffectiveness of the majority of acaricides used in conventional orchards. The present study was designed to collect and morphologically identify specimens from 31 orchards in the five main production regions of Morocco; to study the population dynamics of this pest in Taroudant as well as the molecular identification of a Phytoseiid considered as a potential predator using the mitochondrial 12S rRNA gene. Morphological description confirmed that the collected adult females from all orchards in the five regions belong to E. orientalis. Thus, this exotic pest has invaded all citrus growing regions since its introduction. In the Souss region, two significant peaks of population outbreaks of this pest were observed. A first peak from November until the end of December 2017 and in winter, a second peak is recorded in early autumn 2018. Thereafter, mite infestations remained at lower levels throughout the summer. In addition, it appears that eggs represented between 50 to 88.7% of population in spring and winter seasons respectively, but percentage of adult females does not exceed 2.3% in autumn and winter seasons. Adult females of Neoseiulus californicus, larvae of Stethorus punctillum, were more abundant and very active on orange leaves and weeds during period of observation. Molecular analysis using 12S ribosomal RNA gene confirmed that the best query coverage 99.23% (E-value = 5e-176) with 99% of recovery identical to N. californicus. The phylogenetic tree obtained from comparison of the specimens’ generated DNA sequences with other individuals from Neoseiulus genus revealed the relationship with species N. californicus. These results suggest that orchard management will favour the plant cover associated with citrus trees and thus ensure sustainability, diversity and high density of phytoseiides and other predatory insects. This auxiliary fauna, like N. californicus, S. punctillum, will be able to control spider mites, as well as other phytophagous insects and keep them below damaging levels in citrus orchards in the Souss region.

Protistan grazing impacts microbial communities and carbon cycling at deep-sea hydrothermal vents

Microbial eukaryotes (or protists) in marine ecosystems are a link between primary producers and all higher trophic levels, and the rate at which heterotrophic protistan grazers consume microbial prey is a key mechanism for carbon transport and recycling in microbial food webs. At deep-sea hydrothermal vents, chemosynthetic bacteria and archaea form the base of a food web that functions in the absence of sunlight, but the role of protistan grazers in these highly productive ecosystems is largely unexplored. Here, we pair grazing experiments with a molecular survey to quantify protistan grazing and to characterize the composition of vent-associated protists in low-temperature diffuse venting fluids from Gorda Ridge in the northeast Pacific Ocean. Results reveal protists exert higher predation pressure at vents compared to the surrounding deep seawater environment and may account for consuming 28 to 62% of the daily stock of prokaryotic biomass within discharging hydrothermal vent fluids. The vent-associated protistan community was more species rich relative to the background deep sea, and patterns in the distribution and co-occurrence of vent microbes provide additional insights into potential predator–prey interactions. Ciliates, followed by dinoflagellates, Syndiniales, rhizaria, and stramenopiles, dominated the vent protistan community and included bacterivorous species, species known to host symbionts, and parasites. Our findings provide an estimate of protistan grazing pressure within hydrothermal vent food webs, highlighting the important role that diverse protistan communities play in deep-sea carbon cycling.

Predicting multi-predator risk to elk (Cervus canadensis) using scats: Are migrant elk exposed to different predation risk?

There is evidence that prey can perceive the risk of predation and alter their behaviour in response, resulting in changes in spatial distribution and potential fitness consequences. Previous approaches to mapping predation risk quantify predator space use to estimate potential predator-prey encounters, yet this approach does not account for successful predator attacks resulting in prey mortality. An exception is a prey kill-site, which reflects an encounter resulting in mortality, but obtaining these data can be expensive and requires time to accumulate adequate sample sizes. We illustrate an alternative approach using predator scat locations and their contents to quantify spatial predation risk for elk (Cervus canadensis) from multiple predators in Alberta, Canada. We combined predictions of scat-based resource selection functions for bears (Ursus arctos/U. americanus), cougars (Puma concolor), coyotes (Canis latrans), and wolves (C. lupus) based on scat-detection dog surveys with predictions for the probability that a predator-specific scat in a location contained elk. We evaluated our approach by comparing predictions to a predation risk model developed from elk kill sites and applied it to describing spatial patterns in predation risk that were consistent with changes in the distribution of elk over the past decade. We found a strong correlation between risk predicted by kill sites and risk predicted by our approach (r = 0.98, P < 0.001). There was a spatial pattern to predation risk, where elk that migrated east of their winter range were exposed to highest risk from cougars, non-migratory elk were exposed to high risk from wolves and bears, and risk to elk that migrated west of their winter range into protected areas was high only from bears. The patterns in predator risk were consistent with changes in the migratory tactics in this population. The scat-based approach we present permits broad-scale inferences on predation risk for prey.

Predicting multi-predator risk to elk (Cervus canadensis) using scats: Are migrant elk exposed to different predation risk?

There is evidence that prey can perceive the risk of predation and alter their behaviour in response, resulting in changes in spatial distribution and potential fitness consequences. Previous approaches to mapping predation risk quantify predator space use to estimate potential predator-prey encounters, yet this approach does not account for successful predator attacks resulting in prey mortality. An exception is a prey kill-site, which reflects an encounter resulting in mortality, but obtaining these data can be expensive and requires time to accumulate adequate sample sizes. We illustrate an alternative approach using predator scat locations and their contents to quantify spatial predation risk for elk (Cervus canadensis) from multiple predators in Alberta, Canada. We combined predictions of scat-based resource selection functions for bears (Ursus arctos/U. americanus), cougars (Puma concolor), coyotes (Canis latrans), and wolves (C. lupus) based on scat-detection dog surveys with predictions for the probability that a predator-specific scat in a location contained elk. We evaluated our approach by comparing predictions to a predation risk model developed from elk kill sites and applied it to describing spatial patterns in predation risk that were consistent with changes in the distribution of elk over the past decade. We found a strong correlation between risk predicted by kill sites and risk predicted by our approach (r = 0.98, P < 0.001). There was a spatial pattern to predation risk, where elk that migrated east of their winter range were exposed to highest risk from cougars, non-migratory elk were exposed to high risk from wolves and bears, and risk to elk that migrated west of their winter range into protected areas was high only from bears. The patterns in predator risk were consistent with changes in the migratory tactics in this population. The scat-based approach we present permits broad-scale inferences on predation risk for prey.

DNA screening of Drosophila suzukii predators in berry field orchards shows new predatory taxonomical groups

Drosophila suzukii (spotted wing drosophila, SWD) is a pandemic quarantine pest that attacks mostly red fruits. The high number of life cycles per year, its ability to rapidly invade and spread across new habitats, and highly polyphagous nature, makes this a particularly aggressive invasive species, for which efficient control methods are currently lacking. The use of native natural predators is particularly promising to anchor sustainable and efficient measures to control SWD. While several field studies have suggested the presence of potential predatory species in infested orchards, only a few confirmed the presence of SWD DNA in predators’ gut content. Here, we use a DNA-based approach to identify SWD predators among the arthropod diversity in South Europe, by examining the gut content of potential predator specimens collected in SWD-infested berry fields in North Portugal. These specimens were morphologically identified to the family/order, and their gut content was screened for the presence of SWD DNA using PCR. New SWD predatory taxonomical groups were identified, as Opiliones and Hemerobiidae, in addition to known SWD predators, such as Hemerobiidae, Chrysopidae, Miridae, Carabidae, Formicidae and Araneae. Additionally, the presence of a spider family, Uloboridae, in the orchards was recorded for the first time, posing this family as another SWD-candidate predator. This study sets important bases to further investigate the potential large-scale use of some of these confirmed predator taxa for SWD control in South Europe.

Risk-taking behaviour as a central concept in evolutionary biology

Predation is a common cause of mortality, having resulted in the evolution of a diverse kind of anti-predator behaviour across the animal kingdom. One such key behaviour is flight initiation distance (FID), defined as the distance at which animals take flight, when approached by a potential predator such as a human. Extensive research during the past two decades has revealed that optimal anti-predator behaviour is adjusted to life history (the combination of timing of reproduction, fecundity, survivorship, and others). FID is heritable, responds to natural selection and hence shows rapid micro-evolutionary change when animals are exposed to domestication, climate warming, or when introduced to novel environments. Peri-personal space (PPS) and inter-personal space (IPS) may be linked to FID, opening up the possibility of studying these disparate components of behaviour in a common context. Here, I provide a brief review of the extensive literature on FID, but much less well-studied PPS and IPS, and suggest ways in which such behaviour can provide insights into the evolution of anti-predator behaviour and life history. Such knowledge may help us resolve problems in conservation, effects of human disturbance on wild animals, problems of anti-predator behaviour for animal welfare, and potentially even maladaptive anti-predator behaviour and PPS and IPS in humans.

Effect of Potential Sea Lamprey (Petromyzon marinus) Repellents on the Distribution of Juvenile Rainbow Trout (Oncorhynchus mykiss) in a Laboratory Environment

Recent studies have begun to consider the use of chemosensory alarm cues as potential repellents of invasive Sea Lamprey (Petromyzon marinus Linnaeus, 1758) in the Great Lakes Basin. An important factor in determining the efficacy of potential P. marinus repellents is whether they are species-specific. To that end, using laboratory stream channels, this study investigated whether a non-target species, the Rainbow Trout (Oncorhynchus mykiss Walbaum, 1792), would change their distribution in response to damage-released P. marinus alarm cues, potential mammalian predator cues, and damage-released conspecific cues. In groups of 10 individuals per replicate, with 10 replicates per stimulus type, subjects were exposed to one of the following treatment types: deionized water (control), P. marinus extract (heterospecific alarm cue), O. mykiss extract (conspecific alarm cue), 2-phenylethylamine hydrochloride (potential predator cue), and human saliva (potential predator cue). None of the stimuli induced a significant avoidance response during the stimulus observation period as compared to the control. These findings provide preliminary support for the species-specific nature of these proposed alternative P. marinus control measures.