Selection of flowering forbs for conserving natural enemies in rice fields

The diversity of natural enemies harboured by flowering forbs on rice field bunds was recorded. Ageratum conozoides with a maximum Shannon diversity index of 1.8 followed by Acmella uliginosa, Eclipta alba and Tridax procumbens are amenable for ecological engineering, providing nectar, pollen and alternate prey to natural enemies.     

Guild‐level responses by mammalian predators to afforestation and subsequent restoration in a formerly treeless peatland landscape

Afforestation of formerly open landscapes can transform mammalian predator communities, potentially impacting prey species like ground‐nesting birds. In Scotland's Flow Country, a globally important peatland containing many forestry plantations, earlier studies found reduced densities of breeding waders on open bogs, when forestry plantations were present within 700 m. One plausible explanation for this pattern is mammalian predation. We tested whether mammalian predator indices, based on scats (feces), differed between (1) open bog, forestry plantations, and former plantations being restored as bog (“restoration” habitats); (2) restoration habitats of different ages; and (3) open bogs with differing amounts of nearby forestry. We measured summer scat density and size over 14 years in 26 transects 0.6–4.5 km in length, collecting data during 93, 96, and 79 transect‐years in bog, forestry, and restoration habitats respectively. In forestry, scat density increased eightfold, reaching values ~6 times higher than those of bogs. On open bogs with over 10% forestry within 700 m, scat densities were 2.9 times higher than on open bogs with less forestry nearby. Results support the hypothesis that mammalian predators might be responsible for the low densities of breeding waders close to forests, on adjacent open bogs. In restoration habitats, scat densities rose 6–10 years after felling but fell to levels similar to open bogs in older restoration habitats, supporting restoration management as a means of reducing mammalian predator activity/abundance. We urge caution around decisions to establish forestry plantations in open landscapes of high biodiversity importance.     

Entomophagous insects – an introduction

This special issue contains papers presented at the 6th International Entomophagous Insects Conference. Entomophagous insects consume other insects. They are a fundamental component of ecosystems and are extensively used as biocontrol agents. The first article reviews the role of ladybirds in biological control and the second reviews the biological control of stink bugs. The following nine research articles cover the rearing, behavior, life history, and ecology of parasitoid and predator species.     

Predicting bait uptake by feral cats,Felis catus,in semi‐arid environments

Feral cat control using aerial broadcasting of toxic baits continues to be used in the rangelands of Western Australia. The effectiveness of these operations has sometimes been compromised by different environmental factors that affect prey and cat numbers. This study demonstrates that the ratio of cats to their preferred prey (small mammals) can be used to predict the most effective time to bait. The regular baiting of three conservation sites offered an opportunity to study the relationship between feral cat abundance, the abundance of their prey and ingestion of toxic baits. Peron Peninsula on the mid‐west coast, Lorna Glen station in the northern Goldfields and the central Gibson Desert of Western Australia are sites where cat control using toxic baits has been routinely applied over the last 15 years. We postulated that bait ingestion by cats was linked to the availability of live prey. Small mammal abundance (capture rates in pit‐fall traps) and relative cat abundance (based on daily track counts) were assessed at these sites and the data used to produce a predator‐prey ratio index (PPRI). We used generalised linear mixed models to test the effect of prey abundance, prebaiting cat abundance and PPRI on baiting efficacy (BE). The best model for predicting efficacy of baiting contained only PPRI. This simple model was able to predict baiting success over the entire range of outcomes, from highly successful ( >75% cat reduction) to unsuccessful (0% cat reduction). The ability to predict feral cat BE in advance of planned toxic baiting operations will provide a valuable tool for wildlife managers involved in cat control.     

Does the presence of grassy strips and landscape grain affect the spatial distribution of aphids and their carabid predators?

• 1 We investigated, over the course of 2 years, the spatial distribution and abundance of two species of aphid, Metopolophium dirhodum and Sitobion avenae, and predatory species of carabid. This was undertaken in 24 wheat fields in ‘coarse‐grain’ and ‘fine‐grain’ landscapes in western France. A greater percentage of the latter landscape was covered by hedgerows and grassland and the total area covered by fields and the average size of the fields were smaller.
• 2 The effects on aphid abundance of the distance from field margins, the presence of grassy strips and carabid abundance were determined in both landscapes.
• 3 Both aphid species were more abundant in the ‘fine‐grain’ landscape, which may have been a result of the higher density of semi‐natural elements. In both types of landscape, the total numbers of aphids were negatively correlated with the distance from the field margin. This may have been because aphids were dispersing from overwintering sites in field margins. The abundance of M. dirhodum was strongly negatively correlated with the presence of grassy strips in the ‘coarse‐grain’ landscape, although there were no such significant correlations for either of the aphid species in the ‘fine‐grain’ landscape.
• 4 Aphid and carabid abundances were negatively correlated in the ‘fine‐grain’ and positively in ‘coarse‐grain’ landscape.
• 5 The results obtained in the present study emphasize the importance of semi‐natural areas in agricultural landscapes in shaping the spatial distribution of aphids and carabid beetles, their natural enemies, at different spatial scales.

     

Chemosensory responses of Aporcelaimellus nivalis (Nematoda: Dorylaimida) towards kairomones emitted by prey nematodes belonging to different trophic groups

Abstract

Observations were made on the attraction of Aporcelaimellus nivalis towards kairomones/attractants emitted by prey nematodes belonging to different trophic categories, viz., saprophagous, epidermal, migratory semi-endodermal, predatory nematodes, virus vectors and cortical feeders. Aporcelaimellus nivalis responded positively and significantly to prey kairomones, but showed variation in their individual behaviour. Predators are most attracted towards epidermal feeders and least attracted to virus vectors. The differential responses of A. nivalis towards different prey were attributed to the inert behaviour of predators, their preference for a particular species of prey, chemical composition, concentration, quality, quantity of prey attractant, formation of minimum perceptible attraction gradient of prey and minimum response threshold of predators. Various factors such as prey density, period of prey incubation, starvation of predators, temperature, agar concentration, agar thickness and distance of predators from the source of attraction (prey) govern chemosensory responses of predator. Aporcelaimellus nivalis maximum response was towards Hirschmanniella oryzae, when tested as 10 day starved predators in agar plates containing 2 mm thick layer of 1% water-agar with 200 prey individuals previously incubated for 16 h at 30°C. Prey kairomones were most attractive when A. nivalis were tested from a distance of 2 and 3 cm.     

Laboratory studies on extracts of Melia fruit and Neem fruit on B. brassicae,B. tabaci and their predators and parasites

Abstract

The biological effect of plant extracts on the two predators C. carnea and C. undecimpunctata was studied in the laboratory. Treated B. brassicae was offered to the newly hatched larvae of the two predators. The rate of prey consumption and duration of the larval instars of the two predators were slightly affected as a result of the treatments of the plant extracts. Adults of the aphid parasite D. Rapae and the whitefly parasite E. Mundus were exposed to the plant extracts via feeding on treated honey droplets or parasitized treated hosts. Mortality percentages of D. Rapae fed on honey contaminated with plant extracts were 50 and 80% for extracts of Melia fruits in ethanol and in petroleum ether, respectively. Mortalities in parasites developed in hosts treated with plant extracts of Neem fruits in ethanol and Melia flowers in petroleum ether in were 33.3 and 81.5%, respectively. Similar results were obtained when E. Mundus received the same treatments of the plant extracts.     

The largest European lion Panthera leo spelaea (Goldfuss 1810) population from the Zoolithen Cave,Germany: specialised cave bear predators of Europe

Remains of 13 individuals with 3/1 male/female ratio of the extinct Upper Pleistocene lion Panthera leo spelaea (Goldfuss, 1810) from the Zoolithen Cave near Burggeilenreuth (Bavaria, Germany) include the holotype skull and all paratype material. The highest mortality rate for the Zoolithen Cave lions is in their reproductive adult ages. Bite marks on lion bones or skulls are results of hyena activities, or rare cannibalism of lions under stress situations. Lions were possibly also killed in battles with cave bears during predation on hibernating bears in winter times. This cave bear hunt specialisation in caves overlaps with the ecological behaviour of cave bear feeding by Ice Age-spotted hyenas. Both largest Ice Age predators, lions and hyenas, had to specialise on feeding herbivorous cave bears in boreal forest mountainous cave rich regions, where the mammoth steppe megafauna prey was absent. This cave bear hunt by felids, and scavenging by hyenas and other large carnivores such as leopards and wolves explains why cave bears hibernated deep in to the European caves, for protection reasons against predators. Within such lion–cave bear and even lion–hyena conflicts in the caves lions must have been killed sometimes, explaining mainly the skeleton occurrences in different European caves.     

Broad Salinity Tolerance as a Refuge from Predation in the Harmful Raphidophyte Alga Heterosigma akashiwo (Raphidophyceae)

The ability of harmful algal species to form dense, nearly monospecific blooms remains an ecological and evolutionary puzzle. We hypothesized that predation interacts with estuarine salinity gradients to promote blooms of Heterosigma akashiwo (Y. Hada) Y. Hada ex Y. Hara et M. Chihara, a cosmopolitan toxic raphidophyte. Specifically, H. akashiwo's broad salinity tolerance appears to provide a refuge from predation that enhances the net growth of H. akashiwo populations through several mechanisms. (1) Contrasting salinity tolerance of predators and prey. Estuarine H. akashiwo isolates from the west coast of North America grew rapidly at salinities as low as six, and distributed throughout experimental salinity gradients to salinities as low as three. In contrast, survival of most protistan predator species was restricted to salinities >15. (2) H. akashiwo physiological and behavioral plasticity. Acclimation to low salinity enhanced H. akashiwo's ability to accumulate and grow in low salinity waters. In addition, the presence of a ciliate predator altered H. akashiwo swimming behavior, promoting accumulation in low‐salinity surface layers inhospitable to the ciliate. (3) Negative effects of low salinity on predation processes. Ciliate predation rates decreased sharply at salinities <25 and, for one species, H. akashiwo toxicity increased at low salinities. Taken together, these behaviors and responses imply that blooms can readily initiate in low salinity waters where H. akashiwo would experience decreased predation pressure while maintaining near‐maximal growth rates. The salinity structure of a typical estuary would provide this HAB species a unique refuge from predation. Broad salinity tolerance in raphidophytes may have evolved in part as a response to selective pressures associated with predation.     

Can plant–natural enemy communication withstand disruption by biotic and abiotic factors?

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