Ground beetle assemblages inhabiting various age classes of Norway spruce stands in north-eastern Poland

Assemblages of epigeic ground beetles living in Norway spruce forests in north-eastern Poland in three age ranges: young: 20-30 years (A); middle-aged: 40-50 years (B); old: 70-80 years (C) were investigated. In each age category, 4 plots with 5 Barber traps were set up. Ground beetle assemblages were compared in terms of their abundance, species richness, and the Shannon H' index value. Quantitative ecological description of the carabids captured in the analysed age-classes of Norway spruce forests was performed, and the values of the mean individual biomass (MIB) were calculated. To determine the correlation between mean individual biomass and abundance of various ecological groups of carabid beetles, the Spearman rank correlation coefficient was calculated. The assemblages of ground beetles living in the Norway spruce forests in north-eastern Poland were characterised by quite large species richness (44 species in total). There were significant differences in species richness among the different ages of Norway spruce forests. The oldest Norway spruce stands (70-80 years old) had a smaller number of species and specimens of ground beetles as well as the highest MIB values in comparison with the younger spruce forests A and B. The results revealed that high MIB values were positively correlated with the presence of large ground beetle species with higher moisture requirements. Lower values of the MIB index were due to the presence of smaller open habitat macropterous species, with the spring type of breeding and associated with open areas.

Ground beetles (Coleoptera; Carabidae) as an indicator of ongoing changes in forest habitats due to increased water retention

This study, concerning the epigeic fauna of carabid beetles (Coleoptera; Carabidae), was conducted in the north-east of Poland, in an area which is part of the Dąbrówka Forest Subdistrict and has been included in the “Small water retention program for the Province of Warmia and Mazury in 2006–2015”. The purpose of the study was to assess the impact of the water retention implemented within the framework of the above program on assemblages of ground beetles. These insects are highly sensitive to any anthropogenically induced transformations. This analysis was based on the interactions among the analyzed insects caused by changes occurring in their habitat. During the 3-year study, 5,807 specimens representing 84 species were captured. The water storage had a significant influence on the structure of the Carabidae assemblages. Before the earthworks were constructed for the project, the beetle assemblages had comprised a large group of xerophilous species, whereas after the small retention reservoirs had been created, an increase in the contribution of hygrophilous species was noticed. The results indicate that the retention works cause alterations in the water and environmental conditions of the habitats, and thereby effect changes in the composition of Carabidae assemblages. Moreover, modification in water relations within a habitat causes long-term changes in the structural and functional diversity of the beetles.

It's a matter of design-how pitfall trap design affects trap samples and possible predictions

Background

Pitfall traps are commonly used to assess ground dwelling arthropod communities. The effects of different pitfall trap designs on the trapping outcome are poorly investigated however they might affect conclusions drawn from pitfall trap data greatly.

Methods

We tested four pitfall trap types which have been used in previous studies for their effectiveness: a simple type, a faster exchangeable type with an extended plastic rim plate and two types with guidance barriers (V- and X-shaped). About 20 traps were active for 10 weeks and emptied biweekly resulting in 100 trap samples.

Results

Pitfall traps with guidance barriers were up to five times more effective than simple pitfall traps and trap samples resulted in more similar assemblage approximations. Pitfall traps with extended plastic rim plates did not only perform poorly but also resulted in distinct carabid assemblages with less individuals of small species and a larger variation.

Discussion

Due to the obvious trait filtering and resulting altered assemblages, we suggest not to use pitfall traps with extended plastic rim plates. In comprehensive biodiversity inventories, a smaller number of pitfall traps with guidance barriers and a larger number of spatial replicates is of advantage, while due to comparability reasons, the use of simple pitfall traps will be recommended in most other cases.

Orientation behavior is a good biomarker of trace metal contamination in Parallelomorphus laevigatus (Coleoptera, Carabidae)

Behavioral ecotoxicology has become very important in the short time since a change in behavior is very often the first response to environmental altered conditions. We investigated the influence of trace metal intake on the spatial orientation performances of the carabid beetle Parallelomorphus laevigatus, fundamental ability for its survival. The aim of this study was to consider the solar orientation as behavioral biomarker for exposure to trace metal contamination. Therefore, we tested the ability of solar orientation of specimens of this species, fed with shrimps contaminated with three different concentrations of Cu, Zn, or Hg. We carried out the orientation tests after 1, 3, 7, and 10 days of contaminated feeding. Subsequently, we fed these beetles with not contaminated shrimps and again tested them after 1, 3, 7, and 10 days. For all three metals considered and, regardless of the degree of contamination of the food, we have found a progressive and significant counterclockwise displacement of the angle of orientation and a corresponding progressive reduction in the precision in the directional choices by the animals. We also noticed a clear growing recovery in the normal orientation by these insects after returning to their feeding with uncontaminated food. In conclusion, we can consider the orientation in space of P. laevigatus as a behavioral biomarker for exposure to trace metal contamination. We believe that the intake of trace metals may induce the insects to make mistakes in their spatial orientation, due to an acceleration of their biological clock. Such a clock malfunction is not definitive, since the return to a normal diet restores P. laevigatus the ability to re-make the correct directional choices. Ultimately, our results confirm the usefulness of behavioral ecotoxicology investigations; moreover, they stimulate the opportunity to deepen the understanding of functioning of the biological clock in the animals.

Predatory beetles feed more pest beetles at rising temperature

BACKGROUND

Climate warming is a challenge for many plants and animals as they have to respond to rising temperature. Rising temperature was observed to affect herbivores and predators. Activity-density of abundant predatory carabid beetles, which are considered important natural control agents of agricultural pests, was observed to increase at rising temperature. The pollen beetle Meligethes aeneus is one of the most important insect pests in European oilseed rape fields, and its larvae were observed to be important prey to carabid beetles. Therefore, we performed a laboratory experiment to detect whether rising temperature affects the number of pollen beetle larvae killed by five abundant carabids, and larval biomass ingested by carabids. In three climate chambers actual temperature (T1) was compared to temperatures increased by 3 °C (T2) and 5 °C (T3). This is the first study investigating the feeding of carabid predators on an arable pest insect spanning a realistic forecasted climate warming scenario of 3 and 5 °C, thus providing basic knowledge on that neglected research area. We hypothesized that carabids kill more pollen beetle larvae at rising temperature, and biomass intake by carabids increases with rising temperature.

RESULTS

Both beetle species and temperature had significant effects on the number of killed Meligethes larvae and larval biomass ingested by carabids. Amara ovata, Harpalus distinguendus and Poecilus cupreus killed significantly more pollen beetle larvae at T2 and T3 compared to T1. Anchomenus dorsalis killed significantly more larvae at T2 than T1, and Harpalus affinis showed no significant differences among temperatures. Biomass intake by A. ovata, H. distinguendus and A. dorsalis was significantly larger at T2 and T3 compared to T1. Biomass intake by H. affinis and P. cupreus did not significantly differ among temperatures. Among the five carabids tested P. cupreus exhibited the highest values for both number of killed larvae and biomass intake.

CONCLUSIONS

Our lab results suggest a clear potential for higher feeding of pollen beetle larvae by carabid beetles at rising temperature. As rising temperature leads to increased activity of abundant arable carabids in the field, it may be expected that there is enhanced pest suppression under warmer field conditions.

Diagnostic PCR assays to unravel food web interactions in cereal crops with focus on biological control of aphids

Successful biological control of agricultural pests is dependent on a thorough understanding of the underlying trophic interactions between predators and prey. Studying trophic interactions can be challenging, particularly when generalist predators that frequently use multiple prey and interact with both pest and alternative prey are considered. In this context, diagnostic PCR proved to be a suitable approach, however at present, prey-specific PCR primers necessary for assessing such interactions across trophic levels are missing. Here we present a new set of 45 primers designed to target a wide range of invertebrate taxa common to temperate cereal crops: cereal aphids, their natural enemies such as carabid beetles, ladybeetles, lacewings, and spiders, and potential alternative prey groups (earthworms, springtails, and dipterans). These primers were combined in three 'ready to use' multiplex PCR assays for quick and cost-effective analyses of large numbers of predator samples. The assays were tested on 560 carabids collected in barley fields in Sweden. Results from this screening suggest that aphids constitute a major food source for carabids in cereal crops (overall DNA detection rate: 51 %), whereas alternative extraguild and intraguild prey appear to be less frequently preyed upon when aphids are present (11 % for springtails and 12 % for earthworms; 1 % for spiders and 4 % for carabids). In summary, the newly developed molecular assays proved reliable and effective in assessing previously cryptic predator-prey trophic interactions, specifically with focus on biological control of aphids. The diagnostic PCR assays will be applicable manifold as the targeted invertebrates are common to many agricultural systems of the temperate region.

On testing temporal niche differentiation in carabid beetles

It is first shown that den Boer's (1985) claims that competition should be rejected as a factor explaining community structure are not warranted by his tests on temporal niche differentiation in carabid beetles. The power of these tests is so low that they are unlikely to detect even the most extreme pattern of niche differentiation. A major factor that affects their power is the procedure of building up an artificial species pool from the local communities to which the test is to be applied. Alternative tests are then presented, and applied to data on annual activity cycles of carabids in three forest biotopes in Belgium. Three factors are shown to strongly affect their outcome: the unit into which the time scale is divided, the criteria used to incorporate constraints, and the set of species selected. Nevertheless, they provide some evidence that there is a growing niche differentiation from the successional to the climax forest, as predicted by competition theory. Other hypotheses, however, could explain the observed pattern.