Edge effects on ground beetles at the woodlot–field interface are short‐range and asymmetrical

• 1 Boundaries between woodlots and agricultural habitats are numerous in temperate agricultural landscapes and influence ecological processes in both woodlots and agricultural habitats.
• 2 We aimed to determine how far the species assemblage of ground beetles in woodlot and open habitats was influenced by the presence of the woodlot–field boundary.
• 3 We studied the distribution of ground beetles on both sides of the boundaries of four woodlots along transects of pitfall traps (n = 140). The depth of edge influence (i.e. the distance from the boundary at which the presence of the boundary has no more significant influence) on the species assemblage of ground beetles in each woodlot and in each agricultural habitat was determined with nonlinear canonical analysis of principal coordinates, an ordination method that is followed by nonlinear regression of the principal coordinates on distance from the boundary.
• 4 The depth of edge influence on the species assemblages of ground beetles was asymmetrical relative to the boundary: it was generally higher and had higher variability in open habitats (14.4 ± 12.3 m) than in woodlots (4.9 ± 2.3 m). Species assemblages of ground beetles in edges were a mix between both adjacent species assemblages. Edge effects in woodlots were deeper in the woodlots exhibiting a deeper penetration of open habitat species. Symmetrically, edge effects in open habitat were deeper in the open habitats with a deeper diffusion of forest species into the open habitat.
• 5 Forest ground beetles were not threatened by edge effects. Rather, edge effects are likely to benefit agriculture, mostly through the dispersal of predatory forest species into agricultural fields.

     

Predation by generalist predators on the codling moth versus a closely‐related emerging pest the oriental fruit moth: a molecular analysis

• 1 Biological control by conservation of native natural enemies can, at its best, reduce the need for pesticides and prevent detrimental effects upon the environment. The present study investigated the role of ground‐active generalist predators as natural enemies of two tortricid pests in apple orchards.
• 2 Predation rates were compared on the well established codling moth Cydia pomonella and the emerging oriental fruit moth Grapholita molesta, which has recently switched hosts to apples.
• 3 The present study hypothesized that the ground‐active predators consumed the two tortricid pests in significant numbers without preference, and attacked the pests at different developmental stages.
• 4 Using diagnostic polymerase chain reaction on the gut contents of field‐caught ground‐active predators, no difference in predation rates was found on these two pests. Spiders were the most efficient predators of emergent adult moths in spring, whereas the carabid beetles, feeding on diapausing larvae, were important in the autumn.
• 5 The temporal complementarity between spiders and carabid beetles, attacking different stages of the pests at different times of year, highlights the need for diverse predator assemblages to optimize biological control.

     

Electrophysiological responses of the chemoreceptor neurones in the antennal taste sensilla to plant alkaloids and glucosides in a granivorous ground beetle

The electrophysiological response of chemoreceptor neurones from the antennal chaetoid taste sensilla of the omnivorous ground beetle Pterostichus oblongopunctatus to several plant alkaloids and glucosides is investigated. A quinine‐sensitive neurone responding to quinine and quinine hydrochloride is found, most probably related to the granivorous feeding habit of P. oblongopunctatus. The response to quinine hydrochloride is concentration‐dependent at 0.001–50 mm , with the response threshold at 0.01 mm and a maximum rate of firing of 67 spikes/s at 50 mm . The stimulatory effect of caffeine is very weak, where the firing rate increases by only 1.4 spikes/s at a concentration of 10 mm compared with that evoked by a control stimulus. In addition, both quinine and quinine hydrochloride strongly inhibit spike production by the salt‐ and pH‐sensitive neurones when presented in mixtures with 10 mm NaCl. Several tested plant secondary compounds (i.e. salicin, sinigrin, caffeine and nicotine), which have only little or no effect on the firing rate of the quinine‐sensitive neurone, greatly reduce the responses of the salt‐ and pH‐sensitive neurones. The results of the present study suggest that the antennal taste sensilla of P. oblongopunctatus may detect plant defensive compounds both through the activation of a quinine‐sensitive neurone and via peripheral inhibition of other chemoreceptor neurones of the taste sensillum.     

Field trials to evaluate effects of Bt-transgenic silage corn expressing the Cry1Ab insecticidal toxin on non-target soil arthropods in northern New England, USA

Traditionally, control of European corn borer (Ostrinia nubilalis) Hübner has been achieved through the use of chemical insecticides. With increasing emphasis on reducing pesticide inputs in agricultural production, alternative management technologies are now being used including transgenic silage corn modified to express Cry1Ab protein toxins derived from Bacillus thuringiensis (Bt) Berliner. The Cry1Ab toxin is expressed by all plant cells and throughout the growing season. Furthermore, the toxins are exuded from corn plant roots into the rhizosphere, raising concerns over possible side-effects on non-target beneficial organisms in the same habitat. In addition, detrivores are exposed to crop residues containing the toxin when incorporated into the soil. The current 2-year study (2003, 2004) evaluated effects of two silage-corn varieties: Pioneer var. 38A25 (Bt-corn expressing the Cry1Ab toxin) and Pioneer var. 38A24 (parent isoline) on species diversity and evenness of carabid beetles and Collembola. Pitfall traps were used to collect surface-dwelling species on a bimonthly schedule from April to October. Soil cores were taken once a month from April to October to sample subterranean species, which were extracted using Berlese funnels. All individuals were recorded and identified where possible to species level for analysis in the Simpson’s D and Shannon–Wiener H’ diversity indices. Evenness was measured using Simpson’s E’, after which dominant species were analyzed in a multivariate ordination analysis. Results showed Bt-corn had no negative effects on any of the organisms analyzed. There was a significant year effect on the abundance of surface-dwelling Collembola and on species diversity of soil-dwelling Collembola. Our findings suggest that crop management practices and/or environmental conditions (e.g., heavy rainfall during the 2004 growing season) had the greatest impact on species diversity and evenness, rather than the crop itself (Bt or isoline).     

Tackling the taxonomic impediment: a global assessment for ant‐nest beetle diversity (Coleoptera: Carabidae: Paussini)

We evaluated the completeness and historical trends of the taxonomic knowledge of the myrmecophilous ground beetle tribe Paussini (Coleoptera, Carabidae, Paussinae). Species accumulation curves were modelled using a logistic function. Similar analyses were conducted for genera and subgenera. Although not all biogeographical regions have been equally explored, accumulation curves reached a plateau in all cases. Our models predict that about 96% of the world fauna has been already described. However, the asymptotes calculated for the Australian and Oriental species should be interpreted as false plateaus because of the lack of recent research. Similarly, patterns of genera accumulation indicate that a plateau has been reached. As a result of continued debate on the use and validity of Paussini subgenera, the accumulation curves of subgenera showed stepped patterns, with no evidence of plateaus. Thus, although relatively few species are expected to be described in the future, the species accumulation curves indicate that the taxonomic inventory is not yet complete. Differences in accumulation patterns among biogeographical regions can be used to highlight the areas where more species are expected, and hence where taxonomical efforts should be concentrated. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105 , 330–339.     

Isolation and characterization of microsatellite loci in Galápagos caterpillar hunters (Coleoptera,Carabidae, Calosoma)

Five microsatellite loci were isolated from the Galápagos caterpillar hunter Calosoma granatense. Polymorphism ranges from four to 14 alleles, and observed and expected heterozygosities range from 0.138 to 0.889 and 0.197–0.902, respectively. Cross‐amplification of the developed primers was successful in the related species C. leleuporum.     

Long-termed changes in ground beetle (Coleoptera: Carabidae) assemblages in a field treated by organic fertilizers

In 2001–2006, ground beetles were pitfall-trapped in a temperate lowland area of South Slovakia in an experimental field divided in five plots fertilized by four different doses of manure or biosludge (25 t stable manure ha⁻¹, 50 t biosludge ha⁻¹, 50 t stable manure ha⁻¹, 100 t biosludge ha⁻¹ and without fertilization). The field was subsequently sown by spring barley, sugar beat, maize, sunflower, sugar beat and maize. The ground beetle assemblage consisted of 31 species, but only five species predominated: Pseudoophonus rufipes representing 82.6% of individuals and five species (Poecilus cupreus, Carabus scheidleri, Calathus fuscipes, Trechus quadristriatus, Pterostichus melanarius, Anchomenus dorsalis, Dolichus halensis) representing together 14.5% of individuals. Pseudophonus rufipes represented 81.7% of dry biomass and three species (Carabus scheidleri, Poecilus cupreus Pterostichus melanarius) 15.9% of biomass. There was no significant influence of organic fertilizing on assemblage structure. During the investigation, the number of individuals and their biomass increased in all plots until 2003 and than dropped to the starting values. The culmination of 2003 was preceded by a warmer and more humid season in 2002. After a cold and dry season of 2003 abundance decreased approximately to starting values. Simultaneously, the local maxima and minima of occurrence of ground beetles in individual plots shifted independently on the doses of organic material. At the same time, number of occurring species slightly decreased. The observed changes obviously represent part of long-termed fluctuations in wider surroundings.     

Response of the foraging behaviour of red wood ants (Formica rufa group) to exclusion from trees

Abstract 1 Because of the large numbers within a colony and their aggressive nature, red wood ants (Formica rufa group) have a potential to greatly influence the cold‐temperate forest ecosystem. Wood ants are omnivorous and hunt in trees as well as on the forest floor. 2 A field experiment in a mixed forest in central Sweden was carried out to examine (i) the foraging behaviour of wood ants on the forest floor and (ii) the impact of increased numbers of wood ants on the soil fauna. The foraging behaviour of wood ants was manipulated by excluding the ants from their food resources in the tree canopy, with the intention to increase ant activity on the forest floor. To estimate this activity, the number of trees with foraging ants, the numbers of ants going to and from their nests and the prey carried by home‐running wood ants were determined during the summer period. Pitfall traps were placed in the soil to determine effects on mobile soil invertebrates. 3 When excluded from local trees, wood ants searched other trees further away from the nests rather than searching more intensively for prey on the forest floor. By contrast to the initial hypothesis, more soil‐living prey were caught by ants in the control plots than in the plots where the local trees were not accessible to the wood ants. The proportion of soil‐living to tree‐living prey tended to be greater in the control plots. 4 In the treated plots (no access to the trees), wood ants had a negative effect on the activity of Linyphiidae spiders. There was little effect of wood ants on other soil invertebrates. 5 This study suggests that the role of wood ants as top predators in the forest soil food‐web in central Sweden is limited.     

Investigating the relationships between the distribution of British ground beetle species (Coleoptera, Carabidae) and temperature, precipitation and altitude

Aims We examine the relationships between the distribution of British ground beetle species and climatic and altitude variables with a view to developing models for evaluating the impact of climate change. Location Data from 1684 10‐km squares in Britain were used to model species–climate/altitude relationships. A validation data set was composed of data from 326 British 10‐km squares not used in the model data set. Methods The relationships between incidence and climate and altitude variables for 137 ground beetle species were investigated using logistic regression. The models produced were subjected to a validation exercise using the Kappa statistic with a second data set of 30 species. Distribution patterns for four species were predicted for Britain using the regression equations generated. Results As many as 136 ground beetle species showed significant relationships with one or more of the altitude and climatic variables but the amount of variation explained by the models was generally poor. Models explaining 20% or more of the variation in species incidence were generated for only 10 species. Mean summer temperature and mean annual temperature were the best predictors for eight and six of these 10 species respectively. Few models based on altitude, annual precipitation and mean winter temperature were good predictors of ground beetle species distribution. The results of the validation exercise were mixed, with models for four species showing good or moderate fits whilst the remainder were poor. Main conclusions Whilst there were many significant relationships between British ground beetle species distributions and altitude and climatic variables, these variables did not appear to be good predictors of ground beetle species distribution. The poor model performance appears to be related to the coarse nature of the response and predictor data sets and the absence of key predictors from the models.