Food selection and fitness optimisation in insects

To optimise fitness is a continuous process which assists species survival in changing environments. Choosing an optimal diet is an essential part of the optimisation process and a key element of optimal foraging theory. The relationship between food choice and fitness optimisation has been tested on three ground beetles and several collembolan species by using food items naturally occurring in the same habitat as the animals. The ground beetles Harpalus rufipes and Amara similata are considered being seed-eaters but can include insects in their diet in the field. An addition of insect species to a mixture of seeds did not improve beetle fitness, though a seed mixture was of a higher quality to the beetles than seeds of single plant species. However the beetles did not show a high degree of selectivity between the specific seed species and their choice was not always in agreement with the quality of the seeds. The collembolans, on the other hand, showed a high degree of selectivity and Folsomia fimetaria, Protaphorura armata and Heteromurus nitidus preferred fungi that optimised their growth, survival and fecundity. Folsomia fimetaria could even select the optimal food when a fungal species was grown in different soil substrates. The high degree of selectivity corresponding to food quality that was seen in the collembolans might be due to a production of fungal odour that can be detected by the collembolans. Plants producing proteinase inhibitors experience reduced attacks by herbivores thus the effect on predators feeding on the herbivores was studied. The herbivorous caterpillar Helicoverpa armigera was fed an artificial diet containing a proteinase inhibitor and the ground beetle Harpalus affinis was fed with H. armigera. H. affinis reduced its feeding when the caterpillars had been fed the proteinase inhibitor containing diet. This indicates that changes in food quality at the plant trophic level cascaded to the predator trophic level. In spite of the many laboratory studies we still lack knowledge of selection of food in the field for this insects. A PCR-based method to detect DNA of ingested food species has been developed. Diversity of fungi found in the gut of collembolans was low compared to that of whole animals. This might be due to the dissection method where the head with mouthparts and the uppermost part of the gut was discharged, which presumably contains most undigested fungal material. This method will make it possible to study food selective behaviour of cryptic soil organisms in the future

Carbon quality rather than stoichiometry controls litter decomposition in a tropical rain forest

1. Ecological stoichiometry predicts important control of the relative abundance of the key elements carbon (C), nitrogen (N) and phosphorus (P) on trophic interactions. In a nutrient-poor Amazonian lowland rain forest of French Guiana, we tested the hypothesis that decomposers exploit stoichiometrically diverse plant litter more efficiently, resulting in faster litter decomposition compared to litter with a uniform stoichiometry. 2. In a field experiment in the presence or absence of soil macrofauna, we measured litter mass loss, and N and P dynamics from all possible combinations of leaf litter from four common tree species which were distinctly separated along a C:N and along a N:P gradient. 3. Mean litter mass remaining after 204†days of field exposure varied between 25.2% and 71.3% among litter treatments. Fauna increased litter mass loss by 18%, N loss by 21% and P loss by 14%. Litter species richness had no effect on litter mass loss or nutrient dynamics. In contrast, litter mass and nutrient losses increased with increasing stoichiometric dissimilarity of litter mixtures in presence of fauna, suggesting faster decomposition of a stoichiometrically more heterogeneous litter. 4. However, the effect of stoichiometric dissimilarity was smaller than the strong C quality related litter composition effect and disappeared in the absence of fauna. Increasing proportions of litter that is relatively rich in accessible C compounds (non-structural carbohydrates, phenolics) and relatively poor in recalcitrant C (condensed tannins, lignin), correlated best with litter mass loss irrespective of fauna presence. No correlation was found for any of the nutrient related litter quality parameters and decomposition. 5.Synthesis. Our results suggest that Amazonian decomposer communities studied here are primarily limited by energy, and only secondarily by litter stoichiometry. Tropical tree species might thus influence decomposers and detritivores by the production of litter of specific C quality with potentially important feedback effects on ecosystem nutrient dynamics and availability

Organic amendment and fungal species in combination can alter collembolan fitness

Organic material of different origin is commonly used as fertiliser in agricultural practices. Clover and wheat straw are here used to determine the importance of organic amendment for population development of fungal feeding collembolans. Two fungal species, Alternaria infectoria and Mucor hiemalis, were inoculated in three growth substrates, clover amended soil, straw amended soil and non-amended soil, where both amendments and the soil originated from agricultural fields. Food choice as well as growth rate, survival and fecundity of the collembolan, Folsomia fimetaria, were measured when fed fungi grown in the three substrates. The type of amendment altered food quality of the two fungi, which was reflected in the collembolan food preference. Growth and fecundity of F. fimetaria were enhanced when fed M. hiemalis grown in both types of plant amended soils. F. fimetaria had a slightly higher fitness when fed A. infectoria grown in the straw amended soil, whereas it's fitness decreased when fed with A. infectoria grown in clover amended soil. We also examined how the predatory mite, Hypoaspis aculeifer, was attracted towards the two fungi as it uses the fungal odour as a potential cue of a prey habitat. H. aculeifer was attracted to both fungi when they were grown in clover amended soil where fungal growth also was observed to be massive. Thus, we conclude that amendment applications can cause effects that cascade through several trophic levels. (C) 2013 Elsevier Ltd. All rights reserved

Collembolan dietary specialisation on soil grown fungi

Preferences of six collembolans for eight species of microfungi grown in soil have been investigated. Collembolans (Folsomia fimetaria, Isotoma anglicana, Isotama notabilis, Heteromurus nitidus, Protaphorura armata, Pseudosinella alba) and microfungi where chosen for the experiment on the basis of their abundance and vertical distribution in an organically grown field where all organisms and soil were collected. Collembolans were tested with pairs of different species of microfungi and a control (sterile soil) in petri dishes and their position determined after 90 min. Based on the first two axes in a Principal Component Analysis we could identify two main feeding patterns in the collembolans: (1) their general acceptance of the fungi (the mean value of the preference indices for all eight fungi), and (2) their alternating preference for Cladosporium herbarum and Fusarium culmorum (high preference index for C. herbarum and low for F. culmorum or vice versa). The six collembolan species in our study combined these two feeding patterns with an intraspecific preference for the eight fungal species and seemed to minimise food competition among collembolans co-occurring in the same soil horizons. Our data suggest that differences in preference between collembolan species may help to explain the coexistence of many species in the same microhabitats of the soil

What are the effects of agricultural management on soil organic carbon (SOC) stocks?

Background: Changes in soil organic carbon (SOC) stocks significantly influence the atmospheric C concentration. Agricultural management practices that increase SOC stocks thus may have profound effects on climate mitigation. Additional benefits include higher soil fertility since increased SOC stocks improve the physical and biological properties of the soil. Intensification of agriculture and land-use change from grasslands to croplands are generally known to deplete SOC stocks. The depletion is exacerbated through agricultural practices with low return of organic material and various mechanisms, such as oxidation/mineralization, leaching and erosion. However, a systematic review comparing the efficacy of different agricultural management practices to increase SOC stocks has not yet been produced. Since there are diverging views on this matter, a systematic review would be timely for framing policies not only nationally in Sweden, but also internationally, for promoting long-term sustainable management of soils and mitigating climate change. Methods: The systematic review will examine how changes in SOC are affected by a range of soil-management practices relating to tillage management, addition of crop residues, manure or other organic -wastes-, and different crop rotation schemes. Within the warm temperate and the snow climate zones, agricultural management systems in which wheat, barley, rye, oats, silage maize or oilseed rape can grow in the crop rotation will be selected. The review will exclusively focus on studies conducted over at least 10 years. Searches will be made in 15 publication databases as well as in specialist databases. Articles found will be screened using inclusion/exclusion criteria at title, abstract and full-text levels, and screening consistency will be evaluated using Kappa tests. Data from articles that remain after critical appraisal will be extracted using a predefined spreadsheet. Subgroup analyses will be undertaken to elucidate statistical relationships that are specific to particular type of management interventions. Meta-regression within subgroups will be performed as well as sensitivity analysis to investigate the impact of removing groups of studies with low or unclear quality

What are the effects of agricultural management on soil organic carbon in boreo-temperate systems?

Background: Soils contain the largest stock of organic carbon (C) in terrestrial ecosystems and changes in soil C stocks may significantly affect atmospheric CO2. A significant part of soil C is present in cultivated soils that occupy about 35 % of the global land surface. Agricultural intensification has led to practices that may decrease soil organic carbon (SOC), and agricultural management has the potential to be a powerful tool for climate change mitigation and increased soil fertility through SOC sequestration. Here, we systematically map evidence relating to the impacts of agricultural management on SOC in arable systems of the warm temperate and snow climate zones (subset of temperate and continental climates: Köppen–Geiger Classification). Methods: Seventeen academic citation databases, 3 search engines and 25 organisational websites were searched for literature (academic and grey) using search strings translated into a range of languages relevant to the included geographical scope of the topic. Stakeholders were also contacted with requests for evidence. Bibliographic checking of 127 relevant reviews was undertaken to check for missing articles. Screening for relevance against predefined inclusion criteria was undertaken at title, abstract and full text levels according to a published protocol. All relevant studies were coded in a meta-database describing the citation, study settings, methods and quantitative data available (without extraction of the study findings). A basic critical appraisal of included studies was also performed. A geographical information system (GIS) presenting the map database on a physical, online map was also produced. Results: A total of 735 studies from 553 articles was included in the systematic map database. Studies investigated one or more of five broad categories of interventions: amendments (286 studies), crop rotations (238), fertilisers (307), tillage (306), and multiple interventions (55). Studies were identified from across the includible climate zones, with the notable underrepresentation from Russia. The majority of studies employed only point sampling of SOC, low levels of true spatial replication and moderate study periods (i.e. 10–20 years). Missing key methodological information was found in 28 % of studies. Conclusions: Long-term study sites identified in this map provide a useful addition to existing databases of longterm experiments (LTEs). The identification of knowledge gaps, such as studies from Russia, also identify a need for improved cataloguing or reporting of existing and on-going research. This systematic map database represents a useful resource for decision-makers wishing to identify knowledge gaps warranting further primary research, knowledge gluts warranting further secondary research, and deficiencies and best practice in research methodology. In addition to the systematic map database, we have also produced two further resources: (1) a database of LTE sites investigating agricultural management and SOC, and (2) a database of reviews and meta-analyses. To our knowledge, this is the first systematic review or map that utilises a GIS for presentation of an evidence base, which we believe substantially increases the utility of the map outputs

Ekosystemtjänster i det skånska jordbrukslandskapet

Jordbrukslandskapet tillhandahåller ekosystemtjänster som utgör förutsättningen för en uthållig jordbruksproduktion och är till nytta för samhället i stort. Bakom dessa finns ekologiska processer som beror av samspel mellan en mångfald av organismer. Skånes jordbruk har genomgått betydande förändringar som förändrat landskapet och livsmiljön för många av dessa. För att bevara och förvalta ekosystemtjänsterna krävs en förståelse för sambanden mellan jordbruk, landskap och ekosystemprocesser. Rapporten beskriver ekologiska processer som ligger till grund för några viktiga ekosystemtjänster i Skånes jordbrukslandskap och visar betydelsen av biologisk mångfald för deras funktion. Där så är möjligt beskrivs hur de kan värderas. Slutligen redovisas praktiska åtgärder som gynnar dem. Rapporten visar att ekosystemtjänster inte enkelt går att ersätta med teknologiska lösningar, utan att förvaltning av dessa tjänster lönar sig. Detta kräver ökad ekologisk kunskap och anpassade styrmedel vilket kräver ökat samråd och regelbunden återkoppling mellan lantbrukare, myndigheter och forskare. Förhoppningen är att rapporten, framtagen av Lunds universitet och Region Skåne, inspirerar till detta

The impact of Rhinanthus minor in newly established meadows on a productive site

Question: What is the impact of the presence of Rhinanthus minor on forb abundance in newly established swards? Location: Wetherby, West Yorkshire, UK (53 degrees 55' N, 1 degrees 22(1) W). Method: A standard meadow mix containing six forbs and six grasses was sown on an ex-arable field and immediately over-sown using a randomised plot design with three densities of Rhinanthus minor (0, 600, and 1000 seeds per m(2)). Above-ground biomass was analysed over a period of three years, while detailed assessments of sward composition were performed during the first two years. Results: Values of grass biomass were reduced in the presence of Rhinanthus, especially at the higher sowing density. The ratio of grass: forb biomass was also lower in association with Rhinanthus, but only at the higher sowing density. The presence of Rhinanthus, had no effect on species number or diversity, which decreased between years regardless of treatment. Conclusions: Although not tested in a multi-site experiment, the benefit of introducing Rhinanthus into newly established swards to promote for abundance was determined. The efficacy of Rhinanthus presence is likely to depend on whether species not susceptible to the effects of parasitism are present

Long-term effectiveness of sowing high and low diversity seed mixtures to enhance plant community development on ex-arable fields

Questions: How is succession on ex-arable land affected by sowing high and low diversity mixtures of grassland species as compared to natural succession? How long do effects persist? Location: Experimental plots installed in the Czech Republic, The Netherlands, Spain, Sweden and the United Kingdom. Methods: The experiment was established on ex-arable land, with five blocks, each containing three 10 m x 10 m experiment tal plots: natural colonization, a low- (four species) and high-diversity (15 species) seed mixture. Species composition and biomass was followed for eight years. Results: The sown plants considerably affected the whole successional pathway and the effects persisted during the whole eight year period. Whilst the proportion of sown species (characterized by their cover) increased during the study period, the number of sown species started to decrease from the third season onwards. Sowing caused suppression of natural colonizing species, and the sown plots had more biomass. These effects were on average larger in the high diversity mixtures. However, the low diversity replicate sown with the mixture that produced the largest biomass or largest suppression of natural colonizers fell within the range recorded at the five replicates of the high diversity plots. The natural colonization plots usually had the highest total species richness and lowest productivity at the end of the observation period. Conclusions: The effect of sowing demonstrated dispersal limitation as a factor controlling the rate of early secondary succession. Diversity was important primarily for its 'insurance effect': the high diversity mixtures were always able to compensate for the failure of some species