Crop identity and memory effects on aboveground arthropods in a long‐term crop rotation experiment

Agricultural landscapes are globally dominated by monocultures under intensive management. This is one of the main reasons for biodiversity loss and insect population decline in many regions all over the world. Agroecosystem biodiversity in these areas can be enhanced by cropping system diversification, such as crop rotations. Yet, long‐term studies on effects of crop rotations on aboveground agrobiodiversity are lacking. We set up a 10‐year long‐term crop rotation experiment in Central Germany and monitored the temporal dynamics of aboveground arthropods over a full cultivation period to investigate influence of current and preceding crop identity and cropping system diversification on activity density, species richness, and community structure. We found that species composition was strongly influenced by currently grown crop although effect on arthropods varied between species groups. Especially, winter oilseed rape strongly affects arthropod community structure. Interestingly, we were also able to show an influence of the preceding crops, indicating an ecological memory effect in the aboveground arthropod community. Our results show that crop identity of both currently and previously grown crops in crop rotations may lead to an increase in arthropod activity density and changes in species composition. Diversified crop rotations including appropriate crops can be an easily implemented tool to increase arthropod biodiversity and biomass at large spatial and temporal scales, particularly in areas dominated by a single crop (e.g., wheat, maize). Our results may help to design optimized crop rotations for large‐scale enhancement of insect biodiversity in agroecosystems.     

Symbiotic fungi as biotechnological tools: Methodological challenges and relative benefits in agriculture and forestry

Environmental conditions are becoming increasingly challenging in managed ecosystems, especially in agricultural fields, where environmentally friendly solutions are urgently needed. Fungal symbionts offer great opportunities to enhance crop production and ecosystem sustainability under environmental stress. Some fungi are relatively well investigated (e.g., arbuscular mycorrhiza) and regularly used in commercial products, while others, such as fungal endophytes, are not well-known in this market, yet. Here, we review I) the characteristics and benefits, II) the advantages and challenges of principal isolation, preservation, inoculation, and field applications methods, and III) the environmental stress resistance mechanisms for different beneficial fungi. Utilization of mycorrhizae is still facing many challenges, particularly in terms of acquiring pure cultures and successfully establishing their symbiosis in the field. Effects of mycorrhizal associations on the above-ground organs through molecular mechanisms are not fully understood. Although biochemical values of some endophytes are well recognized, molecular mechanisms involved in endophytic-induced stress tolerance are poorly known. Fungal endophytes present several important advantages over mycorrhizal fungi including broader host range as well as straightforward isolation and application protocols. Further studies are necessary for selecting the best strains and communities, producing inoculum on a large-scale, and understanding the potential environmental hazards.     

Phylogeny and evolutionary history of diplobathrid crinoids (Echinodermata)

Order Diplobathrida is a major clade of camerate crinoids spanning the Ordovician–Mississippian, yet phylogenetic relationships have only been inferred for Ordovician taxa. This has hampered efforts to construct a comprehensive tree of life for crinoids and develop a classification scheme that adequately reflects diplobathrid evolutionary history. Here, I apply maximum parsimony and Bayesian phylogenetic approaches to the fossil record of diplobathrids to infer the largest tree of fossil crinoids to date, with over 100 genera included. Recovered trees provide a framework for evaluating the current classification of diplobathrids. Notably, previous suborder divisions are not supported, and superfamily divisions will require significant modification. Although numerous revisions are required for families, most can be retained through reassignment of genera. In addition, recovered trees were used to produce phylogeny‐based estimates of diplobathrid lineage diversity. By accounting for ghost lineages, phylogeny‐based richness estimates offer greater insight into diversification and extinction dynamics than traditional taxonomy‐based approaches alone and provide a detailed summary of the ~150 million‐year evolutionary history of Diplobathrida. This study constitutes a major step toward producing a phylogeny of the Crinoidea and documenting crinoid diversity dynamics. In addition, it will serve as a framework for subsequent phylogeny‐based investigations of macroevolutionary questions.     

The control of the proventriculus in the honeybee (Apis mellifera carnica L.) II. Feedback mechanisms

The mechanisms underlying the control of solution transport rates through the proventriculus in foraging honeybees were investigated in individuals trained to collect defined amounts of sugar solutions. Following feeding, bees were injected either with metabolisable (glucose, fructose, trehalose), or non-metabolisable (sorbose) sugars, in order to distinguish between haemolymph osmolarity and haemolymph sugar levels as factors controlling the solution transport rates through the proventriculus. After a fixed period, workers were dissected in order to measure crop content and haemolymph sugar titers. Between feeding and dissection, the metabolic rate of every investigated forager was measured using open-flow respirometry. Bees injected with metabolisable sugars 15 min after feeding were observed to reduce their solution transport rates through the proventriculus, but injection of non-metabolisable sugars had no influence on them. This suggests that the solution transport rate through the proventriculus is controlled by the concentration of metabolisable compounds in the haemolymph, and not by the haemolymph osmolarity. A period of 10 min after injection of metabolisable sugars was enough to observe reduced solution transport rates. However, if bees were injected only 5 min after feeding, no reduced solution transport rates were observed 10 min after injection.     

Insect antifeedant activity of clerodane diterpenes and related model compounds

A comprehensive compilation of all test results on the insect antifeedant activity of clerodane diterpenes and related model compounds is reported. To increase the compatibility of data from different sources, some of the results reported in the literature have been converted into a standardized form. The compounds were sorted into groups according to the different types of sidechain attached to C-9. Despite the wealth of information, collected in 15 tables, it remains difficult to assign importance to separate structural elements in relation to the observed antifeedant activity. A detailed analysis of the structure-activity relationships could not be presented, but some interesting trends can be distinguished based on the structures of the strongest antifeedants. The compilation covers the literature up to December 2001.     

Central,but not peripheral,glucagon-like peptide-1 inhibits crop emptying in chicks

We investigated the effect of central and peripheral glucagon-like peptide-1 (GLP-1) on crop emptying in growing chicks. Intracerebroventricular injection of two concentrations of GLP-1 (15 and 60 pmol) similarly suppressed crop emptying, compared with control chicks. The delay in crop emptying induced by GLP-1 (15 pmol) was partly attenuated by co-administration with exendin (5-39) (600 pmol), a GLP-1 receptor antagonist, although exendin (5-39) alone did not affect crop emptying. On the other hand, intraperitoneal administration of several doses of GLP-1 (120, 300 and 3000 pmol) did not alter crop emptying. The present study revealed that central, but not peripheral, GLP-1 inhibits crop emptying in chicks.     

Archaeobotanical investigations in Liguria: preliminary data on the early Iron Age at Monte Trabocchetto (Pietra Ligure,Italy)

The archaeological site we studied is part of an early Iron Age hill fort (8th/7th cent. b.c.), located 800 m from the coast on the top of a hill named MonteTrabocchetto. This paper concerns an excavation, called saggio O, which disclosed a very varied stratigraphy characterised by highly anthropogenic layers and by a pit, presumably used as a silo for food storage, which was very rich in charred seeds and fruits. The study of the pit content showed the dominance of Hordeum vulgare, while Triticum dicoccon, T. monococcum, T. aestivum/durum, Panicum miliaceum and Setaria italica were less strongly represented. Some edible Leguminosae were also found (Lens culinaris, Vicia faba var. minor and V. ervilia). In the frequented areas around the pit, herbaceous weeds and fruit tree macro-remains were present (Prunus cf. spinosa, Corylus avellana, Quercus sp. and Vitis vinifera ssp. sylvestris). The identification of a large number of botanical taxa has provided important information on food of plant origin and agricultural practices during the early Iron Age on the Ligurian coast, the proto-historic archaeobotanical aspects of which are largely unknown.     

An improved model of association for VH-VL immunoglobulin domains: asymmetries between VH and VL in the packing of some interface residues

The antibody-binding site is formed as a result of the association between VH and VL domains. Several studies have shown that this association plays an important role in the mechanism of antigen-antibody interaction (Stanfield et al. Structure 1: 83-93, 1993). Considering this, we propose that variations in the VH-VL association are part of the diversification strategy of the antibody repertoires. Previously, a model of association for VH-VL domains based on geometrical characteristics of the packing at the interface was developed by Chothia et al. (J. Mol. Biol. 186: 61-663, 1985). This model includes a common association form for antibodies and a three-layer structure for the interface. In the present work, a complementary model is introduced to account for the general geometrical restrictions of the VH-VL interface, and particular arrangements related to the chemical properties or the side-chain orientations of participating residues. Groups of residues assume common side-chain orientations, which are apparently related to particular functions of different interface zones. Analyses of amino acid usage and network are in agreement with the side-chain orientation patterns. Based on these observations, a three-zone model has evolved to illuminate geometrical and functional restrictions acting over the VH-VL interface. Additionally, this study has revealed the asymmetrical relationships between VH and VL residues important for the association of the two domains.