Structured populations of the oriental fruit moth in an agricultural ecosystem.

Intercontinental trade has led to multiple introductions of invasive pest species at a global scale. Molecular analyses of the structure of populations support the understanding of ecological strategies and evolutionary patterns that promote successful biological invasions. The oriental fruit moth, Grapholita (= Cydia) molesta, is a cosmopolitan and economically destructive pest of stone and pome fruits, expanding its distribution range concomitantly with global climate warming. We used ten newly developed polymorphic microsatellite markers to examine the genetic structure of G. molesta populations in an agricultural ecosystem in the Emilia-Romagna region of northern Italy. Larvae collected in eight sampling sites were assigned to a mosaic of five populations with significant intra-regional structure. Inferred measures of gene flow within populations implicated both active dispersal, and passive dispersal associated with accidental anthropogenic displacements. Small effective population sizes, coupled with high inbreeding levels, highlighted the effect of orchard management practices on the observed patterns of genetic variation within the sampling sites. Isolation by distance did not appear to play a major role at the spatial scale considered. Our results provide new insights into the population genetics and dynamics of an invasive pest species at a regional scale.

Long foraging distances impose high costs on offspring production in solitary bees.

1. Solitary bees are central place foragers returning to their nests several times a day with pollen and nectar to provision their brood cells. They are especially susceptible to landscape changes that lead to an increased spatial separation of suitable nesting sites and flower rich host plant stands. While knowledge of bee foraging ranges is currently growing, quantitative data on the costs of foraging flights are very scarce, although such data are crucial to understand bee population dynamics. 2. In this study, the impact of increased foraging distance on the duration of foraging bouts and on the number of brood cells provisioned per time unit was experimentally quantified in the two pollen specialist solitary bee species Hoplitis adunca and Chelostoma rapunculi. Females nesting at different sites foraged under the same environmental conditions on a single large and movable flowering host plant patch in an otherwise host plant free landscape. 3. The number of brood cells provisioned per time unit by H. adunca was found to decrease by 23%, 31% and 26% with an increase in the foraging distance by 150, 200 and 300 m, respectively. The number of brood cells provisioned by C. rapunculi decreased by 46% and 36% with an increase in the foraging distance by 500 and 600 m, respectively. 4. Contrary to expectation, a widely scattered arrangement of host plants did not result in longer mean duration of a foraging bout in H. adunca compared to a highly aggregated arrangement, which might be due to a reduced flight directionality combined with a high rate of revisitation of already depleted flowers in the aggregated plant arrangement or by a stronger competition and disturbance by other flower visitors. 5. The results of this study clearly indicate that a close neighbourhood of suitable nesting and foraging habitats is crucial for population persistence and thus conservation of endangered solitary bee species.

Biased dispersal of Metrioptera bicolor, a wing dimorphic bush-cricket.

In the highly fragmented landscape of central Europe, dispersal is of particular importance as it determines the long-term survival of animal populations. Dispersal not only secures the recolonization of patches where populations went extinct, it may also rescue small populations and thus prevent local extinction events. As dispersal involves different individual fitness costs, the decision to disperse should not be random but context-dependent and often will be biased toward a certain group of individuals (e.g., sex- and wing morph-biased dispersal). Although biased dispersal has far-reaching consequences for animal populations, immediate studies of sex- and wing morph-biased dispersal in orthopterans are very rare. Here, we used a combined approach of morphological and genetic analyses to investigate biased dispersal of Metrioptera bicolor, a wing dimorphic bush-cricket. Our results clearly show wing morph-biased dispersal for both sexes of M. bicolor. In addition, we found sex-biased dispersal for macropterous individuals, but not for micropters. Both, morphological and genetic data, favor macropterous males as dispersal unit of this bush-cricket species. To get an idea of the flight ability of M. bicolor, we compared our morphological data with that of Locusta migratoria and Schistocerca gregaria, which are very good flyers. Based on our morphological data, we suggest a good flight ability for macropters of M. bicolor, although flying individuals of this species are seldom observed.

Validation of a novel, fully integrated and flexible microarray benchtop facility for gene expression profiling.

Here we describe a novel microarray platform that integrates all functions needed to perform any array-based experiment in a compact instrument on the researcher's laboratory benchtop. Oligonucle otide probes are synthesized in situ via a light- activated process within the channels of a three-dimensional microfluidic reaction carrier. Arrays can be designed and produced within hours according to the user's requirements. They are processed in a fully automatic workflow. We have characterized this new platform with regard to dynamic range, discrimination power, reproducibility and accuracy of biological results. The instrument detects sample RNAs present at a frequency of 1:100 000. Detection is quantitative over more than two orders of magnitude. Experiments on four identical arrays with 6398 features each revealed a mean coefficient of variation (CV) value of 0.09 for the 6398 unprocessed raw intensities indicating high reproducibility. In a more elaborate experiment targeting 1125 yeast genes from an unbiased selection, a mean CV of 0.11 on the fold change level was found. Analyzing the transcriptional response of yeast to osmotic shock, we found that biological data acquired on our platform are in good agreement with data from Affymetrix GeneChips, quantitative real-time PCR and--albeit somewhat less clearly--to data from spotted cDNA arrays obtained from the literature.

The effect of translocation on movement behaviour--a test of the assumptions of behavioural studies.

Animal movement behaviour is intensively investigated with capture-mark-recapture studies. For the analysis of such experiments, the influence of marking technique, handling and translocation of marked animals on movement pattern is of crucial importance since it may mask or overrule the effects of the main research question. Here we present a capture-mark-recapture experiment on the movement behaviour of the blue-winged grasshopper Oedipoda caerulescens. We analyzed the influence of translocation of individuals from familiar to unfamiliar sites. Our study clearly demonstrates a significant influence of translocation to unfamiliar sites on the movement behaviour of O. caerulescens. Translocated individuals moved longer distances, showed smaller daily turning angles, and thus movements were more directed than those of resident individuals. The effect of translocation on daily moved distances was most pronounced on the first day of the experiment. We thus conclude that at least for the first day after translocation, movement behaviour is significantly influenced by translocation itself. Data ignoring this influence will be unsuitable for the prediction of dispersal behaviour, habitat detection capability or habitat preference.

The glutathione-glutaredoxin system in Rhodobacter capsulatus: part of a complex regulatory network controlling defense against oxidative stress.

Mutants with defects in components of the glutathione-glutaredoxin (GSH/Grx) system of Rhodobacter capsulatus were constructed to study its role in defense against oxidative stress and the redox-dependent formation of photosynthetic complexes. The lack of the glutaredoxin 3 gene (grxC) or the glutathione synthetase B gene (gshB) resulted in lower growth rates under aerobic conditions and higher sensitivity to oxidative stress, confirming the role of the GSH/Grx system in oxidative stress defense. Both mutants are highly sensitive to disulfide stress, indicating a major contribution of the GSH/Grx system to the thiol-disulfide redox buffer in the cytoplasm. Like mutations in the thioredoxin system, mutations in the GSH/Grx system affected the formation of photosynthetic complexes, which is redox dependent in R. capsulatus. Expression of the genes grxC, gshB, grxA for glutaredoxin 1, and gorA for glutathione reductase, all encoding components of the GSH/Grx system, was not induced by oxidative stress. Other genes, for which a role in oxidative stress was established in Escherichia coli, acnA, fpr, fur, and katG, were strongly induced by oxidative stress in R. capsulatus. Mutations in the grxC, and/or gshB, and/or trxC (thioredoxin 2) genes affected expression of these genes, indicating an interplay of the different defense systems against oxidative stress. The OxyR and the SoxRS regulons control the expression of many genes involved in oxidative stress defense in E. coli in response to H2O2 and superoxide, respectively. Our data and the available genome sequence of R. capsulatus suggest that a SoxRS system is lacking but an alternative superoxide specific regulator exists in R. capsulatus. While the expression of gorA and grxA is regulated by H2O2 in E. coli this is not the case in R. capsulatus, indicating that the OxyR regulons of these two species are significantly different.