2014. július 18., péntek

Holst et al. (2013) Ecological Modelling

Holst, N, Lang A, Lövei G, Otto M (2013): Increased mortality is predicted of Inachis io larvae caused by Bt-maize pollen in European farmland. Ecological Modelling 250: 126-133.

A potential environmental risk of the field cultivation of insect-resistant (Bt-toxin expressing) transgenic maize (Zea mays) is the consumption of Bt-containing pollen by herbivorous larvae of butterflies (Lepidoptera). Maize is wind-pollinated, and at flowering time large amounts of pollen can be deposited on various plants growing in the landscape, leading to inadvertent ingestion of toxic pollen with plant biomass consumed by these butterfly larvae. To examine the possible effect of this coincidence, we focused our study on the protected butterfly Inachis io and two regions of Europe. Using climatic records, maize and butterfly phenology data, we built a simulation model of the butterfly’s annual life cycle, overlaid with the phenology of maize pollen deposition on the leaves of the food plant Urtica dioica, and linked these with the dose–response curve of I. io larvae to Bt-maize pollen (event MON810). The simulations indicated that in Northern Europe, where I. io is univoltine, Bt-maize pollen would not be present on the food plant at the same time as the I. io larvae. However, in Central and Southern Europe, where I. io is bivoltine, Bt-maize pollen and the second generation I. io larvae would coincide, and an increased mortality of the larvae was predicted. This prediction differs from earlier studies which predicted negligible effect of field-grown Bt-maize on I. io larvae. Our model is an improvement over previous efforts since it is based on more detailed, empirical data, includes more biological detail, and provides explicit estimation of all model parameters. The model is open-source software and is available for re-use and for modelling the effects on other species or regions.

Risk, GMO, Lepidoptera, Bt-maize, Simulation model, Dose–response

Hansen et al. (2013) Pest Management Science

BACKGROUND: The effect of transgenic maize (Zea mays L.) containing a lepidopteran-specific Bt toxin on a stored-product pest, Sitophilus zeamais Motschulsky, and its parasitoid, Lariophagus distinguendus Förster, was examined in the laboratory to test the impact of transgenicmaize on stored-product pests and their biological control. RESULTS: Weevils were not harmfully affected by transgenic Bt maize in their development characteristics (development time, body mass), and females emerging from transgenicmaize kernels were larger. However, significantly fewer parasitoid females emerged from weevils that developed in transgenic kernels, although parasitoids did not develop more slowly and were not different in size ormass from their conspecifics emerging from hosts in non-transgenicmaize kernels. CONCLUSION: The emergence of female parasitoids was reduced in transgenic Bt maize, and this effect cannot be explained by the known lepidopteran-specific toxicity of Bt Cry1Ab toxin.

Bt maize, stored-product pests, biological control, transgenic maize, biosafety, tritrophic interactions

Andow & Lövei (2012) Environmental Enthomology

transgenic plants, environmental risk, synthesis, biological control

Yang et al. (2012) PLoS One

Destructive host-feeding is common in hymenopteran parasitoids. Such feeding may be restricted to host stages not preferred for oviposition. However, whether this is a fixed strategy or can vary according to resource levels or parasitoid needs is less clear. We tested the trade-off between host feeding and oviposition on two whitefly parasitoids under varying host densities. Females of two aphelinid parasitoids, Eretmocerus hayati and Encarsia sophia were exposed to nine different densities of their whitefly host, Bemisia tabaci, in single-instar tests to identify their functional response. Mixed-instar host choice tests were also conducted by exposing whiteflies at four densities to the parasitoids. We hypothesized that the parasitoid females can detect different host densities, and decide on oviposition vs. host-feeding accordingly. The results showed that both Er. hayati and En. sophia females tended to increase both oviposition and host-feeding with increased host density within a certain range. Oviposition reached a plateau at lower host density than host-feeding in Er. hayati, while En. sophia reached its oviposition plateau at higher densities. At low densities, Er. hayati parasitized most on first and second (the optimal ones), and fed most on third nymphal instars (the suboptimal one) of the whitefly host as theory predicts, while at high densities, both parasitism and host-feeding occurred on first and second instars which are preferred for oviposition. En. sophia parasitized most on third and fourth (the optimal ones), while fed on first instars (the suboptimal one) at low densities, and utilized third and fourth instars for both at high densities. In conclusion, oviposition vs. host-feeding strategy of parasitoid females was found to vary at different host densities. The balance between reserving optimal hosts for oviposition or using them for host-feeding depended on parasitoid life history and the availability of host resources.

parasitoids, host feeding, life history strategies

Lövei et al. (2012) Trends in Ecology and Evolution

invasions, mega-diverse regions, risk

2014. július 15., kedd

Abonyi et al. (2014) Ecological Indicators

Functional groups of phytoplankton make possible various classifications among taxa and this approach has been receiving a growing scientific interest. We compared three frequently used classifications as possible ecological tools in providing river zones along the large, Continental Atlantic River Loire. The different number of functional groups in each classification was synchronized into six clusters using the Self Organizing Map (SOM) method, which clusters (as river zones where relevant) were then compared in their response to geographical location, hydrological and chemical constraints.
Our findings demonstrated that all the three classifications might serve as a rational tool, but at different level of understanding. Only approaches based on fine functional resolution in benthic and planctonic diatoms, as well as in cyanobacteria were able to provide reliable river zones at both whole river, and at spatio-temporal scales. Functional groups of these approaches followed different regional patterns in geographical, physical and chemical constraints, and were useful ecological indicators of natural river longitudinal processes, as well as of human impacts such as damming or agriculture.

Functional groups, Potamoplankton composition, Phytoplankton river zonation, N:P ratio, Si:P ratio, River water quality management

László et al. (2014) PLoS One

Both predators and parasitoids can have significant effects on species’ life history traits, such as longevity or clutch size. In the case of gall inducers, sporadically there is evidence to suggest that both vertebrate predation and insect parasitoid attack may shape the optimal gall size. While the effects of parasitoids have been studied in detail, the influence of vertebrate predation is less well-investigated. To better understand this aspect of gall size evolution, we studied vertebrate predation on galls of Diplolepis rosae on rose (Rosa canina) shrubs. We measured predation frequency, predation incidence, and predation rate in a large-scale observational field study, as well as an experimental field study. Our combined results suggest that, similarly to parasitoids, vertebrate predation makes a considerable contribution to mortality of gall inducer larvae. On the other hand, its influence on gall size is in direct contrast to the effect of parasitoids, as frequency of vertebrate predation increases with gall size. This suggests that the balance between predation and parasitoid attack shapes the optimal size of D. rosae galls.

Cserkész et al. (2014) Mammalia

The Southern birch mouse (Sicista subtilis) is a small-sized rodent species characteristic of the Palearctic steppes with westernmost occurrences in central Europe. The species was considered to be extinct in Transylvania (central Romania), but in our field survey we captured three living individuals near the city of Cluj-Napoca. On the basis of nuclear interphotoreceptor retinoid-binding protein and mitochondrial cytochrome c oxidase subunit 1 sequences, we assessed the taxonomic status of the newly found S. subtilis population by comparing them to available sequences, including the sequences of its subspecies. The Transylvanian samples were found to be genetically closest to the Hungarian samples of S. subtilis trizona. These new records extend the known geographic range of this rediscovered species and provide additional information on its habitat preference and external morphological features. Moreover, our phylogenetic tree reconstruction for seven Sicista taxa provides a basic insight into the phylogenetic relationships of the genus, placing the northern Eurasian taxa (S. betulina and S. subtilis) at the crown of the tree and the central Asian taxa at the base of the tree. The Transylvanian occurrence of S. subtilis trizona, which is endemic to the Carpathian Basin, is of high faunistic value as a result of an increase in the number of known populations of this subspecies – one of the most endangered rodents of Europe – from one to two.

COI, DNA barcoding, endangered species, IRBP, Sminthidae

Tököly et al. (2014) Ecological Research

Clonally reproducing animals, such as freshwater hydra, can achieve very quick population growth, potentially resulting in high density when dispersal is limited. The reproductive value of any offspring produced clonally in such a high density population is low because of the strong competition for food. Therefore, animals experiencing such conditions should allocate their resources to self-maintenance, to increase survival chances. Increased allocation to self-maintenance in turn should enable animals to withstand higher levels of genotoxic stress. To test this prediction, we exposed green hydra (Hydra viridissima Pallas 1766) to a perceived high density (by keeping them in crowded culture medium) or low density (fresh culture medium) without altering food availability. We also manipulated nutritional status (by starving animals for different time periods) and previous exposure to mild stress in a full factorial experimental design. At the end of the experiment we exposed animals to a high concentration of hydrogen-peroxide and scored stress tolerance. We found that stress tolerance is greatly elevated in animals perceiving high density, confirming our prediction. Stress tolerance decreased in animals starved for a few days, suggesting that the ability to maintain an elevated stress tolerance function has nutritional costs and is possible only when resource availability is high. On the other hand, previous exposure to mild stress had a small effect on the ability to tolerate subsequent exposure to stress, and only in the low density treatment group. Thus, stress tolerance in hydra is dynamically modulated in response to social, environmental and nutritional cues.

Asexual reproduction, Density dependence, Somatic maintenance, Life-history evolution, Oxidative stress