Host genotype affects the relative success of competing lines of aphid parasitoids under superparasitism

1. In solitary parasitoids, only one individual can complete development in a given host. Therefore, solitary parasitoids tend to prefer unparasitised hosts for oviposition, yet under high parasitoid densities, superparasitism is frequent and results in fierce competition for the host's limited resources. This may lead to selection for the best intra‐host competitors. 2. Increased intra‐host competitive ability may evolve under a high risk of superparasitism if this trait exhibits genetic variation, and if competitive differences among parasitoid genotypes are consistent across environments, e.g. different host genotypes. 3. These assumptions were addressed in the aphid parasitoid Lysiphlebus fabarum (Hymenoptera: Braconidae: Aphidiinae) and its main host, the black bean aphid, Aphis fabae (Scopoli) (Hemiptera: Aphididae). Three parthenogenetic lines of L. fabarum were allowed to parasitise three aphid clones singly and in all pairwise combinations (superparasitism). The winning parasitoid in superparasitised aphids was determined by microsatellite analysis. 4. The proportions of singly parasitised aphids that were mummified were similar for the three parasitoid lines and did not differ significantly among host clones. 5. Under superparasitism, significant biases in favour of one parasitoid line were observed for some combinations, indicating that there is genetic variation for intra‐host competitive ability. However, the outcome of superparasitism was inconsistent across aphid clones and thus influenced significantly by the host clone in which parasitoids competed. 6. Overall, this study shows that the fitness of aphid parasitoids under superparasitism is determined by complex interactions with competitors as well as hosts, possibly hampering the evolution of improved intra‐host competitive ability.     

Genetic Analysis in Wood-Decaying Fungi I. Genetic Variation and Evidence for Allopatric Speciation in Pleurotus ostreatus using Phenoloxidase Zymograms and Morphological Criteria

Using electropherograms (zymograms) of the phenoloxidase laccase and characteristics of mycelial growth and fruit body production, a distinct morphological and biochemical differentiation of two geographically isolated (allopatric) populations of the wood-rotting basidiomycete Pleurotus ostreatus became evident. No limitation in their outbreeding ability was observed, however. A specific secretory mechanism for an extracellular laccase, genetically different in the two geographical races, could be detected. An approximately 1: 1 segregation of this laccase band in the F₁ generation indicates that specific secretion of this enzyme is controlled by one gene only, Different degrees of genetic variation as shown by differences in the respective laccase spectra were found in the two geographical races. Only one enzyme band out of nine multiple laccases was found to be specific for fruit bodies. The value of zymograms for chemotaxonomic purposes, for the understanding of microevolution and for determination of genetic variation in fungi is critically discussed.     

The Upper Tremadocian (Ordovician) graptolite Bryograptus: taxonomy, biostratigraphy and biogeography

Abstract:  The taxonomy, biostratigraphical and palaeogeographical distribution of the Lower Ordovician graptolite genus Bryograptus is evaluated. Bryograptus is recognized as a distinct triradiate anisograptid with a multiramous, pendent rhabdosome. The species of the genus Bryograptus can be interpreted as shallow water faunal elements with a strongly limited biogeographical distribution to the Atlantic Faunal Realm. Bryograptus is restricted to a narrow interval in the Upper Tremadocian, the Bryograptus Biozone of Scandinavia and South America (Argentina), making it a taxon with a high potential for precise biostratigraphical correlations. The proximal end development can be used to differentiate the genus Bryograptus from other pendent multiramous graptoloid genera with a homoplastic rhabdosome development. Characteristics of the proximal end development and structure easily differentiate these genera in relief specimens, but not in flattened material.     

Cold hardiness of some Alpine Collembola

Abstract.

• 1 Individual supercooling points ranged from -2 to -44°C for six species of springtails, five species from the Swiss Alps and one from lowland Britain. Individuals of Isotomurus alticola (Carl) and Isotoma viridis Bourlet without gut contents had substantially lower supercooling points than those containing food material.
• 2 Juveniles were more cold resistant than adults in both I.alticola and Isotoma hiemalis Schött, both with respect to supercooling point and to their survival at prolonged subzero temperatures.
• 3 Temperature and acclimation time affected the degree of supercooling of four of the Alpine species especially I.hiemalis.
• 4 Duration of culture period had no consistent influence on the supercooling potential of all the species.
• 5 Tests for glycerol in the body fluids of the five Alpine springtails were negative, but the presence of a sugar, probably glucose, together with a five carbon polyhydric alcohol was indicated by chromatography.

     

The performance of fungal xylan-degrading enzyme preparations in elemental chlorine-free bleaching for Eucalyptus pulp

Cellulase-free xylan-degrading enzyme preparations from Acrophialophora nainiana, Humicola grisea var. thermoidea and two Trichoderma harzianum strains were used as bleaching agents for Eucalyptus kraft pulp, prior to a chlorine dioxide and alkaline bleaching sequence. In comparison to the control sequence (performed without xylanase pretreatment), the sequence incorporating enzyme treatment was more effective. Removal of residual lignin was indicated by a reduction in kappa number. Overall, enzyme preparations from T. harzianum were marginally more effective in reducing pulp viscosity and chlorine chemical consumption and improving the brightness of the kraft pulp. However, the highest reduction in pulp viscosity was mediated by the xylanase preparation from A. nainiana. Xylanase pretreatment compares very favorably with that of chemical pulping. Journal of Industrial Microbiology & Biotechnology (2002) 28, 204–206 DOI: 10.1038/sj/jim/7000227 Received 27 April 2001/ Accepted in revised form 03 November 2001     

Extensive physiological integration in intact clonal systems of Carex arenaria

1 Carex arenaria forms large clonal fragments (up to 12 m long) in environments in which soil-bound resources limit growth.
2 We hypothesized that extensive integration of C. arenaria would facilitate the exploitation of scarce and patchily distributed soil resources and that the continued functioning of old roots would enable exploitation of resources that are temporally variable.
3 We used labelling with ¹⁴C and acid fuchsin to study the degree and extent of physiological integration and root function of intact clonal systems of C. arenaria in a sand dune area in south Sweden.
4 The uptake and translocation of dye suggests that old roots remain capable of taking up water and nutrients, in contrast with negative reports from previous studies. Water was translocated both acropetally and basipetally.
5 Thirty per cent of the assimilated carbon was found to be translocated towards the growing apex. Smaller, but significant, amounts of carbon were translocated basipetally throughout the fragments (17–74 ramet generations).
6 The results are discussed in terms of the source–sink relations of large clonal systems in the field. The translocation patterns are considered in relation to soil moisture and nutrient availability.     

The ecological value of Eryngium horridum in maintaining biodiversity in subtropical grasslands

The role of facilitation in the structuring of plant communities has been often demonstrated in environments under high abiotic stress, especially in semi‐arid and arid ecosystems and high elevations. Few studies, however, analysed facilitation in systems that are highly productive and rich in species, which are thought to be theoretically unlikely to demonstrate strong effects of facilitation. Here, we investigate the importance of Eryngium horridum, a rosette species, on the maintenance of plant diversity in subtropical grasslands in southern Brazil. We evaluated facilitation in areas under two different types of management: abandonment and grazing. Plots were established in areas with and without individuals of E. horridum and all species were identified and had their cover estimated. The Relative Neighbour Effect index was calculated in order to verify the presence of competition or facilitation. Our results indicated facilitation in both abandoned and in grazed grasslands, but apparently through different mechanisms. In the first case, the plant's architecture opens the canopy and allows more light to reach small forbs in the grass matrix. In the second case, E. horridum appears to protect more palatable species from herbivores. Otherwise considered an obnoxious species, E. horridum plays an important ecological role in subtropical grasslands in southern Brazil by facilitating other species and consequently, increasing local richness. Areas with this rosette species are important sources of diaspores, which are able to colonize new open sites and thus, maintain biodiversity.     

IGF-1 modulates gene expression of proteins involved in inflammation,cytoskeleton, and liver architecture

Even though the liver synthesizes most of circulating IGF-1, it lacks its receptor under physiological conditions. However, according to previous studies, a damaged liver expresses the receptor. For this reason, herein, we examine hepatic histology and expression of genes encoding proteins of the cytoskeleton, extracellular matrix, and cell-cell molecules and inflammation-related proteins. A partial IGF-1 deficiency murine model was used to investigate IGF-1’s effects on liver by comparing wild-type controls, heterozygous igf1^+/?, and heterozygous mice treated with IGF-1 for 10 days. Histology, microarray for mRNA gene expression, RT-qPCR, and lipid peroxidation were assessed. Microarray analyses revealed significant underexpression of igf1 in heterozygous mice compared to control mice, restoring normal liver expression after treatment, which then normalized its circulating levels. IGF-1 receptor mRNA was overexpressed in Hz mice liver, while treated mice displayed a similar expression to that of the controls. Heterozygous mice showed overexpression of several genes encoding proteins related to inflammatory and acute-phase proteins and underexpression or overexpression of genes which coded for extracellular matrix, cytoskeleton, and cell junction components. Histology revealed an altered hepatic architecture. In addition, liver oxidative damage was found increased in the heterozygous group. The mere IGF-1 partial deficiency is associated with relevant alterations of the hepatic architecture and expression of genes involved in cytoskeleton, hepatocyte polarity, cell junctions, and extracellular matrix proteins. Moreover, it induces hepatic expression of the IGF-1 receptor and elevated acute-phase and inflammation mediators, which all resulted in liver oxidative damage.     

The identity of the Ordovician (Darriwilian) graptolite Fucoides dentatus Brongniart, 1828

Abstract: The biostratigraphically important Middle Ordovician (Darriwilian) biserial graptolite Fucoides dentatus Brongniart, 1828 is redescribed and illustrated from its type material and from additional specimens collected at the type locality – Lévis, Quebec, Canada. It is referred to Levisograptus gen. nov., which includes also the austrodentatus group of early axonophoran graptolites. The species has previously been confused with a younger, mid‐Darriwilian species, now referred to as Eoglyptograptus gerhardi sp. nov., and recognized as the type species of the genus Eoglyptograptus Mitchell. Both species can be differentiated easily by their respective proximal development types and show nonoverlapping biostratigraphical ranges. Levisograptus dentatus (Brongniart) is an important biostratigraphical index species in the early Darriwilian. Eoglyptograptus species are found in the higher Darriwilian and are biogeographically restricted to the Atlantic Faunal Realm.