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Attini are the only ants that use fresh plant material to cultivate species of Leucoagaricus , which are their source of nutrition. Escovopsis species are specialized mycoparasites of Leucoagaricus sp. and Escovopsis parasitism has a negative impact on the health of the ants' colonies. The goals of this work were: to test if the virulence of different isolates of Escovopsis weberi were the same across Leucoagaricus sp. and to analyze if structural mechanisms were related to variation in the virulence of E. weberi isolates. All E. weberi isolates were able to parasitize isolates of Leucoagaricus spp. but with striking differences in virulence, and it was shown that the contact between hyphae of both fungi was the main process that generates the degradation of Leucoagaricus isolates. Additionally, the two most virulent isolates produced hook-like protuberances, increasing the damage caused to its target. Finally, E. weberi was re-classified as a destructive biotrophic parasite. [ABSTRACT FROM AUTHOR]

This study assessed the biodiversity of soil macrofauna along a chronosequence of abandoned rice paddy fields including situations of 2, 4, 7 and 15 years since the last rice harvest, compared to a control without agricultural disturbance. The density of soil macrofauna changed dramatically according to the chronosequence. It was maximum in the 2-year-abandoned rice field (4360 ind m-2) and minimum in the natural grassland (397.3 ind m-2). A total of 133 morphospecies was found, distributed among 20 main families. The highest species richness was observed in the natural grassland and in the 2-year-fallow with 53 and 59 species, respectively, whereas the lowest richness was found in the 7-year-fallow (39 species). The proportion of shared species was minimum (19.1%) when comparing the natural grassland and the 2-year-fallow and remained surprisingly low between the natural grassland and the 15-year-fallow (23.4%). The species diversity as measured by the Shannon index varied strongly along the chronosequence. It was maximum in the natural grassland (1.98), minimum in the 2-year-fallow (1.01) and increased progressively throughout the chronosequence, although, it was still lower in the fallow after 15 years of abandonment as compared to the natural grassland. The same trend was observed using the evenness index. The indicator value index (Indval) was computed for each species and showed that 14 species out of 133 were statistically associated with a given chronosequence stage. This survey showed that soil macrofauna quickly recolonized the ex-rice fields after the abandonment of rice culture and that the species richness was higher in recent ex-rice fields (2 years) as compared to the natural grassland. The pool of species that colonise the newly abandoned rice fields is substantially different from the one inhabiting the natural grassland, therefore suggesting that most of the successful colonisers probably originate from neighbouring fallow plots. This highlights the possible effects of landscape structure upon the dynamics of the soil macrofaunal biodiversity. [Copyright &y& Elsevier]

Abstract: It is widely accepted that damage due to plastic deformation and ductile fracture in metals greatly depends on the triaxiality level (T) of the stress tensor, but according to recent developments described in the literature, it has been observed that the fracture limit εf may depend also on the deviatoric parameter (X) of the stress state. In the present paper, several special fracture tests comprising tensile, torsion, flattening and bending have been devised for the specific purpose of investigating as much wide as possible region of the T, X domain. In addition, numerical simulations of each test have been set up to provide additional information whenever direct measures could not be feasible. Three steel grades for cold working applications, each characterized by two different heat treatments have been investigated in the experimental campaign. The results state that fracture limits in the εf - T plane can be confined between two boundary curves, characterized by the values X =0 and X =1. The paper proposes that this evidence is a consequence of the application of Tresca criterion for shear failure. It is furthermore theoretically derived and experimentally verified that the two limits are linked together through the material hardening behaviour. Finally, it is discussed that an asymmetry between tension and compression states could exist as a consequence of the proposed approach. [Copyright &y& Elsevier]