Search results for "Complex"
showing 10 items of 5889 documents
Plasmodium relictum infection and MHC diversity in the house sparrow (Passer domesticus).
2010
Antagonistic coevolution between hosts and parasites has been proposed as a mechanism maintaining genetic diversity in both host and parasite populations. In particular, the high level of genetic diversity usually observed at the major histocompatibility complex (MHC) is generally thought to be maintained by parasite-driven selection. Among the possible ways through which parasites can maintain MHC diversity, diversifying selection has received relatively less attention. This hypothesis is based on the idea that parasites exert spatially variable selection pressures because of heterogeneity in parasite genetic structure, abundance or virulence. Variable selection pressures should select for…
Identity of the Calcarata species complex in Viola sect. Melanium (Violaceae)
2020
The Calcarata species complex in Viola sect. Melanium (Violaceae) is a group of species from Italy and neighbouring islands. The complex is of considerable evolutionary interest because several hypotheses about hybrid speciation within the group have been previously proposed. Because the Calcarata complex is not well characterized morphologically, we used 142 samples representing 92 (of c. 120) species of V. sect. Melanium plus three outgroup species. Nuclear ITS and ETS and plastid trnS–trnG intergenic spacer sequences were analysed to test the monophyly of the Calcarata complex and to infer relationships among the constituent species. Both nuclear and plastid sequences resulted in very li…
Ten principles for conservation translocations of threatened wood-inhabiting fungi
2020
Abstract Unlike for many other organism groups, conservation translocations of fungi are still rare. Encouraged by recent successful translocations, there is a growing interest in applying this conservation tool to threatened wood-inhabiting fungi. When combined with other conservation or restoration measures, translocation can be an effective measure for preventing further population decline in the short term, and species extinctions in the long term. Translocations can be appropriate for rare and specialist fungal species that occur as small local populations in isolated patches across fragmented landscapes, where there is a low likelihood of successful dispersal between distant host tree…
Arabidopsis SGS2 and SGS3 genes are required for posttranscriptional gene silencing and natural virus resistance.
2000
AbstractPosttranscriptional gene silencing (PTGS) in plants results from the degradation of mRNAs and shows phenomenological similarities with quelling in fungi and RNAi in animals. Here, we report the isolation of sgs2 and sgs3 Arabidopsis mutants impaired in PTGS. We establish a mechanistic link between PTGS, quelling, and RNAi since the Arabidopsis SGS2 protein is similar to an RNA-dependent RNA polymerase like N. crassa QDE-1, controlling quelling, and C. elegans EGO-1, controlling RNAi. In contrast, SGS3 shows no significant similarity with any known or putative protein, thus defining a specific step of PTGS in plants. Both sgs2 and sgs3 mutants show enhanced susceptibility to virus, d…
Large Spatial Scale of the Phenotype-Environment Color Matching in Two Cryptic Species of African Desert Jerboas (Dipodidae: Jaculus)
2014
We tested the camouflage hypothesis, or the linkage between animal (Saharan rodent) and habitat coloration, on the largest geographical scale yet conducted. We aimed to determine whether phenotypic variation is explained by micro-habitat variation and/or genetic polymorphism to determine 1) the strength of linkage between fur color and local substrate color, and 2) the divergence in fur coloration between two genetic clades, representing cryptic species, throughout the complete range of the African desert jerboas (Jaculus jaculus). We used a combination of museum and field-collected specimens, remote sensing tools, satellite and digital photography and molecular genetic and phylogenetic met…
Soil health through soil disease suppression: Which strategy from descriptors to indicators?
2007
International audience; Soil is a component of primary importance in crop production, even if it is often neglected, or only regarded as a physical support for the growth of plants. However, with the increasing societal concerns for the sustainability of agriculture, soil must be considered as a living system. Its quality results from the multiple interactions among physicochemical and biological components, notably the microbial communities, primordial for soil function. Crops are threatened by soil-borne diseases. These are often difficult to control, because of the “hidden” status of the pathogens and also because of the absence, noxiousness or lack of efficacy of chemical treatments. In…
Different lineages of freshwater jellyfishes (Cnidaria, Olindiidae, Craspedacusta) invading Europe: another piece of the puzzle from Sicily, Italy
2018
Correctly identifying and mapping the distribution patterns of passively dispersing freshwater organisms is an important task to understand the mechanisms through which these organisms move across the world and to counteract the introduction of invasive alien species in a timely way; moreover, in the light of the growing evidence of the pervasiveness of cryptic species and cryptic biological invasions among all animal groups, the use of molecular identification tools is strongly advisable. In this context, we present the first record of the freshwater jellyfish Craspedacusta sowerbii Lankester, 1880 in the Mediterranean island of Sicily, Italy. This invasive species, native to China, was fo…
Role of Soil Organisms in the Maintenance of Species-Rich Seminatural Grasslands through Mowing
2009
To preserve species-rich grasslands, management practices such as mowing are often required. Mowing is known to promote aboveground conditions that help to maintain plant species richness, but whether belowground effects are important as well is not known. We hypothesized that if mowing decreases belowground carbon transfer by reducing root mass, this will reduce the abundance and activity of soil decomposers and lead to diminished nutrient availability in soil. In grasslands, this would provide a means to mitigate the negative effects of nitrogen enrichment on plant species richness. We established experimental plots on grassland with one-third of plots growing untouched, one-third mowed o…
Alleviating Soil Acidity: Optimization of Lime and Zinc Use in Maize (Zea mays L.) Grown on Alfisols
2019
ABSTRACTSoil acidity, one of the causes of soil degradation, adversely affects phytoavailability of soil nutrients and crop growth in 50% of arable land of the world. There is a persistent need for...
Root growth and soil carbon turnover in Opuntia ficus-indica as affected by soil volume availability
2019
Abstract The aim of this study was to investigate the effect of soil volume restriction, i.e. root confinement, on below-and-above ground growth of cactus pear (Opuntia ficus-indica (L.) Mill) as well as the effect on root architecture and turnover, and soil carbon turnover. In May 2014, 1- year-old cladodes were planted in five different pots size (50, 33, 18, 9 and 5 L). Soil samples were collected from each pot and dried before SOC and δ13C determination. Roots of each plant were divided visually into three groups depending on their diameter, and then measured and weighed. Results indicated a significant effect of soil volume and sampling dates on total root length, root dry mass and δ13…