Nitrogen transfer within and between plants through common mycorrhizal networks (CMNs)

Mycorthizae play a critical role in nutrient capture from soils. Arbuscular mycorrhizae (AM) and ectomycorrhizae (EM) are the most important mycorrhizae in agricultural and natural ecosystems. AM and EM fungi use inorganic NH4+ and NO3-, and most EM fungi are capable of using organic nitrogen. The heavier stable isotope N-15 is discriminated against during biogeochemical and biochemical processes. Differences in N-15 (atom%) or delta(15)N (parts per thousand) provide nitrogen movement information in an experimental system. A range of 20 to 50% of one-way N-transfer has been observed from legumes to nonlegumes. Mycorrhizal fungal mycelia can extend from one plant's roots to another plant's roots to form common mycorrhizal networks (CMNs). Individual species, genera, even families of plants can be interconnected by CMNs. They are capable of facilitating nutrient uptake and flux. Nutrients such as carbon, nitrogen and phosphorus and other elements may then move via either AM or EM networks from plant to plant. Both N-15 labeling and N-15 natural abundance techniques have been employed to trace N movement between plants interconnected by AM or EM networks. Fine mesh (25similar to45 mum) has been used to separate root systems and allow only hyphal penetration and linkages but no root contact between plants. In many studies, nitrogen from N-2-fixing mycorrhizal plants transferred to non-N-2-fixing mycorrhizal plants (one-way N-transfer). In a few studies, N is also transferred from non-N-2-fixing mycorrhizal plants to N-2-fixing mycorrhizal plants (two-way N-transfer). There is controversy about whether N-transfer is direct through CMNs, or indirect through the soil. The lack of convincing data underlines the need for creative, careful experimental manipulations. Nitrogen is crucial to productivity in most terrestrial ecosystems, and there are potential benefits of management in soil-plant systems to enhance N-transfer. Thus, two-way N-transfer warrants further investigation with many species and under field conditions.

Molecular characterization of Thelastomatoidea (Nematoda : Oxyurida) from cockroaches in Australia

A molecular approach was used to genetically characterize 5 species (Aoruroides queenslandensis. Blattophila sphaerolaima, Cordonicola gibsoni, Desmicola ornato and Leidynemella fusiformis) belonging to the superfamily. Thelastomatoidea fi (Nematoda: Oxyurida), a group of pinworms that parasitizes terrestrial arthropods. The D3 domain of the large subunit Of nuclear ribosomal RNA (LSU) was sequenced for individual specimens, and the analysis of the sequence data allowed the genetic relationships of the 5 species to be studied dagger. The sequence variation in the D3 domain within individual species (0-1-8%) was significantly less than the differences among species (4(.)3-12(.)4%). Phylogenetic analyses, Using maximum parsimony, maximum likelihood, and neighbour-joining, tree-building methods, established relationships among the 5 species of Thelastomatoidea and Oxyuris equi (a species of the order Oxyurida). The molecular approach employed provides the prospect for developing DNA tools for the specific identification of the Thelastomatoidea, irrespective of developmental stage and sex, as a basis for systematic, ecological and/or population genetic investigations of members within this superfamily.

Overview of the conservation status of Australian frogs

A review of the current conservation status of Australian amphibians was recently completed as part of a World Conservation Union (IUCN) sponsored Global Amphibian Assessment (GAA). Fifty of 216 amphibian species (23%) in Australia are now recognized as threatened or extinct in accord with IUCN Red List Categories and Criteria. Here we report on the categories and criteria under which individual species qualified for listing and provide a summary of supporting information pertaining to population and distribution declines. Major threatening processes contributing to listing of species are also reviewed.