Does time since introduction influence enemy release of an invasive weed?

Release from natural enemies is considered to potentially play an important role in the initial establishment and success of introduced plants. With time, the species richness of herbivores using non-native plants may increase [species-time relationship (STR)]. We investigated whether enemy release may be limited to the early stages of invasion. Substituting space for time, we sampled invertebrates and measured leaf damage on the invasive species Senecio madagascariensis Poir. at multiple sites, north and south of the introduction site. Invertebrate communities were collected from plants in the field, and reared from collected plant tissue. We also sampled invertebrates and damage on the native congener Senecio pinnatifolius var. pinnatifolius A. Rich. This species served as a control to account for environmental factors that may vary along the latitudinal gradient and as a comparison for evaluating the enemy release hypothesis (ERH). In contrast to predictions of the ERH, greater damage and herbivore abundances and richness were found on the introduced species S. madagascariensis than on the native S. pinnatifolius. Supporting the STR, total invertebrates (including herbivores) decreased in abundance, richness and Shannon diversity from the point of introduction to the invasion fronts of S. madagascariensis. Leaf damage showed the opposite trend, with highest damage levels at the invasion fronts. Reared herbivore loads (as opposed to external collections) were greater on the invader at the point of introduction than on sites further from this region. These results suggest there is a complex relationship between the invader and invertebrate community response over time. S. madagascariensis may be undergoing rapid changes at its invasion fronts in response to environmental and herbivore pressure.     

Effectiveness of the International Phytosanitary Standard ISPM No. 15 on Reducing Wood Borer Infestation Rates in Wood Packaging Material Entering the United States

Numerous bark- and wood-infesting insects have been introduced to new countries by international trade where some have caused severe environmental and economic damage. Wood packaging material (WPM), such as pallets, is one of the high risk pathways for the introduction of wood pests. International recognition of this risk resulted in adoption of International Standards for Phytosanitary Measures No. 15 (ISPM15) in 2002, which provides treatment standards for WPM used in international trade. ISPM15 was originally developed by members of the International Plant Protection Convention to “practically eliminate” the risk of international transport of most bark and wood pests via WPM. The United States (US) implemented ISPM15 in three phases during 2005–2006. We compared pest interception rates of WPM inspected at US ports before and after US implementation of ISPM15 using the US Department of Agriculture AQIM (Agriculture Quarantine Inspection Monitoring) database. Analyses of records from 2003–2009 indicated that WPM infestation rates declined 36–52% following ISPM15 implementation, with results varying in statistical significance depending on the selected starting parameters. Power analyses of the AQIM data indicated there was at least a 95% chance of detecting a statistically significant reduction in infestation rates if they dropped by 90% post-ISPM15, but the probability fell as the impact of ISPM15 lessened. We discuss several factors that could have reduced the apparent impact of ISPM15 on lowering WPM infestation levels, and suggest ways that ISPM15 could be improved. The paucity of international interception data impeded our ability to conduct more thorough analyses of the impact of ISPM15, and demonstrates the need for well-planned sampling programs before and after implementation of major phytosanitary policies so that their effectiveness can be assessed. We also present summary data for bark- and wood-boring insects intercepted on WPM at US ports during 1984–2008.     

The partial amino acid sequence of the NAD(+)-dependent glutamate dehydrogenase of Clostridium symbiosum: implications for the evolution and structural basis of coenzyme specificity

The amino acid sequence is reported for CNBr and tryptic peptide fragments of the NAD(+)-dependent glutamate dehydrogenase of Clostridium symbiosum. Together with the N-terminal sequence, these make up about 75% of the total sequence. The sequence shows extensive similarity with that of the NADP(+)-dependent glutamate dehydrogenase of Escherichia coli (52% identical residues out of the 332 compared) allowing confident placing of the peptide fragments within the overall sequence. This demonstrated sequence similarity with the E. coli enzyme, despite different coenzyme specificity, is much greater than the similarity (31% identities) between the GDH's of C. symbiosum and Peptostreptococcus asaccharolyticus, both NAD(+)-linked. The evolutionary implications are discussed. In the 'fingerprint' region of the nucleotide binding fold the sequence Gly X Gly X X Ala is found, rather than Gly X Gly X X Gly. The sequence found here has previously been associated with NADP+ specificity and its finding in a strictly NAD(+)-dependent enzyme requires closer examination of the function of this structural motif.     

Domiciliary nebulisers in asthma: a district survey.

Fifty three patients who were found to be using a home nebuliser for asthma completed a questionnaire. The results showed some confusion about the criteria for recommending whether a patient should buy a nebuliser and for its correct use. Twelve patients had not received any instruction on the use of their nebuliser, and only 11 of those old enough used a peak flow meter in conjunction with it. Eight patients aged 7-15 were using inhaled sympathomimetic aerosols only at the time of buying a nebuliser as compared with most of the older patients, who were using regular oral steroids. Forty nine patients assessed their asthma as moderate to severe, but eight of these were not attending a hospital clinic. Several patients were using 20 mg salbutamol or more every day, and on occasion doses of up to 50 mg a day were reported. It is recommended that patients should be assessed before they buy a nebuliser and advice given on correct use by a district nebuliser service, organised either by respiratory function technicians or in physiotherapy departments for adults together with a paediatric health visitor for children.     

The development of cytochromes during the cell cycle of a glucose-repressed fission yeast,Schizosaccharomyces pombe 972h?

1. Spectrophotometric analysis of intact cells of Schizosaccharomyces pombe, harvested from exponentially growing cultures during the phase of glucose repression, revealed the presence of cytochromes a+a(3), c and at least two species of cytochrome b. 2. An absorption maximum at 554nm at 77 degrees K, previously attributed to cytochrome c(1), has been identified as a b-type cytochrome. 3. CO-difference spectra reveal the presence of cytochromes P-420 and P-450 in addition to cytochrome a(3). 4. The cell cycle was analysed by separation of cells into classes representing successive stages in the cell cycle by isopycnic zonal centrifugation. 5. Cytochromes c(548), b(554) and b(560) each exhibited a single broad maximum of synthesis during the cell cycle. 6. Amounts of cytochromes a+a(3) and b(563) (tentatively identified as cytochrome b(T) by its reaction on pulsing anaerobic cell suspensions with O(2)) oscillated in phase, and showed two maxima during the cycle; the second maximum of cytochromes a+a(3) was coincident with a maximum of activity of enzymically active cytochrome c oxidase. 7. The amount of cytochrome P-420 decreased during the first three-quarters of the cell-cycle, whereas that of cytochrome P-450 increased during this period. 8. The discrepancy between spectrophotometric and enzymic assay of cytochrome c oxidase, the changing ratio of cytochrome a(3)/cytochrome a and the relationship between changes in cellular content of cytochromes and previous observations on respiratory oscillations during the cell cycle are discussed.