Diel and spatial drifting patterns of silver perch Bidyanus bidyanus eggs in an Australian lowland river

Densities of silver perch Bidyanus bidyanus eggs drifting in the Murray River, Australia, suggested a peak spawning time between 2100 and 0100 hours, and a propensity to drift in higher densities near shore and at the bottom of the water column. The results highlight the need to consider such spatial and temporal patterns when estimating species-specific drift abundances.     

Persistence and recolonisation determine success of bog restoration for aquatic invertebrates: a comment on Mazerolle et al. (2006)

1. Mazerolle et al. (2006) concluded that some aquatic invertebrate species, including bog‐associated species, readily colonise man‐made bog pools. In contrast, in Dutch bog remnants Van Duinen et al. (2003) found that a considerable number of bog‐associated species do not colonise newly created bog pools. 2. The conclusion of Mazerolle et al. (2006) is based on vagile aquatic invertebrates. Here, we question whether their conclusion can be extended to more sedentary species, which were not captured in the Canadian study, but made up an important part of the invertebrate assemblage in the Dutch study. This discrepancy could be caused by sampling artefacts, low colonisation rates of these species or an incomplete restoration of site conditions. 3. In Canada, chances of recolonisation may be higher than in the Netherlands, as natural and near‐natural bogs are more extensive. In the Netherlands, with low chances of recolonisation, persistence of species may be more important. To disentangle the relative importance of persistence and recolonisation, evaluations of the success of restoration projects need to cover the entire invertebrate assemblage, including both vagile and more sedentary species.     

Winged leaf-cutting ants on nuptial flights used as transport by Attacobius spiders for dispersal

Abstract.  1. Sexuals of a leaf-cutting ant, Atta bisphaerica Forel, left their nest for nuptial flights in October to December.
2. When leaving a nest, 53 of the 479 winged sexuals (or alates) observed (11.1%) carried up to three inquiline spiders of Attacobius luederwaldti .
3. Spiders exclusively selected winged sexuals, not workers, and preferred females, indicating their expectation of the stronger flight ability of females. Neither these sexuals nor workers that appeared out of the nest on flight days attempted to remove or attack spiders on the body of alates.
4. New qucens landing from their nuptial flight did not carry spiders, indicating that the spiders had left the ants in the sky to be dispersed by wind.
5. No spiders were found in more than 100 incipient nests, which were estimated to be 2–3 months old. This suggests that the spiders jumped off the alate during mid-flight and dispersed on the wind to inhabit larger nests.     

Bacterial ecology, antibiotics and selection for virulence

The evolution of antibiotic resistance in bacteria is well known. Here I describe possible mechanisms by which an increased rate of re-colonization of vertebrate guts by microbes caused by antibiotic use could lead to selection for increased virulence in currently mutualistic or benign microbes. The importance of understanding both the source and the frequency of colonization in such mutualisms is stressed and the possible importance of pseudo-vertical transmission in the evolution of these systems is discussed. A number of areas requiring experimental investigation are identified.     

The Hemiptera (Insecta) communities of tropical rain forest in Sulawesi

The structure and composition of Hemiptera communities of tropical rain forest in Dumoga-Bone National Park, Sulawesi, Indonesia were investigated over a 1-year period. The aim was to investigate the extent to which insect samples, obtained using six different techniques, were representative of the whole community, and to explore temporal and spatial variation in Hemiptera community composition. Sampling techniques employed were Rothamsted light trapping, canopy fogging, malaise trapping at both ground and canopy level, flight interception trapping and yellow water pan trapping. Overlap between faunas collected using different techniques was surprisingly low emphasizing the limitations of using any single method to sample and thereby describe the Hemiptera community. Differences were observed at the species, family and suborder levels. Similarly, there were major differences in faunal composition between sites and diversity appeared to peak at elevations between 600–1000 m. Seasonal changes were also significant but generally lower than between methods or sites. Results are discussed in relation to factors such as food availability and host specialization and the efficacy of each sampling method is reviewed in relation to the biology of the different Hemiptera groups and the composition of the samples obtained.     

Nitrogen and Phosphorus in the Finnish Energy System, 1900–2003

In producing power, humans move the nutrients nitrogen (N) and phosphorus (P) from their long‐term geological and biological stocks and release or emit them in soil, water, and the atmosphere. In Finland, peat combustion is an important driver of N and P fluxes from the environment to human economy. The flows of N and P in the Finnish energy system were quantified with partial substance flow analysis, and the driving forces of emissions of nitrogen oxides (NOx) were analyzed using the ImPACT model. In the year 2000 in Finland, 140,000 tonnes of nitrogen entered the energy system, mainly in peat and hard coal. Combustion released an estimated 66,000 tonnes of N as nitrogen oxides (NOx) and nitrous oxides (N2O) and another 74,000 tonnes as elemental N2. Most of the emissions were borne in traffic. At the same time, 6,000 tonnes of P was estimated to enter the Finnish energy system, mostly in peat and wood. Ash was mainly used in earth construction and disposed in landfills; thus negligible levels of P were recycled back to nature. During the twentieth century, fuel‐borne input of N increased 20‐fold, and of P 8‐fold. In 1900–1950, the increasing use of hard coal slowly boosted N input, whereas wood fuels were the main carrier of P. Since 1970, the fluxes have been on the rise. NOx emissions leveled off in the 1980s, though, and then declined in conjunction with improvements in combustion technologies such as NOx removal (de‐NOx) technologies in energy production and catalytic converters in cars.     

Why are there few algae on snail shells? The effects of grazing,nutrients and shell chemistry on the algae on shells of Helisoma trivolvis

1. Freshwater snails often lack visible growths of algae on their shells. We tested three possible mechanisms that may account for this (grazing, snail-derived nutrients and chemical defences), using the ramshorn snail Helisoma trivolvis .
2. The experiments were carried out in floating plastic enclosures in a pond and comprised seven treatments. Grazing treatments were: a lone snail (ungrazed, as self-grazing does not occur), Helisoma with conspecifics, Helisoma with the co-occurring pond snail Physa sp., empty shells with Helisoma , and ungrazed empty shells. Nutrient effects were possible in all treatments with occupied shells (lone snail; Helisoma with conspecifics, and with Physa ) versus absent in other treatments. Testing for chemical defences compared algae on fresh empty shells, weathered shells (outer organic periostracum layer absent) and boiled fresh shells (with denaturization of susceptible proteins).
3. Diatoms dominated algal assemblages on snail shells. Although the upright diatom Gomphonema gracile was abundant on all shells, it was dominant on the shells of snails housed with other snail grazers (either Helisoma or Physa ).
4. Only the lone snail (nutrients but no grazing) showed higher algal biomass, so presumably any nutrient effect in the treatments with grazers was masked. Both Helisoma and Physa were observed apparently grazing on Helisoma shells, and consequently algal biomass in multi-snail treatments was similar to that on empty shells. Scanning electron microscopy revealed that algal density was highest near the aperture of live snails, but not empty shells; this is consistent with a nutrient addition effect. There was no evidence of chemical defences against algal growth.
5. In soft-bottomed freshwater habitats with abundant snails, shells of living snails provide nutrient-augmented substrata that may indirectly boost overall snail production.     

Population structure and the impact of regional and local habitat isolation upon levels of genetic diversity of the endangered damselfly Coenagrion mercuriale (Odonata: Zygoptera)

1. Coenagrion mercuriale is one of Europe's most threatened damselflies. There is concern for the long‐term persistence of many of its U.K. colonies because adult lifetime movement is limited, making isolated populations susceptible to extinction. 2. Using 14 microsatellite loci we characterised levels of genetic diversity, evidence for a recent decline and the spatial genetic structure for C. mercuriale population in Wales, U.K. 3. Spatial isolation is not an absolute predictor of low genetic diversity at either local or regional scales. 4. One population inhabiting a remote, edge of range site is genetically impoverished with levels of variability (at microsatellite loci) among the lowest reported for any insect species. 5. Agricultural land and high ground are physical barriers to dispersal by adults. 6. Consistent with work from elsewhere, movement by mature C. mercuriale in Pembrokeshire is sufficient to prevent significant genetic differentiation throughout a habitat matrix of some 3–4 km if the suitable habitat sites are <2 km apart and lack barriers to movement. Even within a good habitat matrix, however, genetic isolation by distance develops within 10 km.