Worldwide invasion of vector mosquitoes: present European distribution and challenges for Spain

An Asiatic mosquito species, Aedes albopictus, began to spread worldwide in the 1970s thanks to marine transport of tires and other goods, leading to colonization of many areas of the world. This species is a vector of major human diseases such as Dengue, Yellow Fever and the West Nile virus. In Europe, it was established in Albania and Italy and has been detected in other countries such as France; no records exist for Spain as yet. Colonization by Aedes albopictus is a major public health concern considering that the West Nile virus and several other viruses are known to circulate sporadically in the Mediterranean. Additionally, the parent species Aedes aegypti was the vector causing severe outbreaks of Dengue and Yellow Fever two centuries ago. Although Ae. aegypti was also introduced, it was eradicated from Spain. Both mosquitoes shared habitat types, diseases transmitted and many bionomic data. This article contains a review of the present Ae. albopictusdistribution range worldwide and discusses the likelihood of an establishment in Spain in view of climatological and geographical data. This revised version was published online in July 2006 with corrections to the Cover Date.     

Comparing and evaluating process-based ecosystem model predictions of carbon and water fluxes in major European forest biomes

Process‐based models can be classified into: (a) terrestrial biogeochemical models (TBMs), which simulate fluxes of carbon, water and nitrogen coupled within terrestrial ecosystems, and (b) dynamic global vegetation models (DGVMs), which further couple these processes interactively with changes in slow ecosystem processes depending on resource competition, establishment, growth and mortality of different vegetation types. In this study, four models – RHESSys, GOTILWA+, LPJ‐GUESS and ORCHIDEE – representing both modelling approaches were compared and evaluated against benchmarks provided by eddy‐covariance measurements of carbon and water fluxes at 15 forest sites within the EUROFLUX project. Overall, model‐measurement agreement varied greatly among sites. Both modelling approaches have somewhat different strengths, but there was no model among those tested that universally performed well on the two variables evaluated. Small biases and errors suggest that ORCHIDEE and GOTILWA+ performed better in simulating carbon fluxes while LPJ‐GUESS and RHESSys did a better job in simulating water fluxes. In general, the models can be considered as useful tools for studies of climate change impacts on carbon and water cycling in forests. However, the various sources of variation among models simulations and between models simulations and observed data described in this study place some constraints on the results and to some extent reduce their reliability. For example, at most sites in the Mediterranean region all models generally performed poorly most likely because of problems in the representation of water stress effects on both carbon uptake by photosynthesis and carbon release by heterotrophic respiration (R_h). The use of flux data as a means of assessing key processes in models of this type is an important approach to improving model performance. Our results show that the models have value but that further model development is necessary with regard to the representation of the some of the key ecosystem processes.     

Plant-attracted ants affect arthropod community structure but not necessarily herbivory

Abstract.  1. The effectiveness of ants as plant defenders is equivocal for plants that attract ants via extrafloral nectaries (EFNs).
2. This study focused on the myrmecophilic savannah tree Pseudocedrela kotschyi that attracts ants to EFNs and on the arthropod fauna associated with P. kotschyi . Herbivory and arthropod community composition were compared between trees that were dominated by one of three congeneric ant species, Camponotus acvapimensis , C. rufoglaucus , and C. sericeus , and between trees where ants were experimentally excluded and untreated control trees.
3. Short-term ant-exclusion experiments failed to demonstrate a consistent effect of ants on herbivory.
4. Plants dominated by different ant species differed significantly in leaf damage caused by herbivorous insects. The relative ranking of herbivory levels of the trees dominated by different ant species was persistent in three consecutive years.
5. Ants significantly reduced the abundance of different arthropod groups (Araneae, Blattodea, Coleoptera, Homoptera, non-ant Hymenoptera). Other groups, including important herbivores, seemed not to be affected (Lepidoptera, Orthoptera, Thysanoptera, Heteroptera).
6. The study suggests that the presence of ants only benefits plants when specific ant species are attracted, and protection by these ants is not counterbalanced by their negative effect on other beneficial arthropods.     

Karyology and Cytotaxonomy of the Genus Chrysolina Motschulsky (Coleoptera, Chrysomelidae)

Eight species of Chrysolina have been chromosomally studied in male individuals from Central Europe, South France and the Urals, in Russia. Ch. rufa had 2n = 23, Ch. purpurascens crassimargo 2n = 24 and a meioformula of 11 + Xy_p, Ch. globosa and Ch. bigorrensis 12 + Xy_p, Ch. umbratilis 2n = 30 and 14 + XY_p, a new non-chiasmate sex-chromosome system with both male sex-chromosomes of large size, Ch. cf. subcostata 12 + XY_p with large sex-chromosomes also, Ch. interstincta 2n = 40 and 19 + Xy_p, and Ch. obscurella 2n = 47. The taxonomic implications of these findings are discussed in relation with the current subgeneric classification of Chrysolina and principally that of the subgenera Colaphoptera, Sphaerochrysolina, Pleurosticha, Chalcoidea and Threnosoma.     

Isotope exchange at equilibrium indicates a steady state ordered kinetic mechanism for human sulfotransferase

Cytosolic sulfotransferase (SULT)-catalyzed sulfation regulates biosignaling molecular biological activities and detoxifies hydroxyl-containing xenobiotics. The universal sulfuryl group donor for SULTcatalyzed sulfation is adenosine 3'-phosphate 5'-phosphosulfate (PAPS). The reaction products are a sulfated product and adenosine 3',5'-diphosphate (PAP). Although the kinetics has been reported since the 1980s,SULT-catalyzed reaction mechanisms remain unclear. Human SULT1A1 catalyzes the sulfation of xenobiotic phenols and has very broad substrate specificity. It has been recognized as one of the most important phase II drug-metabolizing enzymes. Understanding the kinetic mechanism of this isoform is important in understanding drug metabolism and xenobiotic detoxification. In this report, we investigated the SULT1A1-catalyzed phenol sulfation mechanism. The SULT1A1-catalyzed reaction was brought to equilibrium by varying substrate (1-naphthol) and PAPS initial concentrations. Equilibrium constants were determined. Two isotopic exchanges at equilibrium ([14C]1-naphthol <=>[14C]1-naphthyl sulfate and[35S]PAPS<=>[35S]1-naphthyl sulfate) were conducted. First-order kinetics, observed for all the is otopic exchange reactions studied over the entire time scale that was monitored, indicates that the system was truly at equilibrium prior to addition of an isotopic pulse. Complete suppression of the 35S isotopic exchange rate was observed with an increase in the levels of 1-naphthol and 1-naphthyl sulfate in a constant ratio,while no suppression of the 14C exchange rate was observed with an increase in the levels of PAPS and PAP in a constant ratio. Data are consistent with a steady state ordered kinetic mechanism with PAPS and PAP binding to the free enzyme.     

The causes of spatial patterning of mounds of a fungus-cultivating termite: results from nearest-neighbour analysis and ecological studies

Little is known about processes regulating population dynamics in termites. We investigated the distribution of mound-colonies of the fungus-cultivating termite Macrotermes bellicosus (Smeathman) in two habitats in the Comoé National Park (Côte d'Ivoire) with nearest-neighbour analysis differentiating between different age classes. These results were compared with ecological data on processes influencing population dynamics. High mound densities were recorded in shrub savannah while only a few mounds were found in gallery forest. Mounds were distributed randomly in both habitats when all mounds were considered together, and when inhabited and uninhabited mounds were treated separately. However, distinctive non-random patterns were revealed in the savannah when we distinguished between different age classes. Small, young colonies were aggregated when they coexisted with larger, older colonies, which were more regularly distributed. This indicates that the distribution of older colonies is influenced by intraspecific competition whereas that of younger colonies is influenced by opposing factors that lead to aggregation. This is in accordance with ecological data. Food is a limiting resource for large colonies, while patchily distributed appropriate microclimatic conditions seem to be more important for young colonies. Colonies that had formerly coexisted (i.e. living colonies and recently dead colonies) showed aggregated, random and regular distribution patterns, suggesting several causes of mortality. Colonies that had never had contact with each other were randomly distributed and no specific regulation mechanism was implicated. These results show that different age classes seem to be regulated by different processes and that separation between age classes is necessary to reveal indicative spatial patterns in nearest-neighbour analysis.     

Arboreal ants as key predators in tropical lowland rainforest trees

Ants numerically dominate the canopy fauna of tropical lowland rain forests. They are considered to be key predators but their effects in this regard have only rarely been studied on non-myrmecophytes. A conspicuously low abundance of less mobile, mainly holometabolous arthropods like Lepidoptera larvae corresponds with ant dominance, while hemimetabolous highly mobile nymphs occur regularly and in large numbers in the trees. This is in contrast to the temperate regions where ants are mostly lacking on trees and holometabolous larvae are frequent. In this study we experimentally measured ant predation in the trees by offering caterpillars as baits. Fifty-four ant species were tested, of which 46 killed caterpillars and carried them away to their nests while only eight species ignored the offered larvae. Insecticidal knockdown fogging of ten trees after finishing the prey experiments showed that on average 85% of ant individuals per tree were predacious. With the analysis of another 69 foggings and meticulous observations in many other trees this suggests that arboreal ants are responsible for the low abundance of less mobile arthropods in tropical lowland rain forest canopies. Ant predation was significantly lower in a disturbed forest indicating that human disturbance induces a change in the functional interactions in these ecosystems.     

Plant viability assay

There is no single method in the long list given in Table 1 which can be used as an unequivocal criterion of viability. Many of the present methods of assay do correlate to various degrees with the final performance of the cell, tissue, organ, or the plant as a whole. Use of parallel viability tests indicating different cell functions is highly recommended. Great care should be taken to interpret the results of these assays. With several parallel tests, the validity of the interpretation can be enhanced, and in many cases, the interpretation may change considerably, depending upon the results from other tests, Since active transport systems have been implicated as one of the primary sites of freezing injury, more effort needs to be devoted to standardize viability assays based on this cell property. In general, the most popular viability assays for plants are based on biophysical rather than biochemical or metabolic functions. A specific test may be suited to a certain material more than another, yet our goal should be to devise a unique assay which will reflect the threshold of vitality versus death.