Individual and sex‐related patterns of prolonged flights during both day and night by great reed warblers crossing the Mediterranean Sea and Sahara Desert

A wide variety of the barrier crossing strategies exist among migrating songbirds, ranging from strict nocturnal flights to non‐stop flights over a few days. We evaluate barrier crossing strategies in a nocturnally migrating songbird crossing the Mediterranean Sea and the Sahara Desert, the great reed warbler, exploring variation between the sexes and within individuals. We used data from 31 year‐round light‐level geolocators tracks from 26 individuals (13 males and 13 females), with four individuals tracked for 2–3.5 consecutive years. Almost all individuals (25 of 26) prolonged their flights into the day at least on one occasion. The mean duration of these prolonged flights was 19.9 h and did not differ between sexes or seasons. Fifteen birds performed non‐stop flights during more than one full day and night (≥ 24 h; mean = 31.9 h; max = 55 h) in autumn and/or spring, but these flights were generally too short to cross an entire barrier (such as the Sahara Desert) in one non‐stop flight. Patterns of prolonged flights showed considerable within‐individual variation in females between seasons (autumn versus spring) and in both males and females between years, suggesting high individual flexibility in migration strategy. Significantly more males than females performed prolonged flights during autumn migration, but not spring, possibly reflecting sex‐specific carry‐over effects. We conclude that great reed warblers have the ability to conduct prolonged continuous flights for up to several nights and days, which potentially would allow them to cross the Sahara Desert in one non‐stop flight. However, they typically use a mixed strategy of several nocturnal flights with intermittent stopovers in combination with 1–3 prolonged flights. Prolonged flights covered less than half (44%) of the total flight time across the barriers, and the diurnal parts of the flights covered only 18% of this time.     

The effective size of bryophyte populations

Bryophytes with their dominant haploid stage conform poorly to the life cycles generally treated in population genetical models. Here we make a detailed analysis of what effective sizes bryophyte model populations have as a function of their breeding system. It is found that the effective size is rarely much smaller than the scored number of haploid gametophytic individuals, even when the limited number of diploids (sporophytes) formed is taken into account. The most severe decrease in effective size occurs when unisexual gametophytic females produce only a small number of fertile diploid sporophytes in male biased populations; this effect is due to the restricted sampling of male gametophytic individuals that then occurs. It is shown that the harmonic mean of diploid sporophytes formed per haploid gametophytic individuals is the relevant measure in these calculations and not the standard (and generally larger) arithmetic mean.     

Pyoverdine and PQS mediated subpopulation interactions involved in Pseudomonas aeruginosa biofilm formation

Using flow chamber‐grown Pseudomonas aeruginosa biofilms as model system, we show in the present study that formation of heterogeneous biofilms may occur through mechanisms that involve complex subpopulation interactions. One example of this phenomenon is expression of the iron‐siderophore pyoverdine in one subpopulation being necessary for development of another subpopulation that does not itself express the pyoverdine synthesis genes. Another example is quorum sensing‐controlled DNA release in one subpopulation being necessary for development of another subpopulation that does not itself express the quorum‐sensing genes.     

The rat as an animal model of Alzheimer's disease

As a disease model, the laboratory rat has contributed enormously to neuroscience research over the years. It has also been a popular animal model for Alzheimer's disease but its popularity has diminished during the last decade, as techniques for genetic manipulation in rats have lagged behind that of mice. In recent years, the rat has been making a comeback as an Alzheimer's disease model and the appearance of increasing numbers of transgenic rats will be a welcome and valuable complement to the existing mouse models. This review summarizes the contributions and current status of the rat as an animal model of Alzheimer's disease.     

A module-based analytical strategy to identify novel disease-associated genes shows an inhibitory role for interleukin 7 Receptor in allergic inflammation

Background  

The identification of novel genes by high-throughput studies of complex diseases is complicated by the large number of potential genes. However, since disease-associated genes tend to interact, one solution is to arrange them in modules based on co-expression data and known gene interactions. The hypothesis of this study was that such a module could be a) found and validated in allergic disease and b) used to find and validate one ore more novel disease-associated genes.     

Molecular characterization of UV-treated sugar beet somaclones using RFLP markers

Sugar beet plants regenerated from UV-treated calluses were examined by restriction fragment length polymorphism (RFLP) analysis to determine the extent of somaclonal variation occurring at the DNA level. In total, 50 random sugar beet DNA sequences were used to screen 42 somaclones for genetic alterations. Three polymorphisms were detected among the 7 644 alleles analysed. From these data a mutation frequency of 0.03 ± 0.02% per allele was estimated. This frequency is in agreement with similar studies of somaclonal DNA variation using molecular markers and lies in the upper range of the spontaneous gene mutation frequencies found in plants. The two probegenotype combinations showing independent polymorphisms, were further analysed using the restriction enzymes Bam HI, Eco RI, Eco RV and Hind III. Both polymorphisms are likely to result from structural rearrangements rather than from point mutations. Differences in methylation among 10 of the investigated somaclones were tested for by comparing Hpa II and Msp I generated RFLP patterns. The somaclones showed extensive methylation, but no differences in their degree of methylation. Cytological analysis revealed 34 diploid, 8 tetraploid, but no aneuploid plants.     

The pollination ecology of Listera ovata (Orchidaceae)

Interactions between Listera ovata (L.) R. Br. and anthophilous insects were observed on Öland and in Uppland, Sweden, during 1974–1980. The pollen vectors were mainly ichneumons (Hymenoptera Parasitica, Ichneumonidae), saw–flies (Hymenoptera Symphyta) and beetles (Coleoptera). These three groups transported on Oland 56, 28 and 10% and in Uppland 28, 54 and 15% of the pollinia. The most common visitors were Diptera. In the Ichneumonidae, males were on average over three times as frequent as females and carried 81% of the pollinia. Various data indicated anthecological specialization to about 8–12 mm long, relatively strong insects, which show abundance and diversity in the biotopes with L. ovata. They have medium–sized almost hairless heads with short and rather small mouth–parts. Perhaps optimal interaction takes place with ichneumon males. Since floral adaptation to the legitimate group obviously includes generalized chemical attractants and complete accessibility of nectar, the spectrum of visitors reaches that of an umbelliferous plant. The touch–sensitive rostellum has probably induced evolution of the long nectariferous furrow on the labellum surface. The floral fragrance is essentially a terpene–blend. Experiments indicated strict entomogamy.     

Multicellular Tumour Spheroid as a model for evaluation of [18F]FDG as biomarker for breast cancer treatment monitoring

Background  

In order to explore a pre-clinical method to evaluate if [¹⁸F]FDG is valid for monitoring early response, we investigated the uptake of FDG in Multicellular tumour spheroids (MTS) without and with treatment with five routinely used chemotherapy agents in breast cancer.     

The river domain: why are there more species halfway up the river?

Biologists have long noted higher levels of species diversity in the longitudinal middle‐courses of river systems and have proposed many explanations. As a new explanation for this widespread pattern, we suggest that many middle‐course peaks in richness may be, at least in part, a consequence of geometric constraints on the location of species’ ranges along river courses, considering river headwaters and mouths as boundaries for the taxa considered. We demonstrate this extension of the mid‐domain effect (MDE) to river systems for riparian plants along two rivers in Sweden, where a previous study found a middle‐course peak in richness of natural (non‐ruderal) species. We compare patterns of empirical richness of these species to null model predictions of species richness along the two river systems and to spatial patterns for six environmental variables (channel width, substrate fineness, substrate heterogeneity, ice scour, bank height, and bank area). In addition, we examine the independent prediction of mid‐domain effects models that species with large ranges, because the location of their ranges is more constrained, are more likely to produce a mid‐domain peak in richness than are species with small ranges. Species richness patterns of riparian plants were best predicted by models including both null model predictions and environmental variables. When species were divided into large‐ranged and small‐ranged groups, the mid‐domain effect was more prominent and the null model predictions were a better fit to the empirical richness patterns of large‐ranged species than those of small‐ranged species. Our results suggest that the peak in riparian plant species richness in the middle courses of the rivers studied can be explained by an underlying mid‐domain effect (driven by geometric constraints on large‐ranged species), together with environmental effects on richness patterns (particularly on small‐ranged species). We suggest that the mid‐domain effect may help to explain similar middle‐course richness peaks along other rivers.     

Avoid your neighbours: size-determined spatial distribution patterns among northern pike individuals

The spatial distribution of individual animals may both cause and be caused by intra- and/or interspecific interactions. This work aims primarily on effects of intraspecific interactions. Agonistic and unequally strong interactions among conspecifics should make the within-population distribution of individuals to be characterised by spatial avoidance of potentially risky conspecifics, according to the individual risks perceived. This process should affect individual performance and involve individual tradeoffs, as failing to adequately avoid risky conspecifics could incur unnecessary costs, while, at the same time, successful conspecific avoidance may reduce access to patches favourable for e.g. foraging or sheltering. Intraspecific agonistic behaviours, such as cannibalism and competition, are likely to have prominent effects in size-structured populations. It is therefore reasonable to assume spatial avoidance of intraspecific risks according to individuals' size relationships in such populations. With this field investigation I show that individuals of northern pike spatially avoid larger conspecifics. This avoidance creates a size-influenced and spatially clumped distribution pattern among pike individuals. At low pike densities, however, distances between individuals increase, allowing for an even distribution pattern to appear. The spatial distribution patterns among piscivore individuals should affect both the individual performance of predators and the potential for spatial anti-predatory responses of their prey, and hence be a factor in consumer–resource interactions.