Circadian flight schedules in night-migrating birds caught on migration

Many species of migratory birds migrate in a series of solitary nocturnal flights. Between flights, they stop to rest and refuel for the next segment of their journey. The mechanism controlling this behaviour has long remained elusive. Here, we show that wild-caught migratory redstarts (Phoenicurus phoenicurus) are consistent in their flight scheduling. An advanced videographic system enabled us to determine the precise timing of flight activity in redstarts caught at a northern European stopover site during their return trip from Africa. Birds were held captive for three days in the absence of photoperiodic cues (constant dim light) and under permanent food availability. Despite the absence of external temporal cues, birds showed clear bimodal activity patterns: intense nocturnal activity alternating with diurnal foraging and resting periods. The onset of their migratory activity coincided with the time of local sunset and was individually consistent on consecutive nights. The data demonstrate that night-migrating birds are driven by autonomous circadian clocks entrained by sunset cues. This timekeeping system is probably the key factor in the overall control of nocturnal songbird migration.     

Methane emissions by alpine plant communities in the Qinghai-Tibet Plateau

For the first time to our knowledge, we report here methane emissions by plant communities in alpine ecosystems in the Qinghai-Tibet Plateau. This has been achieved through long-term field observations from June 2003 to July 2006 using a closed chamber technique. Strong methane emission at the rate of 26.2+/-1.2 and 7.8+/-1.1microg CH4 m-2h-1 was observed for a grass community in a Kobresia humilis meadow and a Potentilla fruticosa meadow, respectively. A shrub community in the Potentilla meadow consumed atmospheric methane at the rate of 5.8+/-1.3microg CH4 m-2h-1 on a regional basis; plants from alpine meadows contribute at least 0.13Tg CH4 yr-1 in the Tibetan Plateau. This finding has important implications with regard to the regional methane budget and species-level difference should be considered when assessing methane emissions by plants.     

TECHNICAL ADVANCES: New strategies for telomere-based age estimation

Telomere dynamics link molecular and cellular mechanisms with organismal processes and therefore may explain variation in a number of important life-history traits. Telomere length has been used to estimate age in free-living populations of animals. Such estimation is a potentially powerful tool in the context of population dynamics and management, as well as the study of life-history trade-offs. The number of studies utilizing telomere restriction fragment assays in the fields of ecology and evolution is steadily growing. However, the field lacks methodological and analytical standardization resulting in considerable variation in telomere length and therefore in the usefulness of these techniques. Here, we illustrate new laboratory and analytical methods to reliably measure telomere length from blood erythrocytes and accurately assess the relationship between telomeres and age. We demonstrate the importance of analysing those telomeres most relevant to age-related studies: the shortest telomeres. We present a reliable method to quickly identify an analysis window (the telomere optimal estimate, TOE) which approaches the optimal window for age estimation. Because the TOE focuses on the shortest telomeres - those telomeres which signal cellular senescence and ageing - TOE can also be used to compare telomeres in age-matched individuals. We also compare constant- and pulsed-field gel electrophoresis to show how each can influence telomere measurement. The use of TOE should provide powerful telomere-based age estimation and enable organismal biologists to readily uncover individual and longitudinal differences with regard to telomere dynamics.     

Development and characterization of microsatellites markers from the macaw

Macaw (Acrocomia aculeata) is a native palm tree from tropical forests, highly abundant in Brazil and cited as one of the principal sources of plant oil, thus presenting a high potential for biodiesel production. We have optimized and utilized a set of eight polymorphic microsatellite markers for A. aculeata from an enriched genomic library. Automatic sequencing and fluorescence detection were employed to analyse 43 individuals from natural populations. In this study, we have obtained an average number of five alleles per locus. These loci will be employed in future studies of population genetics by providing subsidy information for the species conservation and genetic breeding.     

Increasing ecological inference from high throughput sequencing of fungi in the environment through a tagging approach

High throughput sequencing methods are widely used in analyses of microbial diversity, but are generally applied to small numbers of samples, which precludes characterization of patterns of microbial diversity across space and time. We have designed a primer-tagging approach that allows pooling and subsequent sorting of numerous samples, which is directed to amplification of a region spanning the nuclear ribosomal internal transcribed spacers and partial large subunit from fungi in environmental samples. To test the method for phylogenetic biases, we constructed a controlled mixture of four taxa representing the Chytridiomycota, Zygomycota, Ascomycota and Basidiomycota. Following cloning and colony restriction fragment length polymorphism analysis, we found no significant difference in representation in 19 of the 23 tested primers. We also generated a clone library from two soil DNA extracts using two primers for each extract and compared 456 clone sequences. Community diversity statistics and contingency table tests applied to counts of operational taxonomic units revealed that the two DNA extracts differed significantly, while the pairs of tagged primers from each extract were indistinguishable. Similar results were obtained using UniFrac phylogenetic comparisons. Together, these results suggest that the pig-tagged primers can be used to increase ecological inference in high throughput sequencing projects on fungi.     

Application of biocathode in microbial fuel cells: cell performance and microbial community

Instead of the utilization of artificial redox mediators or other catalysts, a biocathode has been applied in a two-chamber microbial fuel cell in this study, and the cell performance and microbial community were analyzed. After a 2-month startup, the microorganisms of each compartment in microbial fuel cell were well developed, and the output of microbial fuel cell increased and became stable gradually, in terms of electricity generation. At 20 ml/min flow rate of the cathodic influent, the maximum power density reached 19.53 W/m3, while the corresponding current and cell voltage were 15.36 mA and 223 mV at an external resistor of 14.9 Omega, respectively. With the development of microorganisms in both compartments, the internal resistance decreased from initial 40.2 to 14.0 Omega, too. Microbial community analysis demonstrated that five major groups of the clones were categorized among those 26 clone types derived from the cathode microorganisms. Betaproteobacteria was the most abundant division with 50.0% (37 of 74) of the sequenced clones in the cathode compartment, followed by 21.6% (16 of 74) Bacteroidetes, 9.5% (7 of 74) Alphaproteobacteria, 8.1% (6 of 74) Chlorobi, 4.1% (3 of 74) Deltaproteobacteria, 4.1% (3 of 74) Actinobacteria, and 2.6% (2 of 74) Gammaproteobacteria.     

Grazing, social and comfort behaviour of Ankole and crossbred (Ankole × Holstein) heifers on pasture in south western Uganda

The aim of this study was to assess the grazing, social and comfort behaviour of the indigenous purebred Ankole cattle breed and crossbred (Holstein × Ankole) animals under typical management conditions in south western Uganda. Twelve focal animals in each of four groups (two groups per genotype) were observed regarding their grazing, social and comfort behaviour on pasture.No significant differences in grazing behaviour patterns (eating, walking, standing) were found between the genotypes. Resting occurred only very rarely in both genotypes. Walking distances of Ankole and Ankole × Holstein crosses were also similar. There was no difference in the occurrence of agonistic interactions between the two genotypes. However, Ankole cattle engaged in more non-agonistic social interactions than their crossbred counterparts. Individual distances were lower in Ankole heifers and more herd mates were found within a radius of 5 m around the Ankole animals. The most important comfort behaviour pattern in both genotypes was self-licking, which occurred to similar frequency in Ankole and crossbred heifer groups. Crossbred animals scratched themselves and rubbed on objects more often than Ankole heifers.Although Ankole cattle and their Holstein crosses did not differ in grazing, distances walked and agonistic behaviours, the significant differences between the two genotypes in herd cohesion and comfort behaviour may pose challenges on the management of crossbred animals under extensive open grazing conditions as present in south western Uganda. Thus, apart from (re)productive performance traits, behavioural traits of both genotypes may also be taken into account for breeding decisions and management under current production conditions.     

Foraging mechanics and their outcomes for cattle grazing reproductive tropical swards

For grazing animals an important determinant of animal performance is the rate of nutrient intake (RNI) which depends on diet quality and instantaneous intake rate (IIR). In turn, diet quality and IIR are the outcome of the interaction between the morphology and behaviour of the animal and the structure of the sward. Using artificial microswards of Panicum maximum we evaluated the effect of four levels of the tensile resistance of stems in tropical swards on the grazing behaviour of cattle of two age classes (1- and 3-year-old steers) faced with a stem barrier either in a vertical (experiment 1, E1) or horizontal plane (experiment 2, E2). The animals did not select against low tensile resistance stems (LTRS) but did avoid high tensile resistance stems (HTRS) which resulted in a significant difference (P < 0.001) between diet DM (dry matter) digestibility and forage DM digestibility in swards with HTRS. IIR decreased (P < 0.001) on average 62% in E1 and 67% in E2 as stem tensile resistance increased, 144% and 177% in E1 and E2, respectively. This led to a reduction (P < 0.001) in digestible DM IIR in both young and mature cattle respectively of 56% and 68% in E1, and 45% and 79% in E2, as stem tensile resistance increased. The decline in IIR was due to an increase in time per bite and a reduction in bite dimensions that were the result of different mechanisms in the two experiments: when leaves were taller than the stems (E1) the decrease in bite area was associated with an asymptotic increase (P < 0.001) in bite force in mature animals, and a maintenance (P = 0.456) of bite force in young animals, suggesting that maximum bite force regulated bite area in E1. This was not the case in E2 because both bite area and bite force decreased (P < 0.05) with the increase in stem tensile resistance suggesting that the animals were not able to gather enough plant material with the tongue in order for bite force to regulate bite area. We conclude that bite force and tongue force regulate selectivity and bite dimensions, which are the ultimate determinants of the RNI; IIR is the primary determinant of the RNI with diet quality being of lesser importance; and HTRS act as deterrents to achieving maximum IIR in tropical swards, particularly in mature cattle.     

Community analysis of arbuscular mycorrhizal fungi and bacteria in the maize mycorrhizosphere in a long-term fertilization trial

In this study, we investigated the impact of organic and mineral fertilizers on the community composition of arbuscular mycorrhizal (AM) fungi and bacteria in the mycorrhizosphere of maize in a field experiment established in 1956, in south-east Sweden. Roots and root-associated soil aggregates were sampled four times during the growing season in 2005, in control plots and in plots amended with calcium nitrate, ammonium sulphate, green manure, farmyard manure or sewage sludge. Fungi in roots were identified by cloning and sequencing, and bacteria in soil aggregates were analysed by terminal-restriction fragment length polymorphism, cloning and sequencing. The community composition of AM fungi and bacteria was significantly influenced by the different fertilizers. Changes in microbial community composition were mainly correlated with changes in pH induced by the fertilization regime. However, other factors, including phosphate and soil carbon content, also contributed significantly to these changes. Changes in bacterial community composition and a reduction in bacterial taxon richness throughout the growing season were also manifest. The results of this study highlight the importance and significant effects of the long-term application of different fertilizers on edaphic factors and specific groups of fungi and bacteria playing a key role in arable soils.