Population structure,biometrics and moult of migrant Purple Sandpipers Calidris maritima in southwest Iceland in spring

Capsule Iceland is a stop‐over site for a population of Purple Sandpipers that winter in Britain. Here, they accumulate fuel loads for onward migration along with birds that have wintered in Iceland.

Aims To establish whether Purple Sandpipers from Britain stop‐over in Iceland during spring migration and, if so, to describe their population structure, changes in mass and moult.

Methods Purple Sandpipers were cannon‐netted on the coast of the Reykjanes Peninsula in southwest Iceland during May 2003 and 2005. Birds were aged, sexed (some by DNA) and standard biometric measurements made. Active body moult was scored.

Results Bill and wing lengths showed that the Purple Sandpipers we caught were similar to one of the populations that winter in Britain rather than Icelandic breeding birds. There were more males than females throughout the migration period (63% males for first‐year‐birds and 67% for adult birds). Accounting for a bias due to a higher percentage of males in a less usual habitat (muddy/sandy bays), the values for rocky sites were 52% males for first‐year birds and 62% for adults. The percentage of first‐year birds was 19% in 2003 and 32% in 2005, though the latter figure was biased by catches in muddy/sandy bays where there was a higher percentage of young birds. The percentage of first‐year birds was 25% on just the rocky shores in 2005. Many birds were in latter stages of body moult, and males were slightly in advance of females. Increasing mass showed that they were preparing for onward migration. The average increase of 0.58 g per day was similar to the rate measured in Orkney at an earlier point on the migration route. However, a high turnover of birds could be the reason for these low values. By late May, and close to the assumed departure date, the Purple Sandpipers of the different age/sex classes had fuel indices of 24–29% (33–42% of the lean mass). This was lower than that for the high Arctic sandpipers (Knots and Sanderlings) leaving southwest Iceland for Greenland and Canada.

Conclusions Our study confirmed that Purple Sandpipers do stop‐over in Iceland, and the possible lower rate of fuel accumulation and smaller amount stored, compared with Knots and Sanderlings, suggests a different migration pattern.     

Long-distance relocation of nestboxes reduces nest predation by Pine Marten Martes martes

Capsule Clutches of hole-nesting passerines suffer less predation if nestboxes are moved by 800–3000 m.

Aims To see if Pine Marten predation upon clutches of insectivorous birds increases with the age of nestboxes and to see if predation is affected by the distance nestboxes are relocated from the plots where predation occurred the previous year.

Methods The study was undertaken in two habitats of central Italy (deciduous and Holm Oak wood). In each habitat, nestboxes were placed and relocated in order to have plots with: new (first year of placement) or old (second year of placement) nestboxes; short (100 m) or long-distance (800–3000 m) relocated nestboxes following previous predation.

Results After controlling for habitat, hole-nester density, competition with snakes and nestbox age, the plots with nestboxes replaced at a short distance from the original location suffered higher predation pressure. Pine Marten predation was higher in plots with older nestboxes. A high predation rate was observed in nestboxes replaced in plots where they had not been present for one year and where they had been heavily preyed on in past years.

Conclusion To reduce the risks of predation by mammals, the relocation of old nestboxes should be carried out at a long distance from plots where predation had previously occurred.     

Skull and limb morphology differentially track population history and environmental factors in the transition to agriculture in Europe

The Neolithic transition in Europe was a complex mosaic spatio-temporal process, involving both demic diffusion from the Near East and the cultural adoption of farming practices by indigenous hunter–gatherers. Previous analyses of Mesolithic hunter–gatherers and Early Neolithic farmers suggest that cranial shape variation preserves the population history signature of the Neolithic transition. However, the extent to which these same demographic processes are discernible in the postcranium is poorly understood. Here, for the first time, crania and postcranial elements from the same 11 prehistoric populations are analysed together in an internally consistent theoretical and methodological framework. Results show that while cranial shape reflects the population history differences between Mesolithic and Neolithic lineages, relative limb dimensions exhibit significant congruence with environmental variables such as latitude and temperature, even after controlling for geography and time. Also, overall limb size is found to be consistently larger in hunter–gatherers than farmers, suggesting a reduction in size related to factors other than thermoregulatory adaptation. Therefore, our results suggest that relative limb dimensions are not tracking the same demographic population history as the cranium, and point to the strong influence of climatic, dietary and behavioural factors in determining limb morphology, irrespective of underlying neutral demographic processes.     

Molecular machines

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Highlights? Elastic models of proteins capture large-scale motions of motors. ? Function of motors is embedded in native contacts and evolutionary patterns. ? Reaction path models motor motions by a tube of minimum free energy path. ? Milestoning correlates structure and function of atomic models of motors.     

Yeast-based automated high-throughput screens to identify anti-parasitic lead compounds

We have developed a robust, fully automated anti-parasitic drug-screening method that selects compounds specifically targeting parasite enzymes and not their host counterparts, thus allowing the early elimination of compounds with potential side effects. Our yeast system permits multiple parasite targets to be assayed in parallel owing to the strains’ expression of different fluorescent proteins. A strain expressing the human target is included in the multiplexed screen to exclude compounds that do not discriminate between host and parasite enzymes. This form of assay has the advantages of using known targets and not requiring the in vitro culture of parasites. We performed automated screens for inhibitors of parasite dihydrofolate reductases, N-myristoyltransferases and phosphoglycerate kinases, finding specific inhibitors of parasite targets. We found that our ‘hits’ have significant structural similarities to compounds with in vitro anti-parasitic activity, validating our screens and suggesting targets for hits identified in parasite-based assays. Finally, we demonstrate a 60 per cent success rate for our hit compounds in killing or severely inhibiting the growth of Trypanosoma brucei, the causative agent of African sleeping sickness.     

Promoters maintain their relative activity levels under different growth conditions

Most genes change expression levels across conditions, but it is unclear which of these changes represents specific regulation and what determines their quantitative degree. Here, we accurately measured activities of ～900 S. cerevisiae and ～1800 E. coli promoters using fluorescent reporters. We show that in both organisms 60–90% of promoters change their expression between conditions by a constant global scaling factor that depends only on the conditions and not on the promoter's identity. Quantifying such global effects allows precise characterization of specific regulation—promoters deviating from the global scale line. These are organized into few functionally related groups that also adhere to scale lines and preserve their relative activities across conditions. Thus, only several scaling factors suffice to accurately describe genome‐wide expression profiles across conditions. We present a parameter‐free passive resource allocation model that quantitatively accounts for the global scaling factors. It suggests that many changes in expression across conditions result from global effects and not specific regulation, and provides means for quantitative interpretation of expression profiles.