Absence of seasonal variation in great tit offspring sex ratios

When the timing of breeding affects the reproductive value of sons and daughters differently, parents are expected to increase their fitness by changing the offspring sex ratio during the course of the breeding season. Previous studies have shown that in great tits Parus major hatching date has a stronger effect on the fitness of juvenile males than on that of juvenile females. We tested whether this difference was reflected in a seasonal decline in the proportion of sons per breeding attempt. Although offspring sex ratio was more variable than would be expected from a binomial distribution, there was no significant relationship between the proportion of sons and the laying date of the clutch. Moreover, individual females did not adjust the sex ratio of their offspring following an experimental delay of breeding. This study therefore fails to demonstrate adaptive seasonal variation in great tit offspring sex ratios.     

Physical and functional interactome atlas of human receptor tyrosine kinases

Much cell‐to‐cell communication is facilitated by cell surface receptor tyrosine kinases (RTKs). These proteins phosphorylate their downstream cytoplasmic substrates in response to stimuli such as growth factors. Despite their central roles, the functions of many RTKs are still poorly understood. To resolve the lack of systematic knowledge, we apply three complementary methods to map the molecular context and substrate profiles of RTKs. We use affinity purification coupled to mass spectrometry (AP‐MS) to characterize stable binding partners and RTK–protein complexes, proximity‐dependent biotin identification (BioID) to identify transient and proximal interactions, and an in vitro kinase assay to identify RTK substrates. To identify how kinase interactions depend on kinase activity, we also use kinase‐deficient mutants. Our data represent a comprehensive, systemic mapping of RTK interactions and substrates. This resource adds information regarding well‐studied RTKs, offers insights into the functions of less well‐studied RTKs, and highlights RTK‐RTK interactions and shared signaling pathways.     

Enhanced fibroblast collagen production by a macrophage-derived factor (CEMF)

A basic fraction with pl values of 10.0–10.4 was isolated from macrophage culture medium. This fraction stimulated the production of collagen into fibroblast culture medium but inhibited the production of other proteins. Both changes were strongly dependent on the concentration of the factor. As revealed by SDS-PAGE the production of type I collagen was especially stimulated. The specific enhancement of fibroblast collagen production was also observed in the presence of serum proteins. The collagen synthesis enhancing macrophage-derived factor preparation (CEMF) contained three proteins, one major (M_r 23 kD) and two minor (M_r 49 and 71 kD) fractions in SDS-PAGE. When prelabeled fibroblast medium was exposed to CEMF a protein with M_r of 350 kD or greater was converted to a smaller size. This change was inhibited by EDTA but not by serum proteinase inhibitors.     

Zur Abnahme des Stars(Sturnus vulgaris) in Skandinavien

Zusammenfassung In vielen Teilen Skandinaviens sind übereinstimmend in den letzten Jahren Rückgänge im Bestand des Stars festgestellt worden. Die Gründe hierfür sind unbekannt. Vor allem bleibt zu prüfen, ob auch in südlich gelegenen Teilen des Areals Änderungen in der Siedlungsdichte, Reproduktionsrate usw. des Stars festgestellt wurden. Anregungen zu Untersuchungen der Bestandsentwicklung des Stars in Mittel- und Westeuropa bzw. zur Veröffentlichung bisher noch nicht publizierter Befunde werden gegeben.

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Decrease in Skandinavian starling populations

Summary After an imitial large-scale increase in all parts of Europe the populations of Starlings have been seriously decreased in Scandinavia, northern parts of the species range.Data from 8 populations from Finland, 2 from Sweden (Tab.) and notices from Norway show, that population densities have decreased to the level of 0–50% of their previous size. Many reasons have been proposed to be responsible for this: low productivity, pesticides, actions against Starlings in their wintering areas and shortening of suitable breeding habitats, but non of these gives a sufficient explanation.

     

Brood size manipulations within the natural range did not reveal intragenerational cost of reproduction in the Willow Tit Parus montanus

To test for the existence of a reproductive cost, we manipulated brood sizes (-2 and +2 nestlings) over 6 years in a northern population of Willow Tits Parus montanus breeding in natural holes. Possible effects were sought in subsequent survival and fecundity of the parents. Parents given extra chicks made more feeding visits than did parents with reduced and control broods. However, this was not reflected in differences in parental body-weight between groups at the end of the nestling period. Brood size manipulation did not significantly affect female or male survival. In 4 out of 6 years, there was a weak and nonsignificant effect on male survival, consistent with a cost of reproduction. Female and male fecundity in the year following the experiment was not affected by the manipulations. Thus, the data do not give evidence of an intragenerational cost of reproduction in the Willow Tit. Parents appeared unwilling to increase their breeding effort to a level which jeopardized their own survival or future breeding success. It is possible that, because of the time constraints in northern latitudes, females work under their capacity and lay smaller clutches than would otherwise be most profitable. Thus, no costs to the parents would be expected as a consequence of manipulations. These results suggest that the current reproductive rate is not maintained by reproductive cost in the Willow Tit. However, the results do not rule out the possibility that selection has operated outside the current range of reproductive rates during evolutionary history of the species.