Breeding behaviour of Nuthatch Sitta europaea in relation to natural hole attributes in a primeval forest

Capsule Nuthatches used holes with strong walls, typically in live trees with entrances reduced by plastering, and ‘oversized’ interiors filled with bark flakes.

Aims To describe patterns of nest-site utilization by Nuthatches in primeval conditions, to examine the influence of various hole attributes on nesting success and to consider the adaptive value of nest-site choice.

Methods Observations of birds living in undisturbed conditions in a strictly protected part of the Bia?owie?a National Park (Poland) during 27 breeding seasons coupled with measurements of hole attributes and observations of nests' fate.

Results Tree species used for breeding differed among habitats. Holes were on average 14.0 m above the ground, in trees with girth at breast height 206 cm; both parameters varied strongly among tree species. They were situated mainly in tree trunks (76%), in living trees (89%), in conical knotholes (51%); woodpecker-made holes constituted 32%. Nuthatches bred in very large (mean bottom area: 325 cm²) holes, the preferred tree species (Maple Acer platanoides, Ash Fraxinus excelsior) had larger holes than other tree species. Nuthatches reduced entrances by ‘plastering’ to a mean size of 2.9 × 3.3 cm. They made the holes substantially shallower by filling them with bark flakes (mean depth to nest level: 10 cm), eggs were laid in depressions among flakes, far from the entrance (mean distance: 21 cm), their ‘nests’ occupied only a fraction of the hole area. Broods in holes with smaller entrances were the most successful. Eggs and small young were covered with bark during the absence of the female. Larger nestlings, when endangered, moved to the rear wall of the hole, where they stayed tightly pressed. These behaviour patterns reduced the risk of predation.

Conclusion The features of holes used by Nuthatches (combination of strong walls, small entrances and large bottoms with copious filling) are probably an evolutionary solution to the need to evade predators while keeping contents of the nest dry.     

Disentangling effects of disturbance severity and frequency: Does bioindication really work?

Ecological disturbances are recognized as a crucial factor influencing the attributes of ecological communities. Depending on the specific adaptation or life cycle, plant species show different responses to disturbances of different magnitudes. Herben et al. (Journal of Vegetation Science, 27, 628–636) proposed six disturbance indicator values (DIVs) that describe the niches of Central‐European plant species along gradients of disturbance frequency and severity. Here, we ask if the DIVs can be used in community ecology for bioindication of disturbance regime?We used a dataset of riparian forests sampled within mountain catchments (the Sudetes, SW Poland). As the regime of disturbance is driven by changes in floods from the spring toward the mouth, we calculated the position of every plot along longitudinal (upstream–downstream) gradient and used it as a proxy for the disturbance severity and frequency. We then calculated the community‐weighted means (CWMs) for each of the six indices for each plot and analyzed whether these indices reflected the position of the plots along the rivers. We expected an increase in the severity indices and a decrease in the frequency indices downstream along the rivers. Moreover, we analyzed relationships between disturbance indices and species optima along longitudinal gradient.Surprisingly, means for all analyzed indices increased along the rivers. Severity indices showed the strongest association with the longitudinal gradient. The disturbance severity index for herbs was the only index that differed significantly among species with different responses along longitudinal gradient. On these results, we identified a strong correlation between the severity and frequency indices as the main problem.We conclude that the DIVs have considerable applicative potential; however, the determination of ecological niches separately for disturbance severity and frequency is difficult because different components interact to shape the realized niche of each species. All analyzed indices encompass different attributes of the disturbance regime including both severity and frequency.     

Effects of Titanium Dioxide Nanoparticles Exposure on Human Health—a Review

Biological Trace Element Research - Recently, an increased interest in nanotechnology applications can be observed in various fields (medicine, materials science, pharmacy, environmental...     

Repurposing of synaptonemal complex proteins for kinetochores in Kinetoplastida

Chromosome segregation in eukaryotes is driven by the kinetochore, a macromolecular complex that connects centromeric DNA to microtubules of the spindle apparatus. Kinetochores in well-studied model eukaryotes consist of a core set of proteins that are broadly conserved among distant eukaryotic phyla. By contrast, unicellular flagellates of the class Kinetoplastida have a unique set of 36 kinetochore components. The evolutionary origin and history of these kinetochores remain unknown. Here, we report evidence of homology between axial element components of the synaptonemal complex and three kinetoplastid kinetochore proteins KKT16-18. The synaptonemal complex is a zipper-like structure that assembles between homologous chromosomes during meiosis to promote recombination. By using sensitive homology detection protocols, we identify divergent orthologues of KKT16-18 in most eukaryotic supergroups, including experimentally established chromosomal axis components, such as Red1 and Rec10 in budding and fission yeast, ASY3-4 in plants and SYCP2-3 in vertebrates. Furthermore, we found 12 recurrent duplications within this ancient eukaryotic SYCP^2–3 gene family, providing opportunities for new functional complexes to arise, including KKT16-18 in the kinetoplastid parasite Trypanosoma brucei. We propose the kinetoplastid kinetochore system evolved by repurposing meiotic components of the chromosome synapsis and homologous recombination machinery that were already present in early eukaryotes.