The significance of partial migration for food web and ecosystem dynamics

Migration is ubiquitous and can strongly shape food webs and ecosystems. Less familiar, however, is that the majority of life cycle, seasonal and diel migrations in nature are partial migrations: only a fraction of the population migrates while the other individuals remain in their resident ecosystem. Here, we demonstrate different impacts of partial migration rendering it fundamental to our understanding of the significance of migration for food web and ecosystem dynamics. First, partial migration affects the spatiotemporal distribution of individuals and the food web and ecosystem-level processes they drive differently than expected under full migration. Second, whether an individual migrates or not is regularly correlated with morphological, physiological, and/or behavioural traits that shape its food-web and ecosystem-level impacts. Third, food web and ecosystem dynamics can drive the fraction of the population migrating, enabling the potential for feedbacks between the causes and consequences of migration within and across ecosystems. These impacts, individually and in combination, can yield unintuitive effects of migration and drive the dynamics, diversity and functions of ecosystems. By presenting the first full integration of partial migration and trophic (meta-)community and (meta-)ecosystem ecology, we provide a roadmap for studying how migration affects and is affected by ecosystem dynamics in a changing world.     

White rhinoceros range size in the south-western Kruger National Park

White rhinoceros range size was ascertained telemetrically in the south-western Kruger National Park. The mean annual range size of territorial males was 9.86 km² compared to 22.83 km² for adult females. White rhinoceros females' summer wet season range was larger (21.44 km²) than the winter dry season range (11.64 km²). It is argued that abundant field-water during the wet season enables animals to range further from permanent water supplies and to utilize larger foraging areas. White rhinoceros have core areas in their individual ranges that usually are situated along riverbanks in the preferred grazing regions. These core areas also include some favourite resting spots on high-lying areas. White rhinoceros range sizes in the south-western Kruger National Park were similar to those of other reserves with comparable white rhinoceros densities. In the Umfolozi Game Reserve, which has a higher white rhinoceros density than the Kruger National Park, the individual ranges are much smaller.     

Polymorphism in the Ostertagiinae Lopez-Neyra, 1947 and comments on the systematics of these nematodes

A list of 19 polymorphic species of the generaOstertagia, Orloffia, Teladorsagia, Marshallagia andSpiculopteragia is presented. The morphs of the polymorphic species in question have identical females and show similarities in some male features, e.g. the structure of the oesophagus, the synlophe and the shape of the rays of the copulatory bursa. However, they differ by characters which are recognised as generic features, e.g. the structure of spicules, gulbernaculum and genital cone. The presence or lack of minor morphs is a generic feature in the Ostertagiinae. Each polymorphic genus has a defined type of minor morph.     

Amino acid pool and protein turnover during differentiation (spherulation) ofPhysarum polycephalum

The composition of the amino acid pool during spherulation was determined. It changes in size and in composition, the concentration of each amino acid behaving individually. The first response to the onset of spherulation either by starvation or osmotic shock (0.5 M mannitol) always is a decrease of the pool's size, which during further starvation expands for a short period and then decreases again. During development induces by mannitol in the presence of external amino acids, the pool size increases continuously after the initial depletion.As shown by radioactive labeling, amino acids were actively released from the plasmodium into a medium containing amino acids, but retained by the microplasmodia in an amino acid-free medium. The kinetics of the uptake of radioactive amino acids from the medium is biphasic, indicating the existence of multiple pools. Even after a labeling period of 8 h the amino acid pool is not yet in equilibrium with the medium. The possibility of a compartimentation of the pool was confirmed by density labeling of two different enzymes.Whereas the turnover of total protein is only very low during growth, it is rather high in spherulating microplasmodia. At least 70% of the originally existing protein is degraded during this development, while, simultaneously, at least 50% of the protein present after 24 h starvation is newly synthesized during that period.     

Gelation of xanthan with trivalent metal ions

In-situ gelation of semidilute xanthan solutions with trivalent chromium, aluminum or iron ions was studied by rheology and UV-spectroscopy. Measurements of the elastic modulus of xanthan gel cylinders prepared by dialysis against the complexing ion at pH values from 2 to 6 indicate that monomeric species of the ion are ineffective, whereas dimeric or higher oligomeric species are effective in crosslinking the polysaccharide. When chromium was used as the crosslinking species, the dependence of the gelation rate on the ionic concentration followed a power law with a coefficient of 1·7. The gelation time and the gelation rate were found to extrapolate to zero at 1 m Cr for 2·5 mg/ml xanthan. The limiting concentration of xanthan needed for gelation with 5 m Cr(III) at 20°C was estimated as 0·35 mg/ml. This critical xanthan concentration is close to the overlap concentration c^* estimated from the experimentally determined intrinsic viscosity [η] using c^* = 1·4/[η]. An apparent activation energy for crosslinking of xanthan was calculated as E_a = 42 kJ/mol and E_a = 108 kJ/mol for Cr and Al ions, respectively. The fractal dimensionality of xanthan-Cr at the sol-gel transition was estimated as 1·3 applying the Chambon-Winter criterion for gelation, thus indicating that this gelation criterion is applicable also to stiff-chain polysaccharides such as xanthan.     

Cloning and expression of bacteriophage SP02 DNAZ polymerase gene L in Bacillus subtilis, using the Staphylococcus aureus plasmid pC194

HindIII restriction endonuclease fragments of DNA from temperate Bacillus subtilis bacteriophage SP02 were cloned in B. subtilis by using the plasmid pC194. Three hybrid plasmids which permit growth of the mutant SP02 susL244 in suppressor-negative bacteria were isolated. SP02 gene L is thought to code for a DNA polymerase essential for autonomous replication of SP02 DNA. Extracts of bacteria carrying one of these hybrid plasmids, pC194-96, had 10- to 30-fold increased DNA polymerase activity. The plasmid-induced DNA polymerase activity differed from that of the known B. subtilis DNA polymerases in several respects. The results of the experiments support the idea that phage SP02 codes for a new DNA polymerase.