Why mussels stick together: spatial self-organization affects the evolution of cooperation

Cooperation with neighbours may be crucial for the persistence of populations in stressful environments. Yet, cooperation is often not evolutionarily stable, since non-cooperative individuals can reap the benefits of cooperation without having to pay the costs associated with cooperation. Here we show that active aggregation leading to self-organized spatial pattern formation can promote the evolution of cooperativeness. To this end, we study the effect of movement strategies on the evolution of cooperation in mussel beds. Mussels cooperate by attaching themselves to neighbours via byssal threads, thereby providing mutual protection. Using an individual-based model for mussel bed formation, we first demonstrate that the spatial pattern and the corresponding number of neighbours strongly depends on the movement strategies of the mussels. With an evolutionary model, we then show that this has important implications for the evolution of cooperation, since the evolved level of cooperativeness (the number of byssus threads produced) strongly depends on the number of neighbours and on the harshness and variability of the environment. Our results suggest that spatial aggregation, abundantly found in self-organized ecosystems, may promote the evolution of cooperation.     

PCA2GO: a new multivariate statistics based method to identify highly expressed GO-Terms

Background  

Several tools have been developed to explore and search Gene Ontology (GO) databases allowing efficient GO enrichment analysis and GO tree visualization. Nevertheless, identification of highly specific GO-terms in complex data sets is relatively complicated and the display of GO term assignments and GO enrichment analysis by simple tables or pie charts is not optimal. Valuable information such as the hierarchical position of a single GO term within the GO tree (topological ordering), or enrichment within a complex set of biological experiments is not displayed. Pie charts based on GO tree levels are, themselves, one-dimensional graphs, which cannot properly or efficiently represent the hierarchical specificity for the biological system being studied.     

Redox-induced conformational changes in plastocyanin: an infrared study.

The conformational changes associated with the redox transition of plastocyanin (PC) were investigated by absorption and reaction-induced infrared spectroscopy. In addition to spectral features readily ascribed to beta and turn protein secondary structures, the amide I band shows a major component band at 1647 cm(-1) in both redox states of the protein. The sensitivity of this component to deuteration and increasing temperature suggests that PC adopts an unusual secondary structure in solution, which differs from those described for other type I copper proteins, such as azurin and halocyanin. The conformations of oxidized and reduced PC are different, as evidenced (1) by analysis of their amide I band contour and the electrochemically induced oxidized-minus-reduced difference spectrum and (2) by their different thermal stability. The redox-induced difference spectrum exhibits a number of difference bands within the conformationally sensitive amide I band that could be assigned to peptide C=O modes, in light of their small shift upon deuteration, and to signals attributable to side chain vibrational modes of Tyr residues. Lowering the pH to 4.8 induces destabilization of both redox states of the protein, more pronounced for reduced PC, without significantly affecting their secondary structure. Besides the conformational differences obtained at neutral pH, the oxidized-minus-reduced difference spectrum shows two broad and strong negative bands at 1405 and 1571 cm(-1), assigned to COO(-) vibrations, and a broad positive band at 1710 cm(-1), attributed to the C=O vibration of a COOH group(s). These bands are indicative of a protonation of (an) Asp or Glu side chain(s) upon plastocyanin oxidation at acidic pH.     

Die Flora der Drauterrassen in Unterkärnten

Ohne Zusammenfassung     

Längsgeriefte Sediment-Stäbchen aus dem nordwestdeutschen Kimmeridge und ihre Deutung als Kotpillen mariner Invertebraten

Little rods of sediment with longitudinal furrows from the “Kimmeridge” of NW-Germany are described as faecal pellets in open nomenclature under the name Coprulus (Nuculidarum?) sp. 1, and compared with other, already known bodyfossils. Their greatest diameter is about 0,3 mm.     

Zur Bestimmung des Ascorbinsäuregehaltes in gerbstofführenden Pflanzenteilen

Ohne Zusammenfassung     

Soil microbial biomass and respiration measurements: An automated technique based on infra-red gas analysis

An automated system for continuous soil respiration and microbial biomass measurements based on Infra Red Gas Analysis was constructed. The switching device is computer controlled and allows hourly measurements of up to 24 samples when switching intervals of 2.5 min are selected. This allows the use of the substrate-induced respiration method for biomass determination. A software package to run the system was developed.     

Implications of Liebig's law of the minimum for the use of ecological indicators based on abundance

Many ecological responses to environmental variables or anthropogenic agents are difficult and expensive to measure. Therefore it is attractive to describe such responses in terms of indicators that are easier to measure. In ecosystem management, indicators can be used to monitor spatial and temporal changes in an environmental feature. The aim of this paper is to show that it is important to take Liebig's law of the minimum into consideration to understand when it is appropriate or inappropriate to use ecological indicators based on abundance. When developing indicators that relate the abundance of an organism to an environmental factor, it is likely that this relationship will be polygonal rather than a simple linear relationship. The upper boundary of the distribution describes how abundance is limited by this factor, while the variation below the upper boundary is explained by situations when factors other than the factor of interest limit abundance. The variation below the upper boundary of the distribution means that the use of indicators to examine spatial patterns in the response of abundance to an environmental factor can be problematic. Thus, while abundance-based indicators can identify sites that are in a good condition, they are less useful to detect those affected by environmental degradation. In contrast, abundance-based ecological indicators may enable temporal monitoring of the impact of environmental factors, as it is expected that limiting factors are less variable in time than in space. In conclusion, when multiple factors are limiting, a significant correlation between an indicator and a variable is not enough to validate the status of a factor as an indicator.