Information exchange in policy networks is usually attributed to preference similarity, influence reputation, social trust, and institutional actor roles. We suggest that political opportunity structures and transaction costs play another crucial role and estimate a rich statistical network model on tie formation in the German toxic chemicals policy domain. The results indicate that the effect of preference similarity is absorbed by institutional, relational, and social opportunity structures. Political actors choose contacts who minimize transaction costs while maximizing outreach and information. We also find that different types of information exchange operate in complementary, but not necessarily congruent, ways.

In 2005, the European Parliament rejected the directive ‘on the patentability of computer-implemented inventions’, which had been drafted and supported by the European Commission, the Council and well-organised industrial interests, with an overwhelming majority. In this unusual case, a coalition of opponents of software patents prevailed over a strong industry-led coalition. In this article, an explanation is developed based on political discourse showing that two stable and distinct discourse coalitions can be identified and measured over time. The apparently weak coalition of software patent opponents shows typical properties of a hegemonic discourse coalition. It presents itself as being more coherent, employs a better-integrated set of frames and dominates key economic arguments, while the proponents of software patents are not as well-organised. This configuration of the discourse gave leeway for an alternative course of political action by the European Parliament. The notion of discourse coalitions and related structural features of the discourse are operationalised by drawing on social network analysis. More specifically, discourse network analysis is introduced as a new methodology for the study of policy debates. The approach is capable of measuring empirical discourses both statically and in a longitudinal way, and is compatible with the policy network approach.

To investigate whether reproductive variation in the <I>Daphnia galeata-cucullata-hyalina</I> hybrid species complex can explain the occurrence of hybrids and backcrosses, a total of 43 clones from three north German lakes were tested for allocation to sexual reproduction under equal stress conditions. Six replicates per clone were followed until the seventh adult instar. I used the following cues to promote sexual reproduction: short photoperiod, water from a crowded <I>Daphnia</I> culture, fish-conditioned water and low food concentration. For each animal, clutch size and clutch sex were recorded. Ephippia, which were empty since the animals were cultured individually, were only produced by <I>D. cucullata</I> and <I>D. cucullata</I> × <I>hyalina</I> (26% and 6% of the broods, respectively), whereas almost all taxa produced males (the range was 2–15%). Intraspecific variation for male and ephippial production was also found. The fact that the taxa tested show different responses to the stimuli offered may indicate that there is reproductive isolation between them. This is supported by field data from the Tjeukemeer (The Netherlands) which shows that <I>D. galeata</I> mostly produces ephippia in spring and <I>D. cucullata</I> in autumn. The presence of hybrids with ephippia in both seasons, however, shows that backcrossing is also possible.

Geographic variation in maternal investment in offspring size can be adaptive if differences in investment translate into improved offspring performance in the given environments. We compared two moor frog, <I>Rana arvalis</I>, populations in the laboratory to test the hypothesis that investment in large eggs in populations originating from stressful (acid) environments improves offspring performance when reared in stressful (acid) conditions. We found that large initial size (hatchling mass) had moderate to strong, environment-dependent positive effects on larval and metamorphic traits in the acidic origin population, but only weak effects in the neutral origin population. Our results suggest that interactions between environmental conditions and initial size can be important determinants of individual performance, and that investment in large eggs is adaptive in acid environments. These findings emphasize the role of maternal effects as adaptations to environmental stress.

<br/>Cities are the most complex forms of settlements which man has built in the course of his cultural development. Their “metabolism” is connected with the world economy and is run mainly by fossil energy carriers. Up to now there are no validated models for the evaluation of a sustainable development of urban regions. <br/> The guidelines for a “sustainable development” suggest the reduction of resource consumption. The article is concerned with the problem of how the “sustainable-development concept” can be transformed from a global to a regional scale. In urban settlements the strategy of final storage should be applied. By this, the subsystem waste management can be transformed within 10 to 15 years to a “sustainable status”. <br/> With regard to the system “agronomy”, the article concludes that agriculture in urban systems should focus on food production instead of promoting reduction of food production in favour of energy plants, which is not a suitable strategy.<br/> The main problems are the energy carriers. Transformation to a “sustainble status” is only possible by a reconstruction of the urban system, i.e. of buildings and the transportation network. The rate determining step in achieving such a status is the change in the fabric of buildings and in the type of transportation networks. The reconstruction of an urban system needs, mainly for economical reasons, a time period of two generations.

The release of polycyclic aromatic hydrocarbons (PAHs) into the environment has increased very substantially over the last decades. PAHs are hydrophobic molecules which can accumulate in high concentrations in sediments acting then as major secondary sources. Fish contamination can occur through contact or residence nearby sediments or though dietary exposure. In this study, we analyzed certain physiological traits in unexposed fish (F1) issued from parents (F0) exposed through diet to three PAH mixtures at similar and environmentally relevant concentrations but differing in their compositions. For each mixture, no morphological differences were observed between concentrations. An increase in locomotor activity was observed in larvae issued from fish exposed to the highest concentration of a pyrolytic (PY) mixture. On the contrary, a decrease in locomotor activity was observed in larvae issued from heavy oil mixture (HO). In the case of the third mixture, light oil (LO), a reduction of the diurnal activity was observed during the setup of larval activity. Behavioral disruptions persisted in F1-PY juveniles and in their offspring (F2). Endocrine disruption was analyzed using <I>cyp19a1b:GFP</I> transgenic line and revealed disruptions in PY and LO offspring. Since no PAH metabolites were dosed in larvae, these findings suggest possible underlying mechanisms such as altered parental signaling molecule and/or hormone transferred in the gametes, eventually leading to early imprinting. Taken together, these results indicate that physiological disruptions are observed in offspring of fish exposed to PAH mixtures through diet.

Recent studies have shown that <I>Daphnia</I> hybrids are intermediate to their parental species for several life history traits, and that they combine advantageous traits of the parental species, thereby decreasing their risk of being preyed upon by planktivorous fish. In this study <I>D. galeata</I>, <I>D. cucullata</I> and their interspecific hybrid are compared with respect to cyclomorphosis and juvenile growth as a potential mechanism to avoid invertebrate predation. Helmets and tail spines are known to reduce predation risk, whereas fast juvenile growth reduces the period that Daphnia are vulnerable to predation. In laboratory cultures, I tested the hypothesis that, with regard to cyclomorphosis, juvenile hybrids are more comparable to the juveniles of <I>D. cucullata</I>, and with respect to growth rate, they are more comparable to <I>D. galeata</I>. The hybrid did not differ significantly from <I>D. galeata</I> in the time needed to reach 0.9 mm body length. In contrast, the relative spine and helmet length of juvenile hybrids were more comparable with those of <I>D. cucullata</I>, whereas in adult instars these characters were more similar to <I>D. galeata</I>. Thus during the first juvenile instars, the hybrids combine the relative long helmet and spine of <I>D. cucullata</I>, with the faster growth of <I>D. galeata</I>. This combination of characteristics might reduce hybrid vulnerability to invertebrate predation in field situations.

1. <I>Gloeotrichia echinulata</I> - Klon Cambridge 1432-I - wächst <I>in vitro</I> in verschiedenen rein mineralischen Nährlösungen. Als besonders günstig erweist sich Medium Nr. II mit ein bis zwei Milligramm in chelierter Form gebotenem Eisen. Das Wachstum der Alge wird durch quantitative Änderungen in der Zusammensetzung dieses Mediums innert ziemlich weit auseinanderliegender Grenzen nur unwesentlich beeinflusst.<br/> 2. Ein pH-Wert des Mediums von 8 bis 9 ist für das Wachstum der Alge am besten. In der Nährlösung Nr. II stellt sie während der aktiven Wachstumsphase das ihr passende pH selber ein. Eine künstliche Adjustierung der Kulturen ist damit unnötig.<br/> 3. Ein von ALLEN und ARNON [3] für andere Blaualgen mit grossem Erfolg verwendetes Medium ist für <I>Gloeotrichia</I> ungünstig, wahrscheinlich wegen seines hohen Kaliumgehaltes.<br/> 4. <I>Gloeotrichia echinulata</I> kann vermutlich molekularen Stickstoff assimilieren.<br/> 5. Kulturversuche in grösseren Gefässen («Tower-Type-Fermentors») sind noch nicht befriedigend gelungen. Störend wirkt immer wieder die starke Schaumbildung in durchlüfteten Kulturen, die offenbar auf organische Stoffe zurückzuführen ist, welche die Alge in das Medium ausscheidet.