Why do female mice mate with multiple males?

Females often show multi-male mating (MMM), but the adaptive functions are unclear. We tested whether female house mice (Mus musculus musculus) show MMM when they can choose their mates without male coercion. We released 32 females into separate enclosures where they could choose to mate with two neighboring males that were restricted to their own territories. We also tested whether females increase MMM when the available males appeared unable to exclude intruders from their territories. To manipulate territorial intrusion, we introduced scent-marked tiles from the neighboring males into males' territories, or we rearranged tiles within males' own territories as a control. Each female was tested in treatment and control conditions and we conducted paternity analyses on the 57 litters produced. We found that 46 % of litters were multiply sired, indicating that multiple paternity is common when females can choose their mates. Intrusion did not increase multiple paternity, though multiple paternity was significantly greater in the first trial when the males were virgins compared to the second trial. Since virgin male mice are highly infanticidal, this finding is consistent with the infanticide avoidance hypothesis. We also found that multiple paternity was higher when competing males showed small differences in their amount of scent marking, suggesting that females reduce MMM when they can detect differences in males' quality. Finally, multiple paternity was associated with increased litter size but only in the intrusion treatment, which suggests that the effect of multiple paternity on offspring number is dependent on male–male interactions.     

Tierschutz und Tierversuche: Probleme und Lösungsansätze

In order to discuss the justified and humane demands for more animal protection in science we need first to achieve conceptual clarity. A simple separation of highly developed animals from less developed ones is hardly possible. Although we have no reliable way of assessing pain and suffering in animals we still have the responsibility for protecting them. However, scientists will always require animal experimentation in order to further the understanding of ourselves and to improve health. These experiments should follow strict guidelines. Concrete measures for animal protection must be adapted to each case and the consequences carefully thought out.     

Das Erdbild der Jurazeit

The term “Jurassic” refers to a manifold rock series of an epoch in the earth's history and its organic enclosures, from which-despite the lack of detail -a picture of earth surface and its life at that time can be reconstructed. This article presents the position of research and the problems it faces, which are partly of an objective and partly of a methodical nature.     

Risk assessment of conventional crop plants in analogy to transgenic plants

The risk assessment of genetically-modified plants pursuant to Annex II B of EU Directive 94/15/EC assumes that it is possible to infer the environmental impacts of a crop plant from its characteristics, so most of Annex II should also be applicable to conventional plants. To test this, we surveyed reports on the ecological impacts of the cultivation of non-transgenic crop plants with novel or improved traits and, in three cases, investigated whether Annex II B would have been adequate to indicate the effects. Such an assessment appears to be feasible only if the time frame on which it is based is short, so that long-term effects cannot be assessed. Secondly, the plant must be genetically homogenous which is not always granted, e.g. with forest-trees. Thirdly, the cultivation area must be defined. Differences in the behaviour of foreign plants between their original and cultivation habitats may be ecologically relevant and should be assessed. In the (few) cases where direct inference of the observed effects was possible from inherent traits, these effects often correlated with poor adaptation to local environmental conditions. The ecological impacts of traits that had been introduced in order to overcome poor adaptation may differ widely according to the way in which the traits are exploited. In practice, the effects of agricultural measures are more important than the effects of gene transfer and invasiveness, although the latter currently play a major role in risk assessment. In the light of these deliberations, a modification of Annex II B of EU Directive 94/15/EC is suggested.     

Archetypical patterns and trajectories of land systems in Europe

Regional Environmental Change - Assessments of land-system change have dominantly focused on conversions among broad land-use categories, whereas intensity changes within these categories have...     

Sperm usage in honey bees

Sperm usage was investigated in a naturally mated honey bee queen. We collected worker progeny arising from eggs that were laid sequentially during three sampling periods. Paternity was determined by analysis of three polymorphic microsatellite loci, leading to the conclusion that the queen had mated with seven males. Direct analysis of the sperm from the spermatheca revealed no evidence that sperm from additional males was present inside the spermatheca. Frequencies of different subfamilies differed significantly and ranged from 3.8% to 27.3%. In the short term, the frequencies of subfamilies among the eggs laid did not change over time. The frequency of eggs of a particular subfamily was statistically independent of the previous egg's subfamily. Thus, there is no evidence for non-random fine-scale sperm usage, and we estimate the effect of sperm clumping to be less than 6%. We conclude that the sperm is mixed completely inside the queen's spermatheca. Our results suggest that taking brood samples from comb cells next to each other is a statistically correct way of independent sampling of subfamilies at a given time in honey bee colonies. Furthermore, any bias in subfamily frequencies in offspring queens due to sperm usage can be excluded. However, the analyses of progeny samples taken 12 months apart do not allow us to exclude moderate fluctuations of subfamily frequencies in the long-term. Received: 11 August 1997 / Accepted after revision: 14 November 1997