Genetic population structure, queen supersedure and social polymorphism in a social Hymenoptera.

In social insects, the emergence of multiple queening is linked to changes in a suite of traits such as the reproductive life span of queens, mating patterns and population structure. We investigated queen turnover, colony longevity, spatial distribution patterns and genetic differentiation in a population of the socially polymorphic ant Formica fusca. Genetic differentiation between the social forms was absent, and mating patterns were similar in the two forms. The spatial distribution of single- and multi-queen colonies indicated an absence of colony reproduction by budding in both colony types. However, the rate of queen supersedure was high in multi-queen colonies and absent in single-queen ones. The social structure of colonies remained stable across years, but colony mortality did not differ between the two social forms. These results imply that differences between social types may appear and persist also in sympatry, and that these differences may occur in some traits, but not others, despite the presence of homogenizing gene flow.

An evolutionary analysis of the relationship between spite and altruism.

We investigate the selective pressures on a social trait when evolution occurs in a population of constant size. We show that any social trait that is spiteful simultaneously qualifies as altruistic. In other words, any trait that reduces the fitness of less related individuals necessarily increases that of related ones. Our analysis demonstrates that the distinction between "Hamiltonian spite" and "Wilsonian spite" is not justified on the basis of fitness effects. We illustrate this general result with an explicit model for the evolution of a social act that reduces the recipient's survival ("harming trait"). This model shows that the evolution of harming is favoured if local demes are of small size and migration is low (philopatry). Further, deme size and migration rate determine whether harming evolves as a selfish strategy by increasing the fitness of the actor, or as a spiteful/altruistic strategy through its positive effect on the fitness of close kin.

[Ultrasonically guided Biopty-biopsy of focal liver processes]. / Ultralydvejledt Biopty-biopsi af fokale leverprocesser.

During a period of three years, 51 patients with focal hepatic changes were submitted to 55 ultrasonically guided Biopty-biopsies. Histological diagnoses could be established in 45 patients at the first biopsy which corresponds to a diagnostic certainty of 88.2% Histological diagnoses were established in 49 patients which corresponds to a certainty of 96%. The frequency of complications was 3.9%. Biopty-biopsy is recommended as a good method because it is easy to carry out and provides just as good results as other methods of biopsy. In addition, it can provide more histological information than aspiration biopsies which are, however, somewhat cheaper.