Ployandry versus polygyny versus parasites

Although social insect colonies are most easily conceptualized as consisting of a single, once-mated queen and her worker progeny, the number of queens per colony and the number of times queens mate varies broadly in ants and other social insects. Various hypotheses have been suggested for the resulting range of breeding systems and social organizations, respectively; one set of hypotheses relating to both queen number and mate number at the same time is a need for genetic variation, especially in relation to disease resistance. We here carry out a comparative analysis using phylogenetic information and, contrary to one non-phylogenetic previous study, we find that polyandry and polygyny are not significantly associated. However, the level of relatedness within colonies, a quantity affected by both polyandry and polygyny, is significantly associated with parasite loads: species with colonies with low relatedness levels have lower parasite loads. Given that, under the variance-reduction principle, selection on queens for mating frequency ought to continue even in polygynous colonies, we suggest that while parasite loads indeed seem to correlate with intra-colony genetic variability, the relationship to polyandry and polygyny may be complex and requires considerably more experimental investigation

Genetic variation within social insect colonies reduces parasite load

In colonies of social Hymenoptera (ants, bees and wasps), workers are often not very closely related to each other, because queens mate with several different males (polyandry) or because several functional queens are present (polygyny). Both characteristics increase genetic variation among the queens' reproductive and worker offspring, but the benefits of this increased variation remain obscure. Here we report an experiment where genetically homogeneous and genetically heterogeneous colonies of the bumble bee, Bombus terrestris, have been exposed to parasitism under field conditions. Colonies of high or low genetic variation were achieved by adding and removing brood from donor colonies. The results showed a consistent effect in that genetically variable colonies experienced reduced parasite loads, i.e. lower prevalence, intensity and parasite species richness, for a range of protozoa, nematodes, mites or parasitoids affecting the workers. We therefore propose that polyandry and/or polygyny of social insects may be beneficial under parasitism

Class voting, social change, and the left in Australia, 1943-96

The relationship between class and voting choices has been the subject of controversy in recent years, especially in connection with the apparent decline of the traditional left. This paper examines class voting in Australia, focusing on three major issues: (1) changes in the overall strength of class voting (2) realignment, or changes in the relative political positions of the classes (3) the connection between the strength of class voting and support for Labor. It finds that (1) there is a decline in 'general' class voting (2) much of this decline involves a realignment of certain middle class groups, but there is no support for the popular idea that class alignments have become more complex (3) there is no connection between the strength of class voting and Labor performance. Our results cast doubt on accounts that regard the electoral difficulties of left parties as a symptom of the decline of class