Within-Colony Kin Discrimination in a Social Insect

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From the time of Darwin on, the social insects have posed one of the great puzzles of evolutionary biology. Their worker castes are the prime example of reproductive altruism in the natural world, yet the process of natural selection is expected, for the most part, to lead to reproductive selfishness. How can evolution lead to giving up reproduction? The answer for social insects (and perhaps also to some extent for humans) turns out to be kinship. Colonies of social insects are groups of kin. Workers don't reproduce, but they help relatives to reproduce and this permits selection for genes for working behavior. However, we still don't understand what kind of balance is struck between the interests of the individual and the interests of the group as a whole. The same evolutionary kinship theory that explains how cooperation can evolve also predicts that there may be conflict within colonies. This is particularly true if individuals can distinguish and aid their closest relatives in their colony, but it is not known whether they do this. Drs. Strassmann and Queller will use DNA technology to answer this question. They will use a class of genes called microsatellite genes. Because these genes are both numerous and highly variable, they can be used to make the necessary fine-level estimates of relatedness. Thus, Drs. Strassmann and Queller will determine to what extent social insect colonies really are completely cooperative entities, or if they are in part cryptically contentious assemblies of individuals, each pursuing its own aims. This will greatly increase understanding of the extent and nature of altruism in the natural world. This project will contribute to the new technology surrounding microsatellite genes, which is important in many areas, including all kinds of evolutionary studies, conservation genetics, forensics, and gene-mapping studies for agricultural and medical needs. Besides contributing to the training of postdoctoral and graduate students, Drs. Strassmann and Queller encourage participation of undergraduates, high school students, and teachers who take the knowledge they gain back to the classroom.