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要旨:
One proposed advantage of outcrossing is creating new favourable gene combinations by recombination, which possibly helps adaptation to changing environmental conditions. This model predicts two alternative strategies for reproduction in Caenorhabditis elegans: Selfing would be an advantage under constant conditions because favourable combinations of genes are preserved and the cost of male production is reduced. In contrast outcrossing would be an advantage under changing environmental conditions. If this hypothesis is true and there are genetic determinants for the abundance of males, constant conditions should select for low incidence of males and changing selective pressure for higher number of males. We plan to test this model in the following way: A genetically variable population with a high number of males will be produced by interbreeding the two wild type strains N2 and CB4856. Half of this population will be cultivated under changing selection pressure of different pathogenic bacteria. The other half of the population will be kept under standard laboratory conditions. We have already shown that in N2 and CB4856 males are maintained at different rates in growing cultures under standard laboratory conditions. While N2 males are lost from the population within a few generations, CB4856 males are maintained at significantly higher proportion over longer periods, especially in large populations. This indicates that male abundance is, at least in part, determined genetically and that the corresponding genetic component differs between N2 and CB4856. If the model outlined above is true, we expect that the populations from the two treatments in our selection experiment differ in male frequency. We are also testing parameters that might be the reason for the different maintenance of males, for example mating efficiency and brood size. First Results will be presented.
