GENETIC-VARIATION IN A SEMI-NATURAL DROSOPHILA POPULATION AFTER A BOTTLENECK .1. LETHALS, THEIR ALLELISM AND EFFECTIVE POPULATION-SIZE

A semi-natural D. melanogaster population was twice forced through a genetic bottleneck and allowed to recover naturally. In 1 case additional variation was introduced to the recovering population. The percentage of lethal chromosomes, the level of allelism between these lethals, and the effective population size calculated from the allelism of these lethals all rose sharply in the few generations following each bottleneck, though this was not the case in the very 1st generation. Thereafter this rise decelerated rapidly and never returned to pre-bottleneck levels. Additional introduced variation had little effect. The reasons for and implications of this pattern were considered.