Probability of ultimate survival of a newly occurred inversion in natural populations.

An expression was derived that gave necessary and sufficient conditions for the ultimate probability of survival of a newly occurred inversion to be positive. The assumptions included a large population with a Poisson progeny distribution per parent and a time-heterogeneous average number of inversion heterozygote progeny (λ t ) for one inversion heterozygote parent. It was shown that an inversion, not possessing a unique or constant selective advantage, could have a positive ultimate probability of survival.