Description:
AbstractPopulational interactions among unlinked chromosomal rearrangements with partial heterozygote sterility and multiplicative fitness were studied to verify whether they help such rearrangements to persist in small populations, in spite of a considerable migration rate with a large population. A deterministic island‐continent model was studied by exact recurrence relations connecting gametic frequencies in successive generations.The increase in the number of chromosomal rearrangements with the same sterility rate (s) causes an increase in the critical value of the migration rate (mc) over which the chromosomal rearrangements are eliminated from the small population, mainly for medium s values (0.2 ≤ s ≤ 0.5) (“reciprocal stabilization” of the chromosomal rearrangements).A comparison was made between the velocities of the fixation of a few rearrangements with high heterozygote sterility (low n/high s) and that of many rearrangements with low heterozygote sterility (high n/low s), to reach a given level of populational stability of the rearranged karyotype measured by mc. The former process was shown to be more rapid in small demes, the latter in large ones. However, the increase in the number of unlinked chromosomal rearrangements is more efficient in reducing the neutral gene flow than in increasing the populational stability of the rearranged karyotype.