Abstract
The mean frequency of heterozygous inversions per fly in D. willistoni was found to differ very little from locality to locality, elevation to elevation, or season to season within an island of the Greater Antilles. This relative uniformity is associated with a comparative impoverishment of different kinds of gene arrangements and perhaps also with a close association of the species with man. The distribution of another inversion (XL-D) is described as supporting Dobzhansky''s extension of the Darlington-Simpson hypothesis of certain migration routes for populations of this species in the Antilles (Dobzhansky, T., Evolution 11:280, 1957.).
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