STRUCTURAL HOMOZYGOSITY IN MARGINAL POPULATIONS OF NEARCTIC AND NEOTROPICAL SPECIES OF DROSOPHILA IN FLORIDA

Abstract

New data are presented which indicate that 2 Nearctic species, Drosophila robusta and D. americana, are structurally homozygous on their extreme southern margins in central Florida. The same collecting sites are the apparent northern margin of the Neotropical species, D. acutilabella, which is similarly structurally homozygous. Like other species tending toward reduced polymorphism in Florida (D. euronotus, D. nigromelanica, and D. willistoni), the more central areas of these species show high polymorphism. Structurally monomorphic populations, especially if small, marginal and inbred, are considered ideal sites for species formation.