Nucleotide variation in the Acph-1 gene region was analyzed in a natural population of Drosophila subobscura from Bizerte (Tunisia). The lines studied differed in their gene arrangement for segment I of the O chromosome: 21 lines were O3+4+8, 21 were O3+4+23, and 3 were O3+4. According to chromosomal phylogenies, O3+4 is a central arrangement from which O3+4+8 and O3+4+23 originated. Strong gen...

The population structure of the Anopheles gambiae complex is unusual, with several sibling species often occupying a single area and, in one of these species, An. gambiae sensu stricto, as many as three "chromosomal forms" occurring together. The chromosomal forms are thought to be intermediate between populations and species, distinguishable by patterns of chromosome gene arrangements. The ext...

Chromosomal inversions contribute widely to adaptation and speciation, yet they present a unique evolutionary puzzle as both their allelic content frequency evolve in feedback loop. In this simulation study, we quantified the role of determining long-term fate inversion. Recessive deleterious mutations accumulated on arrangements with most them being private given arrangement. This led increasi...

The colonization of America by Drosophila subobscura has been a unique exper iment in nature that has allowed us to explore the effects of evolution on a continental scale. To analyze this evolutionary event, nucleotide sequences of the Odh (Octanol dehydrogenase) gene were obtained for 43 lethal chromosomal lines from colonizing populations of North America and 5 from South America, in additio...

Chromosomal inversions suppress recombination in heterokaryotypes and may help to maintain positive epistatic interactions among groups of alleles at loci contained in the inversion. Here I evaluate the protective effect of inversions on recombination when different chromosomal segments, or even the whole chromosome O of Drosophila subobscura, can be effectively prevented from undergoing recomb...

ACCORDING to STEPHENS (1950) speciation in the genus Gossypium occurs both by cryptic structural differentiation of chromosomes and by major gene substitution and mutation. In the first paper of this series RHYNE (1958) reported a sizeable reduction of recombination values within linkage groups following a transfer of intact diploid Gossypium linkage groups into allotetraploid G. hirsutum. Thes...