Springer Science and Business Media LLC

The application of ancient DNA techniques is subject to many problems caused primarily by low quality and by low quantity of DNA. For these reasons most studies employing ancient DNA rely on the characterization of mitochondrial DNA, which is present in many more copies per cell than nuclear DNA and hence more copies are likely to survive. We used universal and taxon specific mitochondrial primers to amplify DNA from museum specimens, and found many instances where the amplification of nuclear copies of the mitochondrial gene (numts) instead of the targeted mitochondrial fragment had occurred. Furthermore, the likelihood of amplifying numts increased dramatically when universal primers were utilized. Here we suggest that ancient DNA practitioners must consider the possibility that numts can be amplified at higher rates than previously thought. This is another complication for ancient DNA studies, but it also suggests that more extensive inclusion of nuclear markers in ancient DNA studies should be feasible.

Three approaches to the estimation of the role of balancing selection in maintaining allozyme polymorphism are considered: 1) Analysis of the stationary distributions of allelic frequencies in a native subdivided population; 2) Comparison of the genotypic distributions at the early and late developmental stages in successive generations of the same population; 3) Analysis of the ‘joint’ variability of monogenic and polygenic traits. The conclusion is drawn that allozyme polymorphism must not be regarded as a transient phase of molecular evolution but as its stationary phase. The mechanisms responsible for supporting such stability are discussed.

Crosses were made between geographic races of Drosophila ananassas from different localities in India. All these strains employed in the present experiments were polymorphic for the gene arrangements in the second chromosome due to the occurrence of alpha (subterminal) inversion. After ten generations it was observed that the heterozygotes were the most superior genotype and their frequencies remained above fifty percent in all these strains which served as controls and in the hybrid populations of mixed geographic origin. Thus it was found that interracial hybridization does not lead to breakdown of heterosis. The chief conclusion from these experiments is that evidence for coadaptation is lacking in D. ananassae. This finding apparently conflicts with what has been claimed for other species.