Temporal Stability of Molecular Diversity Measures in Natural Populations of Drosophila pseudoobscura and Drosophila persimilis

Abstract

Many molecular ecological and evolutionary studies sample wild populations at a single point in time, but that data represents genetic variation from a potentially unrepresentative snapshot in time. Variation across time in genetic parameters may occur quickly in species that produce multiple generations of offspring per year. Here, we compare genetic diversity in wild caught populations of Drosophila persimilis and Drosophila pseudoobscura collected 16 years apart at the same time of year and same site at 4 X-linked and 2 mitochondrial loci to assess genetic stability. We found no major changes in nucleotide diversity in either species, but we observed a drastic shift in Tajima's D between D. pseudoobscura timepoints at 1 locus associated with increased abundance of a set of related haplotypes. Our data also suggests that D. persimilis may have recently accelerated its demographic expansion. While the changes we observed were modest, this study reinforces the importance of considering potential temporal variation in genetic parameters within single populations over short evolutionary timescales.

Keywords: Drosophila; genetic variation; large effective population size; population genetics; rapid evolution; temporal molecular evolution.

Figure 1.

Change in Tajima’s D in Drosophila pseudoobscura over the course of 16 years. The DPSX009 locus has undergone a noticeable change from a negative to positive Tajima’s D value.