LACK OF SEASONAL-CHANGES IN MITOCHONDRIAL-DNA VARIABILITY OF A DROSOPHILA-SUBOBSCURA POPULATION

Restriction site analysis of mtDNA of 550 isofemale lines correspondin g to different seasonal samples of a single geographic population of D rosophila subobscura was carried out. The distribution pattern of hapl otypes was similar to that observed for the entire range of the specie s on the European continent: two haplotypes were equally and highly fr equent, and a set of sporadic haplotypes were almost never present in more than one seasonal sampling. No statistically significant evidence was found for between-population heterogeneity across time, and the m ean within-population variation was similar to other mtDNA restriction site analyses previously reported for D. subobscura populations. Thes e observations could be interpreted in terms of the neutral mutation h ypothesis where the entire population has not yet reached an equilibri um. The causes of this non-equilibrium are most likely periodic winter bottlenecks, phenomena that particularly affect the distribution of m tDNA haplotypes across time.