TIME-SERIES ANALYSIS OF SEASONAL-CHANGES OF THE O-INVERSION POLYMORPHISM OF DROSOPHILA-SUBOBSCURA

We have studied seasonal variation (spring, early summer, last summer and autumn) of inversion polymorphisms of the O chromosome of Drosophi la subobscura in a natural population over 15 years. The length of the study allowed us to investigate the temporal behavior (short-term sea sonal changes and long-term directional trends) of the O arrangements by the powerful statistical method of time series analysis. It is show n that the O inversion polymorphisms varied on two different time scal es: short-term seasonal changes repeated over the years superimposed o n long-term directional trends. All the common arrangements (O-3+4+7, O-ST, O-3+4 and O-3+4+8) showed significant cyclic seasonal changes, a nd all but one of these arrangements (O-3+4+7) showed significant long -term trends. Moreover, the degree of seasonality was different for di fferent arrangements. Thus, O-3+4+7 and O-ST showed the highest season ality, which accounted for similar to 61 and 47% of their total varian ces, respectively. The seasonal changes in the frequencies of chromoso me arrangements were significantly associated with the seasonal variat ion of the climate (temperature, rainfall, humidity and insolation). I n particular, O-3+4+7 and O-ST, the arrangements with the greatest sea sonal component, showed the strongest association with all climatic fa ctors investigated, especially to the seasonal changes of extreme temp erature and humidity.