Abstract
The inversion polymorphism of the cactophilic fly Drosophila buzzatii was studied in two natural populations. We assessed the temporal changes and microspatial population structure. We observed a significant increase in the frequency of arrangement 2J at the expense of 2ST in both populations. These gene arrangements appear to affect the life-history of flies differently. Environmental heterogeneity explains the karyotype coexistence in nature. The analysis of population structure showed that differentiation of inversion frequencies among individual breeding sites, the rotting clacodes of Opuntia vulgaris, was highly significant. The karyotypic frequencies did not depart significantly from Hardy-Weinberg expectations, neither in individual rots nor in the total population. These results suggest that the observed population structure can be easily accounted by random genetic drift.
Highlights
The inversion polymorphism of the cactophilic fly DrosopI1iI2 huzzatii was studied in two natural populations
We observed a significant increase in the frequency of arrangement 25 at the expense of 2ST in both populations
The analysis of population structure showed that differentiation of inversion frequencies among individual breeding sites, the rotting clacodes of Opuntiu rulguris, was highly significant
Summary
Otamendi and Arroyo Escobar are located 77 km and 40 km North-West of the city of Buenos Aires, in the Pampa Region. Both localities have a temperate climate with a wide amplitude between winter and summer temperatures. Females were placed in individual vials and inversion frequencies were estimated from the inspection of the salivary gland chromosomes of one progeny larva from each vial. In February 1992, inversion frequencies were estimated in samples of third instar larvae collected from ten rotting clacodes of 0. Temporal variations of inversion frequencies were investigated by means of correlation analysis with time (in months) and climatic data. For each sample and arrangement these deviations were calculated using the for-
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