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Long-term change s in the population ecology of Drosophila pavani not followed by changes in the chromosomal polymorphism

Danko Brncic*

Departamento de Biologia Celular y Genética, Facultad de Medicina, Universidad de Chile, Casula 70061, Santiago (7), Chile
*This work has been supported by Grant B 2308-8835 from the University of Chile

ABSTRACT

During the last 35 years drastic changes in the populations of the native species Drosophila pavani have been detected in suburban localities in Central Chile. Before 1979, the species was the most abundant in the area but now it is an extremely rare one. This change could be attributed to environment degradation by increasing urbanization and coincides with the successful introduction of species such as the paleartic D. subobscura. A comparison of the inversion polymorphism existing in the natural populations of D. pavani, in samples taken in the same place and season in 1955, 1961, 1971, 1980 and 1984-87, shows no differences in the frequency of the different gene arrangements. The extreme stability of the polymorphism in the species contrasts with that found in other species for which changes in the environment are followed by genetic changes. The condition found in D. pavani could be interpreted as an expression of the strong heterotic properties of the inversion heterozygotes.

Keywords: Population ecology; Drosophila pavani; Chromosomal polymorphism.

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