Population Genetics of Mexican Drosophila. V. A High Rate of Multiple Insemination in a Natural Population of Drosophila pseudoobscura

Abstract

The frequency of multiple insemination was studied in female D. pseudoobscura from a Mexican population. This population was highly polymorphic for third chromosome gene arrangements, and simple inspection of the progeny of single females showed that at least 43% of them carried the sperm of two or more males. The number of distinct gene arrangements in the progeny of single females was used to estimate the total frequency of multiple inseminations according to a probabilistic model. The frequency of double insemination was estimated to lie between 60% and 100%, while triple and quadruple inseminations were estimated to be quite rare. Double inseminations were clearly the rule, and not the exception, in the population we studied. We discuss the possible adaptive role of multiple insemination in Drosophila populations and the implications that frequent multiple insemination has for interpreting ecological genetic studies with Drosophila.