SEXUAL ISOLATION IN DROSOPHILA .2. INTRASPECIFIC VARIATION IN MATE RECOGNITION SYSTEMS

A simple behavioral model is used to investigate whether differences i n the specific-mate-recognition system (SMRS), occur within species of the Drosophila genus. This model takes into account, and overcomes, t he distorting effect of vigor differences on experimental results. Ana lysis shows significant deviations from the expected values under the assumption of identical SMRSs in around one fifth of the multiple-choi ce experiments performed with natural strains of twelve different Dros ophila species. Different selection procedures raise the number of sig nificant assortative mating results between strains of D. melanogaster and D. pseudoobscura from 3.0% to 32.8%. Finally, sub- or semispecifi c taxa show variations in their SMRS even more frequently (74.5%). Dif ferences in male vigor and female receptivity are also found. These re sults show that a classification of Drosophila species based on SMRS s tability, as proposed by the ''Recognition concept of species'', is vi rtually impossible.