Inversion polymorphism, longevity, end body size in a natural population of Drosophila buzzatii

In this study we present the results of an analysis of differential longevi ty associated with Drosophila buzzatii second chromosome inversion karyotyp es based on the assessment of more than 1000 individuals collected in a nat ural population. Comparisons of inversion frequencies between emerged and b ait-collected flies showed,not only that inversion arrangements were associ ated with differential longevity, but also that selection was Sex specific. Because each individual fly was scored for thorax length and karyotype, we were able to show that longevity selection favoring larger flies coupled w ith the average effect of inversions on thorax length can account for the c hange of inversion frequencies due to longevity in females. The observed ge notypic-by-sex interaction could be an important mechanism involved in the maintenance of the polymorphism. Arrangement 2Jz(3), which was shown to imp aired fecundity in two independent previous studies, exhibited a positive e ffect on longevity. This pattern of negative pleiotropy may be another plau sible mechanism accounting for the maintenance of the polymorphism.