POPULATION GENERIC STRUCTURE AND ECOLOGIC AL DIFFERENCES AMONG 9 POPULATIONS OF SESAMIA-NONAGRIOIDES LEFEBRE (LEPIDOPTERA, NOCTUIDAE) FROM THE WESTERN BASIN

Electrophoretic analyses of 12 loci on nine populations from Morocco, northern Spain, and southern France have revealed heterogeneity among localities (Fst = 0.064, Nm = 3.65) and a highly significant G test fo r polymorphic loci. The nine populations clustered into two groups on the UPGMA phenogram of genetic distances. Ecophysiological characters were examined (photoperiodic thresholds for diapause induction, develo pment time, and number of larval instars at 25 degrees C, under variou s photoperiods) for four of these populations. According to these ecop hysiological characters, the populations could be divided into two gro ups congruent with these obtained with the genetic analysis. Although the species is known as being sedentary, we can put forward the hypoth esis that insects could fly, not across the Pyrenees, but via the Atla ntic or Mediterranean coast, thus creating a genetic flow between popu lations. Moreover, despite a larval diapause, the high mortality rate observed within certain subpopulations might contribute to genetic dif ferentiation from residual populations surviving hard winters.