Genetic continuity within, and discontinuities among, populations of leafroller moths with distinct sex-pheromones

Abstract

Species belonging to two genera of leafroller moths have been shown to exhibit considerable variation in sex-pheromones. Six different pheromone types have been described, three each belonging to Planotortrix excessana and Ctenopseustis obliquana. We report here the existence of homozygous genotypes in wild-caught individuals and that no heterozygous genotypes for any of the presumptive genetic loci were recorded, despite electrophoresis of 820 individuals belonging to two pheromone types of P. excessana and 781 moths belonging to the two pheromone types of C. obliquana. This is particularly significant given that more than 500 individuals of each pair were collected from areas of sympatry. Hence these data unequivocally support the specific status of P. excessana pheromone type A and type B&C and C. obliquana type I&III and type II. A further study of 30 presumptive genetic loci of these pheromonally-distinct cryptic species reveals considerable differences in allele frequencies at other loci and shows that within pheromonal types there is a remarkable stability in gene frequencies, with little clinal variation. The variation within pheromone types that does exist results largely from regionally-distinct populations which are either geographically isolated, or subject to a range of human disturbances. The bulk of the total genetic variation within the taxonomically-described entities is among the pheromonally-distinct species. The question of the specific status of two pheromonally-distinct but allopatric populations is addressed, and it is suggested that genetic data cannot unequivocally resolve the specific status of such groups. © 1995 The Genetical Society of Great Britain.