Frequency and selection in the industrial melanic moth Odontoptera bidentata

Abstract

Data are presented on morph frequency, selective return and date of emergence of morphs in the polymorphic melanic moth Odontoptera (= Gonodontis) bidentata (CL.). They come from three sites along the Mersey in industrial northwest England, and are used to test predictions from an earlier survey. There has been no decline in melanic frequency over the period studied. Non-melanics returned to traps less frequently than melanics at a site where the melanic frequency is high, agreeing with an earlier result. This suggests selection against non-melanics. Emergence starts later to the east of the region than to the west, and melanics emerge later than non-melanics. The late emergers must include heterozygotes as well as homozygotes. These results are discussed in relation to the question of how the polymorphism is maintained. © 1983, The Genetical Society of Great Britain.