HYBRIDIZATION IN MILKWEED BUGS OF THE GENUS ONCOPELTUS (HEMIPTERA: LYGAEIDAE).

Abstract

Hybridization occurs occasionally in taxonomically well known groups of animals (see reviews by Mayr, 1963; 1970; White, 1973). Most of these reported hybrid forms are sterile or nonreproducing hybrid swarms, and this hybridization has been considered of minor importance in animal evolution (Mayr, 1963, 1970; White, 1973, 1978). However, hybridization does play a major role in evolution particularly if it leads to introgression. Some species of milkweed bugs of the genus Oncopeltus hybridize in nature and possible introgression is occurring. Chaplin (1973) reported that Oncopeltus cingulifer cingulifer Stal commonly interbred with 0. unifasciatellus Slater in Colombia, S. A., and hybrids were laboratory reared. Another species, 0. sandarachatus Say, interbreeds with 0. cingulifer in Trinidad, West Indies (pers. observ.), and hybrids also have been produced between them. Since interbreeding is common between these species in nature and hybrids have been laboratory reared, hybridization may be important in their evolution. This study was initiated to determine the evolutionary significance of hybridization in interbreeding species of Oncopeltus. In the groups of insects thoroughly studied, hybridization is usually associated with habitat disruption often as the result of human interference (see review by Mayr, 1963, 1970). Interbreeding in Oncopeltus is most often observed on their host plants (Asclepias spp.) growing in pastures (Chaplin, 1973; Root and Chaplin, 1976) and along roadsides (pers. observ.); it appears to be associated with disruption caused by agricultural activities