Biosystematic Studies on Trichogramma Species(Hymenoptera: Trichogrammatidae): II. Experimental Hybridization between Some Trichogramma spp. from the New World

Abstract

Nagarkatti, S. and M. Fazaluddin (Indian Station, Commonwealth Institute of Biological Control, Bangalore, India) 1973. Biosystematic Studies on Trichogramma species (Hymenoptera: Trichogrammatidae) II. Experimental Hybridization between some Trichogramma spp. from the New World. Syst. Zool. 22:103-117.-Crossing experiments between 8 different species of Trichogramma from the New World are described. Sexual isolation was found to be generally weak, so that substantial numbers of females were frequently inseminated in interspecific crosses and some cases of mechanical isolation resulting in traumatic injury to females when mated with alien males were recorded. Despite high degrees of insemination of females in interspecific crosses, hybrids were rarely produced, or if so, only in small numbers. This suggested the presence of gametic isolation. In most cases where hybrids were produced, unilateral compatibility was observed. All the hybrids obtained were found to be fertile without exception, and hybrid lines could be established. However, on the basis of morphological differences and crossing relationships, it is concluded that some of the populations dealt with bear semispecies status with respect to each other, namely T. minutum & T. pretiosum, T. fasciatum & T. pretiosum, T. semifumatum & T. californica, but bear species status with respect to all others. The other species, namely, T. maltbyi, T. perkinsi, T. rojasi, are valid species. [Hybridization; Trichogramma.]