HOPKINS HOST-SELECTION IN NASONIA-VITRIPENNIS AND ITS IMPLICATIONS FOR SYMPATRIC SPECIATION

The operation of the Hopkins host-selection principle in the host-selection behaviour of the parasitoid wasp Nasonia vitripennis on three dipteran host species was tested. In order to determine whether larval conditioning influenced adult ovipositional preference, the parasitoids were reared on and then offered choices between host species in two pairwise combinations, Phormia regina/Phaenicia sericata and P. regina/Musca domestica. Hopkins host-selection was evident in the latter combination only. Preference for a given host is not reinforced by conditioning over several generations. The conditioning was not strong enough to serve as a primary isolating mechanism in the speciation process as suggested by Thorpe (1938, 1945), though it could be important as a secondary isolating mechanism. © 1979.