Multiple Hybridisierung von Arten der Ameisen-Gattung Epimyrma (Hymenoptera: Formicidae), und Beobachtungen zur Ausbeutungder Wirtsarten durch die Parasiten

Buschinger, A.

Abstract: Multiple hybridization of ant species of the genus Epimyrma (Hymenoptera: Formicidae), and observations on host exploitation by the parasite species. - Various species of the parasitic ant genus Epimyrma were experimentally hybridized. Because in a number of species the sexuals mate inside the nest it is possible to replace the male pupae of one species by male pupae of another species. After the heterospecific sexuals had mated, young queens were placed singly into artificial nests, together with a few host workers from the mother colony and some host species larvae and worker pupae, for colony foundation. After hibernation, host worker pupae were added until the young colony comprised about 40-50 host workers. Young (hybrid) females and workers developed from the eggs of the cross-mated queens in this first year, or after a second hibernation. Hybrid females in the Same way could be crossmated with males of a third species, and so on. One of the experiments resulted in the production of female hybrids composed of two populations of Epimyrma kraussei (from Morocco and Crete), E. birgitae (from Teneriffa), E. bernardi (from Spain) and an undescribed Epimyrma species close to E. stumperi (from Greece). Other hybridizations were possible with E. birgitae X E. bernardi, and with E. kraussei X E. algeriana, always with production of nuyerous hybrid gynes and variable numbers of workers. However, hybrid females practically never had hybrid male offspring. Whereas it was possible to crossmate females of E. ravouxi with E. kraussei and with E. adlerzi, only one hybrid female each was reared in the two experiments. Four crossmatings of E. (= Myrmoxenus) gordiagini with males of E. kraussei did not yield any progeny although two of the E. gordiagini females survived for four years, laying numerous eggs every year, and still having living sperm in their spermathecae. Both E. ravouxi and E. gordiagini are swarming species. Successfui mating within their nests thus was initiated by the males of E. adlerzi and E. kraussei, respectively, both species being characterized by intranidal mating. It appears that the "degenerate slavemakers" with intranidal mating are very closely related among each other, so that their reproductive Isolation is mainly due to host specificity, intranidal mating, and a very low male production, whereas a more or less strong genetic isolation exists between this group on the one hand, and E. ravouxi and E. gordiagini on the other hand, with species of both groups conducting mating flights. The results of the hybridization experiments thus confirm earlier conclusions On the relationships within the genus. Epimyrma queens slowly throttle their host queens to death during colony foundation, they often sting some host species workers, and they eliminate host male pupae in parasitized nests. These observations are discussed as an optimized strategy of host colony exploitation.

Myrmecologische Nachrichten 4: 25-35; printable