GENERAL-PURPOSE GENOTYPES FOR HOST SPECIES UTILIZATION IN A NEMATODE PARASITE OF DROSOPHILA

The nematode Howardula aoronymphium parasitizes several species of mus hroom-feeding Drosophila. A survey of isofemale strains of H. aoronymp hium and a 25-generation selection experiment revealed that this speci es does not comprise host races, and that it harbors little heritable variation for adaptation to specific hosts. No tradeoffs in performanc e on the different host species were evident. General-purpose genotype s, which can utilize all host species, characterize H. aoronymphium. A n important feature of the natural history of these nematodes-correlat ed epidemiology across host species - is postulated to be both a cause and a consequence of the evolution of general-purpose genotypes in th is species.