PHYLOGENETIC POSITION OF YEAST-LIKE SYMBIONT OF HAMILTONAPHIS-STYRACI(HOMOPTERA, APHIDIDAE) BASED ON 18S RDNA SEQUENCE

Almost all aphids harbor bacterial intracellular symbionts in mycetocy tes. However, some Cerataphidini aphids do not harbor them but possess yeast-like extracellular symbionts in the abdominal hemocoel, suggest ing that in a lineage of this group replacement of symbiont occurred f rom an intracellular bacterium to an extracellular fungus. To investig ate the origin of the newly-acquired symbiont, the 18S rDNA sequence o f the yeast-like symbiont of Hamiltonaphis styraci was determined by P CR direct sequencing. Molecular phylogenetic analyses indicated that t he symbiont belongs to the subphylum Ascomycotina, the class Pyrenomyc etes. It was also suggested that the yeast-like symbiont of H. styraci and that of planthoppers are phylogenetically very closely related to each other. Copyright (C) 1996 Elsevier Science Ltd.